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Description  |
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FIELD OF THE INVENTION
This invention relates to trunked communication systems, including but not
limited to repeater control in a trunked communication systems. Reference
is made to U.S. patent application Ser. No. 07/905,925, titled
"Intelligent Repeater for Trunked Communications," filed Jun. 29, 1992, on
behalf of Lynn M. Monica et al., with the same assignee as the present
invention.
BACKGROUND OF THE INVENTION
Trunked communication systems are known to comprise a plurality of
communication units, a limited number of communication resources that are
transceived via a predetermined number of repeaters, or base stations, and
a communication resource allocator that allocates the limited number of
communication resources among the plurality of communication units. The
communication units may be portable radios and/or mobile radios. The
communication resources may comprise a TDM (time-division multiplexed)
bus, telephone lines, a carrier frequency, a pair of carrier frequencies,
or any RF (radio frequency) transmission means.
Generally, trunked two-way communication systems provide mobile and
portable communication units with wireless services similar to many wired
communication networks. Such examples include full-duplex telephone voice
communication, two-way mobile-to-mobile group dispatch communication, and
two-way mobile-to-dispatcher group dispatch communication. A typical
trunked communication system site, where each different site has a
different physical location, is composed of a number of full-duplex
repeaters, each coupled to a variety of devices to support interconnection
to the public telephone network, mobile-to-mobile calling, and to one or
more dispatcher console positions. These devices typically provide a
centralized control for the repeaters. For example, a single central
controller provides radio channel signaling encode and decode functions,
authorization functions, resource determination functions, and
communication activity logging for multiple repeater resources. A single
telephone interconnect switch typically provides the repeaters with an
interface to one or more telephone lines to support telephone interconnect
communication. In systems employing a single device that is shared among
the repeaters, a failure of the single device may render one or more of
the desired services or functions inoperable, thus impairing
communications in the system.
One method of overcoming a single central controller problem is to
eliminate the use of a single central controller and use intelligent
repeaters that process and store control information, interface directly
to external communication networks, and distribute the needed system
functions throughout the intelligent repeaters. Although such a system has
many advantages over a system utilizing a single central controller, it
would be expensive to replace all of the current non-intelligent repeaters
with intelligent repeaters, particularly if the non-intelligent repeaters
are relatively new or have many useful years remaining.
Therefore, a method of providing centralized control of non-intelligent
repeaters without a central controller is desired.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an intelligent repeater interface for a
non-intelligent repeater in a trunked communication system in accordance
with the invention.
FIG. 2 is a diagram of an intelligent repeater and a non-intelligent
repeater with an intelligent repeater interface in a trunked communication
system with public network and private off-site network interfaces in
accordance with the invention.
FIG. 3 is a flowchart showing operation of a trunked communications system
using a non-intelligent repeater with an intelligent repeater interface in
accordance with the invention.
FIG. 4 and FIG. 5 depict a flowchart showing operation of a trunked
communications system using multiple intelligent repeaters and/or
non-intelligent repeaters with intelligent repeater interfaces in
accordance with the invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
The following describes a method and apparatus that enables continuous
service in a trunked communication system by eliminating the dependence on
single shared devices for system control. Each of a plurality of repeaters
is equipped with an arrangement of components that uniquely distribute
these service functions. The functions of radio channel signaling encode
and decode functions, authorization functions, resource determination
functions, and communication activity logging are distributed among the
repeaters such that function placement adaptation insures continued
service operation.
A block diagram of an intelligent repeater interface for a non-intelligent
repeater in a trunked communication system is shown in FIG. 1. The
combination of an intelligent repeater interface 101 and a non-intelligent
repeater 102 interact with a communication unit 118 with radio frequency
(RF) signals 116 and 117. In the preferred embodiment, the intelligent
repeater interface 101 includes a signal processor 104, a central
processing unit (CPU) 103, memory 107 for storage of information, and a
switch 106. Also included are interfaces for interfacing control
information and processed signals directly to an external communication
network. These interfaces include, for example, a public interface 108 and
111, a private off-site interface 109 and 112, and a private on-site
interface 110 and 113. In the alternative, two or more non-intelligent
repeaters 102 and 119 may be attached to the intelligence interface 105.
