CA2391563A1 - Distributed control architecture for mobile systems with overlapping service coverage regions - Google Patents
Distributed control architecture for mobile systems with overlapping service coverage regions Download PDFInfo
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- CA2391563A1 CA2391563A1 CA002391563A CA2391563A CA2391563A1 CA 2391563 A1 CA2391563 A1 CA 2391563A1 CA 002391563 A CA002391563 A CA 002391563A CA 2391563 A CA2391563 A CA 2391563A CA 2391563 A1 CA2391563 A1 CA 2391563A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/204—Multiple access
- H04B7/2041—Spot beam multiple access
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
- H04W16/28—Cell structures using beam steering
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/04—Large scale networks; Deep hierarchical networks
- H04W84/06—Airborne or Satellite Networks
Abstract
In a mobile satellite communication system wherein a satellite (410) generates a plurality of spot beams, and both mobile stations and fixed terrestrial stations within the spot beams receive and transmit information on traffic channels (402) and command channels (401), two terrestrial stations (450A, 450B) are assigned a single set of common control channels (401, 404, 406, 408) for overlapping spot beams.
Description
DISTRIBUTED CONTROL ARCHITECTURE FOR MOBILE SYSTEMS
WITH OVERLAPPING SERVICE COVERAGE REGIONS
FIELD OF THE INVENTION
This invention is in the field of mobile cellular system design, and in particular mobile satellite systems supporting terrestrial cellular communications technologies.
BACKGROUND OF THE INVENTION
Mobile satellite systems are a significant species of the general class of mobile systems in which there can be service overlap in the geographic areas covered by multiple, autonomous terrestrial communications infrastructure. The overlapping service coverage that occurs in mobile satellite systems arises from the ability of multiple networks to be provided with radio coverage from the same satellite.
The coverage for each network may be provided for a subset of the satellite's coverage area or may even extend across the entire footprint of the satellite.
Figure 1 illustrates a model for a general satellite system 100 for a mufti-beam geostationary (GEO) satellite 110 in which multiple, independent network system infrastructures can be supported by the coverage of that single satellite. In such a mobile communications system, there may be several terrestrial infrastructures (although only one is illustrated), each incorporating an appropriate satellite Base Station Subsystem (BSS) 121 having an antenna and signal processing equipment, and a Network Switching Subsystem (NSS) 122. Each such terrestrial infrastructure can be configured to support services in any geographic region within the satellites) coverage footprint. The BSS 121 provides the radio frequency equipment for communicating with the mobile terminals (MT) 140 and controlling the satellite transmission resources. The NSS 122 includes the network elements necessary for routing and switching traffic to and from mobile terminals and databases for controlling mobility, security and service access. For circuit-switched communications, service access and assignment are provisioned on the basis of dedicated circuits. In the case of packet-switched technology, the NSS 122 will include serving and gateway support nodes in addition to the information databases for the support of mobility and security management functions.
The illustrated system architecture model is based on a reuse of standard terrestrial cellular technology for NSS elements, where the radio access has been extended through the satellite repeater. Given this feature, gateways (GW) 150 between the mobile satellite system 100 and other public or private terrestrial networks 160 also can be formed on the basis of BSS elements 151 and NSS
elements 152. Each network gateway system 150 supports direct communications with mobile terminals (MT) 140, having terminal equipment 145 connected thereto, through the satellite 110 as well as providing access to external networks 160. The service coverage region for any gateway 150 may be limited to specific satellite spot beams 180 or may extend across the entire satellite coverage footprint 190. Thus, the service coverage overlap among plural independent terrestrial gateways 150 may occur within regions of the satellite coverage (a spot beam or groups of spot beams), or may extend across the entire satellite footprint. For beams in which service overlap occurs, each gateway is able to simultaneously support service to mobile users. This is in contrast to terrestrial based cellular systems in which space diversity is at the core of the system architecture in which essentially non-overlapping coverage is desired.
Coordination of operation among the individual network gateway systems in terms of shared access to satellite radio resources may be performed via a network control center (NCC) 170, having BSS equipment 171 and control equipment 172.
Radio frequency channels facilitate the communications between mobile terminals and the supporting network infrastructure. For each communication network two general categories of logical channels can be defined: traffic channels and control channels 101. The traffic channels 102, 103 support the user data transmissions between the mobile and the network, while the control channels are used for control as well as signaling between mobile users and the network. The control channels can be further sub-divided into broadcast control, common control, and dedicated control channels. The broadcast channels are used to provide the same information to all mobile in a given coverage area. That information includes timing and frequency control and general system information. The common control channels are available to all mobiles in a given coverage and are used to convey signaling information to and from any mobile terminal. The dedicated control channels are assigned in conjunction with traffic channels are used by specific mobiles.
For satellite mobile systems, the inherent service coverage area overlap that exists among network gateways 150 within the satellite's footprint 190 implies that multiple gateways may support communications channels in the same coverage spot beams.
To allow service operation, a set of control channels must be provided in each of the satellite spot beams 180. Control channels may be fully distributed, i.e., separately provided by each network gateway 150 in each of the spot beams that cover the gateway's defined service area. Alternately, a centralized Network Control Center (NCC) 170 may be implemented in which a singular set of common control channels 101 is provided per beam by the NCC. As discussed subsequently, each of the centralized NCC and fully distributed network architectures involve disadvantages that can be overcome by the present invention.
Figure 2 illustrates the architecture of a network 200 in which a single, centralized NCC 270 is implemented in the system. For convenience, this figure only shows a single MT 240 connected to mobile terminal equipment TE 245, and two gateways 250A and 250B, each having BSS 251 and NSS 252 equipment, but a number of additional MTs and GWs can be used, as would be understood by one skilled in the art. As can be seen in this illustration, all common control signaling from an MT 240 in an inbound direction (mobile to network) is relayed by common signaling channels 201, via satellite 210 to the NCC 270 by common signaling channel 204. The control signal is sent by the NCC 270 to the appropriate GW
or 250B via an inter-station communications signaling network 275A or 275B, respectively, connected to a corresponding BSS 251 by a link 253A, 253B. The GWs are not operative to transmit or receive common channel signaling information to or from the satellite, but can only carry signaling over channels dedicated to that gateway. Once a service connection has been established from the mobile via the satellite to the GW, the traffic channel (202, 203, 205) as well as other dedicated channel signaling is directly supported through the gateway that provides the service to the MT 240.
The centralized scheme, in which the NCC 270 is used to aggregate the control channels 201, 204, allows the control traffic for the different gateways to be multiplexed onto a minimum number of common control channels. Dedicated control channels that are part of the traffic handling capacity assigned by a gateway will remain within the control of a gateway's capacity assignment.
WITH OVERLAPPING SERVICE COVERAGE REGIONS
FIELD OF THE INVENTION
This invention is in the field of mobile cellular system design, and in particular mobile satellite systems supporting terrestrial cellular communications technologies.
BACKGROUND OF THE INVENTION
Mobile satellite systems are a significant species of the general class of mobile systems in which there can be service overlap in the geographic areas covered by multiple, autonomous terrestrial communications infrastructure. The overlapping service coverage that occurs in mobile satellite systems arises from the ability of multiple networks to be provided with radio coverage from the same satellite.
