Note: Descriptions are shown in the official language in which they were submitted.
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DUAL MODE DATA COMMUNICATION FOR MONITORING AND
DIAGNOSTICS OF REMOTE ASSETS
BACKGROUND OF THE INVENTION
The present invention relates to communication systems, and more particularly
a communication system applicable for both mobile and fixed site remote
assets, such
as locomotives, to communicate with a central monitoring facility for exchange
of
status and monitoring diagnostics data.
S In communication systems, such as the Internet, data communication networks
link end points with a series of nodes. Data transmitted through the network
traverses
interconnecting nodes to reach its destination. In this manner, the network of
nodes
circumvents the need for individual and permanent connection paths between all
possible end points of the data network. Switching refers to the manner in
which data
traverses the network of nodes. Current engineering practice employs two types
of
network switching mechanisms, either circuit or packet switching.
Transportation of data over a communication link is defined by a set of rules
known as a protocol. A protocol stack is a group or "family" of protocols,
each
pertaining to a specific aspect of the data exchange task. The standard
reference
model for communication based upon standard interconnection protocol stack is
the
Open System Interconnection Reference Model (known as "OSI"). Standardized by
the International Organization for Standardization (known as "ISO"), this
model does
not assume any specific system architecture nor does it require a particular
implementation.
Circuit switching implies that a series of interconnecting nodes linking
transmit and receive end points are identified and reserved for the duration
of the
transfer session. Each circuit requires signaling to establish the connection,
known as
a call. The signaling is maintained for the duration of the call and is
disconnected at
the completion of the session. Circuit switching creates temporary but
dedicated
paths between transmit and receive end points. The only delays encountered
with
such a transmission path are those associated with establishment of the
circuit and
propagation over the circuit. For a circuit switched data link, Link, Network,
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Transport, Session, Presentation and Application protocol layers (according to
the
OSI model) are determined by the network end-points, allowing for greater
implementation flexibility. The characteristics of a circuit switched
communication
link lend themselves to the efficient transfer of bulk data (i.e. file
transfers).
A packet switching network does not establish such dedicated circuits.
Rather, a packet switching network forwards individual segments of data from
one
node to another. Each data packet contains identification, control, and user
data
information. In such a network, each node functions as both a switch and a
queue
which receives, holds, and forwards data packets as quickly as possible. A
goal of
such a network configuration is to exploit the burst-nature and short size of
data
packets to allocate network resources only when data is available and its
transfer
required. This network architecture affords transitory connection with end
points and
allows sharing of network links, ports, and routes between many users. A
packet
switched network typically consists of a multiplicity of nodes permitting
multiple
routes to a desired destination. The delay of a packet network is
directionally
proportional to the size of the network, the number of nodes that must handle
a packet
in transit, amount of traffic placed on the network by other users/nodes, and
the
processing required at each node. Protocols for packet data networks are
typically
fixed at the Physical, Link, Network, and Transport Layers. The
characteristics of
packet switched communication links lend themselves to the exchange of short,
bursty, data messages.
An application area involving the exchange of large, bulk data as well as
short,
bursty messages is the remote monitoring of mobile or transportable assets.
Examples
of such assets include containers, rail cars, trailers, power generators,
medical
diagnostic equipment, as well as automobiles, trucks and locomotives. Remote
monitoring of such assets seeks to maintain an awareness of asset operational
status,
location, and characteristic performance data. The mobility of these assets
favors the
use of wireless communication links.
The design of a wireless communication architecture to support remote
monitoring systems typically involves a trade-off between the use of packet
switched
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links offering low latency exchange of small, frequently occurring
status/location
messages versus the use of circuit switched links providing higher throughput
and
protocol flexibility for transfer of accumulated bulk data files and
establishment of
interactive command sessions. While the economics of wireless service costs
tend to
limit remote monitoring applications to the use of either a circuit or packet
based
channel, application performance requirements are often satisfied only by a
wireless
architecture employing switched, dual-mode (i.e. packet and circuit) data
communication links.
U.S. Patent Number 5,729,544 and U.S. Patent Number 4,539,676 appear to
demonstrate data switching systems. It is believed that the '544 patent
utilizes either
a circuit switched channel or a packet switched channel to transmit data based
upon
contents of the data stream. The '544 patent appears to determine whether to
use a
circuit switched channel or a packet switched channel based solely upon the
length of
the message, i.e., by using header information from a specific protocol, TCP,
within
the Transport Layer to trigger communication mode switching. U.S. Patent No.
