Note: Descriptions are shown in the official language in which they were submitted.
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SPECTRAL REUSE TRANSCEIVER-BASED AGGREGATION OF DISJOINT,
RELATIVELY NARROW BANDWIDTH (VOICE) CHANNEL SEGMENTS OF RADIO
SPECTRUM FOR WIDEBAND RF CONMUNICATION APPLICATIONS
CROSS-REFERENCE TO RELATED APPLICATIONS
[001] The present application is a continuation-in-part of and
claims the benefit of previously filed, co-pending U.S. Patent
Application, Serial No. 10/730,753, filed December 8, 2003, by
Brent Saunders et al, entitled: "Radio Communication System
Employing Spectral Reuse Transceivers" (hereinafter referred to
as the '753 application), which claims the benefit of U.S.
Patent Application Serial No. 60/432,223, filed December 10,
2002, by Gerhardt et al entitled: "Link Utilization Mechanism
for Secondary Use of A Radio Band"; and further claims the
benefit of previously filed, co-pending U.S. Patent Application
Serial No. 60/784,105, filed March 20, 2006, by E. Gerhardt et
al, entitled: "Link Utilization Mechanism for Aggregation of
Disjoint Radio Bandwidth," the disclosures of each application
being incorporated herein.
FIELD OF THE INVENTION
[002] The present invention relates in general to communication
systems and subsystems thereof, and is particularly directed to
a radio frequency (RF) communications spectrum usage
methodology, that takes advantage of the clear channel
assessment and frequency-hopping functionality of the spectral
reuse transceiver disclosed in the above-identified '753
application, to effectively aggregate a plurality of disjoint,
relatively narrowband (e.g., voice) RF channels into an overall
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bandwidth for accommodating relatively wideband applications,
such as, but not limited to the transmission of data and/or
video.
BACKGROND OF THE INVENTION
[003] A number of (primary) RF spectrum users, such as, but not
limited to, public service entities (e.g., police, fire, and
utility service organizations), have been licensed by the
Federal Communications Commission (FCC) to use one or more,
relatively narrowband, radio channels, which were originally
intended to support analog voice services (such as push-to-talk
radio communications). In a typical spectral distribution of
these narrowband channels, sizch as the non-limiting spectral
distribution diagrammatically illustrated in the disjointed
channel band 11 in Figure 1, the channels that have been
allocated to a given licensee will likely, over time, include a
plurality of different bandwidth segments, such as one or more
of 50 KHz, 25 KHz, 12.5 KHz and 6.25 KHz segments, which are
not necessarily and are not expected to be mutually spectrally
contiguous.
[004] Namely, as shown by the spectral gaps 13, the channels
which a primary user will have been licensed to use will
typically be separated from one another by one or more other
channels or bandwidth segments (gaps 13) that have been
licensed to other (primary/licensed) users. The spectral
disparity among the licensed channels results from the fact
that they have been sequentially licensed to various users in
response to incremental allocation requests, on the one hand,
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and due to the evolution of tighter spectral efficiency
requirements that have been promulgated by the FCC to meet the
continuously increasing demand for bandwidth.
[005] A principal concern of these licensees is the efficient
utilization of their allocated bandwidth. In the case of push-
to-talk analog voice services, for example, a substantial
number of licensees currently employ fixed-frequency, or
manually channelized, radios. Although these radios are
relatively inexpensive, they offer poor utilization of the
radio channels where they use a dedicated frequency, or pair of
frequencies; if the radio is used only ten-percent of the time,
ninety-percent of the available bandwidth is wasted. In the
above push-to-talk analog voice service example, additional
radios could share the various channels of overall allocated
segments of bandwidth by employing a 'listen-before-talk' user
discipline. While this would improve spectral efficiency, it
has the drawback of requiring some users to wait until a
frequency becomes clear, or to manually adjust the frequency -
if the radio has that capability - and try again.
[006] Trunked radios offer an improvement over these stand-alone
radio designs, since they are able to signal a repeater
station, which then select a clear channel for the caller.