The coverage for each network may be provided for a subset of the satellite's coverage area or may even extend across the entire footprint of the satellite.
Figure 1 illustrates a model for a general satellite system 100 for a mufti-beam geostationary (GEO) satellite 110 in which multiple, independent network system infrastructures can be supported by the coverage of that single satellite. In such a mobile communications system, there may be several terrestrial infrastructures (although only one is illustrated), each incorporating an appropriate satellite Base Station Subsystem (BSS) 121 having an antenna and signal processing equipment, and a Network Switching Subsystem (NSS) 122. Each such terrestrial infrastructure can be configured to support services in any geographic region within the satellites) coverage footprint. The BSS 121 provides the radio frequency equipment for communicating with the mobile terminals (MT) 140 and controlling the satellite transmission resources. The NSS 122 includes the network elements necessary for routing and switching traffic to and from mobile terminals and databases for controlling mobility, security and service access. For circuit-switched communications, service access and assignment are provisioned on the basis of dedicated circuits. In the case of packet-switched technology, the NSS 122 will include serving and gateway support nodes in addition to the information databases for the support of mobility and security management functions.
The illustrated system architecture model is based on a reuse of standard terrestrial cellular technology for NSS elements, where the radio access has been extended through the satellite repeater. Given this feature, gateways (GW) 150 between the mobile satellite system 100 and other public or private terrestrial networks 160 also can be formed on the basis of BSS elements 151 and NSS
elements 152. Each network gateway system 150 supports direct communications with mobile terminals (MT) 140, having terminal equipment 145 connected thereto, through the satellite 110 as well as providing access to external networks 160. The service coverage region for any gateway 150 may be limited to specific satellite spot beams 180 or may extend across the entire satellite coverage footprint 190. Thus, the service coverage overlap among plural independent terrestrial gateways 150 may occur within regions of the satellite coverage (a spot beam or groups of spot beams), or may extend across the entire satellite footprint. For beams in which service overlap occurs, each gateway is able to simultaneously support service to mobile users. This is in contrast to terrestrial based cellular systems in which space diversity is at the core of the system architecture in which essentially non-overlapping coverage is desired.
Coordination of operation among the individual network gateway systems in terms of shared access to satellite radio resources may be performed via a network control center (NCC) 170, having BSS equipment 171 and control equipment 172.
Radio frequency channels facilitate the communications between mobile terminals and the supporting network infrastructure. For each communication network two general categories of logical channels can be defined: traffic channels and control channels 101. The traffic channels 102, 103 support the user data transmissions between the mobile and the network, while the control channels are used for control as well as signaling between mobile users and the network. The control channels can be further sub-divided into broadcast control, common control, and dedicated control channels. The broadcast channels are used to provide the same information to all mobile in a given coverage area. That information includes timing and frequency control and general system information. The common control channels are available to all mobiles in a given coverage and are used to convey signaling information to and from any mobile terminal. The dedicated control channels are assigned in conjunction with traffic channels are used by specific mobiles.
For satellite mobile systems, the inherent service coverage area overlap that exists among network gateways 150 within the satellite's footprint 190 implies that multiple gateways may support communications channels in the same coverage spot beams.
To allow service operation, a set of control channels must be provided in each of the satellite spot beams 180. Control channels may be fully distributed, i.e., separately provided by each network gateway 150 in each of the spot beams that cover the gateway's defined service area. Alternately, a centralized Network Control Center (NCC) 170 may be implemented in which a singular set of common control channels 101 is provided per beam by the NCC. As discussed subsequently, each of the centralized NCC and fully distributed network architectures involve disadvantages that can be overcome by the present invention.
Figure 2 illustrates the architecture of a network 200 in which a single, centralized NCC 270 is implemented in the system. For convenience, this figure only shows a single MT 240 connected to mobile terminal equipment TE 245, and two gateways 250A and 250B, each having BSS 251 and NSS 252 equipment, but a number of additional MTs and GWs can be used, as would be understood by one skilled in the art. As can be seen in this illustration, all common control signaling from an MT 240 in an inbound direction (mobile to network) is relayed by common signaling channels 201, via satellite 210 to the NCC 270 by common signaling channel 204. The control signal is sent by the NCC 270 to the appropriate GW
or 250B via an inter-station communications signaling network 275A or 275B, respectively, connected to a corresponding BSS 251 by a link 253A, 253B. The GWs are not operative to transmit or receive common channel signaling information to or from the satellite, but can only carry signaling over channels dedicated to that gateway. Once a service connection has been established from the mobile via the satellite to the GW, the traffic channel (202, 203, 205) as well as other dedicated channel signaling is directly supported through the gateway that provides the service to the MT 240.
The centralized scheme, in which the NCC 270 is used to aggregate the control channels 201, 204, allows the control traffic for the different gateways to be multiplexed onto a minimum number of common control channels. Dedicated control channels that are part of the traffic handling capacity assigned by a gateway will remain within the control of a gateway's capacity assignment.
A further advantage of the centralized NCC approach is that it also provides savings in the channel unit equipment resources that need to be provided system-wide for supporting the control channels. If control channels were supported on a gateway basis, each gateway would be required to maintain channel unit resources for all satellite beams. Low utilization of the gateway control channels would translate into low utilization of the gateway channel units and would result in an overhead of physical channel units as well as control channel capacity.
The drawback in the use of a centralized NCC 270 to provide control channels across the entire system is the delay that is introduced in the establishment of communication between a MT 240 and the gateway infrastructure through which the service is handled. All service invocation, mobile originated as well as terminated, is initiated through the common control channels provided by the NCC. For service establishment, the NCC is thus in the path of all signaling communication between the MT 240 and the gateways 250A and 250B. Once signaling has been re-assigned to dedicated control channels, direct interaction (through the satellite) can occur between the MT 240 and the gateway. In the centralized NCC system the signaling interactions through the NCC 270 will thus introduce a number of additional hops of delay depending on the number of signaling interactions that occur over the common control channels.
For circuit-switched operations in which the call establishment-signaling period is a very small fraction of the call service time, the additional delay of common control signaling through the NCC 270 is not significant. The additional delay introduced by the initial transmissions between through the NCC 270 is also small relative to the overall call setup time. Furthermore, once signaling has been assigned to dedicated control channels, there is no requirement to return to signaling on the common control channels. The only exception is the condition in which the communication signal between the network 200 and the MT 240 is temporarily lost and an attempt may be made by the mobile 240 to re-establish the call before the network clears the connection.
In a system 300 based on a distributed control model, as illustrated in Fig.
3, a mobile MT 340 with transmission equipment TE 345 may communicate via a satellite 310 with one or more gateways 350A, 350B, 350C. In the model, the satellite communicates control data and traffic with the mobile unit via channels 301 and 302, respectively. As illustrated, each gateway 350A, 350B, 350C will support its own common control channels 304A, 304B, 304C, respectively, in each of the spot beams of its defined service area. This requirement to have each gateway support a set of common control channels per beam significantly increases the system capacity S overhead introduced in the system 300. This system overhead will increase with the number of spot beams and the number of gateways that are supported per beam.
Low utilization of the control channels per gateway will exaggerate the channel capacity overhead incurred in the system.
