Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
MARINE ASSET SECURITY AND TRACKING (MAST) SYSTEM
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER
FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT
This invention was made with United States Government support under prime
contract No. DE-AC05-OOOR22725 to UT-Battelle, L.L.C. awarded by the
Department of
Energy. The Government has certain rights in this invention.
BACKGROUND OF THE INVENTION
Field of the Invention
An embodiment of the invention relates generally to the field of security and
tracking.
More particularly, an embodiment of the invention relates to marine asset
security and
tracking (MAST).
Discussion of the Related Art
The worldwide ocean-going freight transportation infrastructure, known as the
Marine
Transportation System (MTS), is under stress from several fronts including:
terrorism,
antiquated technology, environmental restrictions, just-in-time manufacturing
practices,
overlapping state/federal/local jurisdictions, and a lack of basic
technological infrastructure.
Terrorist attacks may likely focus on economic terrorism to affect change in
the modern
world. One need only look to the open movement of containerized cargo to find
simple,
effective, and efficient means of large-scale economic damage (RFID Journal,
2003). The
destruction, or the stoppage of flow at a few key ports could damage our
economy and
cripple the nation in a matter of weeks (Flynn, 2003). Consequently, there is
a need to
develop and deploy tracking and monitoring technologies at the container level
to help
secure the global supply chain and the critical port facilities that service
the economic well
being of our nation and other nations (Gills and McHugh, 2002; Bonner, 2002;
Verton,
2002).
A port is an assemblage of many facilities, entities and functions including:
federal
stakeholders (e.g., U.S. Customs, Coast Guard, DOD, TSA, FBI, etc.), state
government
stakeholders (e.g., Ports Authority, State Law Enforcement, Emergency
Preparedness,
etc.), and local stakeholders (e.g., local law enforcement, local fire
departments, port
security, and commercial terminal operators, labor unions, etc.). Developing
additional
facilities to network the critical components of operations at each port to
provide for port
security/management and ship/cargo security/tracking/management will aid in
efficient use
and safety of each port. Ultimately, these local port facilities should be
linked to a regional
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center and/or national center with potential for international expansion.
Consequently, there
is a need to adopt technologies, such as geographic information systems (GIS),
global
satellite communications, the Internet, and wireless
monitoring/tracking/security
infrastructure in managing/securing the modern supply chain preferably with an
open
systems architecture to allow multiple public and private entities to
participate.
Shipping via the Marine Transportation System (MTS) totaled $480 billion in
cargo
and contributed $750 billion to the U.S. gross domestic product in calendar
year 1999, and
the current volume of domestic maritime shipping is expected to double (USDOT,
1999)
over the next 20 years. International maritime shipping is expected to triple
over the same
time period (Prince, 2001 ). Many port facilities are under economic stress
from the above-
noted several fronts, including antiquated technology, environmental
restrictions, just-in-time
manufacturing practices, overlapping federal/state/local jurisdictions, and
the lack of basic
technological infrastructure to orchestrate a secure and efficient container
management
system. In addition, land competition and environmental regulations will
restrict the
geographic expansion of most current port facilities. The information systems
tasked with
managing containers are still largely dependent on manual data entry.
Consequently, there
is a need for automated technology solutions to increase efficiency and
security in port
facilities (Gills and McHugh, 2002; Verton, 2002; Gillis, 2002).
In addition to concerns about MTS economic inefficiencies, the MTS currently
has an
unprecedented emphasis on homeland security. In 2001, 5.7 million containers
entered the
U.S. via the MTS (Gills and McHugh, 2002). U.S. Customs inspects less than 2%
of these
containers manually, relying on intelligence to "profile" containers. The
Coast Guard and
U.S. Customs do not have the manpower or resources to manually search each
container
entering the U.S., and doing so would bring the supply chain to a catastrophic
halt (Loy,
2002). Intelligent profiling of cargo and containers is critical to securing
the global supply
chain and enabling legitimate commerce. Tracking and monitoring would provide
better
data from which to build intelligent profiles. Therefore, there is a need for
investment in
appropriate tracking and monitoring technology as the key to increased
security and
economic efficiency (Flynn, 2003).
A key concern with containerized cargo transportation is the relative ease
with which
a thermonuclear device or radioactive material for a "dirty bomb" could be
smuggled into the
target country in a shipping container. A significant specific problem for
Homeland Security
is the potential shipping of radioactive material for a "dirty bomb" into the
United States in a
shipping container. The standard marine shipping container has become the
dominant
method of importing and exporting goods worldwide. The number of containers
arriving and
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departing from US ports each day is so large that only an extremely small
fraction is ever
inspected. Since only a small fraction of containers can ever be inspected,
some method
must be employed to "flag" containers for inspection. Locating sensor portals
through which
each container must pass at each port facility is considered unrealistic. Such
a bottle neck
could cost the US economy billions of dollars each day. Employing a radiation
sensor in, on
or near the cargo container to look for elevated levels of radiation would be
one method of
flagging containers.
However, there are problems with existing radiation sensors that have been
proposed for shipping containers. First, existing radiation sensors must use
power during
the dose integration (active sensing) time. Existing active radiation sensors
must either
utilize very short integration times, thus reducing sensitivity, or they will
use up their
available battery power long before the end of the service life of the
container. Replacing
batteries requires maintenance personal time, coordination between the
maintenance
schedule and the physical location of the container and logistical support.
There is a need
for radiation sensors with a much longer unattended service life.
Second, existing active radiation sensors do not make the dose integration
data
available for secure and uninterrupted monitoring of the each container.
Reading the dose
integration data requires that the individual sensors be removed and read, or
at least
individually read, leading to the same problems of costly maintenance personal
time,
coordination between the data collection schedule and the physical location of
the container
and logistical support. There is a need for radiation sensors that make the
dose integration
data automatically and remotely available for intelligent profiling and
analysis.
Third, existing active radiation sensors are prone to false alarms. Existing
active
radiation sensors cannot discriminate between different types of radiation
leading to false
alarms from substances used for medical diagnosis and even from benign cargo
such as
bananas which naturally contain concentrations of ionizing radiation
substances (e.g.,
potassium). There is a need for more sophisticated and discriminatory
radiation sensors.
Heretofore, the requirements of container-level tracking and monitoring by
long-life
sensors, making the critical data automatically and remotely available for
intelligent profiling
and analysis and reducing false alarms have not been met. What is needed is a
global
container security and asset (ship and cargo) tracking system that satisfies
(preferably
simultaneously all of) these requirements.
SUMMARY OF THE INVENTION
There is a need for the following embodiments of the invention. Of course, the
invention is not limited to these embodiments.
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According to an embodiment of the invention, a method comprises: transmitting
identification data, location data and environmental state sensor data from a
radio frequency
tag. According to another embodiment of the invention, an apparatus comprises:
a radio
frequency tag that transmits identification data, location data and
environmental state
sensor data.
According to another embodiment of the invention, a method comprises
transmitting
identification data and location data from a radio frequency tag using hybrid
spread-
spectrum modulation. According to another embodiment of the invention, an
apparatus
comprises a radio frequency tag that transmits both identification data and
location data
using hybrid spread-spectrum modulation.
According to another embodiment of the invention, a method comprises insitu
polling
a suite of passive integrating ionizing radiation sensors including reading-
out dosimetric data
from a first passive integrating ionizing radiation sensor and a second
passive integrating
ionizing radiation sensor, wherein the first passive integrating ionizing
radiation sensor and
the second passive integrating ionizing radiation sensor remain situated where
the
dosimetric data was integrated while reading-out. According to another
embodiment of the
invention, an apparatus comprises a first passive integrating ionizing
radiation sensor; a
second passive integrating ionizing radiation sensor coupled to the first
passive integrating
ionizing radiation sensor; and a communications circuit coupled to the first
passive
integrating ionizing radiation sensor and the second passive integrating
ionizing radiation
sensor, wherein the first passive integrating ionizing radiation sensor and
the second
passive integrating ionizing radiation sensor read-out dosimetric data to the
communications
circuit.
According to another embodiment of the invention, a method comprises arranging
a
plurality of ionizing radiation sensors in a spatially dispersed array;
determining a relative
position of each of the plurality of sensors to define a volume of interest;
collecting ionizing
radiation data from at least a subset of the plurality of ionizing radiation
sensors; and
triggering an alarm condition when a dose level of an ionizing radiation
source is calculated
to exceed a threshold. According to another embodiment of the invention, an
apparatus
comprises a plurality of ionizing radiation sensors arranged in a spatially
dispersed array
where a relative position of each of the plurality of sensors array is
determined to define a
volume of interest; a data collection circuit coupled to the plurality of
ionizing radiation
sensors to collect ionizing radiation data from at least a subset of the
plurality of ionizing
radiation sensors; and a computer coupled to the data collection circuit to i)
calculate a dose
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level of an ionizing radiation source and compare the dose level to a
threshold and ii) trigger
an alarm when the dose level is equal to or greater than the threshold.
These, and other, embodiments of the invention will be better appreciated and
understood when considered in conjunction with the following description and
the
accompanying drawings. It should be understood, however, that the following
description,
while indicating various embodiments of the invention and numerous specific
details thereof,
is given by way of illustration and not of limitation. Many substitutions,
modifications,
additions and/or rearrangements may be made within the scope of an embodiment
of the
invention without departing from the spirit thereof, and embodiments of the
invention include
all such substitutions, modifications, additions and/or rearrangements.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings accompanying and forming part of this specification are included
to
depict certain embodiments of the invention. A clearer conception of
embodiments of the
invention, and of the components combinable with, and operation of systems
provided with,
embodiments of the invention, will become more readily apparent by referring
to the
exemplary, and therefore nonlimiting, embodiments illustrated in the drawings.
Embodiments of the invention may be better understood by reference to one or
more of
these drawings in combination with the description presented herein. It should
be noted that
the features illustrated in the drawings are not necessarily drawn to scale.
FIG. 1 illustrates a schematic perspective overview of a marine asset security
and
tracking (MAST) system, representing an embodiment of the invention.
FIG. 2 illustrates a schematic view of a radio frequency RF data link
operation for
use both onboard ship and in terminal with radio frequency identification
(RFID) tags able to
communicate with both shore-based and ship-based receivers simultaneously,
representing
an embodiment of the invention.
FIG. 3 illustrates a schematic view of communications between RFID tags and a
network operations center (NOC) via land-side or ship-board site server when
the tags are
utilizing RF for local-area communications (e.g., for ship-board and terminal
local area (land-
side) operations), representing an embodiment of the invention.
FIG. 4 illustrates a schematic view of a bi-directional communications between
RFID
tags and a network operations center (NOC) when utilizing the cellular or
satellite
communications during over-the-road or rail transportation, representing an
embodiment of
the invention.
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FIG. 5 illustrates a schematic block diagram of the functional components
comprising an RFID tag, representing an embodiment of the invention.
FIG. 6 illustrates a schematic perspective view of readers and RFID tags in
the
context of a stacked array of containers, representing an embodiment of the
invention.
FIG. 7 illustrates a flow diagram of a RFID tag boot-up sequence - including a
node
discovery sequence mode that can be implemented by a computer program,
representing
an embodiment of the invention.
FIG. 8 illustrates a flow diagram of a RFID tag boot-up sequence mode that can
be
implemented by a computer program, representing an embodiment of the
invention.
FIG. 9 illustrates a schematic top plan-view of a group of tightly stacked
containers
(nominally 40-footers) on the deck of a ship or within a terminal yard, with a
single RF
emitter (depicted as a radiating dot) mounted near the center of the top of
it's host
container; the arrows denote RF energy leaking from the ends of the container
into adjacent
aisles and then reflecting along the aisles; and potential RF receiving
locations are denoted
by the dots located at the ends of the aisles, representing an embodiment of
the invention.
FIG. 10 illustrates a schematic block diagram of an insitu polled suite of
sensors,
each sensor having a different filter, representing an embodiment of the
invention.
FIG. 11 illustrates a schematic structural diagram of an insitu polled sensor
with
integrated temperature compensation, representing an embodiment of the
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the invention and the various features and advantageous details
thereof are explained more fully with reference to the nonlimiting embodiments
that are
illustrated in the accompanying drawings and detailed in the following
description.
Descriptions of well known starting materials, processing techniques,
components and
equipment are omitted so as not to unnecessarily obscure the embodiments of
the invention
in detail. It should be understood, however, that the detailed description and
the specific
examples, while indicating preferred embodiments of the invention, are given
by way of
illustration only and not by way of limitation. Various substitutions,
modifications, additions
and/or rearrangements within the spirit and/or scope of the underlying
inventive concept will
become apparent to those skilled in the art from this disclosure.