While there lare a number of trunking protocols that may be
employed, they all share a disadvantage that is also shared by
other push-to-talk mechanisms - channelization of the radios
cannot be changed, and.efficiency of band usage may be low.
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[007] The radios described above and other similar radios are
inflexible, in that they can be used only for a single,
relatively narrowband, channel (such as a 12.5 KHz, 25 KHz or
50 KHz channel), and must remain on that channel for the
duration of the communication session - which prevents
efficient utilization of the user's allocated bandwidth.
Moreover, being relatively narrow bandwidth devices, these
radios are unable to provide relatively high bandwidth
services, such as Ethernet and Internet Protocol (IP) digital
services.
[008] As a result, in order to avail themselves of wideband
services, users of such radios will often purchase cellular
radio cards, which they can insert into their personal
computers and thereby gain access to a cellular network that
supports (IP) digital communications. Obvious shortcomings of
this approach include the extra expense of the cellular card
and service subscription, and having to rely upon a (cellular)
network that may overload, or not function at all, in the event
of an emergency situation, such as a natural disaster (e.g.,
hurricane), before, during and after which communications among
emergency service organizations are critical.
SiJNMARY OF THE INVENTION
[009] In accordance with the present invention, the inability of
these and other conventional, relatively narrow bandwidth
radios to more efficiently utilize the entirety of the
(disjoint spectral channels of) bandwidth that has been
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licensed to their users is successfully overcome by taking
advantage of the multiple subcarrier frequency hopping (MSFH)
functionality of the spectral reuse transceiver disclosed in
the above-identified '753 application to effectively
'aggregate' such disjointed channels into an overall bandwidth
that is considerably wider than any licensed channel, so that
the radio may be used for wideband applications, such as the
transmission of data and/or video.
[010] In particular, advantage is taken of the clear channel
detection and frequency agile functionality of the spectral
reuse transceiver of the '753 application to determine which
ones of a plurality of disjoint primary channels (that have
been licensed to the user or to one or more other users that
have agreed to share their licensed channel allocations) are
not being used (e.g., have released the push-to-talk buttons of
their radios) and, based upon this lack of use detection, to
effectively 'aggregate' these multiple disjoint channels into
an overall totality of potentially available bandwidth, the
spectral extent of which is at least sufficient to meet a
prescribed, relatively high bandwidth requirement (such as, but
not limited to the transmission of data and/or video), that
could not otherwise be satisfied by a conventional, single
channel radio.
[011] Typically, only a fraction or subset of this relatively
large number of frequency-hopped, narrowband subcarriers or
sub-channels into which the aggregated bandwidth is sub-
dividable will be required to satisfy the high bandwidth
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requirement for a given application (such as the transmission
of digital data). The frequency agile capability of the
spectral reuse transceiver of the '753 application is used to
selectively frequency hop among subcarriers or sub-channels of
respectively different sub-channel subsets, that are pseudo-
randomly assembled from among all of the available sub-channels
into which the aggregate band has been sub-divided.
BRIEF DESCRIPTION OF THE DRAWINGS
[012] Figure 1 diagrammatically illustrates a non-limiting
example of a distribution of relatively narrowband
communication channels of differing bandwidths that may be
licensed to a primary user of such channels;
[013] Figure 2 corresponds to Figure 1 of the above-referenced
'753 application and diagrammatically illustrates the
architecture of a communication network, respective terminal
unit transceiver sites of which employ the spectral reuse
transceiver disclosed in the '753 application; and
[014] Figure 3 diagrammatically illustrates the manner in which
the plurality of disjoint, different bandwidth user channels of
the channel distribution example of Figure 1 is aggregated into
an overall bandwidth or channel space that is subdivided into a
plurality of sub-channels, in accordance with the methodology
of the present invention.