In addition to the channel capacity overhead, the distributed control model will significantly increase the physical channel unit resources required in the system. Each gateway 350A, 350B, 350C, having similar BSS equipment 351 and NSS equipment 352, will be required to maintain its own sets of channel units to provide access to the common channels that it supports, e.g., 304A, 304B, 304C, respectively. Each gateway operates as an autonomous system within the overall coverage of the satellite. In this architecture there may nonetheless be some element of coordination among gateways via inter-gateway links 353A, 353B for the sharing and coordinated access of satellite resources.
A key advantage of the distributed architecture is the combined operation of common control and traffic channels by each gateway. This operation eliminates the additional signaling delays introduced by the centralized NCC model. The distributed architecture also provides greater flexibility in the adjustment of channel resources between signaling and traffic to meet the communications demands at a given gateway.
For packet-switched data communications, the short, intermittent duration of traffic communications requires that the signaling delay needed to initiate such communications be minimized. With packet-switched communications, the use of common control channels can occur on multiple occasions within a communications session. The intermittent nature of certain data applications means that capacity assigned to a MT 340 may be periodically re-assigned during the communications if there is temporarily no traffic to send. When capacity is once again required the common control channels may be used to obtain a new channel capacity allocations.
In packet data communications, the inbound random access control channel (mobile to NCC) may be used for traffic as well as signaling. A mobile terminal may be able to use the packet random access channel to send small amounts of data.
The multiplexing of mobile data request also means that the network may issue a temporary SUSPEND command to a mobile in response to a request for capacity.
When the required capacity is available, a RESUME command is sent to the mobile.
This SUSPEND/RESUME operation, which provides capacity handling flexibility for the network, makes use of the common control channels for exchanges between the MT and the network. Additional satellite delay hops through a centralized NCC
will thus degrade the operation of the satellite packet-switched services. The distributed architecture however overcomes this delay-related system performance degradation.
Nonetheless, the pure distributed architecture continues to suffer from the problems noted previously.
SUMMARY OF THE INVENTION
In view of the foregoing problems with pure centralized architectures and pure distributed architectures, it is an object of the present invention to implement a new hybrid common control channel architecture and method of communication therein based on a dynamic distributed NCC model.
It is another object of the present invention to achieve the delay reduction and allocation flexibility benefits of the distributed control architecture with the reduced channel capacity and channel unit resource overhead of the centralized architecture.
These and other objects of the present invention are achieved by establishing a hybrid control architecture and method of operation based upon the maintenance of a single set of control channels in each spot beam that is shared among all gateways, These and other objects are also achieved by the dynamic allocation of channel units at each gateway in accordance with the control channel traffic to be supported in each spot beam.
Further, these and other objects are achieved by the implementation of Master and Slave NCCs for the coordination of common channel usage among the network gateways.
The hybrid common control channel architecture disclosed herein allows a mobile satellite system to support a number of independent gateway systems each of which provide service over all or any defined subset of the satellite's coverage. The architecture is adaptable allowing a centralized NCC operation in which all common control signaling occurs through a single NCC entity, or a distributed NCC
model in which additional NCC elements can be introduced by a gateway to serve user traffic in any given beam. In addition to providing efficiency by reducing the channel capacity overhead, the system design is flexible by allowing a gateway to activate a Slave NCC functionality in accordance with its service demands in a particular beam.
Any system gateway is able to provide its own control channels to better support service requests (such as packet-switched communications, for example) that require more integrated interactions between common control and other communications channels.
In accordance with the flexible approach provided by the present invention, the ability to support the intermittent access to physical channel resources that is required by 'bursty' data depends on the speed with which those shared resources can be quickly and efficiently assigned and re-assigned. To the extent that a shared NCC
facilitates such dynamic channel multiplexing the more enhanced will be the system operation. The use of common control channels that are shared across multiple NCCs, in accordance with the present invention, provides an improvement in resource allocation efficiency over systems with a singular, centralized NCC.
The system approach of the present invention can be applied to mobile systems based on any terrestrial cellular or PCS technology standard. The system model provides flexibility by using generic access signaling that can apply equally to the requirements of any mobile communications system standard.
Although not specifically disclosed, one of ordinary skill would understand that there are a number of options for detailed refinements that relate to the operation of the system, including but not limited to the specific allocation of common control paging among active NCCs or the use of the receipt of system information broadcasts from the Master NCC to determine redundancy switchovers of the Master NCC.
These options can be incorporated in accordance with the requirements of a particular system implementation BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an illustration of a general satellite system model for a mufti-beam geostationary (GEO) satellite in which multiple, independent network system infrastructures can be supported with the satellite coverage.
Figure 2 is an illustration of the network architecture in which a single, centralized NCC is implemented in the system.
Figure 3 is an illustration of the fully distributed network architecture model.
Figure 4 is an illustration of the distributed NCC architecture model. In this architecture an inter-station signaling network provides the connectivity between the Master and Slave NCC functional elements.
Figure 5 is an illustration of service establishment signaling over the system's common control channels for the case in which a mobile terminal attempts system operation for the first time.
Figure 6 is an illustration of the initial signaling access for the case in which a registered MT attempts to establish service in a spot beam in which its associated NCC is currently active.
Figure 7 is an illustration of the generic network-initiated service establishment for the case in which only the Master NCC operates in the mobile's current registered spot beam.
Figure 8 illustrates service initiation for a generic network-initiated service where only the Master NCC operates in the mobile's current registered spot beam.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 4 provides a schematic illustration of a system 400 that implements the distributed NCC architecture model of the present invention. A mobile MT 440 having related terminal equipment TE 445 communicates with a satellite 410 that provides plural spot beams 180 within a footprint 190, as illustrated in Fig.
1, via control channels 401 and traffic channels 402. The satellite communicates with one or more gateways 450A, 450B, 450C within the footprint, using traffic channels 403, 405, 407 and common signaling channels 404, 406, 408. Each gateway may be connected to a corresponding external network 460A, 460B, 460C, and each has a respective NCC/BSS 451A, 451B, 451C, and NSS 452A, 452B, 452C. In the preferred architecture, the NCC in one of the gateways will be designated a Master 451B, while the remaining gateways will be designated as Slaves 451A, 451C.
While the Master NCC 451B is shown as associated with a network gateway 450B, it is possible to implement an independent Master NCC without impacting the central operating elements of the proposed system architecture. In this architecture inter-station signaling networks 475A, 475B provide the connectivity between the Master NCC 451B functional elements and Slave NCC functional elements 451A and 451C, respectively. As in the centralized NCC architecture illustrated in Fig. 2, the inter-station network allows service to be supported through a GW that does not have the resources to provide common channel control in a particular satellite spot beam.
However, the limitations of the centralized mode, which limit common channel signaling only to the central controller, is overcome by the capability of plural gateways to receive the common channel signaling.
By maintaining a single set of common control channels (401, 404, 406, 408), the capacity overhead of the system is minimized as in the centralized NCC
architecture model of Fig. 2. However, since these common control channels are shared among plural gateways 450A, 450B, 450C, this introduces the need for coordination among gateways. A distributed NCC functionality is thus implemented at each gateway. Inbound common control channels (mobile to gateway) are shared by having multiple NCCs receive information broadcast on the common frequency channel, for example, using a random access channel (RACH). Outbound common channels (gateway-to-mobile), on the other hand, are shared according to a dynamic allocation approach that is controlled by the Master NCC 451B. The transmission of control information from a gateway NCC may be preceded by transmissions to the mobile on paging channels (PCH).