The below-referenced U.S. patents, PCT published applications designating the
U.S.
and U.S. patent applications disclose embodiments that are useful for the
purposes for
which they are intended. The entire contents of U.S. Pat. Nos. 6,603,818;
6,606,350;
6,625,229; 6,621,878; 6,556,942 are hereby expressly incorporated by reference
herein for
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all purposes. The entire contents of PCT published application Nos. WO
02/27992; WO
02/19550; WO 02/19293; and WO 02/23754 are hereby incorporated by reference
for all
purposes. The entire contents of U.S. Serial Nos. 09/671,636 filed September
27, 2000;
09/653,788 filed September 1, 2000; 09/942,308 filed August 29, 2001;
09/660,743 filed
September 13, 2000; 10/726,446 filed December 3, 2003; 10/726,475 filed
December 3,
20003; and 10/817,759 filed December 31, 2003 are hereby expressly
incorporated by
reference herein for all purposes. The instant application contains disclosure
that is also
contained in copending U.S. Serial No. (Attorney Docket No. UBAT1570), filed
May 6, 2004,
now pending, the entire contents of which are hereby expressly incorporated by
reference
for all purposes.
An embodiment of the invention can include a method and/or apparatus for
monitoring the status of and tracking the location of shipping containers
onboard ship, at the
shipping terminal, and during over-the-road (truck and rail) transportation.
Thus, the
invention can include a true "inter-modal" tracking and monitoring system.
This method
and/or apparatus can utilize hybrid spread-spectrum (HSS) communications for
robust two-
way transmission of data to and from the container onboard the ship and in the
shipping
terminal. The phrase hybrid spread-spectrum (HSS) as used herein is defined as
a
combination of direct sequence spread-spectrum (DSSS), for example code
division multiple
access (CDMA), and at least one of frequency hopping, time hopping, time
division multiple
access (TDMA), orthogonal frequency division multiplexing OFDM and/or spatial
division
multiple access (SDMA), for instance as described by PCT published application
No. WO
02/27992 and/or U.S. Serial No. 10/817,759 filed December 31, 2003. Fast HSS
is a
particularly preferred embodiment where spreading and hopping occurs during a
bit time
(i.e., each bit is spread and hopped individually). The invention can utilize
cellular and/or
satellite data transmissions for communications during over-the-road
transportation.
Sensors for monitoring the container cargo status and condition can be
included in this
system. The location of the container can be determined using the global
positioning
system (GPS) during over-the-road transportation, and by using more localized
radiolocation
techniques utilizing the HSS communication's RF signals. The location and
status of a
container can be relayed to a national operations center, which combines this
data with the
cargo manifest in a geographic information system database for monitoring,
tracking,
managing and displaying container information.
An embodiment of the invention can include a marine asset security and
tracking
(MAST) system linking robust, long-range RFID technology to GIS-based tracking
infrastructure via a global satellite communication network to create a truly
global asset
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management and cargo tracking/visibility system utilizing open systems
architecture. The
MAST system is intended to provide real-time ship/road/rail container and
cargo tracking in
the context of an open systems architecture for port and supply chain security
needs. This
tracking technology will create a number of commercial opportunities,
including homeland
security, supply chain management, port automation, insurance applications,
and potential
recovery/salvage of lost and wayward cargo in the commercial marketplace to
fund the
expansion and adoption of the system. The MAST system effort will also
facilitate the
development of new standards and "best management" practices for tracking and
security
monitoring of containerized cargo and assets.
The invention can be designed to provide real-time asset, container, and cargo
tracking for port security/management needs, and increase safety of life and
property
across intermodal transportation networks. The ability to globally track
containers in real-
time with internal condition monitoring is essential to securing the supply
chain and the port
system. The preferred HSS, two-way low-power wireless communications will work
well in
the context of ship and/or terminal communications distances (e.g., range of
300 - 500
meters) at a power of approximately 10 mW.
The RF propagation problems in and around closely stacked steel shipping
containers dictate the use of extremely robust data-communication techniques
(e.g.,
advanced spread-spectrum modulation and diversity receiving systems) to
successfully
transmit telemetry signals from the individual container RF tags to the ship
receivers
(readers). The goal of highly accurate radiolocation of these containers in
large, closely
packed stacks, especially down in ships' holds, will continue to be elusive
unless numerous
receivers (readers) are distributed throughout the yard facilities and over
the decks and
holds of each ship. If some loss of position resolution can be tolerated in
normal operation,
then in most cases the use of carefully engineered container RF tags and
infrastructure
components, tailored in their deployment to the specific environment (i.e.,
yard or ship),
should provide effective telemetry of container ID and status data (e.g., door
security,
temperature) and reasonably accurate container location information (i.e.,
within one stack
position) in the vast majority of specific environmental cases.
A preferred MAST system implementation can use the 2450-2483.5 MHz ISM band
to comply with international regulations, particularly for ships being loaded
in foreign ports.
Further, port facilities overseas will undoubtedly eventually use some sort of
RF telemetry
for tracking containers. If the MAST system protocol fits the international
allocation in the
2.45-GHz ISM band, it may well be adopted worldwide to track shipping
containers, first in
ports and eventually in other venues such as rail, planes and trucks. For
narrowband system
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alert signals, beacons, and the like, other ISM band possibilities include the
13.56 and 433-
MHz slots; the 868-MHz (Europe) and 915-MHz (North America) bands provide
somewhat
more width for higher-rate and spread-spectrum use. The data protocol of a
commercial
embodiments of the invention is likely to be a hybrid or direct-sequence
spread-spectrum
signal with fairly wide bandwidths (>1 MHz), long code lengths (e.g., >_ 63)
for better process
gain and jamming resistance, and controlled time slotting for lower collision
statistics.
To deploy the MAST system in a marine (yard/ship) environment, several areas
of
functionality should be combined in a system. The first functional group
encompasses the
basic architecture for a sea-based system, which includes (1) communication
links; (2)
antennas; (3) electronics; (4) container-unit power sources; (5) ship-to-shore
system
interface, e.g., satellite link; (6) container telemetry system integration;
(7) container location
detection [GPS, optimally augmented by local RF triangulation]; (8) sensors;
(9) system
central monitoring units; and (10) container database interfaces. The second
functional
group includes the port container-yard system, which is largely the same in
function as the
shipboard setup; except that additional system logic is needed to manage the
tracking-
system handoff between the ship and yard systems.
1. Overview
Referring to Fig. 1, one or more radio frequency identification tags 101
coupled to
containers 105 are in bi-directional radio frequency communication with a
reader 107 on a
ship 110. The ship 110 also includes a site server (not shown in Fig. 1) but
is in bi
directional radio frequency communication with a low earth orbit satellite
120. The low earth
orbit satellite 120 is in bi-directional radio frequency communication with an
earth station
125.
Simultaneously, another radio frequency identification tag 102 and an inter-
modal
container 106 (carried by a truck chassis) is also in contact with the low
earth orbit satellite
120. It is important to note that the radio frequency identification tag 102
can also be
(alternatively and/or simultaneously) in communication with a cell tower 130.
While the radio
frequency identification tag 102 is depicted to be in direct communication
with the low earth
orbit satellite 120 and/or the cell tower 130, it is important to note that
the radio frequency
identification tag 102 could relay through a reader and/or a site server
located on the truck
chassis.
A network operation center 140 is in bi-directional communication with both
the earth
station 125 and the cell tower 130. The network operation center (NOC) is in-
turn
downloading data to a plurality of recipients including in this embodiment
Customs, the
Department of Defense, the National Transportation Safety Board, the
Department of
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Homeland Security, the United States Coast Guard, the Federal Bureau of
Investigation and
commercial stakeholders.
The marine asset security and tracking (MAST) system, illustrated in Fig. 1,
is a
wireless (RF)-based communications and sensing/telemetry system for tracking
and
monitoring maritime industry-standard 20-foot and 40-foot shipping containers,
both during
loading, unloading, and transfer operations at portside dock facilities, as
well as onboard
ships during overseas transport of the containers. This system can provide a
true inter-
modal tracking and monitoring system capable of operating on ships, railroads,
aircraft,
over-the-road trucks and within their associated terminal facilities,
utilizing both local-
terminal communications systems and other wide-area commercial communications
systems, including satellite and/or cellular/PCS. This RFID tagging system can
include
RFID tags attached to each shipping container, local site readers located
throughout the
ship and in the shipping terminal, one central site server on each ship or in
each terminal,
and a network operations center (NOC) where all data can be collected,
consolidated,
stored, analyzed and disseminated. The shipping containers can be both
refrigerated-cargo
shipping containers (reefers) and dry-cargo shipping containers (dry-boxes).
In addition to
identifying and tracking the location of containers or other equipment fitted
with one of the
RFID tags, each tag can be equipped with an (e.g., IEEE 1451) sensor interface
and
optional extra serial interfaces to permit the connection of a wide range of
sensors to the
RFID tag to monitor the condition of the container cargo or other tagged
equipment.
Sensors which can be connected to the RFID tag include (but are not limited
to)
temperature, pressure, relative humidity, accelerometer, radiation, and GPS
(global
positioning system). Additional sensors can be included for condition
monitoring of
machinery, such as refrigeration compressors, or to read from the diagnostic
data port on
some refrigerated cargo containers.
The MAST system has three main operational modes: the first is when the RFID
tag
is on a ship; the second is when the RFID tag is in a terminal; and the third
is when the
RFID tag is being transported over-the-road or rail (this includes all times
that the RFID tag
is not on a ship or in a terminal). A terminal can be considered any local
area served by the
RF communications system. The RFID tagging system can include: a) the network
operations center (NOC), which can include the status and data on all RFID
tags and their
associated cargo containers (or other asset) and provides this information out
to the users;
b) the local site servers (one per ship or terminal), which can manage local-
area
communications (i.e. each ship or terminal) and relay the RFID tag data to a
central system
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server; c) the RFID tag readers, which can receive the communication from the
RFID tags in
the local area and relay it on to the local site receiver; and d) the RFID
tags.
Referring to Fig. 2, the shore and/or ship communications flexibility of the
invention is
depicted. A first radio frequency identification tag 201, coupled to a first
container 211, is
communicatively coupled to multiple radio frequency identification tag readers
221, 222,
223, 224 located on a ship 230. The multiple radio frequency identification
tag readers 221,
222, 223, 224 are communicatively coupled to a site server 235 on the ship
230. The site
server 235 is communicatively coupled to a satellite (not shown in Fig. 2) but
is in-turn
communicatively coupled to the network operation center.
A second radio frequency identification tag 202 coupled to a second container
212 is
communicatively coupled to the multiple radio frequency identification tag
readers 221, 222,
223, 224 and also simultaneously communicatively coupled to multiple site
radio frequency
identification tag readers 241, 242 located on light poles or towers in or
around a terminal.
The multiple site radio frequency identification tag readers 241, 242 are
communicatively
coupled to a site server 250 associated with the terminal. The site server 250
is
communicatively coupled to the network operations center via a satellite data
link or other
communications circuit (e.g., a hardwire Internet connection).
A third radio frequency identification tag 203, coupled to a third container
213, is
communicatively coupled to the multiple site radio frequency identification
tag readers 241,
242. It is important to note that the third radio frequency identification tag
203 is not
depicted as in communication with the multiple radio frequency identification
tag readers
221, 222, 223, 224, but could be if their third container 213 were physically
moved closer to
the ship 230.
Still referring to Fig. 2, the shipboard or terminal communications RFID tags
can
utilize RF communications to communicate with the RFID tag readers. The
preferred RF
communications is a hybrid spread-spectrum (HSS) RF data link operating in the
2.45 GHz
band. Radiolocation or triangulation of the RF signal from each tag can be
utilized to
determine the location of each RFID tag.
Referring to Fig. 3, a network operation center 310 is bi-directionally
coupled to a
landside site server 320 via an Ethernet or satellite data link.
Simultaneously, the network
operation center 310 is bi-directionally connected to a shipboard site server
330 via a
satellite data link.
The landside site server 320 is bi-directionally coupled to a first radio
frequency
identification tag reader 340, a second radio frequency identification tag
reader 350 and a
third radio frequency identification tag reader 360. It is important to note
that in this
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embodiment the communicative coupling between the site server 320 and the
three tag
readers 340, 350, 360 can be any one or more of radio frequency wireless,
power line,
Ethernet or optical data link. A plurality of radio frequency identification
tags located in the
terminal 345 are bi-directionally communicatively coupled to at least one of
the three tag
readers 340, 350, 360.
The shipboard site server 330 is bi-directionally communicatively coupled to a
fourth
radio frequency identification tag reader 370, a fifth radio frequency
identification tag reader
380 and a sixth radio frequency identification tag reader 390. It is important
to note that the
shipboard site server 330 is coupled to the three-tag readers 370, 380, 390
through one or
more of a power line, a radio frequency wireless or Ethernet data link. A
plurality of radio
frequency identification tags located on ship 375 are in bi-directional
communication with at
least one of the three tag readers 370, 380, 390.
