METHOD OF ESTABLISHING COMMUNICATION BETWEEN INDEPENDENT COMMUNICATION SYSTEMS

Abstract: In one embodiment, independent communication systems (101 and 102) are provided with additional receivers (112 and 113) that allow the systems to monitor one anothers' outbound control signalling channels. Secondary control signalling (204) can be interleaved with the primary control signalling (201) information on this communication resource, which secondary control signalling information is intended for reception and use by the monitoring system. In another embodiment, communication systems (301 and 302) having dedicated communication resources are provided with receivers (311 and 316) that monitor the communication resources of other communication systems. Communications between communication units (321 and 323) in various systems are interchanged through appropriate interaction of the repeaters and the dedicated receivers so provided. In another embodiment, communication systems (401 and 402) having dedicated communication resources are provided with receivers (416) that monitor the communication resources of other communication systems, and roamers (423) are preregistered (431) in non-home systems. Using this infrastructure, a group call can be sourced in one system and relayed to roamers located in other systems.

Description: Method of Establishing Communication between indepenrjpi f -*t Communication System". Technical Field This invention relates generally to communication systems, and more particularly to interlinked trunked communication systems. Background Art Trunked communication systems are known in the art. In general such systems include a resource controller (which may be centrally located or distributed) that manages communications between communication units (such as fixed location, mobile, and portable two-way radios) on a plurality of communication resources (such as frequency pairs or TDM time slots) that are supported by a plurality of corresponding repeaters. A number of such systems are available, including the Smartnet and Privacy Plus systems from Motorola, the Clearchannel LTR system from E.F. Johnson, and the Sixteen Plus and Sweet Sixteen systems from General Electric. In general, such systems tend to operate independent of one another. Therefore, a communication unit located in a first system will generally not be able to communicate with a second communication unit located in a second communication system. Some prior art systems interlink one or more communication systems through use of an appropriate dedicated landline. So configured, communication units in different communication systems may be able to communicate with one another. Such an approach, however, poses several disadvantages, including increased cost and relative inflexibility. In addition, even when so linked, such solutions do not readily accommodate group calls. A need exists for a system and method for economically and flexibly interlinking two or more communication systems. Summary of the Invention This need is substantially met through provision of the intersystem communication system disclosed herein. This system functions in conjunction with at least two communication systems that each include a set of communication resources and resource controllers for controlling allocation of these resources. Pursuant to various embodiments of this invention, one or more of these communication systems are also provided with one or more supplemental receivers that are at least substantially compatible with the communication resources that are ordinarily used in the opposing system. So configured, communication requests sourced from a first system can be received by the a second system having such a supplemental receiver tuned to the appropriate resources of the first system, and thereafter be properly processed. In one embodiment, each communication system is provided with a receiver that is compatible with the control communication resource, such as a dedicated control channel, of an opposing system. So configured, communications sourced from one system can be received by the other system and properly processed. In another embodiment, a receiver can be provided to accommodate each communication resource supported by the other communication system. This embodiment offers a high degree of flexibility in communication resource allocation. In another embodiment, the control communication resource supports both primary control signalling used by member communication units of the communications system to facilitate allocation of the communication resources amongst the member communication units. In addition, this control communication resource also supports secondary control signalling that is intended for and used by a second communication system to facilitate system to system communications. In yet another embodiment, the primary control signalling and the secondary control signalling can be transmitted at different data rates, wherein the secondary control signalling is transmitted at a higher data rate. In yet another embodiment, communication units that belong to a common fleet or group share, at least in part, a common group ID in each system. For example, a first ID is used while communicating within the home system. The home system recognizes this ID as representing a local group or fleet. A second ID can also be used by the radios that comprise the group or fleet when in a second system. This second ID is preregistered in the second system as a roaming ID, along with information regarding the home system that corresponds to that particular ID. In a similar manner, additional IDs can be used with different systems for which the radios are preregistered as roamers. When such a non-home system determines that a preregistered roamer has entered its system, the non-home system will use its supplemental receiver to monitor the communication resources of the home system for that roamer. Communications from the