Multiple options exist for the mechanism used to define the sharing of outbound common control channels. For access grant channels (AGCH), which are used in direct response to a mobile's successful inbound random access channel (RACH) attempt, the capacity sharing can be easily coordinated by the Master NCC
451B without an impact on currently specified operation. This occurs because mobiles perform continual reception on the AGCH once a random access attempt has been initiated. For outbound paging channels (PCH) used to alert a mobile to a network-initiated service initiation, the mechanism for sharing the common channels among NCCs must also factor the intermittent paging receive cycles used by mobiles to reduce their receive duty cycles (and corresponding battery life).
To allow for discontinuous reception whereby terminals only need to wake periodically to receive paging alerts, "paging groups" are implemented. Paging groups define the time periods within a control channel transmission frame during which paging alerts will be sent by the network. Multiple subscribers share a common paging group. Each terminal autonomously determines its paging group from its subscriber ID, using a specified system algorithm, and conserves battery power by waking to receive paging only during the time periods specified for its paging group.
The network controller similarly determine the paging group of a that must be alerted and transmits the paging messages during the subscriber's associated paging group period.
A further element of the hybrid distributed NCC design involves a simple modification of the mobile's calculation of paging groups. This modification will allow a mobile's paging group to be adjusted according to the number of NCC
GWs that are currently serving mobiles in a particular spot beam. The Master NCC
will convey the information with regard to those serving NCC GWs as part of the transmitted system information. The algorithm for modifying the standard (terrestrial equivalent) assignment of mobiles to paging groups may be defined in a manner that does not affect the duty cycle of the mobile, as would be understood by one skilled in the art. This will be achieved by allowing the paging group assignment to be shifted in time without changing its frequency. The new time assignment shall be made to correspond to the mobile's associated NCC common channel allocation. In the event that a serving GW does not have a currently active (Slave) NCC in the beam, the Master NCC 451B will be responsible for use of the otherwise assigned common control channel resources.
With regard to channel unit resources, each gateway in this architecture will only maintain channel units in spot beams in which it has active mobile terminals.
Furthermore, gateways with limited channel unit resources may choose to operate only in a subset of the spot beams in which it has active MTs and allow the Master NCC 451B to support its common control channel activity in those beams.
Because each gateway 450A, 450B, 450C is not required to actively share the common channels in every beam of the satellite, the system's channel unit resources overhead can be minimized.
Finally, it should be noted that there is always one NCC that is designated the Master NCC operating in each satellite spot beam. An NCC will support channel unit resources in any beam in which it is the designated Master NCC. Other NCCs operating in that beam will also support the provision of channel unit resources for the given beam.
The operation of the distributed NCC architecture model can be understood by examining the signaling flows involved in the establishment of service to or from a mobile terminal. Figures 5-8 are based on the communications interactions between the network and a mobile terminal for mobile-initiated service access in a given spot beam. These information flows are meant to be general in nature, without providing the details of particular circuit-switched or packet-switched service invocations, yet sufficiently detailed to enable implementation by one of ordinary skill in the art. The signaling and communications assumptions are based on those of standard mobile communications systems in which inbound random access channels (mobile-to gateway) are first accessed to obtain resources for subsequent signaling or communications interactions between the mobile and the network. The network uses outbound (gateway-to-mobile) common control channels to notify mobiles of the result of an initiated service or resource request.
Information regarding the system identification, physical and logical channel organization and access parameters for initiating requests are provided as part of uniformly receivable broadcast control channels (BCCH). In normal operation, the Master NCC 451B provides the BCCH for each spot beam. For purposes of system redundancy this function can be taken over by other system NCCs 451A or 451C.
The methods for taking over BCCH transmission from the Master NCC by one of the Slave NCCs in the event of Master NCC failure would be readily implemented by one skilled in the art. At each NCC, an ordered NCC list will be maintained for each beam that identifies the priority assigned to each Slave NCC for the assumption of the Master NCC function in the event of a failure of the Master. That list is updated and communicated among NCCs in accordance with the NCCs that are active in a particular beam.
Figure 5 illustrates the service establishment signaling over the system's common control channels for the case in which a mobile terminal attempts system operation for the first time. This initial access, illustrated as a Channel Request 501, assumes that the mobile terminal is un-registered in the system and thus not associated with a particular GW and its correspondent NCC. As part of the proposed system architecture design, MTs are required to indicate their associated NCC (which are associated with the mobile's registered NSS gateway). This indication is provided in the initial system access message and allows the mobile's associated NCC to process the service request. Other active NCCs within the spot beam will ignore a request associated with another NCC. If the NCC identified by the mobile as it registered NCC is not currently active in the spot beam, the Master will process the initial access request. As an initial service access attempt, the Master NCC will process the Channel Request message due to the absence of an identified associated NCC and select a GW for assignment to the mobile 502. The Master NCC will also handle service access attempts in which an NCC is identified in the Access Request but for which the identified/associated Slave NCC is not currently active in the particular spot beam.
Based on other information (such as indication of call termination, for example) provided in the Channel Request message, the Master NCC 451B will direct the call to an appropriate GW (in a preferred embodiment, the service access is processed by the associated Master NCC gateway 450B, as seen in Figure 4), step 503. The response from a Slave GW 450A, 450C to which the service request is directed includes a resource allocation for the mobile to establish signaling/communication with the GW as well as a notification to the Master NCC by the gateway of whether the GW will initiate Slave NCC functionality for the beam.
The principle of the system operation is that a gateway may initiate support for Slave NCC functionality in a given beam dependent on its available physical (channel unit) resources and the existence of associated mobiles that it serves in the particular spot beam. The Slave GW 450A, 450C may choose not to activate a NCC for the beam solely based on the first service request received through the Master NCC
451B. In such an event, common channel signaling for the associated gateway NCC will continue to be supported through the Master NCC.
Figure 6 illustrates the initial signaling access for the case in which a registered MT 440 attempts to establish service in a spot beam in which its associated NCC 451A is currently active. The MT 440 will send a channel request in step that is received by both the Master NCC 451B and the slave NCCs 451A and 451C.
As shown, the Master NCC 451B is aware of the active status of the Slave NCC
450A, and will ignore the Channel Request and allow it to be processed by the mobile's associated NCC 451A. Other NCC's 451C that are not associated with the mobile will ignore the Channel Request.
The associated Slave NCC 451A receives the request through its independent processing of the information received on the common control channels) allocated in the particular spot beam. Then, the associated Slave NCC 451A will assign in step 602 a channel for the traffic that is to be exchanged between the mobile 440 and GW
450A. Even though the access request messages that are correctly received and processed by the Master NCC 451B and Slave NCCs may differ, this does not affect the distributed system operation. For requests directed at an identified NCC, e.g., NCC 451A, the particular NCC will handle collision and contention resolution.
For purposes of redundancy the Master NCC 451B may use the occurrence of repeated successfully received access requests to a particular NCC to analyze the operational status of that NCC.
The operation of the proposed distributed NCC architecture model is further highlighted by examining the signaling flows involved in the establishment of network-initiated requests. The information flows are again meant to be general, given the simple schematic arrangement in Figure 4, and is not intended to disclose the details of particular circuit-switched or packet-switched service invocations, as these would be well known to one of ordinary skill without undue experimentation.
