GB2308951A - Radio telecommunication system for layered wide area roaming management - Google Patents

Description

2308951 RADIO TELECOMMUNICATION SYSTEM AND METHOD FOR LAYERED WIDE AREA

ROAMING MANAGEMENT

Field Of the Invention

The present invention relates generally to the provision of roaming management services in radio telecommunication systems.

Background Of the Invention

Subscriber units used with radio telecommunication systems are often registered at a home system but can be used on certain other systems when prior arrangements have been made between the systems' service providers. To be of value to subscribers, such arrangements need to be made with service providers in all areas where the subscribers wish to travel. Since subscribers can potentially travel all over the world, many such prior arrangements can be required to achieve subscriber satisfaction.

A subscriber unit is said to be roaming when it operates upon one of these other systems where prior arrangements have been made. In order to accommodate roaming, certain roaming management services are provided. Roaming management services include maintaining valid subscriber unit location information so that the system upon which a subscriber unit is currently roaming can be identified. Calls being placed to a roaming subscriber unit can then be forwarded to the appropriate system in response to this information. Roaming management services also include maintaining subscriber information which serves a role in authorization and credit verification. Thus, when a roaming subscriber unit attempts to register or place a call through a system at which the subscriber unit is not registered, the system can get assurances that it will receive payment for the requested services.

Conventional radio telecommunication switching nodes treat each other as peers for the,purposes of providing roaming management services for one another. In other words, each switching node has equal status with respect to the provision of roaming management services. For example, the Global System for Mobile communications (GSM) assigns subscriber units to home mobile switching centers (MSCs). A home location register (HLR) is established for each subscriber unit in the subscriber unit's home MSC. The HLR records a complete subscriber and subscriber unit profile. The HLR additionally stores location data which identify any MSC upon which the HLRls subscriber unit can be roaming.

When a roaming subscriber unit (i.e. a roamer) first registers at a roamed-upon MSC, the roamed-upon MSC contacts the home MSC to inform the home MSC of the roamer's roaming status and current geographic location. The home MSC can authorize and/or authenticate the roamer to essentially verify the roamer's credit worthiness for the roamed-upon MSC. If roaming is authorized, the roamed-upon MSC establishes a visiting location register (VLR) for the roamer. Call terminations (i.e. calls being placed to the subscriber unit) are first directed to a roamer's home MSC in response to the roamer's phone number, MIN, or other ID. Such calls are then forwarded to the roamed-upon MSC from the home MSC so that the roamed- upon MSC can set up the calls with the roamer.

while the conventional technique is effective in providing roaming management services, it has some serious drawbacks as the number of radio telecommunication switching nodes increases. Moreover, the number of such switching nodes continues to increase due to the expansion of radio telecommunication services. Increases result from extending radio telecommunication services to new areas and from overlaying new radio telecommunication services in areas already covered by existing systems.

If "N" represents the number of systems which wish to provide roaming management services for one another, then the number of potential contacts conventionally required to permit roaming among the N systems is (N-1)2. In addition, W-1)2 legal contracts must be entered into among the population of service providers, and each service provider must comply with laws, tariffs, rights (including carrier frequency allocations), and regulations associated with communicating with all of the other N-1 service providers. Furthermore, the population of service providers uses diverse types of equipment. The conventional technique requires each of the N systems to be compatible with all types of equipment. Accordingly, conventional roaming management services lead to costly and complex inefficiencies as the number of radio telecommunication service providers grows and as roaming management services are provided over more radio telecommunication systems.

Thus, there is a significant need for a less complex, less expensive global roaming management system.

Brief Description Of the Drawings

A more complete understanding of the present invention can be derived by referring to the detailed description and claims when considered in connection with the figures, wherein like reference numbers refer to similar items throughout the figures, and:

FIG. 1 shows a higher level layout diagram.of an environment within which a radio telecommunication system can operate; FIG. 2 shows a lower level layout diagram of the environment; FIG. 3 shows a block diagram of hardware included in a multimode subscriber unit; FIG. 4 shows a flow chart of an activation process; FIG. 5 shows a flow chart of a multimode subscriber unit process; FIG. 6 shows a flow chart of a local switching node process; FIG. 7 shows a flow chart of a wide area switching node process; and FIG. 8 shows a flow chart of a termination call request process included in the wide area switching node process.

Detailed Description Of the Drawings

The present invention offers a method of providing wide area roaming management services for radio telecommunication units, the method comprising the steps of: a) establishing a wide area communication network having a home switching node and a remote switching node; b) assigning a subscriber unit to the home switching node of the wide area communication network; c) receiving a roaming contact from the subscriber unit at a local communication network switching node; d) contacting, from the local communication network switching node, the remote switching node of the wide area communication network to evaluate the roaming contact; and e) contacting the home switching node of the wide area communication network from the remote switching node of the wide area communication network to evaluate the roaming contact.

The subscriber unit can be a multimode unit and the method can further comprise the steps of: following a first communication protocol to establish a communication session between the subscriber unit and the wide area communication network; and following a second communication protocol to establish a communication session between the subscriber unit and the local communication network. 30 The first communication protocol following step can comprise the step of determining a geographic location for the subscriber unit. The method can additionally comprise the step of determining, at the remote switching node of the wide area communication network, whether to initiate a communication session with the subscriber unit using the first or second communication protocol.

The determining step can comprise the steps of:

recording data describing whether a prior communication session with the subscriber unit used the first or second communication protocol; initiating a communication session with the subscriber unit using the first communication protocol when the prior communication session with the subscriber unit used the first communication protocol; and initiating a communication with the subscriber unit using the second communication protocol when the prior communication session with the subscriber unit used the second communication protocol.