RF signals 116 transmitted by a communication unit 118 are received by the
receiver of a conventional non-intelligent repeater 102 through its
receive antenna. These transmissions may be modulated using a variety of
techniques known in the art, such as, frequency modulation (FM), amplitude
modulation (AM), or a combination of the two. Further, the signals carried
by the modulation may be frequency and/or time division multiplexed. After
reception, the signals are transferred via the signal/control interconnect
115 to an intelligence interface 105 within the intelligent repeater
interface 101. The received signals are buffered and/or multiplexed as
necessary in the intelligence interface 105, digitized if necessary, and
sent on to the signal processor 104, which may be a digital signal
processor or DSP (e.g., a DSP56001 available from Motorola, Inc.), for
further decoding and processing. Control information is extracted from the
signal and transferred to the CPU 103, which may be a microprocessor
(e.g., an MC68302 microprocessor available from Motorola, Inc.). Other
information present in the signal such as voice, images, and user data are
transferred to the switch 106, which may be a cross-point matrix, time
slot interchanger, or multiple-access packet link for routing. The switch
provides a means to transfer control signals and information signals
between the radio channel, the public network, the private off-site
network, and the private on-site local area network (LAN). The other
information may also be transferred, if necessary, to memory 107, which
may be random access memory (RAM), for temporary storage.
Control information generated by the non-intelligent repeater, that is,
control information not embedded in the received signal, is also routed
via signal/control interconnect 115 to the intelligence interface 105 in
the intelligent repeater interface 101. The control information from the
non-intelligent repeater typically contains information about the receiver
and transmitter status. For example, it may simply be signal lines that
are switched to ground potential whenever the receiver is in an
unsquelched condition, when the transmitter is operating at full power, or
it may contain other information such as received power level, transmit
power level, or received signal to noise measurements. The intelligence
interface 105 buffers the incoming control information which is then sent,
via a control bus 114, to the CPU 103 for processing.
Control information that is embedded with the received signal is extracted
by the signal processor 104 and delivered to the CPU 103. This embedded
control information may contain such things as the communication unit's
individual and group identifications (IDs), and type of service requested.
The CPU 103 uses this information in a manner described in FIG. 3, FIG. 4,
and FIG. 5 to allocate resources and communicate with other system
elements in order to appropriately serve the communication unit 118. The
memory 107 is also used by the CPU 103 during the normal course of its
processing to store and retrieve control information and program steps, as
those represented in FIG. 3, FIG. 4, FIG. 5, system database information,
and any dynamic parameters needed during program execution.
The switch 106, under control of the CPU 103, routes information from the
signal processor 104 to one or more of the interfaces 108, 109, and 110.
The content of the signal information and the configuration of the
external network(s) determine to which interface(s) the information is
routed. The public interface 108, if needed, is connected to one or more
of many different public networks 111. The public interface 108 may be a
standard telephone subscriber loop line, or it may be a standard data
network line, such as one from an X.25 standard public packet data
network. The private off-site interface 109, if needed, is typically
connected to a private communications network 112 that is used to connect
other sites of a multi-site radio network. The private off-site network
112 may be constructed of 4-wire analog lines, time division multiplex
carriers, packet data links, and so forth. The private on-site interface
110 is connected to a LAN 113 that forms a communication link shared by
other intelligent repeaters and intelligent repeater interfaces connected
to non-intelligent repeaters of the system that are located at the same
communication site, i.e., the same physical space where the intelligent
repeaters and the intelligent repeater interfaces and their associated
non-intelligent repeaters are located. The LAN 113 that the private
on-site interface 110 is connected to may be a standard LAN, such as a
LocalTalk LAN, an Ethernet LAN, or an FDDI (Fiber-Optic Distribution Data
Interconnect) LAN.
The switch 106 is also used to route information that flows into the
intelligent repeater interface 101 from the interfaces 108, 109, and 110,
to the signal processor 104. These signals are then processed by the
signal processor 104 where any embedded control information needed by the
trunking system is added. This embedded control information may include
filtered subaudible data or any other form of interleaved data that is
used by the communication unit 118. These processed signals are then
transferred to the intelligence interface 105, where they are buffered and
transferred to the non-intelligent repeater 102 via signal/control
interconnect 115 and subsequently transmitted to the communication unit
118 using the non-intelligent repeater's transmit antenna. The RF signal
117 that is transmitted to the communication unit 118 may be modulated
using any of the modulation techniques described above.