DETAILED DESCRIPTION
[015] Before describing the details of the disjoint radio
channel aggregation methodology of the present invention, it.
should be observed that the invention essentially involves
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enabling the spectral reuse transceiver disclosed in the above-
referenced '753 application to perform additional functionality
- that of effecrtively aggregating a plurality of disjoint,
relatively narrowband (e.g., voice) RF channels into an overall
totality of potentially available bandwidth, that is
considerably wider than any individual licensed narrowband
channel, and is able to accommodate relatively wideband
applications, such as, but not limited to the transmission of
data and/or video.
[016] As will be described, this additional functionality is
readily implemented by simply setting the configuration
parameters that are used by the communications controller of
the transceiver disclosed in the '753 application to control
the operation of the transceiver. The architecture of the
transceiver of the 1753 application remains unchanged. As a
consequence, the present invention has been illustrated in the
drawings by readily understandable diagrammatic illustrations,
which include a generalized network architecture diagram, and a
channel aggregation and sub-channel sub-division diagram, that
show only those details that are pertinent to the invention, so
as not to obscure the disclosure with details which will be
readily apparent to one skilled in the art having the benefit
of the description herein.
[017] Attention is now directed to the RF communications network
architecture diagram of Figure 2, which corresponds to Figure 1
of the above-referenced '753 application. As shown in Figure. 2,
the network includes a hub, or 'master' terminal unit site 10,
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and a plurality of 'remote' terminal unit (RTU) sites 12, at
which spectral reuse transceivers of the type disclosed in the
'753 application are located. As noted above, except for the
manner in which the configuration parameters, used by the
communications controllers of 'these transceivers to control
their operation, are predefined in accordance with the primary
channel aggregation sub-channel hopping methodology of the
present invention, to limit the field of search of the clear
channel assessment routine (that is performed by transceiver to
locate available sub-channels among which it may hop) to
prescribed channels licensed to one or more primary users, the
architecture of the transceiver is unchanged.
[018] As the architecture and operation of the transceiver are
set forth in detail in the '753 application, they will not be
repeated here_ Instead, the following description will set
forth the manner in which -the spectral activity-based link
utilization control mechanism employed by the transceiver's
communication controller confines its clear channel assessment
routine to particularly identified primary channels, in
particular, those (typically disjoint) primary channels that
have been licensed to one or more prescribed primary users of a
given user band (e.g., the 217-220 MHz band), and an
aggregation of the respective bandwidth segments effectively
produces an overall bandwidth that enables the radio to be used
for wideband applications.
[019] To this end, in accordance with the aggregation
methodology of the present invention, and similar to the more
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generalized clear channel assessment routine described in the
'753 application, but delimited to the aggregated band of
channels licensed to the prescribed primary user(s), the master
site periodically initiates a clear channel assessment routine
that compiles a list of primary channels available for use in
wideband applications by the primary user(s), based upon an
examination of only primary communication channels which have
been licensed to a specifically identified primary user or
users. This primary channel allocation information, which is
directly obtainable from the FCC, is used to establish, a
priori, configuration parameters of the transceivers of the
prescribed primary user(s), so that the clear channel
assessment routine will be confined to only the pre-specified
channels of interest. The primary channels of the compiled list
will thus be those channels of the aggregated band which are
not being currently used, and are therefore available to sub-
divided into sub-channels that may be assembled in respective
sub-sets of sub-channels for use in a wideband application by
the primary channel user(s).
[020] By one or more primary users is meant that the invention
may be used to aggregate not only primary channels that have
been licensed to a single user, but primary channels that have
licensed to plural users who have decided to 'pool' their
resources, in order to increase bandwidth capacity. As a non-
limiting example, city and county.emergency service providers
may decide to aggregate their primary channels into. a single
aggregated band. As described above, since the channels
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allocated to these users are known, a priori, it is a simple
matter of configuring the configuration parameters of the
spectral reuse transceiver of the '753 application to limit its
search for available frequencies to only those channels that
have been allocated to the users of interest. To the
transceiver, channels are channels. The transceiver operates on
whatever channels are identified in accordance with its
configuration parameters.