The method can additionally comprise the step of locating the remote switching node of the wide area is communication network proximate the local communication network switching node.

The method can additionally comprise the step of receiving data at the local communication network switching node from the subscriber unit, the data indicating that the subscriber unit is assigned to a node included in the wide area communication network.

The method can additionally comprise the step of arranging the wide area communication network and the local network so that area covered by the local network is included in area covered by the wide area communication network.

The present invention additionally offers a method of providing wide area roaming management services for radio telecommunication units, the method comprising the steps of: a) establishing a wide area communication network having a first multiplicity of switching nodes and a network radio coverage area encompassing substantially the entire surface of the earth; b) distributing home assignments for a second multiplicity of multimode subscriber units among the first multiplicity of wide area communication network switching nodes; c) locating a selected one of the first multiplicity of switching nodes proximate a local switching node of a 5_ 1 local network; d) receiving roaming contacts from a portion of the second multiplicity Of subscriber units at the local switching node; e) contacting, from the local switching node, the selected node of the wide area communication network to evaluate the roaming contacts; and f) contacting various ones of the first multiplicity of switching nodes from the selected node to evaluate the roaming contacts, the various ones of the switching nodes being identified in response to the home assignments distributed in the step b).

FIG. 1 shows a higher level layout diagram, and FIG. 2 shows a lower level layout diagram of an environment within which a radio telecommunication system 10 can operate. Referring to FIGs. 1 and 2, system 10 includes a wide area communication network (WACN) 12 and any number of local communication networks (LCNs) 14. In the preferred embodiment, WACN 12 is a satellite-based communication network. WACN 12 offers a wide area communication network radio coverage area encompassing substantially the entire surface of the earth through the use of a constellation of switching nodes placed in satellite vehicles, or satellites, (SVs) 16 located in outer space. For clarity, FIGs. 1 and 2 illustrate only a few of these satellites 16. Within WACN 12, satellites 16 communicate with devices on the ground through up to hundreds of central switching 25 of fice nodes (CS0s) 18, of which FIGs. 1 and 2 show only a few, and up to millions of multimode subscriber units 20, of which FIGs. 1 and 2 show only a few. CS0s 18 and subscriber units 20 can be located anywhere on or near the surface of the earth. However, CS0s 18 are desirably positioned to accommodate geopolitical considerations. For example, each CSO 18 can control WACN communications for a country where the CSO 18 is located. However, large countries can have multiple CS0s 18, and small countries can share CS0s with neighbor countries. 35 Terrestrial-based communication systems, such as conventional LCNs 14 and other components of the worldwide -6 Public switched telecommunication network (PSTN) 26, can access WACN 12 through CS0s 18. Desirably, the constellation of satellites 16 is configured so that at least one of satellites 16 is within view of each point on the surface of the earth at all times. Accordingly, WAW 12 can establish a communication circuit through the constellation of satellites 16 between any two subscriber units 20, between any subscriber unit 20 and a CSO 18, or between any two CS0s 18. Other telephonic and communication devices can couple to such circuits through CSO-to-PSTN interfaces. As shown in FIGS. 1 and 2, satellites 16 communicate with adjacent satellites via cross-links 33.

WAW 12 can be viewed as a higher layer communication network. Conversely, LCNs 14 can be viewed as lower layer communication networks. Conventional terrestrial cellular communication systems represent one form of an WN 14. A variety of such systems are known to those skilled in the art by the acronyms GSM, CD11A, JDC, USDC, AMPS, and the like. Each WN 14 has a local radio coverage area which is overlapped by or included in the radio coverage area of WACN 12. Up to thousands of LCNs 14 can be provided throughout the world, and nothing requires LCNs 14 to be of a common variety. Each WN 14 is controlled by a local mobile switching center (MSC) 28. Any number of base stations 30 couple to a local MSC 28 and provide radio transmitters and receivers (not shown) through which radio communications take place with multimode subscriber units 20 located within the WN radio coverage area. Some of these systems provide for roaming between LCNs using network roaming standards such as GSM or IS-41. These standards provide for roaming only between LCNs that use a common standard and have direct MSCto-MSC communications.

In a typical scenario, a subscriber will wish to communicate through any available WN 14 rather than WACN 12 because communication services, including roaming communication services, will mostAikely be less expensive.

However, WAW 12 is available over substantially the entire surface of the earth for use by multimode subscriber units 20 when an WN 14 is not available. Of course, preference for an WN 14 is no requirement of the present invention, and nothing prevents a multimode subscriber unit 20 from communicating through WAW 12 even when and where an WN 14 is available for providing communication services.

WAW communications involving subscriber units 20 take place via RF communication links 32 with satellites 16. WN communications involving subscriber units 20 take place via RF communication links 34 with base stations 30. Desirably, RF communication links 32 and 34 employ sufficiently different communication protocols to minimize interference within the common radio coverage areas. A communication protocol represents the time, frequency, and/or coding rules, procedures, formats, and conventions which are followed by two devices in order to communicate with one another. Accordingly, RF communication links 32 employ a communication protocol referred to below as protocol A and RF communication links 34 employ a communication protocol referred to below as protocol B. The specific nature of protocols A and B is unimportant for the purposes of the present invention.