4,539,676 appears to employ communication mode switching by using data bits
set by
the Physical Layer of the OSI model.
Remote monitoring of a locomotive presents significant challenges as such an
asset's utilization modes fit that of a mobile, transportable and, at least
temporarily,
fixed site asset. Furthermore, a locomotive is comprised of a multitude of
subsystems, controllers, computers, and sensors each generating a significant
quantity
of status messages and bulk operational data. While it is believed that U.S.
Patent No.
5,845,272 details a system for isolating failures in a locomotive based upon
this
multitude operational performance data, there is still a need to collect,
store, and
exchange the bulk and status message data with a central monitoring facility
at a
higher cyclic rate than normal monitoring wherein the system does not
determine the
switched channel to use based solely upon the length or type of message sent.
Such
an approach could also result in a significant increase in efficiency for the
management of remote assets as a packet network permits continuous and
parallel
monitoring of status from multiple assets while a circuit network connection
provides
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dedicated information exchange with an individual asset. Establishment of a
dedicated circuit connection only when its functionality is required allows
the circuit
switched network resource to be shared by an entire fleet of assets.
Maintenance of
packet network resources affords the ability to remain in contact with the
entire asset
fleet while servicing information exchange needs of individual fleet members.
SUMMARY OF THE INVENTION
This invention can be directly applied to the management of locomotives. As
remote and mobile assets, locomotives require wireless communication links
with
wide coverage areas. Transmission of information is accomplished over a dual
mode
communication system where the dual modes are a circuit switched network and a
packet switched network. The present invention is comprised of sensor outputs
used
to gather system status and health data of a locomotive, remote asset. This
data is
stored in an electronic database that is managed by an on-board computer. The
locomotive also has a transceiver where data is transmitted to and information
is
received from a central monitoring facility.
This invention leverages the Application Layer of the Open System
Interconnection Model and a set of system states to determine whether it sends
and
receives using a packet switched network or a circuit switched network.
Utilization of
the Application Layer affords communication switching based upon a desired
transmission functionality. The present invention defines four system states
for
communication between the central monitoring facility and remote assets. Both
the
central monitoring facility and the individual remote asset can initiate
transitions
between these states. The four states are Asset Monitoring State, Help State,
Asset
Diagnostics State, and Polling State.
While in the Asset Monitoring State, a packet switched network is employed.
Locomotives periodically transmit short status messages consisting of
subsystem
health indicators, GPS position, wireless coverage availability, etc. to the
central
monitoring facility. On a periodic basis the Polling State is entered via the
packet
network. This state allows the central monitoring facility to convey its
desire for
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retrieval of fault logs and controller data in order to monitor engine
performance and
predict system failures. Fault trigger thresholds are defined within the
locomotive
system controllers. A transition to the Help State is conveyed from the
locomotive
via packet network if these thresholds are exceeded during normal locomotive
operation. Both the Polling and Help States utilize the packet switched,
wireless
network.
A circuit switched network is employed during the Asset Diagnostic State. In
this state, bulk data consisting of asset controller, monitor, and/or sensor
information
may be retrieved from the remote asset by the central monitoring facility for
analysis
and diagnosis. This state also permits the download of application or
operating
system software modifications from the central monitoring facility to remote
asset. In
addition, the central monitoring facility may initiate an interactive terminal
session
with the asset to take corrective action or reconfigure the asset. Data
exchanged
during such an interactive session tends to be transactional in nature,
requiring the
1 S combination of high data throughput and low latency often available only
via circuit
switch connection in order to maintain the interactive user's satisfaction.
Upon
completion of the Asset Diagnostic State, both network end-points return to
Asset
Monitoring State and the packet switched network.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a simplified schematic drawing of a dual mode
communication system that carnes both circuit switched and packet switched
networks for monitoring and diagnostics of a fleet of locomotives.
FIG. 2 illustrates a plurality of sensors interfaced with a computer which is
capable of electronically storing sensor data, and a transceiver aboard a
locomotive.
FIG. 3 is an exemplary illustration of the Open System Interconnection (OSI)
reference model for data communication protocol layers.
FIG. 4 depicts the application oriented state diagram for the present
invention.
FIG. S illustrates the transfer of data during an Asset Monitoring State, Help
State, and Polling State.
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FIG. 6 illustrates the transfer of data during an Asset Diagnostic State.