[021] Thus, as in the case of the transceiver operation
described in the '753 application, except when transmitting a
message to the master node, each remote user site sequentially
steps through and monitors the current list of clear channels
(of the 'aggregated' band) that it has previously obtained from
the master unit, in accordance with a pseudo random hopping
sequence that is known, a priori, by all the users of the
aggregated band, for a message that may be transmitted to it by
the master site. During a prescribed time interval, such as the
preamble period of any message transmitted by the master, each
such user's transceiver scans all (6.25 KHz) sub-channels, or
frequency bins, within the aggregated band for the presence of
RF energy. Any bin containing energy above a prescribed
threshold is marked as a non-clear channel, while the remaining
channels of the aggregated band are marked as clear channels
available for wideband signaling applications.
[022] Whenever a remote site notices a change in its clear
channel assessment, it reports this to the master. at the first
opportunity. When the master site has received clear channel
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lists from all the remote sites, it logically combines all of
the clear channel lists from all the interrogated remote
transceivers to produce a composite clear channel list.
[023] This composite clear channel list is stored in the master
site's transceiver and is broadcast to all of the remote
transceivers over a prescribed one of the clear channels that
is selected in accordance with a PN sequence through which
clear channels are selectively used among the users of the
aggregated channel band. When the clear channel list is
received at a respective remote transceiver, it is stored.
[024] In order to ensure that all communications among the users
of the network are properly synchronized (in terms of the clear
channel list and the order through which the transceivers
traverse or 'hop' through the clear channel entries of the
list), the master site's transceiver transmits an
initialization message on an a priori established clear channel
(preamble channel), which each of the remote transceivers
monitors. This initialization message contains the aggregate
clear channel list, the preamble channel (and the next preamble
channel), a PN sequence tap list, and the PN seed that defines
the initial channel and hopping sequence for the duration of an
upcoming transmit burst. Once a remote transceiver has received
an initialization message, that transceiver transitions to
normal multiple access mode, as described in the '753
application. For further details of the transceiver with which
the invention may be employed,= attention may be directed to the
'753 application.
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[025] Attention is now directed to Figure 3, which illustrates
the manner in which the plurality of disjoint and differing
bandwidth (50 KHz, 25 KHz, 12.5 KHz and 6.25 KHz) primary user
channel segments of the example of Figure 1, described above,
are 'aggregated' in accordance with the present invention into
a composite channel space 15, as well as the subdivision of
this aggregation of primary channels into an associated
plurality of equal bandwidth (e.g., 6.25 KHz) narrowband sub-
channels within a sub-divided channel space 16. As described
previously, being disjoint user channels means that, within the
overall radio band 11, there are one or more additional
segments 12 of interleaved bandwidth, not allocated to primary
channel licensees, that occupy one or more portions of the
radio frequency spectrum between two or more of the primary
channels 14 that have been allocated to a prescribed user (or
users ) .
[026] As a result, even though a summation of the individual
bandwidths of the respective user channels 14 may produce a
relatively large accumulated or total bandwidth which, if
continuous, would readily accommodate'substantially any type of
communication signal (including, but not limited to, high
bandwidth video/imagery signals), the interleaved (non-user
channel) bandwidth segments 12 cause a fragmentation of the
user's overall licensed bandwidth into relatively small
bandwidth segments 14, which limits the potential utilization
of the ove.rall user channel bandwidth by a conventional fixed-
frequency, or manually channelized, radio, described above.
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[027] Pursuant to the bandwidth aggregation methodology of the
present invention, however, using a priori knowledge of this
allocation of the disjointed primary user channels 14 within
the primary user band 11, advantage is taken of the clear
channel assessment and sub-channel frequency hopping
functionality of the transceiver of the '753 application, to
enable that transceiver to confine its operational spectrum to
only those particular allocated primary user channels 14 within
the user's primary channel band 11. As diagrammatically
illustrated in Figure 3, this confinement of the transceiver's
operational spectrum may be represented as an aggregation of
the individual bandwidths of such channels into a composite
channel space 15, in which the respective narrow bandwidth
channels 14 within band 11 are shown as being mutually
spectrally contiguous with one another, in order to illustrate
the considerable overall bandwidth that is available within
these channels.