The signaling and communications assumptions are based on those of standard mobile communications systems in which network-initiated service is based on the use of common control paging (alerting) channels to notify mobiles of an intended establishment of network service. The mobile, if available, responds via the inbound random access channels and the process is completed as identified above.
The generic establishment of network-initiated service for the case in which only the Master NCC 451B operates in the mobile's current registered spot beam is illustrated in Figure 7. This Figure shows the case in which the service access is initiated by the transmission of a paging request to the Master NCC 451B in step 701 from a GW 450C that does not support an Active NCC for the beam in which the mobile is registered. The request is sent by the master NCC 451B to the mobile as a page in step 702. However, based on the response of the mobile as a channel request in step 703 to the Master NCC 451B, a page response in step 704 is provided to the Slave NCC 451C and the Slave NCC is made active in step 705. Then, in step 706 the GW 450C indicates to the Master NCC 451B its decision to activate a Slave NCC
451C in the spot beam. The Master NCC 451B will note the newly activated Slave NCC 451C, will provide a channel assignment to the mobile 440 in step 707 and will relinquish its own control over the outbound channel resources that had been apportioned to the gateway, due to its support of mobiles in the particular spot beam.
In the event that the GW 450C chooses not to activate an NCC 451C in the particular beam, all common control channel signaling to mobile terminals in the beam are supported through the Master NCC 451B.
Finally, for the case in which a network-initiated service is established through a GW 450A that supports an Active NCC 451A in the registered beam of the intended mobile, the service access occurs directly via the Slave NCC's outbound common control assignment. Figure 8 illustrates the signaling flow for the service initiation, which is begun with a mobile page from the Slave NCC 451A to the mobile 440 in step 801. The mobile responds with a channel request in step 802, which is followed y a channel assignment by the Slave NCC 451C in step 803. Those channels will be consistent with the paging group operation of the mobile terminal 440. As indicated above, the system may implement mechanisms in which the Master NCC 451B
always controls the common paging channels. Where the Master NCC 451B controls all common control paging, the request will be initiated through the Master NCC
451B. However, in such a case, the Slave NCC 451A or C will still process the Channel Request message and transmit the corresponding access grant Channel Assignment using its assigned access grant capacity.
While the invention has been disclosed in connection with certain preferred embodiments, it is not limited thereto, and the full scope of the invention is defined in the appended claims, as interpreted in accordance with applicable law.
The drawback in the use of a centralized NCC 270 to provide control channels across the entire system is the delay that is introduced in the establishment of communication between a MT 240 and the gateway infrastructure through which the service is handled. All service invocation, mobile originated as well as terminated, is initiated through the common control channels provided by the NCC. For service establishment, the NCC is thus in the path of all signaling communication between the MT 240 and the gateways 250A and 250B. Once signaling has been re-assigned to dedicated control channels, direct interaction (through the satellite) can occur between the MT 240 and the gateway. In the centralized NCC system the signaling interactions through the NCC 270 will thus introduce a number of additional hops of delay depending on the number of signaling interactions that occur over the common control channels.
For circuit-switched operations in which the call establishment-signaling period is a very small fraction of the call service time, the additional delay of common control signaling through the NCC 270 is not significant. The additional delay introduced by the initial transmissions between through the NCC 270 is also small relative to the overall call setup time. Furthermore, once signaling has been assigned to dedicated control channels, there is no requirement to return to signaling on the common control channels. The only exception is the condition in which the communication signal between the network 200 and the MT 240 is temporarily lost and an attempt may be made by the mobile 240 to re-establish the call before the network clears the connection.
In a system 300 based on a distributed control model, as illustrated in Fig.
3, a mobile MT 340 with transmission equipment TE 345 may communicate via a satellite 310 with one or more gateways 350A, 350B, 350C. In the model, the satellite communicates control data and traffic with the mobile unit via channels 301 and 302, respectively. As illustrated, each gateway 350A, 350B, 350C will support its own common control channels 304A, 304B, 304C, respectively, in each of the spot beams of its defined service area. This requirement to have each gateway support a set of common control channels per beam significantly increases the system capacity S overhead introduced in the system 300. This system overhead will increase with the number of spot beams and the number of gateways that are supported per beam.
Low utilization of the control channels per gateway will exaggerate the channel capacity overhead incurred in the system.
In addition to the channel capacity overhead, the distributed control model will significantly increase the physical channel unit resources required in the system. Each gateway 350A, 350B, 350C, having similar BSS equipment 351 and NSS equipment 352, will be required to maintain its own sets of channel units to provide access to the common channels that it supports, e.g., 304A, 304B, 304C, respectively. Each gateway operates as an autonomous system within the overall coverage of the satellite. In this architecture there may nonetheless be some element of coordination among gateways via inter-gateway links 353A, 353B for the sharing and coordinated access of satellite resources.
A key advantage of the distributed architecture is the combined operation of common control and traffic channels by each gateway. This operation eliminates the additional signaling delays introduced by the centralized NCC model. The distributed architecture also provides greater flexibility in the adjustment of channel resources between signaling and traffic to meet the communications demands at a given gateway.
For packet-switched data communications, the short, intermittent duration of traffic communications requires that the signaling delay needed to initiate such communications be minimized. With packet-switched communications, the use of common control channels can occur on multiple occasions within a communications session. The intermittent nature of certain data applications means that capacity assigned to a MT 340 may be periodically re-assigned during the communications if there is temporarily no traffic to send. When capacity is once again required the common control channels may be used to obtain a new channel capacity allocations.
In packet data communications, the inbound random access control channel (mobile to NCC) may be used for traffic as well as signaling. A mobile terminal may be able to use the packet random access channel to send small amounts of data.
The multiplexing of mobile data request also means that the network may issue a temporary SUSPEND command to a mobile in response to a request for capacity.
When the required capacity is available, a RESUME command is sent to the mobile.
This SUSPEND/RESUME operation, which provides capacity handling flexibility for the network, makes use of the common control channels for exchanges between the MT and the network. Additional satellite delay hops through a centralized NCC
will thus degrade the operation of the satellite packet-switched services. The distributed architecture however overcomes this delay-related system performance degradation.
Nonetheless, the pure distributed architecture continues to suffer from the problems noted previously.
SUMMARY OF THE INVENTION
In view of the foregoing problems with pure centralized architectures and pure distributed architectures, it is an object of the present invention to implement a new hybrid common control channel architecture and method of communication therein based on a dynamic distributed NCC model.
It is another object of the present invention to achieve the delay reduction and allocation flexibility benefits of the distributed control architecture with the reduced channel capacity and channel unit resource overhead of the centralized architecture.
These and other objects of the present invention are achieved by establishing a hybrid control architecture and method of operation based upon the maintenance of a single set of control channels in each spot beam that is shared among all gateways, These and other objects are also achieved by the dynamic allocation of channel units at each gateway in accordance with the control channel traffic to be supported in each spot beam.
Further, these and other objects are achieved by the implementation of Master and Slave NCCs for the coordination of common channel usage among the network gateways.