In accordance with the preferred embodiment of the present invention, roaming management services are provided by WAW 12 for any number of WNs 14 with respect to any multimode subscriber unit 20 in a simple and efficient manner. CS0s 18 and MSCs 28 are substantially conventional radio telecommunication switches. Such switches perform processes, discussed below, under the control of software 30, programming. Generally, a multimode subscriber unit 20 is assigned to a CSO 18 which thereafter adopts the role of a "home" node within WAW 12 for that subscriber unit. Over a population of CS0s 18 and subscriber units 20, home assignments are distributed throughout CS0s 18 of WAW 12. Any CSO 18 which is not the home node can serve the role of being a "remote" node within WAM12 for a subscriber unit 1' 20. For an exemplary situation, FIGs. 1 and 2 refer to the home node as CSO 181 and the remote node as CSO 1811.

At the same time, a subscriber unit 20 can be assigned to a home local MSC 28, which has an agreement to store subscription records in the home location register of CSO 18.

When a subscriber unit 20 attempts to engage in communications through any local MSC 28 other than the home local MSC 28, a roaming situation occurs. For the exemplary situation, FIG. 1 refers to a home local MSC 28 as MSC 281, and FIGs. 1 and 2 refer to a roamed-upon local MSC 28 as MSC 2V. When roaming on MSC 2V, roaming management services are preferably provided exclusively through the CSO 18 located proximate the MSC 2811. Thus, whether this CSO 18 is a home CSO 181 or a remote CSO 18", the roamed-upon local MSC 28" follows the same process to obtain roaming management services. FIGs. 1 and 2 show only a single roamed-upon local MSC 2V being associated with a single CSO 18. However, any number of roamed-upon local MSCs 2C can be associated with a single CSO 18.

This process includes contacting or otherwise establishing a communication link 36 to proximately located remote CSO 1C. Roamed-upon local MSC 2V need not contact home nodes for roaming subscriber units 20. Thus, global roaming management services are provided by making arrangements with only the providers of WACN 12 rather than with a multitude of potential "home" service providers.

Likewise, roamed-upon local MSC 2V need only comply with interface requirements of a single CSO 18 rather than a plurality of interface requirements imposed by any number of diverse switching centers. Further, by providing the appropriate set of standards inter-working functions, any CSO 18 may connect to many MSCs 28 where each of the MSCs 28 could use a different roaming support interface standard. In addition, for most situations the roamed-upon WN 14 need not concern itself with complying with inter-geopolitical jurisdiction communication requirements, including complying with rules and regulations and paying tariffs, to obtain roaming management services.

FIG. 3 shows a block diagram of multimode subscriber unit 20. Subscriber unit 20 includes a controller and signal processing section 38. Section 38 couples to A and B transceivers 40 and 42, respectively, to a memory 44, and to an I/0 section 46. Section 38 includes microprocessor or other controller components and related peripheral devices in addition to components which process call traffic. The controller portion of section 38 causes subscriber unit 20 to perform processes defined by computer software stored in memory 44. In addition, memory 44 records tables, databases, variables, and other memory structures which are used in the operation of subscriber unit 20. 1/0 section 46 includes any sort of user or electronic interface between subscriber unit 20 and the world outside of subscriber unit 20. Such interfaces can include a keypad, display, microphone, speaker, and the like.

The software recorded in memory 44 includes a protocol A program 48, a protocol B program 50, and a general program 52. Protocol A program 48 includes software which causes multimode subscriber unit 20 to operate on WACN 12 (see FIGs. 1-2) over RF communication link 32 (see FIG. 2) using protocol A. Transceiver 40 accommodates communication over link 32 using protocol A. Protocol B program 50 includes software which causes multimode subscriber unit 20 to operate on an WN 14 (see FIGs. 1- 2) over RF communication link 34 (see FIG. 2) using protocol B. Transceiver 42 accommodates communication over link 34 using protocol B. Nothing requires transceivers 40 and 42 to be similar to one another in frequency, modulation format, coding techniques, or the like. General program 52 includes software which is common to or independent of protocol A or B operation. Such software controls I/0 section 46 and determines whether to execute protocol A program 48 or protocol B program 50.

FIG. 4 shows a flow chart of,an activation process 54.

10- Generally, process 54 is performed to personalize system 10 and a newly acquired multimode subscriber unit 20 so that the newly acquired subscriber unit 20 can be used on system 10. While FIG. 4 shows a particular sequencing of tasks, those skilled in the art will appreciate that the tasks need not follow in the indicated sequence.

In a task 56, data which describe the newly acquired subscriber unit 20 and its subscriber are collected. Such data include subscriber unit identification information, subscriber identification information, billing information, feature packages to be activated, and other information commonly collected during activation of conventional radiotelephones. In addition, a task 58 is performed to assign a home CSO node 181 for the subscriber unit 20 within WACN 12, and a task 60 is performed to assign a WAW subscriber unit ID to the subscriber unit 20. Desirably, the subscriber unit ID assigned in task 60 is consistent with the home CSO node 181 assigned in task 58. Other nodes in WACN 12 can uniquely identify a subscriber unit's home CSO node 181 by evaluating the subscriber unit's ID.

A task 62 stores a subscriber profile in a home location register (HLR) 64 (see FIG. 2) at the home CSO node 181. The subscriber profile is a relatively complete record of information concerning the subscriber and subscriber unit 20.

A task 65 stores the WAM subscriber unit ID in subscriber unit 20. As discussed in more detail below, subscriber unit 20 uses its WACN subscriber unit ID to identify itself when operating on either an LCN 14 or WAM 12. A task 66 is optional. Task 66 repeats the home and ID assignments for a particular selected LCN 14. Thus, through task 66 subscriber unit 20 can have a home LCN 14 and an ID which identifies the subscriber unit 20 to the home LCN 14. Task 66 is optional because nothing prevents any LCN 14 wishing to be the home LCN 14 for a.multimode subscriber unit 20 from adopting the WACN activation as its own. In this situation, a multimode subscriber unit 20 uses its WACN ID for LCN 14 and WACN 12 operation.

FIG. 5 shows a flow chart of a multimode subscriber unit process 68. Desirably, substantially all multimode subscriber units 20 perform a process similar to that described in FIG. 5. Process 68 is defined through software programming stored in memory 44 (see FIG. 3).

Process 68 includes a task 70 which identifies the networks which are available to provide communication services. More precisely, task 70 determines whether WAW 12, WN 14, or both are available at the time and location where task 70 is performed. Task 70 monitors predetermined protocol A and protocol B communication channels to identify the available networks. Next, a query task 72 decides whether to use an WN 14 for subsequent communication services. In a typical scenario, any WN 14 will be preferred over WACN 12 because communication service fees are less expensive. However, this is not a requirement. The precise selection criteria used in task 72 is unimportant for the purposes of the present invention.

When task 72 decides to use an WN 14, a task 74 selects protocol B. The selection of protocol B causes subsequent communication sessions to use transceiver 42 and to be controlled by protocol B program 50 (see FIG. 3). Next, a task 76 makes a roaming contact with the WN 14, assuming that subscriber unit 20 is not already registered to operate on the WN 14 and that subscriber unit 20 is, in fact, roaming. The roaming contact is made by sending a registration request message to a local MSC 28 (see FIG. 2).

The registration request message is sent using RF communication link 34 and protocol B via a base station 30 (see FIGs. 1-2). The registration request message includes the subscriber unit's WAW ID. Although not shown in FIG. 5, if subscriber unit 20 is already registered on the WN 14, task 76 can be omitted. If subscriber unit 20 is not roaming, then any contact or message sent to an MSC 28 can be considered a homing contact rather than a roaming contact. A 12 homing contact registration request message can but is not required to include the subscriber unit's WACN ID.

After task 76, a query task 78 determines whether access to the network is approved. Process 68 can remain at task 78 until a message is received from the contacted network before making its determination. However, additional tasks (not shown) can be included to prevent program control from remaining at task 78 should no return message be forthcoming.

The return message should indicate whether the request for registration was granted (i.e. access approved) or denied.

If access is not approved, then a task 80 performs an appropriate error handling process. Task 80 can, for example, inform the user of the problem, repeat the registration request message a certain number of times, or the like. After task 80, program control loops back to task to continue to identify available networks.

When task 78 determines that access on the contacted network is approved, a query task 82 determines whether a call origination event is occurring. A call origination event can occur when, for example, a user dials a phone number to make an outgoing call. If call origination is occurring, a task 84 performs a call origination process.

Task 84 includes conventional call setup, call monitoring, and call tear down activities. After task 84, program control loops back to task 70 to continue to identify available networks.

When task 82 determines that no call origination is occurring, a query task E6 determines whether a call termination event is occurring. A call termination event can occur when, for example, a third party attempts to place a call subscriber unit 20. In this situation, the network on which subscriber unit 20 is currently registered will direct a page message to subscriber unit 20. The page message will include identifying data that essentially address subscriber unit 20. Thus, task 86 determines whether such a page message addressed to subscriber unit 20 has been received.

If a call termination is occurring, a task 88 performs a call termination process. Task 88 includes conventional call setup, call monitoring, and call tear down activities. After task 88, program control loops back to task 70 to continue to identify available networks. Likewise, when task 86 determines that no call termination is occurring, program control loops back to task 70.

Referring back to task 72, when task 72 decides not to use an WN 14, a task 90 selects protocol A. The selection of protocol A causes subsequent communication sessions to use transceiver 40 and to be controlled by protocol A program 48 (see FIG. 3). Next, a query task 92 determines whether a registration event has occurred. In the preferred embodiment, a registration event occurs when subscriber unit 20 moves a predetermined distance since it last registered with WAW 12 or if a predetermined duration has elapsed since subscriber unit 20 last registered with WAW 12. When no registration event has occurred, program control flows to task 82 to test whether call origination or termination events are occurring.

When task 92 determines that a registration event has occurred, a task 94 sends a registration request message to WAW 12. The registration request message is sent using RF communication link 32 and protocol A via a satellite 16 (see FIGs. 1-2). The registration request message in cludes the subscriber unit's WAW ID. After or in conjunction with task 94, a task 96 performs a location determination process to determine a current geographical location for subscriber unit 20. In the preferred embodiment, task 96 monitors position information broadcast from overhead satellites 16 and evaluates Doppler and signal propagation delays in communications with WAW 12 to determine location. As a result of task 96, WAW 12 resolves the subscriber unit's location. After task 96, program control flows to task 78 to evaluate whether access is approved on WAW 12.

Accordingly, subscriber unit,20 operates in multiple modes to communicate with multiple communication networks.

When roaming contacts are made to an WN 14, the subscriber unit 20 identifies itself using its WAW ID. Based upon the WAW ID, the WN 14 can conclude that the subscriber unit 20 has a home node in WAW 12.

FIG. 6 shows a flow chart of a local switching node process 98. Process 98 is performed by a local MSC 28 or a local MSC 28 in conjunction with its base stations 30 (see FIG. 2). Desirably, substantially all local MSCs 28 and base stations 30 perform a process similar to that described in FIG. 6. All communications with subscriber unit 20 which take place through MSC 28 are compatible with protocol B. Process 98 includes numerous sub-processes. A roaming contact process 100, a termination call request process 102, and an origination call request process 104 are included among these sub-processes. Numerous other processes performed by MSC 28,such as a homing contact process, are not shown for the purpose of clarity. Roaming contact process 100 is performed when a roaming contact is received from a subscriber unit 20. A roaming contact occurs when subscriber unit 20 attempts to register for communication services on the WN 14. Process 100 is performed for all subscriber units 20 which have a WAW ID regardless of which CS0s 18 (see FIGs. 1-2) are the subscriber units' homes.

Process 100 includes a task 106 which evaluates the WAW subscriber unit ID. In response to task 106, a query task 108 determines whether the subscriber unit has a home node included in WAW 12. If the subscriber unit ID does not indicate a home node within WAW 12, then a task 110 performs 30- a suitable error handling process. If task 110 is being performed, the subscriber unit making a roaming contact can have a home node on some network other than WAW 12. So long as the WN 14 has made prior arrangements with this other network, task 110 can perform conventional procedures for obtaining roaming management services. If no prior arrangements have been made, task,110 can simply ignore the roaming contact, or preferably return an access denied message. After task 110, program control exits process 100. When task 108 determines that a roaming contact comes from a subscriber unit 20 having a home in WACN 12, a task 112 establishes a communicatlon session with the remote CSO node 1V assigned to the MSC 28" (see FIG. 2) performing process 100. The communication session can be established using land line links 36 formed through PSTN 26 (see FIG. 2). As discussed above, the assigned CSO node 18" is desirably 10 located proximate MSC 2V relative to the scope of WAW 12. The assigned MSC 2V desirably remains the same regardless of the subscriber unit's home CSO 18. Thus, each MSC 28 follows a single process to obtain roaming management services with respect to all subscriber units 20, and all CS0s 18 appear as 15 a single node to each local MSC 28. After task 112 contacts the assigned remote CSO 1V, a task 114 passes the subscriber unit's registration request to the remote node of WACN 12 to evaluate the roaming contact. This registration request includes the subscriber unit's ID. 20 The roaming contact is evaluated through the receipt of roaming management services with respect to the requesting subscriber unit 20. Next, a query task 116 determines whether access is approved for the roaming subscriber unit 20. Process 100 can remain at task 116 until a message is received from the contacted remote CSO 18" before making its determination. However, additional tasks (not shown) can be included to prevent program control from remaining at task 116 should no return message be forthcoming. If access is not approved, then a task 118 performs an appropriate error 30 handling process. Task 118 can, for example, return an access denied message to the requesting subscriber unit 20 over RF communication link 34 (see FIG. 2). After task 118, program control exits process 100. When task 116 determines that access has been approved, 35 a task 120 constructs a visitor location register (VLR) 122 (see FIG. 2) for the roaming subscriber unit 20. VLR 122 16contains, among other things, a subset of the information from the roamer's HLR 64 (see FIG. 2). This information is returned to the roamed-upon MSC 28" from WAW 12. In addition, task 120 can assign a temporary ID to the roaming subscriber unit 20 for use by the subscriber unit 20 while it is roaming upon tie MSC 2811.

After task 120, a task 124 sends an access granted message to the roaming subscriber unit 20. The access granted message is sent in accordance with protocol B. At this point, the subscriber unit 20 is operational on the WN 14 as a roamer. After task 124, program control exits process 100.

Termination call request process 102 is performed to process a call setup being directed to a subscriber unit, is such as the roaming subscriber unit 20. The request to terminate a call at the subscriber unit can be received at the MSC 28 from remote node 1811 of WAW 12, but it can also come from PSTN 26. Process 102 is performed in a conventional manner to page the subscriber unit 20 identified in the request using protocol B communications, determine whether the call is answered, monitor any answered call, and tear down the call after completion.

Origination call request process 104 is performed to process a call setup request originating at a registered subscriber unit, such as a roaming subscriber unit 20. The origination call request is received at MSC 28 from subscriber unit 20 via protocol B communications.

Conventional processes are used to setup the call through the PSTN 26. However, in an alternate embodiment the call is setup through WAW 12. Process 104 performs call setup, monitors the call, and tears down the call after completion.

FIG. 7 shows a flow chart of a wide area switching node process 126. Process 126 is performed by a CSO 18 of WAW 12. Desirably, substantially all CS0s 18 perform a process similar to that described in FIG. 7.

Process 126 includes numerou's sub-processes. A receive registration request process 128, a termination call request process 130, and an origination call request process 132 are included among these subprocesses. Numerous other processes performed by a CSO 18 are omitted for the purposes of clarity. Receive registration request process 128 is performed when a request for registration is received from a subscriber unit 20. The registration request can come to CSO 18 via protocol A, RF communication link 32 (see FIG. 2), and a satellite 16. Alternatively, the registration request can come to CSO 18 via a WN 14 using protocol B, RF communication link 34 (see FIG. 2), and an MSC 28 performing process 100 (see FIG. 6). The CSO 18 receiving the registration request can be either a home CSO 181 for the requesting subscriber unit 20 or a remote CSO 1811.

Process 128 includes a query task 134 which determines whether the registration request received from a subscriber unit 20 came through an WN 14. If the registration request did not come through an WN 14, then it was received directly from subscriber unit 20 in accordance with protocol A. When received in accordance with protocol A, a task 136 clears a local-net flag to record data which describe the protocol subscriber unit 20 is using for this and subsequent communication sessions. The communication protocol used by the subscriber unit 20 for subsequent communication sessions is normally by default that for which data was recorded in a prior communication session. Next, a task 138 performs a location determination process. Task 138 complements task 96 (see FIG. 5). During task 138, protocol A communications take place to identify the location of subscriber unit 20.

When task 134 determines that the registration request came through an WN 14, a task 140 sets the local - net flag to record data which describe the protocol subscriber unit 20 is using for this and subsequent communication sessions. In addition, when multiple LCNs 14 are assigned to the CSO 18 performing process 128, task 140 can record the identity of the WN 14 through which the registration request was 18- received so that future calls being terminated to subscriber unit 20 can be routed through that WN 14.

After tasks 138 or 140, a query task 142 determines whether the CSO 18 performing process 128 is the home CSO 18 for subscriber unit 20. Task 142 can make its determination by evaluating the WAW subscriber unit ID included in the registration request. If the subject CSO 18 is not the home node, then it is a remote WAW node for subscriber unit 20. When the subject CSO 18 is a remote node, a task 144 sends the registration request message and current location information for subscriber unit 20 to the subscriber unit's home node to evaluate the roaming contact. For the purposes of the home node, the identity of the subject CSO 18 can serve as the location information. Such identity information will inform a home node how to contact subscriber unit 20 in the future.

After task 144, a query task 146 determines whether access is approved for subscriber unit 20. Process 128 can remain at task 146 until a message is received from the contacted home CSO 18 before making its determination. However, additional tasks (not shown) can be included to prevent program control from remaining at task 146 should no return message be forthcoming. If access is not approved, then a task 148 performs an appropriate error handling process. Task 148 can, for example, return an access denied message to the requesting subscriber unit. This message is returned in accordance with the protocol through which the registration request was received. Protocol A communications are returned via a satellite 16 and protocol B communications are returned via an WN 14.

When task 148 determines that access has been approved, a task 150 establishes a visitor location register (VLR) 152 (see FIG. 2) for the roaming subscriber unit 20. VLR 152 contains a subset of the information contained in the roamer's HLR 64 (see FIG. 2). This information is obtained from the home CSO 18 in a message,which responds to the registration request message. Task 150 is optional to the extent that protocol B communications are being used because the roamed-upon MSC 2V (see FIG. 2) will maintain its own VLR 122 (see FIG. 2) to support a roaming subscriber unit. However, implementation efficiencies can result from establishing VLR 152 even though it can not be needed. This task is not optional when protocol A communications are being used.

Referring back to task 142, when the CSO node 18 of WACN 12 which receives a registration request message from a subscriber unit is the home node, a task 154 performs an authorization process. For example, task 154 can perform a suitable authentication algorithm in response to a cryptographic key passed to the home CSO 18 in the registration request. In addition, task 154 may investigate billing records to determine the credit worthiness of the subscriber unit 20. If the registration request was sent to the home CSO 18 from a remote CSO 18, task 154 desirably returns the results of the authorization process to this 20 remote CSO 18, where the remote CSO is waiting at task 146, then exits (not shown). Assuming that authorization occurs, a task 156 updates the subscriber unit's HLR 64 (see FIG. 2) with a current indication of subscriber unit location. After each of tasks 148, 150, and 156, process 128 25 performs a task 158. Task 158 routes an access granted or access denied message back to subscriber unit 20. Access is either granted or denied in response to the authorization process performed at the home CSO 18 in task 154. If the registration request came through an WN 14, then task 158 passes the access granted or denied message back to the local MSC 28 through link 36 (see FIG. 2). The message will be passed back to subscriber unit 20 using protocol B in tasks 118 or 124 (see FIG. 6). If the registration request came via a satellite 16, then task J.58 sends the access granted or denied massage back to subscriber unit 20 via a satellite 16 using protocol A. After task 158, process 128 exits.

FIG. 8 shows a flow chart of termination call request process 130, which is performed by a remote and/or home CSO 18 in WAW 12. Process 130 generally attempts to complete a call to a subscriber unit 20. Process 130 includes a query task 160 which determines whether the CSO 18 performing process 130 is the called subscriber unit's home node within WAW 12. If the CSO 18 performing process 130 is the home node, a task 162 gets a current location for subscriber unit from HLR 64 (see FIG. 2). The location is updated each time subscriber unit 20 re-registers. However, this location data need not define location more precisely than to provide the identity of a CSO 18 through which the subscriber unit 20 can be reached. After task 162, a task 164 passes the termination call request on to the CSO 18 associated with the current location for subscriber unit 20. If the current location for subscriber unit 20 is the home CSO 18, then task 164 simply passes the termination call request to itself.

Otherwise, task 164 passes the termination call request to a remote CSO 18.

After task 164 and when task 160 determines that the CSO 18 performing process 130 is not the home CSO 18, a query task 166 determines whether a location register (LR), such as an HLR 64 or VLR 152 (see FIG. 2), is active for the subscriber unit 20 being called. If a location register is active, then an attempt to page the called subscriber unit 20 should be attempted through this CSO 18. However, if a location register is not active, then a task 168 forwards the termination call request to the called subscriber unit's home CSO 18. Of course, if the CSO 18 performing task 168 is the called subscriber unit's home CSO 18, then an appropriate error handling process can be performed instead. After task 168, program control exits process 130.

When task 166 determines that an HLR or VLR is active for the called subscriber unit 20, a query task 170 determines whether the local net flag is set for the called subscriber unit 20. The local_net flag was set or cleared during a prior registration at tasks 140 or 136 (see FIG. 7). If the local - net flag is set, a task 172 passes the termination call request to the appropriate MSC 28. The MSC 28 will page the called subscriber unit through process 102 (see FIG. 6) using protocol B communications. If the local-net flag is clear, a task 174 pages the called subscriber unit 20 via a satellite 16 using protocol A communications. After tasks 172 or 174, program control exits process 130 after following other conventional termination call request tasks related to call setup, call monitoring, and call tear down activities. Referring back to FIG. 7, origination call request process 132 is performed to process a call setup request originating at a registered subscriber unit 20. The origination call request is received at CSO 18 from a subscriber unit via protocol A or B communications. Conventional processes are used to setup the call through the PSTN 26. Process 132 performs call setup, monitors the call, and tears down the call after completion. 20 In summary, the present invention provides an improved radio telecommunication system and method for layered wide area roaming management. Roaming management services are provided for the entire globe by a single contact from a local communication network switch. In addition, roaming management services are provided for the diverse modes of multimode subscriber units by a single contact from a local network switch. Further, a wide area communication network provides roaming management services for any number of local communication networks which can reside within the wide area. The present invention has been described above with reference to preferred embodiments. However, those skilled in the art will recognize that changes and modifications can be made in these preferred embodiments without departing from the scope of the present invention. For example, the wide area communication network need not be global in scope. Likewise, roaming management services can be provided for more than two layers of communication networks. Moreover, those skilled in the art will appreciate that the processes and tasks identified herein can be categorized and organized differently than described herein while achieving equivalent results. These and other changes and modifications which are obvious to those skilled in the art are intended to be included within the scope of the present invention.

Claims (38)

CLAIMS What is claimed is:

1. A method of providing wide area roaming management services for radio telecommunication units, said method comprising the steps of:

a) establishing a wide area communication network having a home switching node and a remote switching node; b) assigning a subscriber unit to said home switching node of said wide area communication network; c) receiving a roaming contact from said subscriber unit at a local communication network switching node; d) contacting, from said local communication network switching node, said remote switching node of said wide area communication network to evaluate said roaming contact; and e) contacting said home switching node of said wide area communication network from said remote switching node of said wide area communication network to evaluate said roaming contact.

2. A method as claimed in claim 1 wherein said subscriber unit is a multimode unit and said method comprises the steps of:

following a first communication protocol to establish a communication session between said subscriber unit and said wide area communication network; and following a second communication protocol to establish a communication session between said subscriber unit and said local communication network.

3. A method as claimed in claim 2 wherein said first communication protocol following step comprises the step of determining a geographic location for said subscriber unit.

4. A method as claimed in claim 2 additionally comprising the step of determining, at said remote switching node of said wide area communication network, whether to initiate a communication session with said subscriber unit using said first or second communication protocol.

5. A method as claimed in claim 4 wherein said determining step comprises the steps of: recording data describing whether a prior communication session with said subscriber unit used said first or second communication protocol; initiating a communication session with said subscriber unit using said first communication protocol when said prior communication session with said subscriber unit used said first communication protocol; and initiating a communication with said subscriber unit using said second communication protocol when said prior communication session with said subscriber unit used said second communication protocol.

6. A method as claimed in claim 1 additionally comprising the step of locating said remote switching node of said wide area communication network proximate said local communication network switching node.

7. A method as claimed in claim 1 additionally comprising the step of receiving data at said local communication network switching node from said subscriber unit, said data indicating that said subscriber unit is assigned to a node included in said wide area communication network.

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8. A method as claimed in claim 1 additionally comprising the step of arranging said wide area communication network and said local network so that area covered by said local network is included in area covered by said wide area communication network.

9. A method as claimed in claim 1 wherein: said step a) establishes said wide area communication network to have a first multiplicity of switching nodes, including said home and remote switching nodes; said step b) distributes home assignments for a second multiplicity of subscriber units among said first multiplicity of wide area communication network switching nodes; said step c) receives roaming contacts from a portion of said second multiplicity of subscriber units at said local communication network switching node; said step d) contacts, from said local communication network switching node, said remote switching node of said wide area communication network to evaluate each of said contacts; and said step e) contacts various ones of said first multiplicity of switching nodes to evaluate said roaming contacts, said various ones of said switching nodes being identified in response to said home assignments distributed in said step b).

10. A method as claimed in claim 1 wherein: said wide area communication network covers substantially the entire surface of the earth using a plurality of switching nodes located proximate the surface of the earth and a plurality of switching nodes located in outer space; and said home switching nodes and remote switching nodes are located proximate the surface of the earth.

11. A method as claimed in claim 1 wherein said roaming contact is a registration request.

12. A radio telecommunication system with layered wide area roaming management services, said radio telecommunication system comprising: a wide area communication network having a home switching node and a remote switching node and being configured to have a wide radio coverage area; and a local network having a local switching node and being configured to have a local radio coverage area included in said wide radio coverage area, said local switching node being configured to communicate with said remote switching node to evaluate a roaming contact received from a multimode subscriber unit having a home assignment at said home switching node.

13. A radio telecommunication system as claimed in claim 12 wherein said remote switching node of said wide area communication network is configured to contact said home switching node of said wide area communication network to evaluate said roaming contact.

14. A radio telecommunication system as claimed in claim 12 wherein:

said nodes of said wide area communication network are configured to follow a first communication protocol to establish a communication session with said subscriber unit; and said local switching node of said local network is configured to follow a second communication protocol to establish a communication session with said subscriber unit.

15. A radio telecommunication system as claimed in claim 14 wherein said remote switching node of said wide area communication network is configured to determine, when a call termination is being directed to said subscriber unit, whether to initiate a communication session with said subscriber unit using said first or second communication protocol.

16. A radio telecommunication system as claimed in claim 12 wherein said remote switching node of said wide area communication network is located proximate said local node of said local network.

17. A radio telecommunication system as claimed in claim 12 wherein:

said wide radio coverage area encompasses substantially the entire surface of the earth and said wide area communication network has a first plurality of switching nodes located proximate the surface of the earth and a second plurality of switching nodes located in outer space; and said home switching nodes and remote switching nodes are located proximate the surface of the earth.

18. A radio telecommunication system as claimed in claim 12 wherein:

said wide area communication network has a first multiplicity of wide area communication network switching nodes, including said home and remote switching nodes; home assignments for a second multiplicity of subscriber units are distributed among said first multiplicity of switching nodes; a portion of said second multiplicity of subscriber units makes roaming contacts at said local network switching node; and said local switching node communicates with said remote switching node of said wide area communication network to evaluate each of said contacts.

19. A radio telecommunication system as claimed in claim 18 additionally comprising a plurality of additional local networks each of which has a local switching node, wherein each local switching node is configured to communicate with a specified one of said first multiplicity of wide area communication network switching nodes to evaluate roaming contacts from said second multiplicity of subscriber units.

20. A method of providing wide area roaming management services for radio telecommunication units, said method comprising the steps of:

a) establishing a wide area communication network having a first multiplicity of switching nodes and a network radio coverage area encompassing substantially the entire surface of the earth; b) distributing home assignments for a second multiplicity of multimode subscriber units among said first multiplicity of wide area communication network switching nodes; c) locating a selected one of said first multiplicity of switching nodes proximate a local switching node of a local network; d) receiving roaming contacts from a portion of said second multiplicity of subscriber units at said local switching node; e) contacting, from said local switching node, said selected node of said wide area communication network to evaluate said roaming contacts; and f) contacting various ones of said first multiplicity of switching nodes from said selected node to evaluate said roaming contacts, said various ones of said switching nodes being identified in response to said home assignments distributed in said step b).

21. A subscriber unit enabling a user of said subscriber unit to roam within a wide area communication network (WACN) or within a local communication network (LCN), or within both said WAW and said WN, said subscriber unit comprising:

a radio transceiver for communicating with said WACN and with said WN; and a memory for storing first and second protocols for enabling said subscriber unit to operate within said WACN and said WN, respectively.

22. The subscriber unit recited in claim 21, and further comprising a user interface adapted to receive a selection of one of said first and second protocols by a user of said subscriber unit.

23. The subscriber unit recited in claim 22, and further comprising a controller responsive to said user interface and coupled to said radio transceiver for communicating with said WAM if said first protocol is selected by said user and for communicating with said WN if said second protocol is selected by said user.

24. The subscriber unit recited in claim 21, wherein said memory stores a task which identifies whether said WAW, said WN, or both are available for telecommunication with said subscriber unit.

25. The subscriber unit recited in claim 24, wherein said task monitors said subscriber unit's telecommunications using said first and second protocols to identify the availability of said WACN, said WN, or both.

26. The subscriber unit recited in claim 23, wherein if said subscriber unit is not registered on the WN, said subscriber unit can make a roaming request to said WN.

27. The subscriber unit recited in claim 26, wherein said roaming request comprises a subscriber unit identity number within the WAW, said identity number being stored within said subscriber unit's memory.

28. The subscriber unit recited in claim 23, wherein said controller initiates a new telecommunication session by said subscriber unit with whichever protocol was utilized for a prior telecommunication session,

29. A local switching node (LSN) adapted for operation within a wide area communication network (WACN) and within a local communication network (LCN), said WN being further adapted to communicate with a radio telecommunication subscriber unit operating within said WAW, within said WN, or within both said WAW and said WN, said WN comprising:

a controller responsive to a radio communication from said radio telecommunication subscriber unit requesting a call operation, said controller determining whether said radio telecommunication subscriber unit is registered with said LSN; if so, completing said call operation; and if not, sending a registration request message to said WAW, including a subscriber unit identity number for said radio telecommunication subscriber unit.

30. The WN recited in claim 29, wherein said registration request message is sent to said radio telecommunication subscriber unit's home central switching office of said WACN.

31. The MN recited in claim 29, wherein said call operation is a call origination or call termination.

32. The WN recited in claim 29, wherein if said radio telecommunication subscriber unit is registered with said local switching node, said controller accesses information in a visitor location register (VLR) regarding said radio telecommunication subscriber unit.

33. The WN recited in claim 29, wherein if said radio telecommunication subscriber unit is registered with said LSN, said controller transmits a message to said radio telecommunication subscriber unit that access has been approved for said call operation., -32

34. A central switching office (CSO) node adapted for operation within a wide area communication network (WACN) and within a local communication network (LCN) which comprises a local switching node (LSN), said CSO node being further adapted to communicate with a radio telecommunication subscriber unit operating within said WAW, within said WN, or within both said WAW and said WN, and with an WN operating within said LW, said CSO node comprising:

a controller responsive to a radio communication transmitted to it through said WN from said subscriber uni requesting a call operation, said controller determining whether said radio telecommunication subscriber unit is registered with said CSO node; if so, completing said call operation; and if not, sending a registration request messagef including a subscriber unit identity number for said radio telecommunication subscriber unit, through said WAW to a different CSO node in which said radio telecommunication subscriber unit is registered.

35. The CSO node recited in claim 34, wherein said registration request message is sent to said radio telecommunication subscriber unit's home CSO node of said WAW.

36. The CSO node recited in claim 34, wherein said call operation is a call origination or call termination.

37. The CSO node recited in claim 34, wherein if said radio telecommunication subscriber unit is registered with either of said CSO nodes, a controller associated with said CSO node accesses information in said CSO node's visitor location register (VLR) regarding said radio telecommunication subscriber unit.

38. The CSO node recited in claim 34, wherein if said radio telecommunication subscriber unit is registered with either of said CSO nodes, a controller associated with said CSO node transmits a message to said radio telecommunication subscriber unit that access has been approved for said call operation.