[028] In the illustrated example, therefore, the respective
disjoint channels 14 of the primary, user channel band 11 of
Figure 1 are shown as being effectively 'mapped' into mutually
abutting relationship as an aggregated channel space 15
comprising user channels 25 - 20 - 20 - 21 - 20 - 21 - 22,
which, as a whole, represent an overall bandwidth that is
considerably wider than any one of the disjoint channels. As
shown directly therebeneath, the aggregated channel space 15 is
subdivided into a plurality of relatively narrowband =sub-
channels lying within the sub-divided channel space 16. It. is
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these sub-channels onto which a relatively wideband signal,
such as but not limited to a digital data or video signal (the
data rate of which is considerably wider than any individual
one of of the disjoint narrowband channels 14) is modulated,
and among which the transceiver hops during a communication
session with the hub or master site, in the manner described in
the above-referenced '753 application. It should be noted that
the composite spectral representation of the channel space 15
does not mean that the channels 14 themselves have been
spectrally shifted or changed so that they become mutually
contiguous. The user channels 14 remain unchanged. Rather the
composite spectral space illustrates the overall or total
bandwidth that the transceiver of the 1753 application is able
to use for wideband signaling applications, by virtue of its
sub-channel frequency-hopping functionality.
[029] --In the example of Figure 3, each sub-channel wi=thin the
sub-divided channel space 16 has a bandwidth corresponding to
that of the narrowest channel bandwidth segment of all the
aggregated user channels. In the illustrated example, the
narrowest user channel bandwidth segment is 6.25 KHz -wide;
therefore, each sub-channel within sub-divided channel space 16
is a 6.25 KHz wide sub-channel. As such, within the sub-divided
channel space 16, the single 6.25 KHz wide user channel 25 of
channel space 15 will produce a single .6.25 KHz hopped sub-
channel 24, while each of the 12.5 KHz user channels 20 of
channel space 15 will produce a pair of mutually contiguous
6.25 KHz hopped sub-channels 17. In a like manner, each 25 KHz
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user channel 21 within channel space 15 will produce four sub-
channels, that include two 'outer' 6.25 KHz sub-channels 18
that are contiguous with the 'outer' edges of their associated
25 KHz user channel, and two 'inner' 6.25 KHz sub-channels 19,
that are contiguous with the center frequency of their
associated 25 KHz user channel. Similarly, the 50 KHz user
channel 22 of channel space 15 produces two pairs of mutually
contiguous 'inner' 6.25 KHz sub-channels 22, and two pairs of
contiguous 'outer' 6.25 KHz sub-channels 23.
[030j Now, although the channel space 15 of the illustrated
example is shown comprising allocated user channels that have
been aggregated from channels lying in a single band, it is to
be understood that the continuous channel space may be
aggregated from user channels lying in a plurality of bands,
without a loss in generality. It should also be noted that the
term 'band' is not limited to any particular portion or
portions of the radio frequency spectrum. For example, it may
cover the entire range of UHF frequencies (the UHF band). In
addition, or alternatively, it may also encompass
administrative or regulatory subdivisions of larger bands, such
as the 420-450 MHz UHF band, or the yet smaller police band
within the 420-450 MHz band.
[031] Since the functionality of the transceiver described in
the '753 application includes its ability to selectively
frequency hop among all (6.25 KHz) sub-channels, or any
selected number or sub-set, of- the sub-channels of the
(aggregated) channel space in a controlled manner, and to
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modulate an information signal of interest upon these hopped
sub-channels, in accordance with the aggregation methodology of
the present invention, that transceiver is able to optimize its
utilization of the total available bandwidth of all of the
disjointed user channels that have been mapped into the
aggregated channel space. This provides a significant
performance advantage over conventional fixed-frequency or
manually agile radios.