The hybrid common control channel architecture disclosed herein allows a mobile satellite system to support a number of independent gateway systems each of which provide service over all or any defined subset of the satellite's coverage. The architecture is adaptable allowing a centralized NCC operation in which all common control signaling occurs through a single NCC entity, or a distributed NCC
model in which additional NCC elements can be introduced by a gateway to serve user traffic in any given beam. In addition to providing efficiency by reducing the channel capacity overhead, the system design is flexible by allowing a gateway to activate a Slave NCC functionality in accordance with its service demands in a particular beam.
Any system gateway is able to provide its own control channels to better support service requests (such as packet-switched communications, for example) that require more integrated interactions between common control and other communications channels.
In accordance with the flexible approach provided by the present invention, the ability to support the intermittent access to physical channel resources that is required by 'bursty' data depends on the speed with which those shared resources can be quickly and efficiently assigned and re-assigned. To the extent that a shared NCC
facilitates such dynamic channel multiplexing the more enhanced will be the system operation. The use of common control channels that are shared across multiple NCCs, in accordance with the present invention, provides an improvement in resource allocation efficiency over systems with a singular, centralized NCC.
The system approach of the present invention can be applied to mobile systems based on any terrestrial cellular or PCS technology standard. The system model provides flexibility by using generic access signaling that can apply equally to the requirements of any mobile communications system standard.
Although not specifically disclosed, one of ordinary skill would understand that there are a number of options for detailed refinements that relate to the operation of the system, including but not limited to the specific allocation of common control paging among active NCCs or the use of the receipt of system information broadcasts from the Master NCC to determine redundancy switchovers of the Master NCC.
These options can be incorporated in accordance with the requirements of a particular system implementation BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an illustration of a general satellite system model for a mufti-beam geostationary (GEO) satellite in which multiple, independent network system infrastructures can be supported with the satellite coverage.
Figure 2 is an illustration of the network architecture in which a single, centralized NCC is implemented in the system.
Figure 3 is an illustration of the fully distributed network architecture model.
Figure 4 is an illustration of the distributed NCC architecture model. In this architecture an inter-station signaling network provides the connectivity between the Master and Slave NCC functional elements.
Figure 5 is an illustration of service establishment signaling over the system's common control channels for the case in which a mobile terminal attempts system operation for the first time.
Figure 6 is an illustration of the initial signaling access for the case in which a registered MT attempts to establish service in a spot beam in which its associated NCC is currently active.
Figure 7 is an illustration of the generic network-initiated service establishment for the case in which only the Master NCC operates in the mobile's current registered spot beam.
Figure 8 illustrates service initiation for a generic network-initiated service where only the Master NCC operates in the mobile's current registered spot beam.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 4 provides a schematic illustration of a system 400 that implements the distributed NCC architecture model of the present invention. A mobile MT 440 having related terminal equipment TE 445 communicates with a satellite 410 that provides plural spot beams 180 within a footprint 190, as illustrated in Fig.
1, via control channels 401 and traffic channels 402. The satellite communicates with one or more gateways 450A, 450B, 450C within the footprint, using traffic channels 403, 405, 407 and common signaling channels 404, 406, 408. Each gateway may be connected to a corresponding external network 460A, 460B, 460C, and each has a respective NCC/BSS 451A, 451B, 451C, and NSS 452A, 452B, 452C. In the preferred architecture, the NCC in one of the gateways will be designated a Master 451B, while the remaining gateways will be designated as Slaves 451A, 451C.
While the Master NCC 451B is shown as associated with a network gateway 450B, it is possible to implement an independent Master NCC without impacting the central operating elements of the proposed system architecture. In this architecture inter-station signaling networks 475A, 475B provide the connectivity between the Master NCC 451B functional elements and Slave NCC functional elements 451A and 451C, respectively. As in the centralized NCC architecture illustrated in Fig. 2, the inter-station network allows service to be supported through a GW that does not have the resources to provide common channel control in a particular satellite spot beam.
However, the limitations of the centralized mode, which limit common channel signaling only to the central controller, is overcome by the capability of plural gateways to receive the common channel signaling.
By maintaining a single set of common control channels (401, 404, 406, 408), the capacity overhead of the system is minimized as in the centralized NCC
architecture model of Fig. 2. However, since these common control channels are shared among plural gateways 450A, 450B, 450C, this introduces the need for coordination among gateways. A distributed NCC functionality is thus implemented at each gateway. Inbound common control channels (mobile to gateway) are shared by having multiple NCCs receive information broadcast on the common frequency channel, for example, using a random access channel (RACH). Outbound common channels (gateway-to-mobile), on the other hand, are shared according to a dynamic allocation approach that is controlled by the Master NCC 451B. The transmission of control information from a gateway NCC may be preceded by transmissions to the mobile on paging channels (PCH).
Multiple options exist for the mechanism used to define the sharing of outbound common control channels. For access grant channels (AGCH), which are used in direct response to a mobile's successful inbound random access channel (RACH) attempt, the capacity sharing can be easily coordinated by the Master NCC
451B without an impact on currently specified operation. This occurs because mobiles perform continual reception on the AGCH once a random access attempt has been initiated. For outbound paging channels (PCH) used to alert a mobile to a network-initiated service initiation, the mechanism for sharing the common channels among NCCs must also factor the intermittent paging receive cycles used by mobiles to reduce their receive duty cycles (and corresponding battery life).
To allow for discontinuous reception whereby terminals only need to wake periodically to receive paging alerts, "paging groups" are implemented. Paging groups define the time periods within a control channel transmission frame during which paging alerts will be sent by the network. Multiple subscribers share a common paging group. Each terminal autonomously determines its paging group from its subscriber ID, using a specified system algorithm, and conserves battery power by waking to receive paging only during the time periods specified for its paging group.
The network controller similarly determine the paging group of a that must be alerted and transmits the paging messages during the subscriber's associated paging group period.
A further element of the hybrid distributed NCC design involves a simple modification of the mobile's calculation of paging groups. This modification will allow a mobile's paging group to be adjusted according to the number of NCC
GWs that are currently serving mobiles in a particular spot beam. The Master NCC
will convey the information with regard to those serving NCC GWs as part of the transmitted system information. The algorithm for modifying the standard (terrestrial equivalent) assignment of mobiles to paging groups may be defined in a manner that does not affect the duty cycle of the mobile, as would be understood by one skilled in the art. This will be achieved by allowing the paging group assignment to be shifted in time without changing its frequency. The new time assignment shall be made to correspond to the mobile's associated NCC common channel allocation. In the event that a serving GW does not have a currently active (Slave) NCC in the beam, the Master NCC 451B will be responsible for use of the otherwise assigned common control channel resources.
With regard to channel unit resources, each gateway in this architecture will only maintain channel units in spot beams in which it has active mobile terminals.
Furthermore, gateways with limited channel unit resources may choose to operate only in a subset of the spot beams in which it has active MTs and allow the Master NCC 451B to support its common control channel activity in those beams.
Because each gateway 450A, 450B, 450C is not required to actively share the common channels in every beam of the satellite, the system's channel unit resources overhead can be minimized.
Finally, it should be noted that there is always one NCC that is designated the Master NCC operating in each satellite spot beam. An NCC will support channel unit resources in any beam in which it is the designated Master NCC. Other NCCs operating in that beam will also support the provision of channel unit resources for the given beam.