The non-intelligent repeater 102 also receives control information from the
intelligent repeater interface 101 via the signal/control interconnect
115. This control information typically contains information used to
control various aspects of the non-intelligent repeater 102 such as
Push-to-Talk (PTT), transmitter mute, control channel indication, and so
forth. This control information originates from the CPU 103 and is
transferred to the intelligence interface 105 via the control bus 114,
where it is buffered and transferred to the non-intelligent repeater 102
through signal/control interconnect 115. This control information, like
the control information that is originated by the non-intelligent repeater
102, may be activated by a simple connection to ground potential, or it
may be a serial or parallel data stream that may carry information such as
desired transmit power level, allowable inbound private line tone
frequencies, and so forth.
Some signals to and from the interfaces 108, 109, and 110 may be
transferred directly between the interfaces 108, 109, and 110 as well as
the CPU 103 using a control bus 114, which may be a multi-drop parallel
data bus, serial data bus, or a time division multiplexed parallel or
serial bus. In the preferred embodiment, each of the interfaces 105, 108,
109, and 110 contains a microprocessor (e.g., an MC68302 microprocessor)
that monitors the signal flow and determines whether the signals should be
transferred to the CPU 103 or to the signal processor 104 via the switch
106.
A diagram of one or more intelligent repeaters 203 and non-intelligent
repeaters 202 and 216 with intelligent repeater interfaces 201 and 215 in
a trunked communication system with public network 210 and private
off-site network 209 interfaces is shown in FIG. 2. In a trunked radio
system, there may be one or more intelligent repeaters 203 and/or
combinations of intelligent repeater interfaces 201 and 215, as shown by
reference numeral 101 in FIG. 1, and non-intelligent repeaters 202 and 216
located at one or more physical locations or sites. A single system may
use any combination of intelligent repeaters 203 and intelligent repeater
interfaces 201 and 215 with non-intelligent repeaters 202 and 216,
including exclusively intelligent repeaters or exclusively intelligent
repeater interfaces 201 with non-intelligent repeaters 202 and 216. The
number of intelligent repeaters 203 or controlled non-intelligent
repeaters 202 and 216 needed per location is based on the required
capacity of the sum of the interfaces provided in terms of radio channel
and external network interfaces. The locations of sites are chosen based
on the desired RF coverage of a particular geographical area. Although the
system may contain many of each, one or more intelligent repeaters 203,
two intelligent repeater interfaces 201 and 215 with non-intelligent
repeaters 202 and 215, and two communication unit 206 are shown in FIG. 2
for the sake of simplicity of the drawing. For simplicity of narration in
the remainder of this description, whenever an intelligent repeater
interface is referred to, it will be assumed that a non-intelligent
repeater is connected to that intelligent repeater interface.
Communication between the intelligent repeaters 203 and intelligent
repeater interfaces 201 is necessary to enable the system's repeaters to
operate in concert to provide consistent services. This communication is
provided by assigning each component of the call establishment process to
the communication units 206, because those units roam throughout the RF
coverage area. For example, at a particular site, a specific intelligent
repeater 203 or intelligent repeater interface 201 may be dedicated to
transceiving control information to and from the communication units 206.
This particular repeater is considered to provide the "control channel," a
term well known in the art. Other intelligent repeaters 203 or intelligent
repeater interfaces 201 may be present at the site to be used for
transceiving the typical voice, data, or image messages to and from the
communication units 206. When a communication unit 206 makes a request for
service on the control channel, that information is passed via the private
on-site network 207 to the other intelligent repeaters 203 and intelligent
repeater interfaces 201 and 215 at the site for request authentication and
appropriate resource allocation in accordance with the methods described
below. As a second example, when a communication unit 206 roams from the
coverage area of one site into the coverage area of another, information
is passed via the private off-site network 209 using communication links
211 and 212 such that appropriate resources may be placed into service at
the new site, while the resources that were in service at the old site are
deactivated. As a third example, a communication unit 206 may request a
telephone interconnect call. To connect this type of service to the
communication unit 206, the intelligent repeater 203 or intelligent
repeater interface 201 that is transceiving the communication unit's RF
signals 204 and 205 is typically connected directly into the public
telephone network 210 via a standard telephone line 213 or 214.
A flowchart depicting operation of a trunked communications system using a
single intelligent repeater interface connected to a non-intelligent
repeater is shown in FIG. 3. The non-intelligent repeater 102 receives a
request for service 116 from a communication unit 118 and transfers it
directly to the intelligent repeater interface 101 at step 301. The
intelligent repeater interface 101 decodes the request at step 302 using
the signal processor 104 and CPU 103 to determine what type of service is
required by the communication unit. The request is authorized at step 303
by scanning a list stored in memory and comparing the ID of the
communication unit sourcing the resource request to the stored list, which
is a predetermined list of authorized IDs and the resources each ID may
access, as different communication units may be authorized to use only
certain communication resources. If the communication unit that sourced
the request is not authorized for the requested communication resource,
the request is rejected at step 304, which entails transmitting a
rejection message to the requesting communication unit, and the processing
ends for this call request.
If at step 303 the communication unit that sourced the request is
authorized to use the requested communication resources, the appropriate
resources needed to service the request are determined at step 305. If at
step 306 the resource required is a public resource, the public interface
is connected to the public resource via the switch 106 at step 307. If at
step 308 the resource required is a private off-site resource, the private
off-site interface is connected via the switch 106 at step 309. The
non-intelligent repeater 102, operably coupled to the intelligence
interface 105, which is in turn operably coupled to the signal processor
104, is also connected via the switch 106 at step 310, and processed
signals are transferred between the communication unit and the requested
resources, thus communications occur.
These connections remain until the completion of the call at step 312, when
the resources are disconnected at step 313 by deactivating the interfaces
and stopping the transfer of processed signals through the switch 106. The
call is logged at step 314 by storing information such as the
communication unit's individual and/or talkgroup IDs, the duration of the
call, and the types of resources used.
A flowchart depicting operation of a trunked communications system using
multiple intelligent repeaters and/or intelligent repeater interfaces at a
trunked communication site is shown in FIG. 4 and FIG. 5. Because an
intelligent repeater interface connected to a non-intelligent repeater is
intended to provide the same functions within a system as an intelligent
repeater, an intelligent repeater may be substituted for an intelligent
repeater interface connected to a non-intelligent repeater without loss of
system function. For simplicity of narration, the description for FIG. 4
and FIG. 5 is written with the assumption that the particular site
described within the system is comprised entirely of intelligent repeater
interfaces connected to non-intelligent repeaters.
An intelligent repeater interface 101 supporting control channel
communications, where resource requests are received from communications
units and resource grants and transmitted in response, receives a resource
request sourced by a communication unit at step 401. In the preferred
embodiment, the communication unit 118 encodes the information in the
resource request with an error control coding method to provide reliable
operation in the RF environment. The intelligent repeater interface 101
supporting the control channel operations decodes 402 the information in
the requesting transmission. The request information contains an ID of the
requesting communication unit 118 and also indicates what type of service
is requested.
The present invention enables the distribution of the component tasks of
the call establishment process. Accordingly, the intelligent repeater
interface supporting the control channel operations decides which of the
intelligent repeater interfaces will authorize access for the
communication resource request at step 403. Each intelligent repeater
interface has a list of which intelligent repeater interface and
intelligent repeater is assigned to carry out each component of the call
establishment process so that each step is directed to the appropriate
entity. The appropriate intelligent repeater interface is either the same
intelligent repeater interface, the local choice, or another intelligent
repeater interface. If the authorization function is carried out by
another of the intelligent repeater interfaces, then the request
information is transmitted via the private on-site interface over the site
LAN at step 404 to the intelligent repeater interface that will carry out
the authorization at step 405. At step 406, the intelligent repeater
interface assigned to carry out the authorization compares the identity of
the requesting communication unit against a predetermined list of
authorized communication unit IDs, as was previously described. If at step
406 the requesting communication unit's ID is not authorized for access,
the request is rejected at step 407, which entails transmitting a
rejection message to the requesting communication unit, and the process
ends for this call request.
If at step 406 the requesting communication unit is authorized for access,
the intelligent repeater interface supporting the control channel
operations establishes at step 408 which of the intelligent repeater
interfaces or intelligent repeaters will determine the required
communication resources to fulfill the communication resource request. The
appropriate intelligent repeater interface is either the same intelligent
repeater interface, the local choice, or another intelligent repeater
interface. If the resource determination function is carried out by
another of the intelligent repeater interfaces, then, at step 409, the
request information is transmitted via the private on-site interface over
the site LAN 207 to the intelligent repeater interface that will carry out
the resource determination. At step 410, the intelligent repeater
interface assigned to carry out the resource determination analyzes what
resources are required by looking at the type of service requested and
matching it against a predetermined list of resources required for that
service and checking if the resource(s) is available for that type of
call, and the process continues with step 411. A radio channel resource is
chosen to serve the requesting communication unit.
The intelligent repeater interface providing the radio channel resource may
also be interconnected to the public telephone network and/or to a private
network to establish the desired service. Depending on the availability of
the public interface and private off-site interface locally associated
with the intelligent repeater interface, the interconnect may be routed
through the private on-site interface to the LAN 207 and to another
on-site intelligent repeater interface with an available public network or
private off-site network resource. In this way, the distributed resources
of the plurality of intelligent repeater interfaces and non-intelligent
repeaters at the trunked communication site are utilized to maintain
communications at all times.
The intelligent repeater interface supporting resource allocation decides
whether public and private network resources are to be used, and if so,
whether the resources are local or non-local. At step 411, the need for a
public resource is considered. If at step 411 the public network is not
required, the process continues with step 504 of FIG. 5. If a public
interface is required, its local availability is considered at step 501 of
FIG. 2. If at step 501 a public interface is not available within the same
intelligent repeater interface, then a connection is made at step 502
through the on-site LAN 207 to an on-site intelligent repeater interface
with an available public network resource (interface 108). If at step 501
the local public network interface is available, it is connected within
the same intelligent repeater interface at step 503, and the process
continues with step 504.
At step 504, the need for a private resource is considered. If at step 504
the private network is not required, and the process continues with step
508. If a private interface is required at step 504, its local
availability is considered at step 505. If a private interface is not
available within the same intelligent repeater interface, then a
connection is made at step 506 through the on-site LAN 207 to an on-site
intelligent repeater interface with an available private network resource
(interface 109). If at step 505 the local private network interface is
available, it is connected within the same intelligent repeater interface
at step 507.
The network interfaces chosen and assigned are connected at step 508 to the
chosen non-intelligent repeater radio resource, such as a frequency-pair
channel to complete the requested call which transfers processed signals
at step 509. Processed signals may be voice, data, and image information
carried in any one of many formats by different physical media. This
process then continues with step 510.
The intelligent repeater interface tests to see if the call is done at step
510. When the call is completed, the communication unit transmits a call
end signal that is detected and transferred to the intelligent repeater
interface that provided the resources. The resources allocated to the call
are disconnected by stopping the transfer of processed signals at step
511. At step 512, a decision is made where to log the call activity.
Logging typically involves storing key statistics related to the call into
the memory of the intelligent repeater. If the intelligent repeater
interface that is assigned the logging function is not the intelligent
repeater interface that provided the radio link, then the call information
is passed to that logging intelligent repeater interface over the on-site
LAN 207 at step 513. The call information is logged into the memory of the
appropriate intelligent repeater interface at step 514, and the process
ends.
A communication system designer may see fit to incorporate additional
intelligent repeater interfaces without connection to a non-intelligent
repeater in order to gain extra public 108, private off-site 109, and/or
private on-site 110 interfaces to maximize the ability to provide
communications services to its users. An extra intelligent repeater
interface may be provided for redundancy to prevent lost communications.
At the other extreme, two or more non-intelligent repeaters may be
attached to a single intelligent repeater interface, which then acts as a
central controller that provides public and private interfaces.
A network of distributed processing elements operates together when each
element has been assigned a particular task(s) related to the overall
objective. Thus, call processing functions are distributed amongst a
plurality of intelligent repeater interfaces and/or intelligent repeaters.
In a trunked communication system site comprised of intelligent repeater
interfaces operably coupled to non-intelligent repeaters, each intelligent
repeater interface is capable of performing each component, or function,
of the call process, e.g., receiving a resource request over the
non-intelligent repeater's radio channel, decoding the request,
authorizing access, determining the required resources, connecting the
resources, and logging the call summary. In the present invention, when a
plurality of such intelligent repeater interfaces and non-intelligent
repeaters comprise a trunked communication system, the components of the
call establishment process may be distributed among the intelligent
repeater interfaces that are capable of each component task. Such an
arrangement is desired to provide non-stop system operation in the event
that one of the intelligent repeater interfaces suffers a partial or
complete failure. The assignment of the call components may be carried out
such that the combination of the intelligent repeater interfaces and their
associated non-intelligent repeaters work efficiently together to provide
the desired communication services.
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