home system that are intended for the roamer can then be intercepted and forwarded on to the roamer through use of the non-home system resources. Brief Description of the Drawings Fig. 1 comprises a block diagram depiction of a first embodiment of the invention; Fig. 2 comprises a timing diagram of the control communication resource in accordance with the first embodiment; Fig. 3 comprises a block diagram depiction of a second embodiment of the invention; and Fig. 4 comprises a block diagram depiction of a third embodiment of the invention. Best Mode For Carrying Out The Invention Referring to Fig. 1 , a first embodiment can be seen as depicted generally by the numeral 100. The system (100) operates in conjunction with other communication systems. For purposes of this description, only two such communication systems (101 and 102) will be described. The first communication system (101) includes a resource controller (103) that functions to control allocation of a first set of communication resources. In this embodiment, it will be presumed that the communication resources are supported by a plurality of repeaters (104), and that the communication resources themselves comprise a first set of three frequency pairs A- C. In addition, for purposes of this description, it will be presumed that one of the repeaters (104) supports system control information related to resource allocation requests and grants. Such system control information intended for member communication units (106) of that system (101 ) is referred to herein as primary signalling information. The resource controller (103) controls the repeaters (104) and interchanges resource allocation request and grant information as primary control signalling through the repeaters (104) via an appropriate link (107) as well understood in the art. A second communication system (102) similarly includes a resource controller (108), repeaters (109) (that support communication resources D-F), and an appropriate link (111 ) therebetween. In this embodiment, the communication resources A-C of the first system (101) are different from the communication resources D-F of the second system (102). Therefore, the two systems (101 and 102) are not able to communicate directly with one another through the repeaters provided. Pursuant to this invention, each system (101 and 102) is also provided with a receiver (112 and 113) that is capable of compatibly receiving at least one communication resource of the other system. In this embodiment, the communication resource so received is the control communication resource. Received signalling information is then coupled from the receiver (112 and 113) to the associated resource controller (103 and 108, respectively) via an appropriate link (114 and 115, respectively). So tconfigured, the resource controller (103 and 108) are capable of monitoring the control communication resource of the other system. With reference to Fig. 2, the signalling as supported by the control communication resource of each system (101 and 102) will be described. The outbound primary control signalling uses a slotted Aloha channel access protocol. Typically, outbound primary control signalling words (PCS) (201) are sourced by the resource controller and transmitted by the appropriate control communication resource repeater. These PCS (201) data transmissions are interleaved with appropriate synchronization words (202). Further, a system ID (203) is occasionally transmitted, all as well understood in the art. Pursuant to this invention, the next available data slot (204) following the system ID (203) supports an outbound secondary control signal (SCS) intended for the adjacent communication system. By using the system ID (203) as the marker, the adjacent system can correctly identify and respond as appropriate to the secondary control signalling that has been transmitted by the sourcing system. Typical outbound primary control signalling words (201 ) usually contain 76 bits of information, plus an additional 8 bits of frame sync information. In one embodiment of this invention, the secondary control signalling word (204) can utilize a higher bit rate, thereby increasing the data rate by perhaps a factor of 10. For example, the outbound secondary control signal word could hold from 760 to 840 bits of data presuming a transmission rate of about 36 K BPS. By using this higher data rate, capacity of the control communication resource will not be substantially impaired. At the same time, the high bit rate will provide satisfactory performance because only fixed site to fixed site communications need be supported. So configured, a resource controller can source an appropriate secondary control signal intended for reception and processing by another communication system. Such information could be, for example, to establish intersystem communications between communication units (106) as described below in more detail. Referring to Fig. 3, a second embodiment can be seen as depicted generally by the numeral 300. The system (300) again operates in conjunction with other communication systems. For purposes of this description, only two such communication systems (301 and 302) will be described. The first communication system (301 ) again includes a resource controller (303) that functions to control allocation of a first set of communication resources. In this embodiment, it will be again presumed that the communication resources are supported by a plurality of repeaters (304), and that the communication resources themselves comprise a first set of frequency pairs A-C, and that one of the repeaters (304) supports system control information related to resource allocation requests and grants. The resource controller (303) controls the repeaters (304) and interchanges resource allocation request and grant information through the repeaters (304), via an appropriate link (306). The second communication system (302) similarly includes a resource controller (307), repeaters (308) (which support communication resources D-F) and an appropriate link (309) therebetween. In this embodiment, the communication resources A-C of the first system (301 ) are different from the communication resources D-F of the second system (302). Therefore, the two systems (301 and 302) are not able to communicate directly with one another through the repeaters provided. In this embodiment, the first communication system (301 ) also includes a plurality of receivers (311 ) that are capable of compatibly receiving the communication resources D-F of the second communication system (302). Although it would not necessarily be required that a receiver (311) be provided to accommodate each communication resource of the opposite system, in this embodiment such a receiver (311) has been so provided. An appropriate communication link (312) is provided between the receivers (311 ) and the resource controller (303) to allow operation of the receivers (311 ) to be controlled, at least in part, by the resource controller (303), and also to allow the resource controller (303) to receive signalling information as received by the receivers (311) and as sourced from the resource controller (307) of the second system (302). In addition, an appropriate link (313) is provided between the receivers (311 ) and the repeaters (304) of the first system (301 ). This link (313) is appropriately gated (314) to allow the resource controller (303) to control provision of signals received by the receivers (311 ) to the repeaters (304). So configured, the resource controller (303) can cause a particular repeater (304) to retransmit a communication, such as a voice message, that has been received by one of the receivers (311 ). A similar group of receivers (316), links (317 and 318) and gate unit (319) are provided in the second communication system (302) to provide an identical configuration as that described above. Operation of this embodiment may now be described. A first communication unit (321 ) situated within range of the first communication system (301 ) initiates the process by transmitting a request (322) to communicate with one or more other communication units (although this request could be to communicate with a particular identified talk group, for purposes of simplicity, this description will presume that the first communication unit identifies a particular second communication unit (323) as the desired communication target). This talk request is transmitted on the appropriate control resource for the first communication system (301), and is relayed by the appropriate control resource repeater (304) to the resource controller (303) for the first communication system (301). If the resource controller (303) recognizes the communication target as being local (as may be determined, for example, by the ID of the communication target), then the resource controller (303) can allocate a communication resource to support the requested communication as is currently done in the prior art. If, however, the resource controller (303) determines that the communication target is not local (or, if dealing with a talk group, is not completely local in all instances), then the resource controller -can transmit, on the control resource, an outbound signalling word constituting a notification that a communication with the second communication unit is desired. This outbound communication (324) as sourced by the resource controller (303) and as transmitted by the appropriate control resource repeater (304) will be received by whichever of the receivers (316) in the second communication system (302) is monitoring that particular communication resource of the first system (301 ). That particular receiver (316) will then provide the signalling information via the appropriate link (317) to the resource controller (307) for the second communication system (302). If the second resource controller (307) recognizes the identified communication target as local, the resource controller (307) will assign one of its communication resources to support the communication, and will provide information identifying the allocated resource in an outbound transmission (326) on its control resource. This transmission (326) will be received by the second communication unit (323) and cause the second communication unit (323) to begin monitoring the allocated communication resource of the second communication system. This outbound transmission (326) will also be received by the corresponding receiver (311) of the first communication system (301 ). This received signalling information will be provided to the resource controller (303) thereof via the appropriate link (312). The resource controller (303) can now determine that the communication target has been located and that a communication resource in the second system (302) has been assigned to support the desired communication, will now assign one of its own communication resources to the first communication unit (321 ) to support the communication. Thereafter, the first communication unit (321 ) will transmit its messages (for example, voice messages) using communication resources of the first communication system (301). The repeater (304) in the first communication system (301) assigned to support this communication will receive these signals from the first communication unit (321) and will repeat them on the allocated communication resource (327). The repeated voice message (327) will be received by the appropriate receiver (316) in the second communication system (302). The resource controller (307) in the second communication system (302) will gate (319) this received voice message to the repeater (308) that has been assigned to support this communication. The assigned repeater (308) will then retransmit the received signal (328) and this retransmission will be received by the second communication unit (323). If the second communication unit (323) were to transmit a response to the first communication unit (321 ), the same procedure could be implemented in reverse in a transmission trunked mode, or the already allocated resources could be used in a reversed pattern to accommodate a message trunked methodology. In Fig. 4, a third general embodiment can be seen as depicted generally by the numeral 400. In this embodiment, the first communication system (401) comprises a home system. As before, this system includes a resource controller (403) that functions to control allocation of a first set of communication resources for benefit of a plurality of member communication units. In this embodiment, it will be presumed that the communication resources are supported by a plurality of repeaters (404), that the communication resources themselves comprise a first set of frequency pairs A-C, and that one of the repeaters (404) supports system control information related to resource allocation requests and grants. The resource controller (403) controls the repeaters (404) and interchanges resource allocation request and grant information through the repeaters (404), via an appropriate link (406). The second communication system (402) similarly includes a resource controller (407), repeaters (408) (which support communication resources D-F) and an appropriate link (409) therebetween. In this embodiment, the communication resources A-C of the first system (401 ) are different from the communication resources D-F of the second system (402). Therefore, the two systems (401 and 402) are not able to communicate directly with one another through the repeaters provided. The second communication system (402) also includes a plurality of receivers (416) that are capable of compatibly receiving the communication resources A-C of the home communication system (406). Although it would not necessarily be required that a receiver (416) be provided to accommodate each communication resource of the opposite system, in this embodiment such a receiver (416) has been so provided. An appropriate communication link (417) is provided between the receivers (416) and the resource controller (407) to allow operation of the receivers (416) to be controlled, at least in part, by the resource controller (407), and also to allow the resource controller (407) to receive signalling information as received by the receivers (416) and as sourced from the resource controller (403) of the home system (401). In addition, an appropriate link (418) is provided between the receivers (416) and the repeaters (408) of the second system (402). This link (418) is appropriately gated (419) to allow the resource controller (407) to control provision of signals received by the receivers (416) to the repeaters (408). So configured, the resource controller (407) can cause a particular repeater (408) to retransmit a communication, such as a voice message, that has been received by one of the receivers (416). If desired, a similar group of receivers, links, and gate unit may be provided in the home communication system (401) to ørovide an identical configuration as that described above for the second system (402). The plurality of member communication units for the home system will typically include one or more fleets or groups. Pursuant to this invention, each such group is assigned an ID for each system that the radios are preregistered with. This preregistration includes information regarding whether the ID represents a local group or roaming group. If the ID relates to a roaming (non- home) group, then the preregistration information should also include information regarding the home system for that group, including control resource information and the group ID for that home system. To accomplish this, the resource controller (407) for the second system (i.e., the non-home system) can be provided with an appropriate data base (431) that retains such information regarding the preregistered IDs. Operation of this embodiment may now be described. A communication unit (423) that belongs to a home system group roams out of the home system (401) and into range of the second system (402). This communication unit (423) then locates the appropriate control resource for this system (this can be done in a number of ways; for example, the communication unit (423) can be previously provided with a list of likely adjacent control resources, or the unit (423) can automatically scan for a control resource when it loses the control resource for its home channel) and transmits (432) a message to the resource controller (407) for the second system to inform the second system of its presence. This message includes the preregistered ID, which the resource controller (407) compares against its database (431) to identify the roaming unit (423) as belonging to a preregistered group from the first system (401 ). The resource controller (407) for the second system can then determine that a roamer from the first system (401) has entered the second system (402), and a receiver (416) can be assigned to monitor the control resource of the first system (401 ). A different communication unit (421), belonging to the group having the preregistered ID and being situated within range of the first communication system (401), may at any moment initiate a group call by transmitting a request (422) to communicate with its group. This talk request is transmitted on the appropriate control resource for the first communication system (401), and is relayed by the appropriate control resource repeater (404) to the resource controller (403) for the first communication system (401 ). The resource controller (403) responds to the request by allocating a communication resource to support the requested communication as is currently done in the prior art. The allocation message from the resource controller includes the group ID for that home system (401) (which ID has been preregistered in the second system's (402) ID database (431)). This outbound allocation message (424) as sourced by the resource controller (403) and as transmitted by the appropriate control resource repeater (404) will be received by whichever of the receivers (416) in the second communication system (402) is monitoring that particular communication resource of the first system (401 ). That particular receiver (416) will then provide the signalling information via the appropriate link (417) to the resource controller (407) for the second communication system (402). The second resource controller (407) will recognize the ID as belonging to a roamer located in its system, and the resource controller (407) will assign one of the receivers (416) to monitor the allocated communication resource from the first system (401). The controller (407) will also assign one of its own communication resources to support the communication, and cause an allocation message (426) to be transmitted. This allocation will occur in the usual manner via the control resource of the second system (402), and will be received by the second communication unit (423) and cause the second communication unit (423) to begin monitoring the allocated communication resource of the second communication system. Thereafter, the first communication unit (421 ) will transmit its messages (for example, voice messages) using communication resources of the first communication system (401). The repeater (404) in the first communication system (401) assigned to support this communication will receive these signals from the first communication unit (421 ) and repeat them on the allocated communication resource (427). The repeated voice message (427) will be received by the appropriate receiver (416) in the second communication system (402). The resource controller (407) in the second communication system (402) will gate (419) this received voice message to the repeater (408) that has been assigned to support this communication. The assigned repeater (408) will then retransmit (428) the received signal and this retransmission will be received by the second communication unit (423), thereby including the second communication unit (423) in the group call. Eventually, of course, the roaming unit (423) will leave the second system (402) and return to its home system (401). When this occurs, the roaming unit (423) will lose contact with the second system (402) and subsequently gain contact with the home system (401). Upon detecting the control resource of the home system (402), the roaming unit (423) will again register itself with the home system (401 ). As part of this process, the home system (401 ) will transmit a registration acknowledgement to the roaming unit (423) on the appropriate control resource. The second system (402), which is still monitoring the control resource for the home system (401 ), will detect this acknowledgement, and determine that the roaming unit (423) is no longer within the second system (402). The second system (402) will then deassign the roaming unit (423) and de-allocate the receiver (416) that had been previously allocated to monitor the home system (401). What is claimed is:

Claims: Claims 1. A communication system that supports communications amongst a plurality of member communication units, the communication system having: a first set of communication resources that are allocatable amongst the member communication units, wherein at least one of the communication resources supports primary control signalling for use by the member communication units to facilitate allocation of the communication resources amongst the member communication units; and a resource controller for allocating the communication resources amongst the member communication units and for sourcing, at least in part, the primary control signalling; characterized such that: A) at least one of the communication resources also supports secondary control signalling for use by at least one other communication system to facilitate system-to- system communications; and B) the resource controller sources, at least in part, the secondary control signalling. 2. The commuinication system of claim 1 , further characterized in that: A) the communication resource that supports the primary control signalling comprises a dedicated control resource; B) the dedicated control resource also supports the secondary control signalling. 3. The communication system of claim 2, further characterized in that the primary control signalling includes data transmitted at a first data rate, and the secondary control signalling includes data transmitted at a second data rate, wherein the first data rate is different than the second data rate. 4. A communication system, comprising: A) a set of predetermined communication resources; B) resource control means for allocating the communication resources amongst communication units; and being characterized by: C) receiver means for receiving radio frequency communications supported by communication resources that are ordinarily used in a separate communication system and that are not included in the set of predetermined communication resources; - D) means for selectively coupling the receiver means and. the set of predetermined communication resources to allow communications received by the receiver means from the separate communication system to be retransmitted using the predetermined communication resources. 5. A communication system that includes: a first communication system that includes a first set of communication resources, and first resource control means for controlling the first set of communication resources; and a second communication system that includes a second set of communication resources, and second resource control means for controlling the second set of communication resources; characterized by: a method of establishing communications between a first communication unit and a second communication unit, comprising the steps of: A) providing the first communication system with first receiver means substantially compatible with the second set of communication resources for receiving communications sourced by the second communication system; B) providing the second communication system with second receiver means substantially compatible with the first set of communication resources for receiving communications sourced by the first communication system; C) receiving, at the first communication system, a request from the first communication unit to communicate with at least the second communication unit; D) sourcing, from the first resource control means using the first set of communication resources, a notification for at least the second communication unit of a need to communicate; E) receiving, at the second receiver means, the notification from the first communication system and providing that notification to the second resource control means; F) sourcing, at the second resource control means using the second set of communication resources, a notification of the need to communicate. 6. The method of claim 5, further characterized in that step F of sourcing a notification of the need to communicate includes identifying a communication resource from the second set of communication resources that has been allocated to support the requested communication. 7. A communication system that includes: a first communication system that includes a first set of communication resources, and first resource control means for controlling, at least in part, allocation of the first set of communication resources amongst a first plurality of member communication units; and a second communication system that includes a second set of communication resources, and second resource control means for controlling, at least in part, allocation of the second set of communication resources amongst a second plurality of member communication units, wherein the first set of communication resources are substantially noncompatible with the second set of communication resources; characterized by: a method of establishing communications between: a first communication unit that is a member of the first plurality of member communication units and that is located within the first communication system; and a second communication unit that is a member of the first plurality of member communication units and that is located within the second communication system; the method comprising the steps of: A) providing at least some of the radios in the first plurality of member communication units, including the first and second communication units, with a first ID; B) pre-registering the first ID with the second communication system as a roaming ID; C) providing the second communication system with receiver means substantially compatible with at least one of the communication resources of the first communication system to allow the second communication system to monitor at least some communications supported by the first communication system; D) determining, in the second communication system, that the second communication system is located within the second communication system; E) monitoring, in the second communication system using the receiver means, at least one communication resource belonging to the first set of communication resources to detect a first system communication intended, at least in part, for communication units that have at least the first ID; F) when the first system communication is detected, allocating in the second communication system a communication resource from the second set of communication resources to be used by the second communication unit to receive at least part of the first system communication. 8. A home communication system that includes a set of communication resources, and resource control means for controlling, at least in part, allocation of the set of communication resources amongst a plurality of member communication units, characterized by a method of establishing communications between: a first communication unit that is a member of the plurality of member communication units and that is located within the home communication system; and a second communication unit that is a member of the plurality of member communication units and that is located within a second communication system, wherein the second communication system includes a second set of communication resources and second resource control means for controlling, at least in part, allocation of the second set of communication resources amongst a second plurality of member communication units, wherein the second set of communication resources are substantially noncompatible with the communication resources of the home system; the method comprising the steps of: A) providing at least the first and second communication units with an ID; B) pre-registering the ID with the second communication system as a roaming ID; C) providing the second communication system with receiver means substantially compatible with at least one of the communication resources of the home communication system to allow the second communication system to monitor at least some communications sourced by the home communication system; D) monitoring, in the second communication system using the receiver means, at least one communication resource belonging to the home communication system to detect a communication intended, at least in part, for communication units that have at least the first ID; E) when the communication is detected, allocating in the second communication system a communication resource from the second set of communication resources to be used by the second communication unit to receive at least part of the communication.

Inventors: COMROE RICHARD ALAN, ERICKSON GARY DEAN, MAJOR JOHN EDWARD, SASUTA MICHAEL DAVID, SOBTI ARUN, COMROE, RICHARD, ALAN, ERICKSON, GARY, DEAN, MAJOR, JOHN, EDWARD, SASUTA, MICHAEL, DAVID, SOBTI, ARUN
Applicants: MOTOROLA INC, MOTOROLA, INC.
Application year: 1990
Main classification: H04Q7
IPC codes: H04B7, H04W84