[032] For example, because the selective frequency-hopping radio
of the '753 application is able to selectively hop among (the
sub-divided sub-channels of) the entire aggregated allocation
of user channels, it is able to provide a significant gain in
throughput efficiency gain afforded by packet multiplexing. In
the case of voice applications, for example, conventional
analog push-to-talk radios may be unable to complete a call, if
the required allocation is not available. Namely, if no 25 KHz
user channel is available for a conventional 25 KHz radio, that
radio will be unable' to place a call, even if there are two or
more 12.5 KHz user channels available. On the other hand,
because the selective frequency-hopping radio of the '753
application used in the methodology the present invention is
able to frequency hop among any of the sub-channels within the
aggregated channel space, it is readily able to access the (25
KHz) bandwidth required to complete the call.
[033] It may be recalled that digital radios can provide voice,
video and data service capabilities at adjustable-or selectable
qualities of service and voice or ima-ge quality. In addition,
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spare capacity in the aggregated network may be used for a
variety of data services, including Ethernet bridging and IP,
which are not be readily available in conventional or trunked
analog voice services. The methodology of the present invention
enables the functionality of the spectral reuse radio described
in the '753 application to aggregate the various licensed
users' bandwidths, so that users may enjoy these and other
services.
[034] For example, one organization may have only conventional
or trunked analog radios, and therefore have no access to
digital services, such as Ethernet-bridging, IP (Internet
Protocol) applications and others. By using the spectral reuse
transceiver system described in the '753 application to
aggregate multiple disjoint bandwidth segments, users are able
to enjoy digital services. Users can employ the aggregated
bandwidth to- the extent that is appropriate to a respective
organization. For example, users of the aggregated bandwidth
may continue to use their analog radios in a normal manner as
well as for IP applications. Similarly, users may replace some
or all of their analog radios with the radio described in the
'753 application, and configured in accordance with the
invention to aggregate bandwidth, to take advantage of digital
services and more throughput-, as needed.
[035] As described briefly above, one example of an allocated
user band that is shared by a collection of organizations
which, individually, may have a relatively =small allocation=
but, as a whole, has a relatively large allocation, is the 450-
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470 MHz band in the United States. This band is available to
various public safety groups, such as firefighters and police,
as well as some businesses and other applications. Aggregating
some or all of the band allows all participants in the
aggregated bandwidth to have access to a much larger range of
dynamic bandwidth and provides for a host of new applications.
[036] One such application involves pooling all public safety
allocations; this enables various public safety organizations
to continue to use their present radio assets, while adding new
ones as needed for new services. An example of such a new
service is to provide critical imagery data, such as building
drawings, to fire department personnel in real time, prior to
having fire-fighters enter a distressed building. Providing
imagery data generally requires the use of IP service, which is
currently unavailable to many public safety organizations. For
example, pooling multiple public service allocations that
provide an aggregated bandwidth on the order of 200 KHz will
accommodate multiple sub-sets of forty (4 KB) sub-channels, the
composite bandwidth of each of which is 160 kilobits, which
will readily transport data and/or imagery.
[037] The bandwidth aggregation methodology of the invention may
also be used to provide a digital network for providing
communications between different public safety organizations
(inter-operability). It is presently estimated that such
communications will not be widely available in the United
States until the year 2023.at a cost of US .$60 billion, without
a significant change in current planning. Using the present
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invention to aggregate public safety bandwidth allocations
enables inter-operability at the network layer, rather than the
physical layer. This provides a significant advantage, since
achieving inter-operability using established network protocols
(such as IP) is much more obtainable than requiring all devices
(from various manufacturers) to have the same radio physical
layer. Using the invention to aggregate public safety bandwidth
for Internet access will allow police to quickly acquire
information about a suspect driver, for example. Providing
Internet access in this manner will also supply a conduit for
the above-referenced example of making building drawing images
available to fire department personnel.
[038] The invention may also be used to aggregate disjointed
public safety bandwidth into what may be termed an 'Event
Coordination Channel'. Such a channel may be used to provide a
special se-rvice through which various public safety
organizations may obtain information about a public safety
'event', such as a fire, explosion, or hostage situation.
Ideally, this Event Coordination Channel comprises a single
service that is available to all public service organizations,
and serves to produce more complete and consistent information,
compared to multiple, parallel services (or worse, no such
service). Such an aggregation of bandwidth allows commonly
available content management systems (CMSs) having various
security levels to be shared, so as to jointly produce event
information as it becomes available. The users of this s-ervice
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may select from a list of events on the radio access device to
view the information for a specific event.
[039] Aggregating public safety bandwidth allows the radio to
fall back to peer-to-peer operation, if the radio cannot reach
a radio repeater. This allows local communications at a site
where public safety workers are operating. Moreover, because
the radio can be managed remotely, priority can be given to
selected users, as necessary, e.g., based on circumstances or
events. For example, a large building fire may require that
bandwidth priority be given to firefighters and certain other
public safety groups. A flood, forest fire, terrorist activity,
hostage situation, or other event may present new sets of
priorities. One method of managing priority is to include an
electronic serial number (ESN) in the radio, by which a central
management system may set the current priority in the radios in
the network. The ESNs may contain sub-fields which identify,
for example, the organization, classes and subclasses within
the organization.
[040] The radios' repeaters may operate in a repeater-to-
repeater mode, as a backup, in case wired-connectivity between
repeaters becomes unavailable. This provides increased
robustness to the network. The repeaters may continuously poll
their neighbors over the wired network and fall back to
(possibly reduced bandwidth) radio connections. Another
advantage of the invention is that it allows users outside the
licensed group to employ the pooled bandwidth on a secondary-
use basis. This provides higher utilization of radio bandwidth.
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In the case of public safety frequencies, the ESN mechanism may
be used to disable secondary users during a public emergency.
[041] The interference-detection (clear channel assessment)
functionality of the spectral reuse transceiver of the '753
application may also be employed to enable sharing of the
continuous channel space resulting from the aggregation of the
disjointed user channels by a mixture of conventional and
digital radios. As described above, and in the '753
application, although interference-detection is customarily
used to avoid interfering with primary licensees, or other,
secondary licensees, the interference-detection functionality
of the spectral reuse transceiver may be used to detect the
activity of conventional radios that employ user channels
within the aggregated band on an equal basis with other radios
in the aggregated band. Licensees may be motivated to allow a
mixture of analog and digital radios due to the- cost of
complete equipment replacement; thus, some analog radios may
continue to operate without change, while the network enjoys
the advantages of the present invention, improving spectral
efficiency for new installations or replacement radios in a
phased replacement program.
[042] As will be appreciated from the foregoing description, by
taking advantage of the clear channel detection and frequency
agile functionality of the spectral reuse transceiver of the
'753 application, the bandwidth usage control methodology of
.the present invention enables that receiver to. effectively
'aggregate' disjoint user channels into an overall totality of
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WO 2007/108963 PCT/US2007/006078
potentially available bandwidth, the spectral extent of which
is at least sufficient to meet a prescribed, relatively high
bandwidth requirement (such as, but not limited to the
transmission of data and/or video), that could not otherwise be
satisfied by a conventional, single channel-based radio. The
frequency agile capability of the spectral reuse transceiver of
the '753 application is employed to selectively hop among sub-
channels of respectively different sub-channel subsets, that
are pseudo-randomly assembled from among all of the available
sub-channels into which the aggregate band has been sub-
divided.
[043] While we have shown and described an embodiment in
accordance with the present invention, it is to be understood
that the same is not limited thereto but is susceptible to
numerous changes and modifications as known to a person skilled
in the art, and we therefore do not wish to be limited to the
details shown and described herein, but intend to cover all
such changes and modifications as are obvious to one of
ordinary skill in the art.
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