As shown in Fig. 3, the RFID tag communications can be picked up by the RF1D
tag
readers and relayed to the local site server by one or more of several
possible methods: a)
1 S RF data link; b) Ethernet; c) power-line data link; d) optical; and/or e)
other(s). Once the
tag data is relayed to the local site server, the data can be uploaded to the
NOC by either a
satellite-based data link or other Internet service provider link (e.g.,
Ethernet). The local site
servers may also generate reports for use by local personnel, such as the
engineers on the
ships. Once the data is uploaded to the NOC, the NOC can communicate back to
the tag
instructions, verifications and/or queries. The data for any specific
container can be made
available to any user world-wide with Internet access and the proper security
validation.
Referring to Fig. 4, a network operation center 410 is coupled to a first
cellular or
satellite system 420, a second cellular or satellite system 430 and a third
satellite or cellular
system 440. The bi-directional communicative couplings between the network
operation
center 410 and the systems 420, 430, 440 can be via a phone line or a base
station
connection. Each of the three systems 420, 430, 440 is associated with a
subset of a
plurality of radio frequency identification tags outside of local area (RF
coverage) zone 450.
The bi-directional communicative coupling between the three systems 420, 430,
440 with
their respective subset of the RFID tags outside of local-area zone 450 can be
via a cellular
or satellite data link.
For over-the-road and rail communications, as illustrated in Fig. 4, the RFID
tags can
communicate to the NOC by cellular or satellite data links. The preferred
method is direct
satellite communications, since cellular will not give world-wide coverage.
The satellite or
cellular system can relay the RFID tag data to the NOC through a base station
(satellite)
connected to the NOC or through a modem bank (cellular) connected to the NOC.
Over-
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the-road operation can include all operations when the RFID tag is not onboard
a ship or in
a terminal (any local area served by the RF communications system). A GPS
receiver in
each tag can be utilized during over-the-road transportation to track the
movement of and
the location of the container. It is preferred that the containers are not
stacked during over-
the-road operation. If a tagged container is stacked with another container on
top of it, as is
possible on some rail cars, the satellite or cellular modem data links and the
GPS system
may not function. It is possible for another tagged container on the top of a
stack to act as a
repeater or relay (extender) for the first container. In more detail, the
first container can
utilize the HSS RF communications when its other methods fail. The second
container can
receive these communications with its HSS RF receiver and then relay them to
the NOC
utilizing its satellite or cellular modem data link.
2. RFID Tag Description
Each RFID tag can include four main functional blocks; (1) a microprocessor
control
subsystem; (2) a sensor subsystem; (3) a communications subsystem; and (4) a
power
supply subsystem. Fig. 5 shows a block diagram of an RFID tag.
Referring to Fig. 5, a radio frequency identification tag 500 includes a
microprocessor control subsystem 510, a power supply subsystem 520, a sensors
subsystem 530 and a communications subsystem 540. The microprocessor control
subsystem 510 includes an input/output interfaces circuit 511. A
microprocessor circuit 512
is coupled to the input/output interfaces circuit 511. A flash memory circuit
513 is coupled to
the microprocessor circuit 512. A random access memory circuit 514 is also
coupled to the
microprocessor circuit 512. The microprocessor circuit 512 is coupled to the
power supply
subsystem 520 via a power line 515.
The power supply subsystem 520 includes a power management module circuit 521.
An AC to DC power circuit 522 is coupled to the power management module 521. A
battery
523 (e.g., lithium ion) is coupled to the power management module 521. An
alternative
power source 524 is coupled to the power management module 521. The power
supply
subsystem 520 provides power to the sensors subsystem 530 through a set of
power lines
525. The power supply subsystem 520 provides power to the communications
subsystem
540 through a set of power lines 526.
The sensors subsystem 530 includes a serial interface 531 coupled to the
input/output interface circuit 511 of the microprocessor control subsystem 510
through line
532. A temperature sensor 533 is coupled to the serial interface 531. A
relative humidity
sensor 534 is coupled to the serial interface 531. A door ajar sensor 535 is
coupled to the
serial interface 531. Other sensors 536 (e.g., ionizing radiation sensors) are
coupled to the
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serial interface 531. The sensors subsystem 530 includes a GPS module 537
coupled to
the input/output interface circuit 511 of the microprocessor control subsystem
510. The
sensors subsystem 530 includes a refer unit data port 538 coupled to the
input/output
intertace circuit 511 of the microprocessor control subsystem 510 via an
interface converter
circuit 539.
The communications subsystem 540 includes a local/serial communication circuit
541, a cellular modem module 542, a hybrid spread-spectrum radio frequency
module 543
and a satellite module 544, all of which are coupled to input/output intertace
circuit 511 of
the microprocessor control subsystem 510 through line 545. One or more
antennas 546 are
coupled to the cellular modem module 542, the hybrid spread-spectrum radio
frequency
module 543 and/or the satellite module 544.
Microprocessor Control Subsystem: The microprocessor control subsystem can
operate as the controller for the RFID tag. It can interface with the
communications
modules, with the sensor modules, and the power modules. The microprocessor
can utilize
both non-volatile and volatile memory to store the system software, system
commands, and
sensor data.
Sensor Subsystem: The sensor subsystem can utilize IEEE 1451-compliant
protocols for communicating with one or more sensor modules. This allows the
future
addition of any sensor as long as it is compliant with the 1451 protocol. Some
of the basic
sensors, such as the GPS and the reefer data port reader, may utilize serial
communications ports on the microprocessor. Sensor types that may be part of
the RFID
tag can include temperature, relative humidity, radiation, biological,
chemical,
accelerometer, door switch, intrusion, etc.
Communications Subsystem: The communications subsystem can allow multiple
different types of communication's links to be incorporated into the tag
platform. They may
connect through, for example, a serial port or an Ethernet port.
The basic communication's modes can be as follows:
RF Communications - the RF communications can take the form of any number of
available wireless communications protocols. However, the preferred method is
a hybrid
spread-spectrum protocol. This protocol provides higher reliability, lower
power, and more
robust communications than other wireless techniques. The RF communications
can be
intended for use primarily when the tags are located on a ship or in terminal
(local-area
communications).
Cellular/PCS Communications - standard commercial cellular analog or digital
modems, such as CDMA or GSM, can be utilized by the tag for over-the-road
(truck or rail
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transportation) communications. However, there is not a standard cellular
infrastructure
installed worldwide. Therefore, each tag could require several different
protocols to be able
to operate in more than just a limited market area. In addition, the tags are
likely to travel
through areas that have no cellular coverage.
Satellite Communications - utilize a satellite-based communications network to
provide an over-the-road communications link that can function anywhere in the
world. This
provides simpler, more robust, and more secure communications system as an
alternative
to, or in addition to the cellular system. A preferred embodiment can use a
Low-Earth Orbit
(LEO) satellite network system.
Local Communications - Each tag can have a serial port used for development,
troubleshooting, and/or initial setup. The serial port may take the form of,
for example,
RS232, USB or IrDA (infrared).
Power Supply Subsystem: The power supply subsystem can provide power to all
the
other subsystems. The sources of power that may be utilized include battery,
AC power
(e.g., from the refrigeration power supply on reefers) and other power
scavenging and/or
generating devices such as a photovoltaic, a vibrational transducer, an
electrostatic charger,
a radio frequency power rectifier, a thermo-electric generator and/or a
radioisotope decay
energy recovery device. For RFID tags located on assets other than containers,
DC power
from the assets electrical system may also be utilized. The power supply
subsystem can
convert the voltage of the power source to the required voltage for each
subsystem. It also
can perform power management functions to monitor battery condition and power
source
availability.
3. RFID Tag Reader
The RFID tag readers relay the RFID tags' communications to (and from) the
site
server. The RFID tag readers can be similar to RFID tags, but with different
communications modules, and optionally no sensors. The RFID tag readers can
communicate with the RFID tags through a local RF communications module
(preferably
using the HSS protocol). The RFID tag readers can communicate with the site
servers by
one of several possible techniques: wireless RF communications (preferably the
HSS
communications at a frequency other than the RFID tag communications, such as
for
example at 5.8 GHz), wired communications (such as power-line communications,
Ethernet
or serial), and/or optical communications (such as by fiber optic or line-of-
sight laser
communications).
Referring to Fig. 6, a plurality of inter-modal shipping containers 610 are
stacked in a
two-tier high array. Each of the inter-modal shipping containers 610 includes
a radio
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frequency identification tag 620. A plurality of tag readers 630 are located
at the ends of
open aisles defined by the two-tier high array.
Another optional feature of the MAST system is the use of "hand-held
(portable)
readers" for reading the RFID tag data and cargo manifest directly from the
container. The
hand-held reader can be used by Customs, Coast Guard, shippers, or other
certified groups
to ascertain the contents of a container and its cargo status (sensor data,
movement history
etc.). The hand-held reader can be located and then operated near the
container. The
appropriate identifying code (or perhaps bar code) can be entered into the
hand-held reader,
and then RF communications used for the hand-held reader to communicate with
the RFID
tag. The RF communications can preferably utilize the HSS communications
utilized for the
local terminal and ship communications. The RFID tag would then download to
the hand-
held reader the container manifest (from the manifest stored on the RFID tag
or downloaded
from the NOC via a uplinked request from the RFID tag) and a trip log of the
container
sensor(s). This trip log could contain history reports for all sensors, any
sensor alarms
(including container intrusions, temperature excursions, etc.), and a history
of the
container's specific geographic route.
The hand-held readers can also be used to upload a container's cargo manifest
(this
could also be done by using a portal). As the container is loaded, bar codes
or other types
of packaging-type RFID tags can be read into the hand-held reader. From the
hand-held
reader (or other type of RFID reader), the cargo identifiers can be loaded
into the container
manifest on the container's RFID tag and then uploaded to the NOC.
An alternate approach would be to utilize an IrDA (infrared) data port on the
container. The hand-held reader would then be pointed at the IrDA port and
communications established. The data download would then be the same as above.
4. Site Server
The site servers can receive the RFID tags' data from the RFID tag readers.
The
site servers can send the RFID tag data to the NOC. The site server can also
perform local
analysis of the RFID tags' data and manage the mufti-access aspect of the
invention that
allows for tens of thousands of tags to be in a terminal or on a ship. The
site servers can
include three main subsystems: (1 ) a computer-based server and system
controller; (2) an
RFID tag reader communications subsystem which includes the same
communications
modules as the RFID tag readers for communicating with the RFID tag readers
[i.e., they
can have wireless RF communications (preferably the HSS communications at a
frequency
other than the RFID tag communications, such as at 5.8 GHz), wired
communications (such
as power-line communications, Ethernet or serial), or optical communications
(such as by
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fiber optic or line-of-sight laser communications)]; and (3) a NOC
communications
subsystem which can utilize hardwired, cellular, optical or satellite
communications modules.
5. Network Operations Center
The Network Operations Center (NOC) can be the information center for a world-
wide Maritime Transportation Control System. All RFID tag data from all RFID
tags located
around the world can be relayed to the NOC by the local site servers or via
direct cellular or
satellite communications. The NOC collects, stores and disseminates RFID tag
data,
including location, sensor data, and RFID tag status.
The invention can include the merging of technologies in a central operations
center
architecture including: global positioning systems; radio frequency
identification (RFID)
based tracking system for assets and cargo containers; globally available
commercial
satellite and Internet communication systems; geographic information systems
(GIS) and
real-time logistical analysis capabilities; fault-tolerant systems to provide
hardened
continuous data flow to private sector asset and cargo owners, relevant state
and federal
governmental entities (Coast Guard, TSA, Customs, NTSB, and DoD, etc.), and
local first
response stakeholders (law enforcement, fire departments, local government);
and existing
federal systems and commercial programs for asset and cargo tracking.
The use of a geographic information system (GIS) in the NOC will allow for the
analysis and presentation of asset location in a variety of formats from
simple web-browser
based Latitude/Longitude reports to map-based city/state/zip/country
information. This
system can provide the ability to monitor and profile assets in real-time
based on criteria
specified including geographic patterns. This approach also provides for the
incorporation
of real-time logistical analysis regarding the movement of assets. The long-
term goal of the
GIS development is to create an information infrastructure capable of
analyzing the
movement of commodities and assets throughout the supply chain and
intelligently profile
containers including geographic patterns.
The RFID tag data can be integrated to a centralized GIS-based tracking
infrastructure via a global satellite communication network to create the MAST
system. A
preferred embodiment of the MAST system invention utilizes one or more global
satellite
networks.
Satellite networks provide the ability to track and monitor assets globally in
real-time
with the ability to concentrate all the information effectively in one
location. This provides
advantages for security, fault-tolerance, data back-up/archiving, and
maintenance. The
NOC can integrate the geographic information systems (GIS) technology,
satellite
communications, global positioning systems, RFID (electronic seals, etc.), and
the Internet
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in an open systems architecture to create a real-time tracking and asset
management
system. The NOC can provide one single location for real-time logistical
support for the
global management of mobile assets using a web-based tracking system that will
allow
individuals or organizations to manage assets in real-time via the Internet
with strict
information protection protocols (e.g., login and/or encryption). The
information can be
distributed to relevant parties through secure transactions on a need-to-know
basis thus
precluding the use of the system to target assets for theft.
The NOC can have one or more of the following resultant operational
capabilities: 1)
real-time, global ship location tracking with detailed history of passage; 2)
tracking container
location and condition with tampering notification and internal environmental
and radiation
status; 3) early warning/threat identification of ships and containers arrival
in US waters and
ports with an audit trail that identifies potential threats, risks, and
responsibilities; 4)
detecting and monitoring suspicious shipping activities (unscheduled port
calls, etc.) and
identify long-term patterns of activity at both ship and container level; 5)
secure data to
(and/or from) the Department of Defense, US Coast Guard, US Customs,
Department of
Homeland Security, as well as local "first response" law enforcement agencies
for homeland
security, port security, smuggling, and theft concerns; 6) secure data to
(and/or from)
shippers and ports to plan and manage cargo arrival and distribution on an as-
needed basis;
7) system for comprehensive port, ship, and container management and "fast-
track"
protocols for Customs inspection; 8) real-time monitoring capability for
refrigerated, critical,
and HAZMAT cargo; 9) remote control towers) for marine industry to maximize
efficiency
and central point of contact for important information (e.g., rules,
regulations, weather
notices, notices to mariners, etc.); and 10) integrate intermodal warehousing,
port, ship,
road, and rail supply chain management and security applications on a global
scale.
6. Multiple-Access
The multiple access approach described herein enables a multiple access
network
that can operationally accommodate roughly 10,000 RFID tags spread over a
terminal or
ship located in an environment that may include upwards of 90,000 additional
RFID tags
(potential interference sources) located in/on nearby terminals or ships. This
multiple-
access design can utilize one or more of CDMA, FDMA, TDMA and/or SDMA (spatial
division multiple access) to achieve these requirements. The RFID tags can
each report
electronic identification codes, sensor data, and location information to an
array of RFID tag
readers that form either a perimeter around or a grid throughout the terminal
or ship. The
RFID tag reader locations may utilize the existing infrastructure of lighting
towers that are
currently in the yards. These RFID tag readers can coordinate the data from
the tags and
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report all useful data to a nearby site server. The site server can then relay
significant
events and sensor data to the NOC. A description will follow of the
terminal/ship area
communications with a focus on the RFID tag to RFID tag reader links.
General Strategy
The following describes elements of a preferred overall communications
strategy. An
embodiment of the invention can include a combination of Code-Division
Multiple Access
(CDMA) utilizing both Direct Sequence Spread-Spectrum (DSSS) and Frequency-
Hopping
Spread-spectrum (FHSS), Time-Division Multiple Access (TDMA) and Spatial-
Division
Multiple Access (SDMA) can be used for the tag-to-reader link. An embodiment
of the
invention can include a reader-to-server link utilizing a different frequency
band (e.g. 5
GHz). An embodiment of the invention can include bi-directional communications
that can
enable power control to be employed to optimize CDMA and SDMA methods. An
embodiment of the invention can include independent terminals (yards) in close
proximity
being given distinguishable groups of spreading codes from proximate
neighboring yards.
An embodiment of the invention can include an option of sub-dividing yard into
micro-cells.
The following describes key performance parameters of the above described
preferred overall communications strategy. A site server can receive updates
from 10,000
proximate tags at least once every 100 seconds with 99.99% probability of
success. The
network that includes the site server can have the ability to "ignore" up to
90,000 semi
proximate tags. High-priority messages) from the tags) can be sent within 1
second of
delay.
Implementation
The following implementation analysis includes the following assumptions. One
thousand bits are used from each node once every 100 seconds. Offset-
Quadrature Phase
Shift Keying (OQPSK) modulation with a 5 MHz bandwidth and nearly constant-
envelope
signals is used. Sixteen or more non-overlapping hop frequencies with managed
overlap
fraction. Length-63 spreading codes for Direct Sequence are used.
Based on the above explicit assumptions, the 1000 bit (125 byte) packets will
be
transmitted once every 100 seconds from each of the 10,000 nodes at a bit rate
of 80 kbps
with a chipping length of 63. Thus, the embodiment of the invention has a
chipping rate of
about 2.5 Mbps which translates to a spectral bandwidth of about 5 MHz with
OQPSK
modulation. It is assumed that the RFID tag readers will need to communicate
with each
RFID tag about once every 100 seconds. Therefore, 10,000 RFID tags translates
to an
average of 20,000 packets every 100 seconds. These 20,000 packets will be
multiplexed
into 4000 time slots (25 ms long) and 32 CDMA users (combination of 63 length
codes with
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16 hops - assuming the maximum simultaneous users is approximately square root
of chip
length times square root number of hops.)
The perimeter RFID tag readers can use directional antennas aimed between rows
of containers for RFID tag communications. Directional antennas operating in a
different
frequency band (e.g. 5 GHz) [or alternatively, power-line communications] may
be used for
tower-to-tower/server communications. Depending upon yard size and other
environmental
parameters, the towers may also be required to provide relayed communications
The main functions of the RFID tag readers can be to capture information from
all of
the RFID tags and then relay this information to the site server. They may
coordinate with
each other in a fashion that optimizes the multiple access plan for upwards of
10K tags, or
they may only communicate directly to the site server. For example, if several
readers are
capturing the data from a single RFID tag, then the readers can cooperatively
determine the
lowest power level at which at least one reader can reliably communicate with
the RFID tag.
Power Control
As mentioned above, power control can be used to optimize the network
communications. Of course, power control is desirable to a great extent by the
use of DS-
CDMA. This multiple access approach can include protocols for network
discovery, power
back-off, and interference mitigation techniques that all involve controlling
the transmitted
power from the RFID tag.
Re-transmission Redundancy
The above analysis assumes that the system needs to hear from every RFID tag
at a
rate of once every 100 seconds and that about 1000-bit messages are
sufficient. This
includes a conservative estimate for inter-packet guard time of 100% of packet
length. In
the above example, packets would be approximately 12.5 ms long and the average
guard
time would be about 12.5 ms also. This guard time is very conservative and can
probably
be reduced by upwards of 90%, thus enabling almost another doubling of the
throughput or
redundancy. A subsection of the guard time is to be used for "emergency"
events in a
CSMA fashion. Furthermore, most applications will not require 100-second
update rates;
therefore, successive time slots during the next 100-second cycle can be used
to re-transmit
bad packets. For instance, an update rates of once an hour, or every second or
even third
hour could be sufficient for most applications.
In order to perform power control as discussed above and to carry out the
typical
duties of channel assignment and network optimization, a strict flow control
should be
established for the boot-up sequence of all nodes. This following description
in conjunction
with Figs. 7-8 (flow charts) present a design example of that process.
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Discovery Process
As shown in Fig. 7, the nodes will boot-up on a system control (default) RF
channel.
The nodes will cycle through a small set of "pilot" channels until they
establish a link with
one of the RFID tag readers. This loop is necessarily endless until or unless
successful
communication is established with a reader (or another tag if an alternative
tag-to-tag
approach is available in a given system). An embodiment of the invention can
include
stepping the power up and/or during this process.
Referring to Fig. 7, an exemplarily tag boot-up sequence can begin with a tag
turn on
step 710. At step 720, the tag sets a default receiver code. At step 730, the
tag listens for a
pilot transmission signal from a tower. At step 740, if a signal from a tower
is identified, then
the tag proceeds to a transmission-to-network communications 750. If a tower
is not
identified, then the tag determines whether a time-out period has elapsed at
step 760. If the
time-out period has not elapsed, then the tag continues to attempt to identify
a tower. If the
time-out period has elapsed, then the tag proceeds to a step 770 including
setting
alternative receiver frequency codes. After setting an alternative receiver
frequency code,
the tag then proceeds to step 730 and again listens for a pilot transmission
from a tower.
During the discovery process, it can be desirable to minimize the number of
tags
transmitting at a given time. This can be accomplished by having the reader
node control
the discovery process. The reader will send out an ID Request that prompts all
tags within
its range to transmit in a given order on a given temporary code (see Network
ID Transmit
Order below). Then the reader will start receiving and processing messages
from the tags.
After the first cycle of node identification is completed, the reader will
send a message to the
tags acknowledging receipt and assigning both a network ID and a time slot
allocation for
the tag. The cycle will be repeated, with the qualification that all tags
having network ID
assignments (associated with that reader ID) will not acknowledge the ID
Request message.
The invention can include protocol for resolving conflicts, etc.
Network ID Transmit Order
The reader can request that all tags that are able to decode its ID Request
(and
which have not been previously logged by that reader) transmit a 5-ms message
x times 10
ms after receipt of the request where x is the 3 least significant digits of
the tags UUID. (For
instance, a tag having a UUID of 12345678 could wait 6,780 ms before
transmitting to the
reader.) In addition, the tag can use the next 2 higher digits (in this
example 45) to select a
combination of FH and DS codes. Thus, a reader should be capable of handling
100,000
tags unambiguously.
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Once the RFID tag and the RFID Tag Reader have established a link, the reader
will
assign the RFID tag a code and frequency combination that makes it part of an
optimized
network. This process is shown in Fig. 8.
Referring to Fig. 8, upon a transmission from communications discovery 810,
the tag
obtains or adopts a default transmission frequency code at step 820. At step
830, the tag
sends the default transmission frequency code to the tower. At step 840, if
the tower
acknowledges the default transmission frequency code, then the site server
will assign to
the tag a code frequency and time slot at step 850. If the tower does not
acknowledge at
step 840, then the tag will proceed to step 860 where it determines whether a
time-out
period has elapsed. If the time-out period has not elapsed, then the tag
returns to step 840
and will continue to await acknowledgement from the tower. If the time-out
period has
elapsed at step 860, then the tag will proceed to a step 870 where an
alternative
transmission frequency code will be obtained or adopted. The tag then proceeds
back to
step 830.
Packet Structure
This section focuses on the portions of the packet dedicated to ensuring
robust
communications such as the preamble and error correction/detection coding. The
payload
of the packet can be any useful payload (e.g., identity, location, dosimetric,
etc.).
Since the preferred waveform utilizes frequency hopping as well as direct
sequence
spread-spectrum, the preamble can have two portions: a 64-bit constant
frequency DSSS
portion and then a 63-bit hybrid FH/DSSS portion. The receiver correlator can
search the
beginning of the transmitted waveform for autocorrelation peaks on a known
frequency.
Once the receiver has derived the location (in time) of the "bit" edges, it
can start hopping its
carrier frequency. The transmitted waveform can start hopping at the start of
the second
portion of the preamble that can act as a data delimiter word. The receiver
can re-establish
synchronization with the hopping sequence at the start of this second (63-bit)
sequence.
This allows the receiver to miss upwards of 5 bits of the sequence and still
successfully find
the start of the data payload. A CRC word 32 bits in length will complete the
packet and can
be used to ensure the integrity of the actual data payload.
Direct Sequence Spread-spectrum
The DSSS assignments can be chosen from a Kasami code generator that produces
about 520 codes of length 63. Only about 32 codes can be in use within a given
cell, within
a given time slot. However, utilization of this large set of codes makes the
code assignment
processes easier to manage.
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Frequency Hopping Spread-spectrum
During any given packet slot, some of the channel orthogonality can be
achieved via
frequency hopping assignments. Since, the assumed RF tag spectrum is about 5
MHz and
the Industrial, Scientific, and Medical (ISM) band at 2.45 GHz is 80 MHz, only
16 hopping
center frequencies would in this example be utilized. While hybrid spread-
spectrum is
preferred primarily to improve the robustness of individual links exposed to a
harsh multi-
path environment, it can also be advantageously utilized to increase the
number of
simultaneous users occupying a time slot. If timing synchronization for this
system in a
particular implementation is not sufficient to support the high-speed hopping
scheme, then
the DSSS spread-spectrum alone can be used for distinguishing multiple
simultaneous
users.
7. Marine Systems Observations and Analyses
The size of the ship terminal facility will strongly affect the configuration
of the
shore-side RF system (i.e., number and distribution of receivers) required to
track
containers throughout this facility expanse. The light poles at a terminal are
preferred
locations for facility receivers and transmitters (or transceivers).
Shipboard RF container-monitoring receivers) could be sited on the mast at the
ship's bow end. It is important to note that containers are not always stacked
to a uniform
height on deck or in a very consistent distribution. RF propagation into or
out of covered
holds (steel hatches) may be essentially nil; therefore, it may be necessary
to provide RF
system receivers) inside the holds to facilitate monitoring of containers
there.
In a loaded ship, containers are often stacked above-deck right up to the
edges of
the hull. The bridge wings and masts, can be used for mounting RF
infrastructure
components for the MAST system. Gaps between each row and stack of containers
can
permit an RF signal of suitable wavelength to bounce back and forth before
finally reaching
the edge of the ship. It can be desirable to place a system antenna at each
end of this
space, along the periphery of the ship, to achieve consistent coverage of all
the containers
above deck.
Containers are typically stacked tightly in the hold. The containers slide
down vertical
retaining rails attached to the ship's structure. The metal bulkheads
effectively
compartmentalize the areas around the ends of the containers, further
hindering RF
propagation from the containers within the hold. Once the hatch is placed over
the hold, a
fairly good Faraday cage is formed and very little RF can enter or leave.
Therefore, it may
be necessary to install some in-hold RF infrastructure (i.e., receivers and
associated data
links back to the central monitoring station on the ship's bridge) if near-
real-time (e.g., daily)
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telemetry is required from containers stacked down in the holds. The container
locking
mechanism ensures a 2- to 3-in. gap between the tops and bottoms of the
stacked
containers. The roughly 2- to 3-in. space between the tops and bottoms of
containers
should be sufficient to provide an RF path (at suitable frequencies) between
the containers.
The corresponding space between the sides of the containers typically varies
from 0.5 in. to
about 2 in. This arrangement can create an ohmic flossy) and/or capacitive
connection at
radio frequencies between the containers, which may somewhat impair the signal
propagation out of the stack.
Referring to Fig. 9, a plurality of inter-modal shipping containers 910 are
arranged in
an orthogonal array. A radio frequency identification tag 920 is depicted on
the top of one of
the inter-modal shipping containers 910. A plurality of readers 930 are
located at the ends
of the aisles formed by the plurality of multi-modal shipping containers 910.
Fig. 9 depicts a plan-view of a group of tightly stacked containers (nominally
40-
footers) as they might be arranged on the deck of a ship or on the ground
within a terminal
yard. A single RF emitter (represented by a radiating red dot in the diagram)
can be
mounted near the center of the top of a container. Because the containers'
undercarriages
and top side rails tend to channel the signal lengthwise, most of the RF
energy will leak out
of the two ends of the container into the adjacent aisles in both directions
(up and down on
the diagram). These signals will bounce between the ends of the containers
bounding the
aisle until they emerge at the edges of the array, suffering moderate losses
and significant
waveshape distortion. Fairly wideband (i.e., several-MHz) spread-spectrum
signals with high
immunity to scattering and multipath-type distortions are likely to be
received best. Of
course, the invention is not limited to any particular contextual
configuration.
Potential RF receiving and/or transmitting locations are denoted in Fig. 9 by
dots at
the ends of the aisles. Although each dot could represent a discrete antenna,
a more
practical, robust configuration might employ short pieces of "leaky coax"
cables to span the
aisles and standard low-loss coax sections in between. To afford better
physical protection,
the "leaky" cable could be housed inside sections of heavy-walled PVC pipe,
which presents
relatively low losses at up to a few GHz in frequency; the standard cables
could be run in
PVC or even metal conduit for the best crush resistance, since the
conventional coax is fully
shielded. These receiving and/or transmitting location systems could be
mounted
(semi)permanently at the ship's periphery, at or near deck levels, and perhaps
even on
handrails or other convenient structures. There is typically a personnel
catwalk between
rows of containers on each side of the cargo holds. It is possible to locate
RF system
antennas for container telemetry links at appropriate spots on catwalk
assemblies.
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The precise locations and models) for mounting these antenna components will
be
highly dependent on the detailed specifics of an individual ship's
construction. In the case of
containers in one of the ship's holds, the leaky-coax cable could be installed
along the side
wall, in roughly the same vertical plane as the container guide rails. In both
instances, the
orientation of the leaky-coax cable should be maintained to provide the most
efficient energy
transfer with respect to the polarization and orientation of the antennas on
the
containers. For example, for horizontal container RF launchers, the cable
should also run
approximately horizontally to maintain relatively low coupling losses in the
container-to-local-
receiver RF links (assuming horizontally polarized container antennas).
Other major system design considerations lie in the selection of appropriate
RF
operating frequencies. Legal and licensing constraints favor the use of
allocated license-free
bands such as the current Industrial, Scientific, and Medical (ISM) bands of
13.56, 27.55,
433, 902-928, 2450-2483.5, and 5725-5825 MHz and the so-called Unlicensed
National
Information Infrastructure (U-NII) bands of 5150-5250 and 5250-5350 MHz in the
United
States and the rest of North America [and/or similar allocations in other
parts of the world].
The first three segments are narrow in width (well under 1 MHz), while the
latter five are
intended for various forms of spread-spectrum signaling.
Although the narrow bands may support very low-rate data transmission, their
capabilities for radiolocation and highly robust links are decidedly limited.
On the other hand,
the spread-spectrum bands permit significantly higher RF power levels and will
support
much more resilient modulation techniques. Overall, the 902-928 MHz band will
provide the
greatest range, but the 2450-2483.5 MHz band is essentially universal and can
be utilized
(at least in part) throughout the world. There are several emerging RF
standards in the
general fields of radiolocation and telemetry. The HSS protocol is already
explicitly permitted
in the ISM and U-NII bands by current Federal Communications Commission rules.
The flexibility of multi-band and/or multi-protocol devices for container
tracking can
also be used by the invention, although the penalty in tag cost, power
efficiency, and
complexity can be fairly serious. The invention can utilize highly integrated
multiple-band RF
devices (including transmitter and receiver electronics, filter structures,
and antennas) that
are preferred for worldwide versions of the MAST system concept.
An additional consideration is the specific type of RF system architecture
required to
achieve the desired level of functionality. A bi-directional data-telemetry
system will permit a
more sophisticated tag-device feature set, including accurate RF-signal power
control;
remote reprogrammability; individual tag (addressable) queries; multi-tag
relay capabilities;
ad-hoc dynamic tag-to-tag data routing to overcome RF path blockages and nodes
with low-
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battery conditions; and networking tasks, such as rolling security codes,
remote software
changes/updates via the network, and node-status inquiries. The overall node
power
efficiency and energy utilization is also usually optimum with a bi-
directional protocol,
resulting in the longest possible battery lifetimes and most timely node-alarm
reporting and
diagnosis capabilities. Of course, the penalty for this type of RFID tag node
is increased
complexity and cost increase due to the presence of an onboard RF receiver,
but the
additional acquisition cost may well be more than offset by the increased
battery life and,
therefore, reduced maintenance interventions by ships' crews or other
maintenance/service
personnel.
By contrast, the basic unidirectional network comprises autonomous tags that
generally operate in a "dumb chirper" mode, in which the tags simply burst
their data out to
the system infrastructure receivers) at predetermined intervals. These
transmission
intervals may be regular, randomized, slot-randomized, or even altered by the
nature of the
tag's data. For instance, a highly preferred embodiment is a "smart" tag that
would simply
omit transmissions of redundant data, instead sending only new, changed
readings. A slight
modification to this protocol would involve the straightforward insertion of a
few additional
transmissions at a selectable interval to reiterate the true data value (in
case a change was
inadvertently missed) and convey some basic status information to confirm that
the node is
still operating properly.
A third type of telemetry-system architecture would support the strategic (or
even
happenstance) mixing of bi-directional and unidirectional tags as dictated by
a particular
implementation scenario. This format permits significant flexibility in
selection of the tag
types, though at some cost in overall RF system performance and generally
reduced tag
battery lives. Although the preceding descriptions are based on nominally
single-band
network setups, even more flexibility and higher performance can be obtained
in a multi-
band system, albeit at a significant cost penalty (principally in the total
price of alf the tags).
In all these instances, the use of the HSS technique affords advantages in bit-
error rates,
loss of packets, collision rates, RF power efficiencies, and apparent
interference levels
toward other facility RF systems, particularly those sharing the same general
bands. An
embodiment of the invention can include mixing bi-directional relay tags with
"dumb chirper"
tags in one system.
A refrigerated container ("reefer") typically includes a 3-phase power cable
that plugs
into an above-deck outlet fed from the ship's electrical distribution system.
In general, the
reefer-monitoring application is particularly important because of the high
values of the
cooled cargoes (e.g., pharmaceuticals, perishable foods, and medical
supplies). The current
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practice is for ship personnel periodically to manually monitor and record
(i.e., with pencil
and clipboard) a single internal temperature while at sea; any deviations are
reported to the
ship's engineering crew. In addition to the internal temperature (perhaps at
several spots),
additional data such as relative humidity, compressor pressures, coolant
flows, electrical
supply voltagelcurrent, and container integrity (door breach) can be acquired
via automatic
monitoring and alarm telemetry. This information could add great economic
value to an
embodiment of the invention by providing early warnings of refrigeration
failures, thereby
facilitating rapid repairs and avoiding costly cargo spoilage. This telemetry
could be handled
via RF techniques, as discussed earlier, or through robust data transport over
the ship's ac
power system. Even more advanced methods-such as electrical signature analysis
can
more accurately assess the conditions of operating compressors, fans, pumps,
valves, and
other motor- and solenoid-driven loads and provide a high level of real-time
condition-
monitoring capability for critical shipboard equipment.
8. Analysis of RFID Tagging System Communication Requirements
Perhaps the paramount technical issue in the development of a workable RF-
based
tagging system protocol is the need for highly reliable, robust, low-power RF
communication
links, particularly between the sensor/ID tags mounted on the containers and
the facility or
shipboard receiver infrastructure. A telemetry approach using a hybrid (direct-
sequence/frequency-hopping) spread-spectrum transmission technique to
simultaneously
improve RF tag performance markedly (re: data and locational accuracies) and
reduce RF
interference generation and susceptibility with respect to other tags and
facility RF systems
is preferably to be used. As noted above, the phrase hybrid spread-spectrum
(HSS) as used
herein is defined as a combination of direct sequence spread-spectrum (DSSS),
for
example code division multiple access (CDMA), and at least one of frequency
hopping, time
hopping, time division multiple access (TDMA), orthogonal frequency division
multiplexing
OFDM and/or spatial division multiple access (SDMA), for instance as described
by PCT
published application No. WO 02/27992 and/or U.S. Serial No. 10/817,759 filed
December
31, 2003. Another benefit of this technique is in the area of power
utilization-the HSS
protocol incorporates features to facilitate power savings by limiting the
number of RF
transmissions from each tag and concurrently dynamically minimizing collisions
with other
tags, thus reducing the requirements for tag data messages (e.g., re-
transmission(s)) to an
(absolute) minimum. Another key system operational issue is that of internal
power
management for the tag subsystem (i.e., logic, RF circuitry, and sensors).
To maintain useful battery-recharge intervals, both the command-receiving and
data-
transmitting functions of the RFID tags can be performed on a very low duty-
cycle basis,
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since receive-system power consumption levels often are not very much lower
than those of
the transmitters. In addition, all data from the smart-tag sensors can be
processed to
eliminate redundant transmissions altogether. Finally, low-battery warnings
can be
transmitted as needed (embedded in tag data bursts) to the facility receivers)
to ensure
proper tag operability (i.e., data access and tag location), preferably at all
times. Alternative
tag-energizing options can include local passive-style powering via an
interrogator wand,
onboard photovoltaics, or other energy sources. Some of the system protocols
described
above assume bi-directional transmission to the container tags, but it is
feasible to consider
unidirectional "dumb-chirper" tags for some system implementations that do not
require on-
demand tag interrogation capabilities.
Pertinent port (shoreside) facility-system design issues include placement of
the
distributed transceiver/radiolocation units, internal infrastructure signaling
options, and the
use of RF repeaters to provide adequate and consistent spatial RF coverage
throughout the
facility. The basic infrastructure may use twisted-pair wires, coaxial cables,
power-line RF
transmission techniques, or wireless RF transceivers to transfer data between
the facility
transceivers and the central container monitoring and control point. Yard RF
transceivers will
most likely be mounted on existing structures, although such an arrangement
will depend
largely on the specific setup of the terminal. The corresponding shipboard RF
infrastructure
will be much more constrained by the layout of the vessel and the limited
opportunities for
optimally siting the RF equipment for best coverage. Numerous compromises can
be
accommodated, since the fixed RF gear may need to operate from ship's power
and may
have to be mounted in locations out of the way of normal shipboard operations
and
maintenance activities. To this end, it is highly desirable to handle RF
infrastructure data
communication via the ship's AC power-distribution system; doing so will
provide a
physically protected path and obviate the need to run additional cabling
throughout the ship
when retrofitting a system embodiment of the invention into the vessel.
9. Requirements for Container Monitoring and Sensors
Container location tracking can require different solutions for ship transport
versus
rail and truck transport. Onboard a ship, a GPS-based tag alone may not be
viable unless
combined with a triangulation function. In more detail, GPS is a line-of-sight
location system
in which the receiver must be able to "see" three or more satellite sources.
Containers
buried in stacks on deck or inside a ship's hold will not be able to obtain
the required line-of-
sight signals to use the GPS satellite sources; adding a local GPS repeater
onboard the ship
may not solve this problem either. Even if GPS signals of adequate strength
are received
and repeated, the high levels of local RF multipath reflections in the stacks
may cause major
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uncertainties in the locating accuracies and render the results generally
unacceptable.
Further, the requirements for extremely low tag operating powers will almost
certainly
exclude individual GPS receivers even where adequate satellite reception might
be possible.
The preferred on-board solution includes the use of a local triangulation
system. Using a
local triangulation system tailored for the local onboard environment can
permit the best
possible container-location performance. Because of the severe multipath
reflections and
limited (power-constrained) tag transmitting times, such a system may not in
all instances be
able to give an exact container position, but rather give just the approximate
location,
probably within ~1 container up/down, fore/aft, and port/starboard. In a great
majority of
cases, this level of accuracy should be quite adequate.
For shipboard triangulation, multiple receivers may be required. The lack of
line-of-
sight propagation from a given container to a fixed central receiver will make
a suite of
receivers necessary to localize the position of the container transmission for
containers
stacked above deck. In addition, it will be difficult to localize containers
in holds beyond
identifying which hold they are in. Because of the overwhelming levels of
multipath and
obstructions to the RF signal paths, each hold could require up to one
receiver and antenna
per container, mounted on a bulkhead near the end of each container, to
accurately localize
the container position within that hold. This is probably beyond the number
acceptable for a
cost-effective solution with current technology. Further, the incremental
value of knowing the
exact location of each container in the hold is probably not great, as there
is no practical
way of accessing most containers once they are stacked into the hold. In any
event, the
priority of finding a specific container within a hold is certainly lower than
that of accurately
tracing it through loading and unloading, which has a strong economic effect
(because of
time) on the overall cargo shipping and transfer process.
A solution to this problem is to deploy smart antenna structures (i.e.,
multiple
interconnected, horizontally polarized wire-type dipole antennas mounted on
the walls of the
holds, all coupled into common cables with remotely controlled RF PIN-diode
switches). This
setup would effectively implement a group of scanning antenna arrays for the
hold, which
could identify a container being loaded into the hold and give its location as
it is loaded. The
locating function for the specific hold can be triggered by a local container-
tag RF
interrogation signal (i.e., a burst of coded RF energy at 13.56 MHz or another
convenient
frequency) which would be passively or semi-passively sensed by the container
tags as an
"alert" or "wakeup" signal. The containers so interrogated whose codes match
the alerting
signal (e.g., the last few digits of the container serial ID number) would
then each respond in
a pseudo-random-timed fashion with an HSS burst signal. The hold receiving
subsystem
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would acquire these signals and relay the results to the main shipboard system
for
correlation with the full serial numbers in the ship's container manifest
database.
Another key part of the MAST system is to track the location of containers at
the
loading dock or container yard. Given the tremendous volume of containers
moving in and
out of these facilities, a tracking system capable of telling the facility
operator where a
particular container is located could be a significant time-saver. Within the
yard, a local
spread-spectrum RF triangulation system can be used to track the container
location. The
strategic location of four or more receivers around the yard (more for very
large facilities)
would provide for dynamically tracking container locations. Additional
receiving units would
generally be located at the entries and exits of the terminal, where their
data can be used to
record the entry and departure of containers from the facility. Typical direct
line-of-sight
communication distances in open yards should be approximately from 300 m to
approximately 500 m for tag RF transmission power levels of 10 mW, easily
extending to
about 1 km for 100 mW tags. Radiolocation accuracies can be well within 1 m
for typical
(short) tag-read averaging times, In addition, greater position resolution can
be obtained if
longer averaging times are utilized. A set of radiolocating receivers equipped
with adaptive
beam-steering antennas would typically be installed on each loading crane to
obtain
complete telemetry and location data on each container at short range as it is
being
transferred to or from the ship. This data set is likely to be the most
reliable verification to
the tracking database system that a particular container has actually moved
from yard to
ship, or vice versa. A optional feature that can be incorporated into the
container-location
monitoring software is that of motion detection-whenever a container's
position changes by
more than an incidental amount (i.e., greater than the system position-
uncertainty
specification), a security routine can be activated that would then track the
container's
motion as its ID was compared against active shipping manifests. If the
container were
moved a significant distance (more than normal yard unstacking/restacking
operations
would typically entail) but was not scheduled to be transferred, yard
personnel would
automatically be alerted to a potential misplacement or theft attempt.
In general, GPS container location tracking is theoretically possible for
containers
with clear line-of-sight to the GPS satellites; but it may not be practical in
the terminal yard,
particularly in stacks, for the reasons outlined previously with regard to
shipboard containers
(i.e., light of sufficient line-of-sight reception). The same logic applies to
containers being
transported by rail or truck.
The invention can also include optional technologies for monitoring or sensing
container cargo status including a wide range of sensor devices capable of
detecting
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tampering with a container cargo, container temperature, mechanical shock,
radiation,
stowaway, or chemical/biological agents. Some of these sensors (e.g.,
temperature
sensors, door switches, accelerometers, bead-type shock sensors) are
essentially off-the-
shelf devices that need only minor engineering effort to be incorporated into
a container
monitoring system.
Door-integrity monitoring would use a sensor to indicate if container doors
are
opened or removed. This sensor probably would be a mechanical or magnetic
switch,
although other means such as optical, capacitive, or reluctance-measuring
devices also
could be employed. All these items are off the-shelf and should be easily
deployed at low
cost.
Radiation monitoring can be accomplished using a sensor that records the
interaction of the radiation with a material, such as a standard
thermoluminescent dosimeter
(TLD) of the type employed for general employee dosimetry monitoring. Analysis
of the
radiation-induced changes in the material over several days could detect even
very low
levels of radiation. This sensor would not require continuous battery power,
but only battery
power to intermittently measure the alteration in the sensing medium. TLDs are
off-the-shelf
items, and reasonably inexpensive automated reader units are commercially
available, but
the container application will probably dictate a moderate optimization-
engineering effort. To
provide continuous, in-container radiation sensing, a number of methods are
available at
moderate cost, depending on whether the measurement of alpha, beta, gamma, X-
ray,
and/or neutron emissions is desired, and at what sensitivity levels. For large-
scale
applications, the invention can include inexpensive multilayer detector
materials that can
respond to small radiation fluxes with low-level photocurrents readable by low-
power CMOS
electrometer circuitry (similar to inexpensive home smoke detectors).
Radiation monitoring
can also be accomplished using the passive integrating ionizing radiation
sensors described
in detail below.
An alternative strategy for rapid, wide-scale radiation screening of
containers would
probably best be implemented via a sensitive multi-detector arrayed scanning
system
mounted on the loading crane or within the shore facility. However, because of
the extreme
economic time pressure in loading/unloading operations, such container scans
must be
conducted on the fly or else offline before (or just after) the crane-transfer
operation to avoid
impacting the overall container throughput rate.
Monitoring for stowaways within containers can be accomplished with several
types
of sensors. The invention can include the use of a heartbeat detector, known
as the
Enclosed-Space Detection System. This sensor system, including a vibration
probe (e.g.,
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accelerometer) and detection and recognition electronics, can periodically
record micro-
vibrations in the container and analyze them via wavelet-transform methods for
the
time/frequency signal signatures characteristic of human (or animal)
heartbeats. This
system is most effective for monitoring single, isolated containers (e.g.,
within the dock-
yard) but could even be adapted for on-ship use. Another potential method of
detecting
stowaways or other unauthorized items inserted into containers would be a
device to
generate a specific electromagnetic field pulse inside (or into) the
container. The field levels
at two or more locations would then be detected, telemetered out, and
recorded. Periodic re-
sending of the electromagnetic field pulse and comparison of the new and the
original
responses would reveal any significant changes in the field patterns dictated
by the
distribution of material within the container. This, in turn, would indicate
movement of the
material within the container due to either cargo shifting or the presence of
humans (or
animals). Although the technology is available commercially, more conventional
(and
probably less expensive) approaches to this problem include simpler but less-
sensitive
steady-state or pulsed ultrasonic and/or RF (microwave) systems similar in
function to
commercial intrusion alarms. The latter technologies are fundamentally off-the-
shelf, but
may be blocked or screened by cargo stacked in front of the sensor.
Chemical/biological agents will be difficult and costly to detect, principally
because
extremely small amounts of these agents must be sensed with high accuracy (low
false
negatives and false positives). The invention can include a chemical or
biochemical "lab-on-
a-chip" detector. A less expensive chem/bio detection system for containers
can mount the
detector on or close to the transfer crane, where the container could be
passed through a
"sniffer tunnel" for rapid online examination. In addition, individual
chem./bio detectors) can
be mounted in and/or on the container(s).
Shock and/or acceleration sensing for sensitive cargoes can be realized with
any
one of several technologies, including MEMS/electronic devices (similar to
automotive
airbag sensors), glass beads or granules (for shock or tilt-limit sensing),
piezoelectric
devices (e.g., classic accelerometers), microcantilevers and induction sensors
(e.g.,
geophones). The principal constraint is generally that of available power;
most of these
devices require too much power to be easily handled by a small battery for a
significant time
(e.g., a month). However, the use of a continually time-sampled acceleration
profile could be
of great value in tracking fragile cargoes and determining instances of overly
rough handling
of containers in transit. Most of these types of sensors are currently
available commercially,
and appropriately packaging and interfacing them to the container telemetry
system would
be quick and easy.
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Refrigerated container systems, particularly the compressor and cooling system
components, would ideally be monitored using the techniques discussed
previously related
to the reefers. This compressor and cooling system technology, including the
electrical-
signature analysis components, is readily available commercially and would be
straightforward to implement for the transportation environment.
The typical container tag-whether a simple long-range ID device or a more
elaborate
data-acquisition/telemetry device for detailed monitoring of container
security and internal
conditions (i.e., temperature, humidity, shock) is preferably battery-powered.
Thus, careful
unit and system design is also preferred to ensure proper unattended operation
for long
intervals, thereby ensuring wide acceptance by the shipping industry. The tags
should
preferably have periods of maintenance-free use of at least approximately one
year. Most
shipping firms would desire intervals of 3 to 5 years, approximating the
lightly-loaded life of a
camera-style lithium battery, which is the highest energy-density format
currently available in
an easily obtainable commercial product. Since the shelf life of lithium ion
batteries is
typically on the order of 10 years, sealed container tags stored in a
deenergized state for
several years before use should still exhibit the normal operational lifetime
goal of 3-5
years. Suggested tag query intervals in most projected scenarios range from
one to four
times daily, depending on the type of container; the relative fragility or
sensitivity of its cargo;
and other factors such as security, cargo value, theft potential, and
traumatic events (e.g., a
container going overboard). Some of the latter factors may also dictate the
deployment of an
emergency transmitter or beacon on the container to facilitate immediate crew
response to
such urgent situations. A routine query once per hour (expending an average of
10 mA for
10 seconds), assuming a typical battery capacity of 1400 mAh (3-V AA size),
would result in
an effective operational battery life of slightly over 5 years. If recharging
were implemented,
this interval could easily exceed 20 years, which is probably close to the
expected lifetime of
the electronics package. Although solar recharging is a preferred recharging
mechanism to
be employed, other power mechanisms are possible, including micro-fuel cells,
kinetic
generators (e.g., micro-pendulum or MEMS types), thermopiles (temperature-
differential),
and even RF energy scavenging.
An embodiment of the invention can include embedding the RFID tag into the
structure of a container. An embodiment of the invention can include providing
a plurality of
RFID tags on a single container for redundancy or as (non)functional decoy(s).
Space Charge Dosimeters for Extremely Low Power Measurements of Radiation in
Shipping Containers
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Electronic dosimeter devices can measure the dose in the container, but they
must
be powered (active) during integration times. Therefore, they must integrate
over short
periods to conserve battery power (thus reducing sensitivity). Utilizing large
size or
quantities of batteries is not economically feasible, nor is replacing
batteries during the life of
the container (typical shipping container life is 5 to 7 years).
What is needed is a simple, rugged, low cost, low power device which can be
installed in every shipping container to passively integrate radiation dose.
During transport
this device could integrate the radiation dose over very long periods to
obtain a very
sensitive measurement of the presence of radiation in the container. Even well
shielded
radioactive material will result in a slight increase in the background
radiation levels in the
container. What is also needed is a device that can reduce the incidence of
false positives.
Space charge dosimeters (SCD) are capable of passively integrating radiation
dose
continuously, while only requiring power for readout or to recharge the
device. These
devices work by charging or generating an initial potential between an anode
and a cathode.
A dielectric media is located between the cathode and anode. This potential
creates an
electric field across the dielectric media. As radiation passes through the
dielectric material,
it causes ionization of the dielectric. The electric field then sweeps the
ions or charge
carriers out of the dielectric, thus reducing the potential between the anode
and cathode.
The measurement of the depleted charge during the exposure period is a measure
of
integrated ionization during the measurement period. The charge (or some
physical aspect
of the device controlled by the charge) is read before and after the exposure
to obtain a
dose rate.
Utilizing various materials as filters around an SCD, the type of radiation
sensed can
be determined or the energy range of the radiation determined. A suite
(plurality) of these
low-cost sensors in each container with a different filter around each SCD can
give, not only
an indication of increased background radiation, but an indication of the type
and energy
levels of the radiation. This can help identify the potential type of
radioactive material in a
container, e.g., identify whether increased radiation levels in a container
are due to bananas
(potassium-40) rather than from cobalt-60 in a lead shielded box.
An embodiment of the invention can solve the problem of how to measure
radiation
in a shipping container where the radiation sensor must be low cost and
battery powered but
still have a battery life of many years. An embodiment of the invention can
utilize very low
cost space charge dosimeters (SCDs), such as electret ion chambers (EICs),
field effect
transistors (FETs) such as IGFETs (Insulated Gate Field Effect Transistor),
MOSFETs
(Metal Oxide Semiconductor Field Effect Transistors) and/or micro-cantilevers,
to passively
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integrate radiation dose. In these devices, radiation passing through the
sensitive volume of
the dosimeter (the air chamber for EIC's or the dielectric layer for FETs and
microcantilevers) ionizes the gas or dielectric (i.e., creates charge pairs).
These radiation
induced charges then lead to a change in the potential or electric field of
the device. This
change in the potential or electric field is proportional to the radiation
dose received.
An embodiment of the invention can include an active radiation detection
volume of
material that is an electrical insulator. When radiation impacts this volume,
electric charge
is created that is trapped within the volume. This trapped charge changes the
electric field
distribution within the volume. An embodiment of the invention can then sense
this change
in field by placing electrodes on opposite sides of the volume. It is
important to note that
these electrodes will react to this field. If these electrodes are, for
example, the gate and
body of a IGFET transistor, an embodiment of the invention can indirectly
measure the
change in field by monitoring the channel conductance of the transistor
without disturbing
the trapped charge. Alternatively, if an embodiment of the invention includes
a detection
volume in which the generated charge moves toward an insulated electrode, such
as, for
example, a microcantilever, the embodiment of the invention can read the
cantilever
deflection and achieve the same results.
Intermittently reading the voltage or potential of the SCD dosimeter gives a
reading
proportional to the radiation dose received by the device. One or more SCDs
can be
mounted into the shipping container, optionally in the context of a radio
frequency
identification tag. During transportation of the container (such as by ship or
rail), the SCDs
integrate received radiation dose. After a time interval, such as every 24
hours, the voltage
potential of each SCD can be read out. The change in potential from reading to
reading is
proportional to the radiation dose.
Multiple SCDs with various types of filters can be used to discriminate by
types of
radiation, e.g. gamma, x-ray, neutron or beta, and to discriminate between
energy levels of
these particles or photons. An SCD placed outside the container or well
shielded inside the
container can be used to subtract ambient or background radiation.
The data from these radiation sensors can then be relayed to an RFID tag on
the
container. This RFID tag can collect the data from the radiation sensors,
other sensors (for
example, temperature, acoustic, etc.), and location information (from, for
example GPS or
triangulation), and send all of it by wireless communications (e.g., HSS) to a
receiver
coupled to a central database. At the central database, the radiation dose
readings can be
analyzed to look for indications that a container has a higher than normal
radiation field. A
higher than normal radiation level can indicate that a hazardous (radioactive)
cargo may be
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in the container and, therefore, that a particular container needs to be
flagged for more
detailed inspection.
An embodiment of the invention can include a system that utilizes Space Charge
Dosimeters (SCDs). SCDs include Electret Ion Chambers (EICs), semiconductor
devices
such as Insulated Gate Field Effect Transistors (IGFETs) and/or
microcantilevers. The
SCDs can be used to continuously monitor radiation levels in shipping
containers. These
radiation sensors can be combined with a communications and tracking system
located on
each container to allow real-time world-wide monitoring of the radiation-level
in the container
as well as the position of the container. Unexplained or higher than expected
radiation
levels in a container can then used to flag a container for more detailed
inspection at the US
port of entry, or preferably before the ship ever docks at a US port.
As noted above, the basic principle of operation of SCDs is that the ionizing
radiation
interacts with a material (such as air or a dielectric) to create charge pairs
(ionization).
These charge pairs then migrate through the material due to the presence of an
electric
field. The migration and collection of the charge carriers then causes a
reduction in the
voltage potential across the device. Once the SCD is charged up, ionization in
the active
region causes a reduction in the potential. Charging the device takes an
extremely small
amount of power. Once charged, the device continuously integrates the received
dose,
measured as a drop in the potential. Thus, reading this potential before and
after exposure
gives an indication of the received dose. Significantly, the SCD requires no
power during
the dose integration period. The only time power is required is when charging
the device or
reading the potential. As also noted above, three possible SCDs that can
passively
integrate dose are the Electret Ion Chamber (EIC) dosimeter, the Insulated
Gate Field Effect
Transistor (IGFET) dosimeter, and the Microcantilever dosimeter.
A preferred method of operation of the radiation sensors in this invention is
as
follows. A container fitted with one or more-radiation sensors and the RFID
communications
system and then the container is loaded with cargo. The container is then
transported to the
shipping terminal. The container is then loaded onto a ship for transport to
the US or other
importing country. During the ocean voyage, a signal is sent to the RFID
system to activate
the radiation sensor (read sensor to get base-line reading, or recharge sensor
and then get
baseline reading). The radiation sensor then passively integrates received
radiation dose
until the RFID system directs the sensor for another reading or a preset
amount of time has
passed. The radiation sensor then powers up, reads the voltage level, and
sends the
reading to the RFID system. This reading is then relayed to a surrounding RFID
system for
collection at one or more central locations and analysis. The dose integration
time
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(intervals) can be anywhere from minutes to days. Since the ocean voyage may
last days, it
is possible to allow several days of dose integration for extremely sensitive
measurements.
A central RFID system can send a message to each container to take a baseline
reading when the ship leaves port. The central system can then direct the RFID
tags to
read the radiation sensors at some regular interval (e.g., every 12 hours or
24 hours) for the
duration of the voyage. The sensor readings can be passed up to the RFID
central system
by the RFID tags, tag readers, site servers, etc., whereupon the received
doses are
collected and analyzed. As the ship transits the ocean (i.e. during the
voyage), any
radiation dose readings above expected background levels will be flagged and
the
appropriate authorities notified. This could permit the ship to be stopped and
the container
inspected before the ship reaches a US port (or other importing country).
Electrete Ion Chamber (EIC) Dosimeters
An EIC consists of an electrically charged polymer (e.g., Teflon) filament or
disk,
called an electret, located inside an electrically conductive plastic chamber
having a known
air volume. The electret serves as a source of high voltage (anode) needed for
the chamber
to operate as an ion chamber. It also serves as a sensor for the measurement
of ionization
in the chamber air. The negative ions produced inside the sensitive volume of
the chamber
by radiation induced ionization of the air are collected by the electret
causing a depletion of
charge. The measurement of the depleted charge during the exposure period is a
measure
of integrated ionization during the measurement period. The electret charge
can be read
before and after the exposure or on a known schedule using a non-contact
electret voltage
reader.
In a preferred embodiment of this invention, the electret charge reading
voltmeter is
a very small low cost electronics circuit, or possibly an ASIC chip, which not
only reads the
electret charge but also recharges the electret as needed. This circuit or
chip can also
contain sufficient data to convert the measured voltage to a radiation dose
and transmit this
data over a (e.g., IEEE 1451 compliant) sensor bus.
An additional optional feature of the invention is the incorporation of
radiation filtering
materials or converters around EICs to make each EIC sensitive to different
radiation types
(e.g. neutron, gamma or x-ray) or energies (hard x-ray, soft x-ray, etc).
Measuring not only
the presence or quantity of increased radiation levels but also some
qualitative
characteristics of the radiation can help distinguish hazardous radioactive
cargo from normal
safe cargo having a normally higher radiation level (such as bananas, some
pottery, etc).
Additionally, one EIC sensor can be mounted and shielded to measure background
radiation
for background subtraction from the sensor measurements inside the container.
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EIC devices are shock sensitive and can be partially discharged when shaken or
dropped. To prevent false positive radiation measurements due to the severe
handling
experienced by shipping containers, the invention can incorporate active and
passive
preventative measures. First, the ability to communicate to each sensor via
the RFID tag on
each container permits the radiation sensors to integrate does and then be
readout during
times of known low shock potential, such as during marine transport. Readings
can be
taken starting when the ship leaves port and during the duration of the
voyage. Second, an
accelerometer can be co-located with the sensors to identify shock events of
sufficient
magnitude to cause discharge of the EIC. After such events, the EIC can be
readout and
the dose integration time re-initiated.
Field Effect Transistor Dosimeters
FET dosimeter operation is based on the generation of electron-hole pairs in
the
oxide (or other insulator material having very low hole mobility) of the
(e.g., IGFET) structure
(gate oxide) due to the ionizing radiation. The energy to produce one electron-
hole (e-h)
1 S pair in silicon oxide is about 18 eV. The electron mobility is such that
electrons collect on
the gate of the transistor (assuming an n-channel device) but the hole
mobility is much
smaller. The holes are therefore effectively immobilized within the oxide
between the gate
and body. This causes a variation in the electric field between the gate and
the channel of
the transistor which changes the current-carrying capabilities of the channel.
This change
can then be read at any time without affecting the dosimetrically-altered
electric field.
Therefore, the gate bias voltage is a direct measure of the absorbed radiation
dose. This
technique can be applied to both FETs intentionally manufactured in a given
CMOS process
or to field-oxide FETs (parasitic FETs, IGFETs). The latter of which will
exhibit more
sensitivity due to thicker oxides.
Microcantilever Dosimeters
Microcantilever dosimeters are created by making the microcantilever an
electrode
separated from ground by an insulator. A charge is applied to the
microcantilever. This
charge remains unchanged until radiation creates electron-hole pairs in the
insulator. Thus,
absorbed radiation dose is continuously and passively integrated. To read-out
the radiation
dose, the change in the voltage potential on the microcantilever is measured.
This potential
or change in potential is determined by measuring the deflection of the
microcantilever.
Filters and Converters for Discriminating between Types of Radiation or Energy
Levels
The invention can include the use of different types and thicknesses of
materials to
make radiation sensors sensitive to particular types of radiation or to
different energy levels.
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The invention can include the use of a plurality (e.g., an array) of low-cost
detectors, each
with a different filter, in the shipping container. Since the types of SCD
radiation detectors
described above can be mass produced at a very low cost, an array of detectors
can be
located throughout a container. Filters of varying density metals such as
lead, tin, and
aluminum can be used to coarsely determine the energy of impinging gamma or x-
rays. A
radiation converter such as boron or lithium-6 can be used to make the devices
sensitive to
thermal neutrons. Teflon or a high hydrogen content plastic can be used to
increase
sensitivity to intermediate energy neutrons. By using an array of detectors,
each utilizing a
different filter and converter, located inside the container, any radiation
detected in the
container can be categorized into energy bands (for example, low, mid, and
high) and
radiation type (beta, x-ray, gamma).
RFID Communications System
The invention can combine the radiation sensors with a communications and
tracking
system that relays the sensor data and container location to a centralized
database where
the radiation data from every container can be analyzed to flag containers
requiring further
detailed inspection. The overall RFID system can be termed a "Marine Asset
Security and
Tracking (MAST) System." The MAST System is preferably a wireless (RF)-based
communications and sensing/telemetry system for tracking and monitoring
maritime
industry-standard shipping containers, both during loading, unloading, and
transfer
operations at portside dock facilities, as well as onboard ships during
overseas transport of
the containers. This system also provides a true inter-modal tracking and
monitoring system
capable of operating on ships, railroads, over-the-road trucks and within
their associated
terminal facilities, utilizing both local-terminal communications systems and
other wide-area
commercial communications systems, including satellite and/or cellular/PCS.
This RFID
tagging system can include RFID tags attached to each shipping container,
local site
readers located throughout the ship and in the shipping terminal, one central
site server on
each ship or in each terminal, and a National Operations Center (NOC) where
all data is
collected, consolidated, stored, analyzed and disseminated. The shipping
containers can be
both refrigerated-cargo shipping containers (reefers) and dry-cargo shipping
containers (dry-
boxes). In addition to identifying and tracking the location of containers or
other equipment
fitted with one of the RFID tags, each tag is equipped with, for example, an
IEEE 1451
sensor interface and extra serial interfaces to permit the connection of a
wide range of
sensors to the RFID tag to monitor the condition of the container cargo or
other tagged
equipment. Other sensors which can be connected to the RFID tag include (but
are not
limited to) temperature, pressure, relative humidity, accelerometer,
radiation, door seals,
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and GPS (Global Positioning System). Additional sensors can also be included
for condition
monitoring of machinery, such as refrigeration compressors, or to read the
diagnostic data
port on some refrigerated cargo containers.
This invention can include implementation of a radiation sensor system for the
MAST
system RFID tags. The MAST system provides the solution to the problem of
combining the
data from a container installation with an overall monitoring, tracking or
communications
system, while the problem of not using power during the dose integration time
is addressed
by using a suite of passively-integrating radiation sensors. An embodiment of
the invention
can include a class of radiation dosimeters that continuously, passively
integrate radiation
dose, send this data to the RFID tag on the container via a IEEE 1451 sensor
interface, and
then transmits this data with position and other sensor data to the MAST
system National
Operations Center (NOC). At the NOC, all sensor data, container manifest,
route traveled
by the container and other information is analyzed and used to identify
containers for
detailed inspection at Ports of Entry.
The invention can include passively integrating radiation dose over long
periods,
while only using power to read out the received dose. The invention can
include connecting
a radiation sensor to a RFID system which will communicate out the sensor data
in near-real
time to a central database where analysis of the sensor data can be performed
to identify
and flag containers with abnormal radiation readings.
The invention can include insitu polling a suite of passive integrating
ionizing
radiation sensors including reading-out dosimetric data from a first passive
integrating
ionizing radiation sensor and a second passive integrating ionizing radiation
sensor, wherein
the first passive integrating ionizing radiation sensor and the second passive
integrating
ionizing radiation sensor remain situated where the dosimetric data was
integrated while
reading-out dosimetric data and wherein the first passive integrating
radiation sensor and
the second integrating radiation sensor are connected to read-out circuits
presenting
extremely high impedance while in a passive integration mode and while in an
active read-
out mode, without destruction of integrated dosimetric data allowing
continuous integration
of ionizing radiation to a maximum extent of the first passive integrating
ionizing radiation
sensor and the second passive integrating ionizing radiation sensor. Upon
sensing the
attainment of maximum integration limits, readout circuits can reset passive
integrating
radiation sensors and accumulate in a non-volatile manner the number of sensor
reset
cycles.
The invention can include a first passive integrating ionizing radiation
sensor; a
second passive integrating ionizing radiation sensor; a read-out circuit
coupled to both the
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first passive integrating ionizing radiation sensor and the second passive
integrating ionizing
radiation sensor, the read-out circuit presenting an extremely high impedance
to both the
first passive integrating ionizing radiation sensor and the second passive
integrating ionizing
radiation sensor both while the read-out circuit is in a passive integration
mode and while the
read-out circuit is in an active read-out mode; and a communication circuit
coupled to the
read-out circuit, wherein read-out dosimetric data from both the first passive
integrating radiation sensor and the second passive integrating radiation
sensor is
presented to the communications circuit.
One or both of the first passive integrating ionizing radiation sensor and the
second
passive integrating ionizing radiation sensor can include a thick oxide
insulated gate field
effect transistor space charge dosimeter. The read-out circuits can present
impedance of
from approximately 10" ohms to approximately 10'5 ohms, preferably from
approximately
10'2 ohms to approximately 10'° ohms, most preferably approximately
10'3 ohms.
As noted above, the invention can include a thick oxide dosimeter (TOD). In
such a
TOD, the FETs can be arranged such that the gates are connected to two or more
levels of
metal or polysilicon. This will increase the active volume of Si02 that can
interact with
ionizing radiation. These devices have the significant optional advantage of
temperature
and process compensation by reading out the voltage between the drains
assuming the
sources are connected to a common electrical potential. The gates and drains
for a given
IGFET can be connected together.
This technique can be extended by simply adding FETS and stacking metal layers
on top of each other to the limits of the semiconductor fabrication process
being used. The
advantage of this is that the active volume of the oxide used for detection is
increased but
the electric field created by a trapped charge between any two plates is
reduced by the
increase in distance between the plates. As many plates as the fabrication
process allows
can be used to obtain the greatest electric field for a given ionizing
radiation event to ensure
the greatest probability of detection.
Figs. 10-11 depict two IGFET examples of the invention. The use of the terms
first,
second and third in describing elements depicted in these figures is only for
distinguishing
between similar elements and the assignment of these terms is arbitrary.
Referring to Fig. 10, a suite of passive integrating ionizing radiation
sensors includes
a first sensor 1010 shielded by a first filter 1011. This suite of passive
integrating ionizing
radiation sensors also includes a second sensor 1020 shielded by a second
filter 1021. The
first sensor 1010 and the second sensor 1020 are both coupled to a
communications circuit
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1030. A temperature compensation circuit 1040 is coupled to the communications
circuit
1030. A calibration circuit 1050 is also coupled to the communications circuit
1030. Each of
the sensors 1010, 1020 is based on a pair of insulated gate field effect
transistors.
The invention can include an apparatus, comprising: a thick oxide dosimeter;
and a
readout circuit coupled to the thick oxide dosimeter, wherein both the thick
oxide dosimeter
and the readout circuit are constructed on a single high impedance and low
leakage
substrate. The thick oxide dosimeter can include a thick oxide insulated gate
field effect
transistor space charge dosimeter. The single high impedance and low leakage
substrate
can include a construction of silicon on sapphire, silicon on insulator and/or
transmutated
high resistivity silicon. The substrate can have an impedance of from
approximately 10"
ohms to approximately 10'5 ohms, preferably from approximately 10'z ohms to
approximately 10'4 ohms, most preferably approximately 10'3 ohms.
Referring to Fig. 11, a passive integrating ionizing radiation sensor 1100
includes a
first active area (region) 1110 and a second active area (region) 1120. The
second active
area 1110 is sandwiched between a common conductor 1130 and a first active
area
conductor 1140. The second active area 1120 is sandwiched between the common
conductor 1130 and a second active area conductor 1150. The first active area
conductor
1140 is coupled to the gate of a first insulated gate field effect transistor
1160. The second
active area conductor 1150 is coupled to the gate of a second insulated gate
field effect
transistor 1170. The sources of both the first insulated gate field effect
transistor 1160 and
the second insulated gate field effect transistor 1170 are connected together
and coupled to
the common conductor 1130. A third insulated gate field effect transistor 1180
provides an
integrated temperature compensation functionality.
During passive-mode dosimetry operation of the examples depicted in Figs. 11,
ionizing radiation passes through the active area and generates a net charge
that is trapped
in the oxide. This charge generates an electric field between the adjacent
conductors thus
creating a net change in the resistance seen between the source and gate of
the FET
whose active area was hit. During readout operation of the examples depicted
in Figs. 11,
the resistance between the source and each drain is read. The net amount of
radiation is
proportional to the change in resistance. Temperature compensation is applied
by tracking
the change in the third IGFET which has a much smaller radiation sensitivity
than the others.
The invention can include a first insulated gate field effect transistor
including a first
source, a first drain and a first insulated gate; a second insulated gate
field effect transistor
including a second source, a second drain and a second insulated gate, the
second source
coupled to the first source; a first conductor coupled to the second gate; a
first active region
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connected to the first conductor, the first active region accumulating
dosimetric data from
incident ionizing radiation; a second conductor connected to the first active
region; a second
active region coupled to the second conductor, the second active region
accumulating
dosimetric data from incident ionizing radiation; and a third conductor
coupled between the
second active region and the first gate, wherein the second conductor is
coupled to both the
first source and the second source. A third insulated gate field effect
transistor can provide
temperature compensation data.
The invention can include arranging a plurality of sensors in a spatially
dispersed
(e.g., an array) configuration and setting an alarm condition based on a
reading in multiple
sensors.
The invention can include pattern recognition. For example, a method can
include
arranging a plurality of passive integrating ionizing radiation sensors in a
spatially dispersed
array; determining a relative position of each of the plurality of passive
integrating ionizing
radiation sensors to define a volume of interest; collecting ionizing
radiation data from at
least a subset of the plurality of passive integrating ionizing radiation
sensors; and triggering
an alarm condition when collected ionizing radiation data from the subset of
the plurality of
passive integrating ionizing radiation sensors meets a predetermined spatial
pattern
criterion. The predetermined spatial pattern criterion can include a plurality
of alternative
patterns. The predetermined spatial pattern criterion can include a dosimetric
data pattern
defined by a function that includes a cube root of a radius from an
approximate location of
an ionizing radiation source.
Embodiments of the invention, can be cost effective and advantageous for at
least
the following reasons. An embodiment of the invention can provide world-wide
asset and/or
cargo tracking, monitoring and security. An embodiment of the invention can
include
Integrating RFID tag data in a GIS-based system for asset tracking,
management, and
visualization. An embodiment of the invention can include RFID tag
communications utilizing
hybrid spread-spectrum signaling. An embodiment of the invention can include
multi-access
technology allowing communications with over 10,000 RFID tags, while ignoring
up to
90,000 tags, in the same RFID tag reader zone. Embodiments of the invention
improves
quality and/or reduces costs compared to previous approaches.
The phrase hybrid spread-spectrum (HSS) as used herein is defined as a
combination of direct sequence spread-spectrum (DSSS), for example code
division multiple
access (CDMA), and at least one of frequency hopping, time hopping, time
division multiple
access (TDMA), orthogonal frequency division multiplexing OFDM and/or spatial
division
multiple access (SDMA). The terms a or an, as used herein, are defined as one
or more
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than one. The term plurality, as used herein, is defined as two or more than
two. The term
another, as used herein, is defined as at least a second or more. The terms
"comprising"
(comprises, comprised), "including" (includes, included) and/or "having" (has,
had), as used
herein, are defined as open language (i.e., requiring what is thereafter
recited, but open for
the inclusion of unspecified procedure(s), structures) and/or ingredients)
even in major
amounts. The terms "consisting" (consists, consisted) and/or "composing"
(composes,
composed), as used herein, close the recited method, apparatus or composition
to the
inclusion of procedures, structures) and/or ingredients) other than those
recited except for
ancillaries, adjuncts and/or impurities ordinarily associated therewith. The
recital of the term
"essentially" along with the terms "consisting" or "composing" renders the
recited method,
apparatus andlor composition open only for the inclusion of unspecified
procedure(s),
structures) and/or ingredients) which do not materially affect the basic novel
characteristics
of the composition. The term coupled, as used herein, is defined as connected,
although not
necessarily directly, and not necessarily mechanically. The term any, as used
herein, is
defined as all applicable members of a set or at least a subset of all
applicable members of
the set. The term approximately, as used herein, is defined as at least close
to a given value
(e.g., preferably within 10% of, more preferably within 1 % of, and most
preferably within
0.1 % of). The term substantially, as used herein, is defined as largely but
not necessarily
wholly that which is specified. The term generally, as used herein, is defined
as at least
approaching a given state. The term deploying, as used herein, is defined as
designing,
building, shipping, installing and/or operating. The term means, as used
herein, is defined
as hardware, firmware and/or software for achieving a result. The term program
or phrase
computer program, as used herein, is defined as a sequence of instructions
designed for
execution on a computer system. A program, or computer program, may include a
subroutine, a function, a procedure, an object method, an object
implementation, an
executable application, an applet, a servlet, a source code, an object code, a
shared
library/dynamic load library and/or other sequence of instructions designed
for execution on
a computer or computer system. The term proximate, as used herein, is defined
as close,
near adjacent andlor coincident; and includes spatial situations where the
specified
functions and/or results can be carried out and/or achieved. The phrase radio
frequency, as
used herein, is defined as including infrared, as well as frequencies less
than or equal to
approximately 300 GHz.
All the disclosed embodiments of the invention disclosed herein can be made
and
used without undue experimentation in light of the disclosure. An embodiment
of the
invention is not limited by theoretical statements recited herein. Although
the best mode of
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carrying out embodiments of the invention contemplated by the inventors) is
disclosed,
practice of an embodiment of the invention is not limited thereto.
Accordingly, it will be
appreciated by those skilled in the art that an embodiment of the invention
may be practiced
otherwise than as specifically described herein.
It will be manifest that various substitutions, modifications, additions
and/or
rearrangements of the features of an embodiment of the invention may be made
without
deviating from the spirit and/or scope of the underlying inventive concept. It
is deemed that
the spirit and/or scope of the underlying inventive concept as defined by the
appended
claims and their equivalents cover all such substitutions, modifications,
additions and/or
rearrangements.
All the disclosed elements and features of each disclosed embodiment can be
combined with, or substituted for, the disclosed elements and features of
every other
disclosed embodiment except where such elements or features are mutually
exclusive.
Variation may be made in the steps or in the sequence of steps defining
methods described
1 S herein.
Although the sensors) with or without their filters described herein can be a
separate
module, it will be manifest that the sensors) may be integrated into the
system with which it
is (they are) associated. The individual components need not be formed in the
disclosed
shapes, or combined in the disclosed configurations, but could be provided in
all shapes,
and/or combined in all configurations. The individual components need not be
fabricated
from the disclosed materials, but could be fabricated from all suitable
materials.
The appended claims are not to be interpreted as including means-plus-function
limitations, unless such a limitation is explicitly recited in a given claim
using the phrases)
"means for" and/or "step for." Subgeneric embodiments of the invention are
delineated by
the appended independent claims and their equivalents. Specific embodiments of
the
invention are differentiated by the appended dependent claims and their
equivalents.