The operation of the distributed NCC architecture model can be understood by examining the signaling flows involved in the establishment of service to or from a mobile terminal. Figures 5-8 are based on the communications interactions between the network and a mobile terminal for mobile-initiated service access in a given spot beam. These information flows are meant to be general in nature, without providing the details of particular circuit-switched or packet-switched service invocations, yet sufficiently detailed to enable implementation by one of ordinary skill in the art. The signaling and communications assumptions are based on those of standard mobile communications systems in which inbound random access channels (mobile-to gateway) are first accessed to obtain resources for subsequent signaling or communications interactions between the mobile and the network. The network uses outbound (gateway-to-mobile) common control channels to notify mobiles of the result of an initiated service or resource request.
Information regarding the system identification, physical and logical channel organization and access parameters for initiating requests are provided as part of uniformly receivable broadcast control channels (BCCH). In normal operation, the Master NCC 451B provides the BCCH for each spot beam. For purposes of system redundancy this function can be taken over by other system NCCs 451A or 451C.
The methods for taking over BCCH transmission from the Master NCC by one of the Slave NCCs in the event of Master NCC failure would be readily implemented by one skilled in the art. At each NCC, an ordered NCC list will be maintained for each beam that identifies the priority assigned to each Slave NCC for the assumption of the Master NCC function in the event of a failure of the Master. That list is updated and communicated among NCCs in accordance with the NCCs that are active in a particular beam.
Figure 5 illustrates the service establishment signaling over the system's common control channels for the case in which a mobile terminal attempts system operation for the first time. This initial access, illustrated as a Channel Request 501, assumes that the mobile terminal is un-registered in the system and thus not associated with a particular GW and its correspondent NCC. As part of the proposed system architecture design, MTs are required to indicate their associated NCC (which are associated with the mobile's registered NSS gateway). This indication is provided in the initial system access message and allows the mobile's associated NCC to process the service request. Other active NCCs within the spot beam will ignore a request associated with another NCC. If the NCC identified by the mobile as it registered NCC is not currently active in the spot beam, the Master will process the initial access request. As an initial service access attempt, the Master NCC will process the Channel Request message due to the absence of an identified associated NCC and select a GW for assignment to the mobile 502. The Master NCC will also handle service access attempts in which an NCC is identified in the Access Request but for which the identified/associated Slave NCC is not currently active in the particular spot beam.
Based on other information (such as indication of call termination, for example) provided in the Channel Request message, the Master NCC 451B will direct the call to an appropriate GW (in a preferred embodiment, the service access is processed by the associated Master NCC gateway 450B, as seen in Figure 4), step 503. The response from a Slave GW 450A, 450C to which the service request is directed includes a resource allocation for the mobile to establish signaling/communication with the GW as well as a notification to the Master NCC by the gateway of whether the GW will initiate Slave NCC functionality for the beam.
The principle of the system operation is that a gateway may initiate support for Slave NCC functionality in a given beam dependent on its available physical (channel unit) resources and the existence of associated mobiles that it serves in the particular spot beam. The Slave GW 450A, 450C may choose not to activate a NCC for the beam solely based on the first service request received through the Master NCC
451B. In such an event, common channel signaling for the associated gateway NCC will continue to be supported through the Master NCC.
Figure 6 illustrates the initial signaling access for the case in which a registered MT 440 attempts to establish service in a spot beam in which its associated NCC 451A is currently active. The MT 440 will send a channel request in step that is received by both the Master NCC 451B and the slave NCCs 451A and 451C.
As shown, the Master NCC 451B is aware of the active status of the Slave NCC
450A, and will ignore the Channel Request and allow it to be processed by the mobile's associated NCC 451A. Other NCC's 451C that are not associated with the mobile will ignore the Channel Request.
The associated Slave NCC 451A receives the request through its independent processing of the information received on the common control channels) allocated in the particular spot beam. Then, the associated Slave NCC 451A will assign in step 602 a channel for the traffic that is to be exchanged between the mobile 440 and GW
450A. Even though the access request messages that are correctly received and processed by the Master NCC 451B and Slave NCCs may differ, this does not affect the distributed system operation. For requests directed at an identified NCC, e.g., NCC 451A, the particular NCC will handle collision and contention resolution.
For purposes of redundancy the Master NCC 451B may use the occurrence of repeated successfully received access requests to a particular NCC to analyze the operational status of that NCC.
The operation of the proposed distributed NCC architecture model is further highlighted by examining the signaling flows involved in the establishment of network-initiated requests. The information flows are again meant to be general, given the simple schematic arrangement in Figure 4, and is not intended to disclose the details of particular circuit-switched or packet-switched service invocations, as these would be well known to one of ordinary skill without undue experimentation.
The signaling and communications assumptions are based on those of standard mobile communications systems in which network-initiated service is based on the use of common control paging (alerting) channels to notify mobiles of an intended establishment of network service. The mobile, if available, responds via the inbound random access channels and the process is completed as identified above.
The generic establishment of network-initiated service for the case in which only the Master NCC 451B operates in the mobile's current registered spot beam is illustrated in Figure 7. This Figure shows the case in which the service access is initiated by the transmission of a paging request to the Master NCC 451B in step 701 from a GW 450C that does not support an Active NCC for the beam in which the mobile is registered. The request is sent by the master NCC 451B to the mobile as a page in step 702. However, based on the response of the mobile as a channel request in step 703 to the Master NCC 451B, a page response in step 704 is provided to the Slave NCC 451C and the Slave NCC is made active in step 705. Then, in step 706 the GW 450C indicates to the Master NCC 451B its decision to activate a Slave NCC
451C in the spot beam. The Master NCC 451B will note the newly activated Slave NCC 451C, will provide a channel assignment to the mobile 440 in step 707 and will relinquish its own control over the outbound channel resources that had been apportioned to the gateway, due to its support of mobiles in the particular spot beam.
In the event that the GW 450C chooses not to activate an NCC 451C in the particular beam, all common control channel signaling to mobile terminals in the beam are supported through the Master NCC 451B.
Finally, for the case in which a network-initiated service is established through a GW 450A that supports an Active NCC 451A in the registered beam of the intended mobile, the service access occurs directly via the Slave NCC's outbound common control assignment. Figure 8 illustrates the signaling flow for the service initiation, which is begun with a mobile page from the Slave NCC 451A to the mobile 440 in step 801. The mobile responds with a channel request in step 802, which is followed y a channel assignment by the Slave NCC 451C in step 803. Those channels will be consistent with the paging group operation of the mobile terminal 440. As indicated above, the system may implement mechanisms in which the Master NCC 451B
always controls the common paging channels. Where the Master NCC 451B controls all common control paging, the request will be initiated through the Master NCC
451B. However, in such a case, the Slave NCC 451A or C will still process the Channel Request message and transmit the corresponding access grant Channel Assignment using its assigned access grant capacity.
While the invention has been disclosed in connection with certain preferred embodiments, it is not limited thereto, and the full scope of the invention is defined in the appended claims, as interpreted in accordance with applicable law.
Claims (16)
1. A mobile satellite communication system comprising:
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; and said first and second terrestrial stations being assigned a single set of common control channels for said overlapping spot beams.
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; and said first and second terrestrial stations being assigned a single set of common control channels for said overlapping spot beams.