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DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a simplified schematic drawing of a dual mode
communication system that carries both circuit switched and packet switched
networks for monitoring and diagnostics of a fleet of locomotives. In the
embodiment
of FIG. 1, the present invention allows simultaneous communication between
each
locomotive or remote asset 10 in a fleet 9 of locomotives and a central, or
remote,
monitoring facility 15 via a satellite link 20. The satellite link 20 affords
both circuit
switched network 40 and packet switched network 25 connectivity to the remote
asset
10. Though not illustrated, communications between a remote asset 10 and a
central
monitoring facility 15 may be accomplished with a terrestrial, wired network
running
between the remote asset 10 and monitoring facility 15 for connecting to a
packet or
circuit network when the remote asset 10 is in close proximity of the
monitoring
facility 15 or annex facility. Examples of such annex facilities include fuel
depots,
and maintenance facilities.
FIG. 2 illustrates a plurality of data gathering modules or sensor modules 16
interfaced with a computer which is capable of electronically storing sensor
data and
facilitates transfernng and receiving of said data, and a transceiver aboard a
locomotive. Examples of sensor modules 16 aboard the locomotive or remote
asset
10, include, but are not limited to fuel flow sensor modules, oil pressure
sensor
modules, oil filter sensor modules, current sensor modules, voltage sensor
modules,
temperature sensor modules, and global positioning system (GPS) receiver. The
readings or outputs from the sensor modules 16 are fed into a computer or
processor
17 where the information is stored in an electronic storage database or device
19 and
then, depending on a state of a communication system, transmitted through a
transceiver 18 to the remote monitoring facility 15 either over a packet
switched
network or a circuit switched network. The remote monitoring facility 1 S
receives the
information through a transceiver 14 via a satellite link 20. The transceiver
14 may be
located at the remote monitoring facility 15 or on the premises of the
wireless network
service provider and a terrestrial, wired network, such as the public switched
telephone network (PSTN), used to connect to the remote monitoring facility
15.
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Though not shown, the remote monitoring facility includes a computer to
facilitate the
sending and receiving of data, and additional systems to generate data to send
to the
remote asset and to analyze the data received from the remote asset.
By way of illustration, FIG. 3 is an exemplary illustration of the Open System
S Interconnection Model (OSI) model for data communication protocol layers.
The OSI
includes seven layers; Physical Layer 1, Data Link Layer 2, Network Layer 3,
Transport Layer 4, Session Layer S, Presentation Layer 6, and Application
Layer 7.
The present invention selects a data communication network by utilizing the
Application Layer 7 which results in a more efficient communication network.
FIG. 4 depicts the application oriented state diagram for the present
invention.
This figure reflects the transitions between states and differentiates those
transitions
initiated by the remote asset 10 from those initiated by the central
monitoring facility
15. Transitioning at 60 from an Asset Monitoring State 21 to a Polling State
23 is
initiated by the central monitoring facility 15. Transitioning at 62, 64 from
the
Polling State 23 to either the Asset Monitoring State 21 or an Asset
Diagnostic State
34 is also initiated by the central monitoring facility 15. Transitioning at
66 from the
Asset Monitoring State 21 to a Help State 22 is initiated by the remote asset
10.
Transitioning at 68, 70 from the Help State 22 to either the Asset Monitoring
State 21
or Asset Diagnostic State 34 is also initiated by the remote asset 10.
Transitioning at
72 from the Asset Diagnostic State 34 to the Asset Monitoring State 21 is
initiated by
the central monitoring facility if the Asset Diagnostic State 34 was reached
by going
through the Polling State 23. Transitioning 74 from the Asset Diagnostic State
34 to
the Asset Monitoring State 21 is initiated by the remote asset 10 if the Asset
Diagnostic State 34 is reached by going through the Help State 22. The Asset
Monitoring State, Polling State 23, and Help State 22 operate in a packet
switched
network 25. The Asset Diagnostic State 34 operates in a circuit switched
network 40.
FIG. 5 illustrates the transfer of data during the Asset Monitoring State 21,
Help State 22, and Polling State 23. While in any of these states, messages
are
transmitted over the packet switched network 25. In the Asset Monitoring State
21,
also known as the default state, short messages 30, 32 containing monitoring
and/or
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control data, such as speed, temperature, subsystem health via Go/NoGo flags,
or
geographic position determined by using the global positioning system (GPS),
are
exchanged between the locomotive, or remote asset 10, and the central
monitoring
facility 15. The remote asset 10 may also communicate a desire to change its
current
system state to the central monitoring facility 1 S. Use of the packet
switched network
25 for this state allows all members of the asset fleet 9 to transmit status
messages at
will, without requiring the schedule and establishment of a dedicated
connection with
the central monitoring facility 15. Since the central monitoring facility 15
exists as a
peer end point on the packet network, it is also able to send status messages
or state
transition requests to an individual asset 10.
In the Help State 22, the remote asset 10 sends a message 30 to the central
monitoring facility 1 S indicating a need for assistance as fault indicator
occurred. In
general, the central monitoring facility 15 will send an acknowledgment
message 32
at which time both the remote asset 10 and the central monitoring facility 15
will
transition to the Asset Diagnostic State 34, illustrated in FIG. 6.
More specifically, in this state, based on previously defined events, the
remote
asset 10 transmits a status message 30 to the central monitoring facility 1 S
requesting
assistance in the form of data retrieval and diagnosis. If the severity of the
previously
defined event dictates, the asset 10 and central monitoring facility 1 S will
negotiate
information required to establish a dedicated, circuit switched connection.
The
negotiated information might include a connection delay period, a phone number
for
the asset 10 to use to call the central monitoring facility 15, or the type of
circuit
connection that the central monitoring facility 15 should employ to reach the
remote
asset 10 (i.e. cellular, satellite, terrestrial phone networks). The central
monitoring
facility 15 acknowledges this "Help" request and both the remote asset 10 and
central
monitoring facility 15 transition to the Asset Diagnostic State 34.
The Polling State 23 may be initiated with remote asset fleet members 10 on a
periodic basis. An example would be initiate the daily retrieval of
operational fault
logs from a locomotive 10. The Polling State 23 may include a request for an
immediate status message containing a specific variable or the same content as
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periodically generated by the asset during the Asset Monitoring State. In
other words,
the Polling State can be used to force an immediate status update at an
interval other
than the periodic interval of the Asset Monitoring State. Depending upon the
central
monitoring facility's polling purpose, a transition to the Asset Diagnostics
State 34
may be negotiated in order to leverage the benefits of the circuit switched
connect for
asset data investigation and retrieval. Such a transition from Polling State
23 to Asset
Diagnostic State 34 may also be triggered to facilitate the download of
application or
operating system software upgrades to the remote asset 10.
To command a transition from Polling State 23 to Asset Diagnostic State 34,
the central monitoring facility 15 first sends a message 32 to the remote
asset 10
indicating a desire to retrieve bulk data from the remote asset 10 or a desire
for an
interactive terminal session for, as example, to download software upgrades to
the
remote asset 10. The remote asset 10 will acknowledge this request with a
second
message 30. At this time both the remote asset 10 and central monitoring 15
will
transition to the Asset Diagnostic State 34.
FIG. 6 illustrates the transfer of data during the Asset Diagnostic State 34.
While in this state a circuit switched network 40 is utilized for exchange of
bulk data
35, 37 and/or establishment of an interactive session 38, 39. Generally, bulk
data 35
is transferred from the remote asset 10 to the central monitoring facility 15.
Occasionally, such as when upgrading software, bulk data 37 is sent from the
central
monitoring facility 15 to the remote asset 10. Interactive troubleshooting
steps or
operational configuration may be performed by the central monitoring facility
15 in
this state. When the bulk data transfer is complete, the invention returns to
the Asset
Monitoring State 21. Use of the circuit switch network for this state affords
lower
latency and higher data throughput rates, benefiting both bulk data exchange
and
interactive sessions. Circuit switch communication resources promise cost
savings
for transfer of bulk data versus packet networks, especially when wireless
communication networks are employed.
One implementation of this invention is with the use of mobile satellite
services based upon L-band geostationary satellites. The Asset Diagnostic
State 34
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can be implemented using TCP/IP and PPP protocols over circuit switch data
satellite
nerivorks such as those operated by Motient and TMI Communications. Asset
Monitoring 21, Help 22 and Polling 23 States are possible with packet data
satellite
networks, such as those operated by Motient, Norcom Networks, and TMI
Communications. Use of a mobile satellite terminal, transceiver 18, such as
the
Westinghouse Series 1000 and its HVDM software, allows an on-board locomotive
computer 17 to interface with both circuit and packet communication links.
This
example presents but a single embodiment of the present invention. By
utilizing an
application orientated approach to switching between circuit and packet
networks,
significant cost, efficacy, and capacity benefits are realized when monitoring
a fleet of
remote assets.
Numerous variations, changes and substitutions will occur to those of skill in
the art without departing from the invention herein. For example, simply as an
illustration, the invention herein can be applied to individual entities in a
fleet of any
remote assets, such as a fleet of trucks. Accordingly, it is intended that
only the spirit
and scope of the appended claims limit the invention.