2. The satellite communication system of claim 1, wherein said control channels comprise inbound common control channels and outbound common control channels that are shared among said overlapping terrestrial stations under central control.
3. The satellite communication system of claim 1, further comprising a master station operative to receive control information on said single set of common control channels and to control traffic communication of said plurality of terrestrial stations, acting as slave stations.
4. The satellite communication system of claim 3 wherein one of said first and second terminals is a master station and the other of said first and second terminals is a slave station, said master station providing coordination of common channel usage among said other of said first and second terminals and other of said plurality of terminals sharing control channels in overlapping ones of said spot beams.
5. The satellite communication system of claim 1 wherein each of said first and second terminals comprise equipment operative to control the active sharing of the common channels of said overlapping satellite beams.
6. The satellite communication system of claim 3 further comprising an inter-station synchronizing network, for communicating control information between said master station and said slave stations.
7. The satellite communication system of claim 6, wherein said one of said first and second stations is not operative to receive said control channels and is operative to receive control information from said master station that provides channel assignments via said inter-station signaling network.
8. The satellite communication system of claim 7 wherein said master station is part of one of said first or second terrestrial stations.
9. The satellite communication system of claim 3 wherein said mobile terminals comprise means for transmitting on random access channels a request for capacity and means having access grant channels for receiving an access grant from a slave station or said master station.
10. The satellite communication system of claim 3 where each said mobile comprises means for establishing paging receiver cycles and means for receiving intermittent pages from a slave stations or said master station.
11. In a mobile satellite communication system comprising:
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams; and a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; a method for permitting said network switching systems to use common control channels comprising:
assigning said first and second terrestrial stations a single set of common control channels for said overlapping spot beams.
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams; and a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; a method for permitting said network switching systems to use common control channels comprising:
assigning said first and second terrestrial stations a single set of common control channels for said overlapping spot beams.
12. The method of claim 11 wherein said assigning step is conducted by a master station, and said method further comprises transmitting from said master station to other slave stations information about said assignment of said common control channels.
13. In a mobile satellite communication system comprising:
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; and a master station;
a method for assigning to a mobile terminal the control channels of an associated network switching system in a beam in which multiple network switching systems share use of the common control channels comprising:
requesting said master station to provide a channel at said mobile terminal;
selecting one of said first and second stations as assigned to said mobile terminal;
requesting from said selected station a capacity; and activating said network switching system for said mobile terminal.
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; and a master station;
a method for assigning to a mobile terminal the control channels of an associated network switching system in a beam in which multiple network switching systems share use of the common control channels comprising:
requesting said master station to provide a channel at said mobile terminal;
selecting one of said first and second stations as assigned to said mobile terminal;
requesting from said selected station a capacity; and activating said network switching system for said mobile terminal.
14. The method of claim 13 further comprising the steps of:
at said master station, assigning a channel to said mobile station.
at said master station, assigning a channel to said mobile station.
15. In a mobile satellite communication system comprising:
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams ; and a master station;
a method for providing a network initiated service access through a terrestrial station acting as a slave station comprising:
paging said mobile terminal by said slave station;
in response to receipt of said page by said mobile terminal, requesting a channel assignment; and in response to said request, providing a channel assignment.
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams ; and a master station;
a method for providing a network initiated service access through a terrestrial station acting as a slave station comprising:
paging said mobile terminal by said slave station;
in response to receipt of said page by said mobile terminal, requesting a channel assignment; and in response to said request, providing a channel assignment.
16. In a mobile satellite communication system comprising:
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; and a master station;
a method for providing a network initiated service access through said master station comprising:
at a slave station, requesting the master station to issue a page to said mobile station;
paging said mobile terminal by said master station;
in response to receipt of said page by said mobile terminal, requesting a channel assignment by said master station;
advising said slave station of said page response at said slave station, activating an appropriate network switching system; and providing a capacity allocation and channel assignment.
selecting
a satellite operative to generate a plurality of communication spot beams within a beam footprint, at least a first and second of said spot beams being overlapping;
a plurality of mobile terminals operative to receive and transmit information on traffic channels and command channels provided within at least one of said spot beams;
a plurality of terrestrial stations, comprising at least a first and second station, each station comprising satellite base station equipment for communicating with the satellite via traffic channels and command channels formed within a plurality of spot beams, and a network switching subsystem acting as a gateway, at least one of said terrestrial stations being operative to provide service to at least one of said mobile users via the traffic channels in overlapping ones of said spot beams; and a master station;
a method for providing a network initiated service access through said master station comprising:
at a slave station, requesting the master station to issue a page to said mobile station;
paging said mobile terminal by said master station;
in response to receipt of said page by said mobile terminal, requesting a channel assignment by said master station;
advising said slave station of said page response at said slave station, activating an appropriate network switching system; and providing a capacity allocation and channel assignment.
selecting
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16587899P | 1999-11-16 | 1999-11-16 | |
| US60/165,878 | 1999-11-16 | ||
| PCT/US2000/031463 WO2001037450A1 (en) | 1999-11-16 | 2000-11-16 | Distributed control architecture for mobile systems with overlapping service coverage regions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2391563A1 true CA2391563A1 (en) | 2001-05-25 |
Family
ID=22600857
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002391563A Abandoned CA2391563A1 (en) | 1999-11-16 | 2000-11-16 | Distributed control architecture for mobile systems with overlapping service coverage regions |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU769052B2 (en) |
| CA (1) | CA2391563A1 (en) |
| GB (1) | GB2373971B (en) |
| WO (1) | WO2001037450A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030050072A1 (en) * | 2001-09-06 | 2003-03-13 | Anthony Noerpel | Dark beam operation scenario |
| US10601502B2 (en) * | 2018-02-05 | 2020-03-24 | Hughes Network Systems, Llc | Systems and methods for flexible assignment of beams to gateways in a high throughput digital payload satellite network |
| CN110769426B (en) * | 2018-07-27 | 2023-06-09 | 哈尔滨海能达科技有限公司 | Method and control device for dynamically allocating channels based on converged base station |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5634190A (en) * | 1995-06-06 | 1997-05-27 | Globalstar L.P. | Low earth orbit communication satellite gateway-to-gateway relay system |
| FR2735302B1 (en) * | 1995-06-12 | 1997-07-11 | Alcatel Espace | SCREENED SATELLITE COMMUNICATION SYSTEM, STATION AND TERMINAL INCLUDING SAME |
| US5905943A (en) * | 1997-04-29 | 1999-05-18 | Globalstar L.P. | System for generating and using global radio frequency maps |
-
2000
- 2000-11-16 CA CA002391563A patent/CA2391563A1/en not_active Abandoned
- 2000-11-16 GB GB0210232A patent/GB2373971B/en not_active Expired - Fee Related
- 2000-11-16 WO PCT/US2000/031463 patent/WO2001037450A1/en active IP Right Grant
- 2000-11-16 AU AU17684/01A patent/AU769052B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| GB0210232D0 (en) | 2002-06-12 |
| GB2373971A (en) | 2002-10-02 |
| AU1768401A (en) | 2001-05-30 |
| AU769052B2 (en) | 2004-01-15 |
| WO2001037450A1 (en) | 2001-05-25 |
| GB2373971B (en) | 2003-10-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |