Method and apparatus for roaming in hierarchical mobile communications network

METHOD AND APPARATUS FOR ROAMING IN HIERARCHICAL MOBILE COMMUNICATIONS NETWORK

BACKGROUND OF THE INVENTION

0003Field of the Invention This invention relates to the field of communication networks. In particular, the invention relates to a method and apparatus for roaming in a mobile communications network. Description of the Related Art

0004A mobile communications system may include various systems between which a subscriber may wish to travel. Often a subscriber is associated with a particular system and when the subscriber is present in a region serviced by another system, the subscriber is considered to be roaming. A subscriber's home system is typically a system for which the subscriber is registered. Several techniques allow mobile subscribers to roam into systems different from the subscriber's home system. An example is the IS-41 based system.

0005Some prior art systems use home location and visited location registers (HLR/VLR) and even dedicated switching networks for mobile subscribers. A disadvantage of some prior systems is the possibility of single point of failure, the need for a dedicated signaling network, the need for central coordination between entities entering into roaming agreements and difficulties in billing. Some methods in the prior art rely on explicit rules for determining the home location of a roaming subscriber and how to handle a call to and from such a subscriber. Typically in such applications these functions are carried out by interrogation of an HLR. Such an approach introduces complexity and delay. Prior art methods also may require additional signaling traffic to establish correct billing for each call since the path may go through a different exchange than the subscriber's home exchange. Such additional signaling may be complex. SUMMARY OF THE INVENTION

0006One aspect of the invention is directed to a method of modifying an existing telephone network. Interface devices serve various geographic regions of the telephone network. The interface devices are coupled to the telephone network. The interface devices are coupled to circuitry coupled to radio transceivers that service mobile subscribers that may be located in ones of the geographic regions. The mobile subscribers are each assigned to a respective geographic region. When a subscriber is located in a region other than the geographic region to which the subscriber is assigned, circuitry coupled to the interface devices routes a call with a mobile subscriber through a path including a radio transceiver that serves the region in which the mobile subscriber is currently located and an interface device that serves the region to which the subscriber is assigned.

0007One embodiment of the present invention is directed to a communications system that includes a first network dispersed throughout a national area. The communications system also includes a second network coupled to the first network by interfaces in a plurality of geographic regions in the national area. The second network includes radio transceivers for communicating with subscribers located in the plurality of geographic regions. Each subscriber has a home region, and various subscribers are located outside of their home regions. The system includes circuitry that routes all communication between a subscriber and the first network through an interface between the first network and the second network in the subscriber's home region. Another embodiment of the present invention is directed to a communications system that includes a set of interfaces adapted to be coupled to a public switched telephone network (PSTN). The interfaces are configured to serve various geographic regions. For communication between the PSTN and a subscriber located in a region other than a region in which an interface to which the subscriber is assigned is located, circuitry included by the system and coupled to the set of interfaces causes the communication to take place via the interface to which the subscriber is assigned. According to one embodiment to the invention, the circuitry coupled to the set of interfaces is coupled to the interfaces via an El interface.

0008Yet another embodiment to the invention is directed to a communications system comprising radio transceivers and a set of interface devices adapted to be coupled to a PSTN. The interface devices are configured to serve various geographic regions. The radio transceivers are coupled to the interface devices in the set of interface devices. The radio transceivers are for communication with mobile subscribers. The mobile subscribers each have a home region. The circuitry coupled to the set of interfaces routes a call through a path including an interface device that serves the mobile subscriber's home region, for a call involving the PSTN and a mobile subscriber located outside the mobile subscriber's home region.

0009Another aspect of the invention is directed to a method of modifying an existing telephone network in which interface devices are located in various geographic regions of the telephone network. The interface devices are coupled to the telephone network in the various geographic regions. The interface devices are coupled to circuitry coupled to radio transceivers that service mobile subscribers that may be located in ones of the geographic regions. The mobile subscribers are each assigned to a respective geographic region. When a subscriber is located in a region other than the geographic region to which the subscriber is assigned, circuitry coupled to the interface devices routes a call with a mobile subscriber through a path including a radio transceiver in the region in which the mobile subscriber is currently located and an interface device in the region to which the subscriber is assigned. In yet another embodiment of the invention, each subscriber is associated with one or more directory numbers. Routing of incoming calls is conditioned upon a subscriber profile when the subscriber is out of the subscriber's home geographic region. Incoming calls may be routed to the subscriber in the subscriber's new location or to another subscriber or to voice mail depending on the subscriber's feature profile and which directory number with which the call is associated. If a subscriber has for example directory numbers 1, 2, 3 assigned, the subscriber may set up the subscriber profile to cause the interface device to act as follows when the subscriber is out of the area:

0010- for incoming calls associated with number 1 , route to the subscriber's new location ("follow-me" number); - for incoming calls associated with number 2, route another directory number; or

0011- for incoming calls associated with number 3, route to voice mail.

BRIEF DESCRIPTION OF THE FIGURES

0013FIG. 1 is a block diagram of a telephone communications system, according to an embodiment of the invention.

0014FIG. 2 is a block diagram illustrating circuitry acting as a proxy for radio ports belonging to other interface devices for terminating calls, according to an embodiment of the invention.

0015FIG. 3 is a block diagram illustrating circuitry acting as a proxy for network ports for a first interface for calls originating from mobile subscribers assigned to another region, according to an embodiment of the invention. FIG. 4 is a flow diagram of location registration, according to an embodiment of the invention.

0016FIG. 5 is a flow diagram of an originating call process, according to an embodiment of the invention.

0017FIG. 6 is a flow diagram of a terminating call process, according to an embodiment of the invention.

0018FIG. 7 is a flow diagram of an interface handover process, according to an embodiment of the invention. FIG. 8 is a block diagram illustrating the circuitry that routes calls configured as regional circuitry interconnected centrally, according to an embodiment of the invention.

0019FIG. 9 is a block diagram illustrating expanded circuitry for routing calls connected by a local or distributed control bus, according to an embodiment of the invention. FIG. 10 is a block diagram illustrating circuitry that routes calls implemented in a mesh configuration, according to an embodiment of the invention.

0020FIG. 11 is a block diagram showing circuitry that routes calls configured to route calls to home interfaces through the public switched telephone network (PSTN) by including a gateway functionality inside interface devices, according to an embodiment of the invention.

DETAILED DESCRIPTION

0022One embodiment of the invention is directed to a system for routing calls when subscribers are located outside of the coverage area of an interface to the public network in their home area. When such a subscriber wants to make a call, the circuitry routes the call to an interface to the public network that serves the home area. Similarly, incoming calls from the public network are routed through the interface that services the home region, to equipment in the region outside of the home region where the subscriber is currently located. Such an arrangement has an advantage of, according to one embodiment, making roaming transparent to the public network and billing systems.

0023FIG. 1 is a block diagram of a telephone communications system, according to an embodiment of the invention. The system includes interface devices that are coupled to the public network (NIUA 111, NIUB 112, and NIUc 113). Radio port controllers are coupled to the various interfaces ~ as shown, NIUA 111 is coupled to RPC_Aι 115 and RPCA2 117, NIU_B 112 is coupled to RPCBI 119 and RPC_B2 121, and NIU_C 113 is coupled to RPC 124 and RPC_C2 125. The radio port controllers are coupled to radio transmitters ~ RPC_AI 115 is coupled to radio transceivers 116, RPC_A2 117 to radio transceivers 118, RPC_BI 119 is coupled to radio transceivers 120, RPCβ₂ 121 is coupled to radio transceivers 122, RPCci 124 is coupled to radio transceivers 126, and RPCc₂ 125 is coupled to radio transceivers 127. Radio transceivers are used to communicate with mobile subscribers, for example, PS_A 123. Radio transceivers include radio ports and appropriate transceiver circuitry.

0024The interfaces each serve a different geographic region by being coupled, through the radio port controllers, to radio transmitters that serve the respective geographic region. According to one embodiment of the invention, such interfaces are located in the respective regions that they serve. According to another embodiment of the invention, such interfaces are not necessarily located in the respective regions that they serve. For example, the interfaces may be co-located. Circuitry ATCi 114 couples the various interface devices (NIUA 111, NIU_B 112, and NIUc 113. Circuitry ATCi 114 may be implemented in the form of dedicated circuits, or a computerized system. Typically, circuitry AT 114 includes bearer channels and control channels. El links are provided to interconnect the various interface devices via ATCi 114. Circuitry that routes calls between interface devices, circuitry ATC as shown in Fig. 1 , may be implemented as a computer system. The ATC circuitry acts as a controller and includes an El interface. The circuitry ATC includes bearer and control circuitry. The bearer circuitry provides a path for transmission of information, such as voice from a subscriber, to the correct interface. Such transmission typically occurs over an El interface. The circuitry that routes between the interfaces (e.g., ATC) includes a cross connect, which is a split that maps between various incoming and outgoing lines. An ATC may have, in one example, 30 multiplexed lines. An interface device, shown in FIG. 1 as, for example, NIU_A 111, may be implemented as a computer with controllers. The interface device includes interface boards for interfacing with radio port controllers (e.g., RPC_AI 115). Such interfacing takes place typically via an El standard. The interface from the interface device to the PSTN (PSTN 110) may take place via an analog, Tl interface, or other interface. The interface device is typically coupled to a class 5 switch in the PSTN.

0025According to one embodiment of the invention, an interface device can have a large number of subscribers assigned to it, e.g., 10,000 subscribers, and a large number of roaming subscribers. According to one embodiment of the invention, subscribers are registered in a particular home interface device for billing purposes and because of telephone number assignment to the particular PSTN ports to which the home interface device is connected. The sizing of connectivity between interface devices and circuitry ATCs is determined by the amount of roaming traffic between respective interface devices and the desired grade of service for such roaming traffic.

0026When a subscriber, for example, PS_A 123 is located out of the subscriber's home area, the following may occur, according to an embodiment of the invention. Radio ports under a network interface emit a paging area identifier unique for each network interface. This paging area identifier is received by subscribers in the network interface's coverage area. As a subscriber moves away from the region served by the subscriber's home network interface device, say, NIU_A 111 , it notices that the paging area identifier changes. The subscriber then knows that it has moved into the coverage area of a new network interface device. At this point, the subscriber, say PS_A 123, sends a registration message including its own identification to the new network interface device, say NIUB 112. NIUB 122 receives the registration request and notices from the subscriber identification that PS_A 123 is not assigned in an NIU_B'S 112 database.

0027NIUB 112 forwards a registration request to circuitry ATCi 114. ATCi 114 either knows about the subscriber PS_A 123 (through previous registration or calls made by a subscriber PS_A 123) or does not know about subscriber PS_A 123. If ATd 114 knows about subscriber PS_A 123, then circuitry ATd 114 updates the location entry in its database for subscriber PSA 123 to indicate that the subscriber PS_A 123 is located in the area covered by interface device NIU_B 112 and sends the registration request on to interface device NIU_A HI. If circuitry ATCi 114 does not know about subscriber PSA 123, then circuitry ATCi 114 sends the registration request on to NIUs connected to ATCi 114 except to the interface device that originated the request. In this case, for example, the registration request is sent to interface device NIUA 111 and interface device NIUc 113 but not to interface device NIU_B 112. The one interface device recognizes the subscriber PS_A 123 from the subscriber identification contained in the registration message. Such interface device recognizes subscriber PS_A 123 as assigned to that interface device's database and responds to the registration request. The circuitry ATd 114 then updates its table to reflect that subscriber PS_A 123 belongs to interface device NIU_A 111 and is currently assigned to NIUB 112. In another embodiment of the invention, subscriber PS_A 123 is programmed with the identity of its assigned or home region, or is programmed with the identity of the assigned or home network interface device. According to one embodiment of the invention, such assignment is made at the time the subscriber is activated for service and has the ability to inform the network about the subscriber's home region and/or corresponding interface device. Upon receipt of such notification, an interface device serving each visited region can directly forward the registration to the proper home interface device through the circuitry ATC.

0028In another embodiment of the invention, each interface device and circuitry ATC can deduce from the construction of the subscriber identification to which region the subscriber belongs. The registration is then forwarded to the proper home interface device corresponding to the region through the circuitry ATC. An example of such subscriber identification structuring is the use of prefixes unique to each interface device.

0029When a call comes in for subscriber PS_A 123 from the public network (terminating call), interface device NIU_A 111 sends a page request to radio port controllers under NIU_A 111 and also to circuitry ATCi 114. Because subscriber PS_A 123 is outside of the coverage of network interface NIUA H I, none of the radio port controllers under interface device NIUA 111 respond with a positive page acknowledgement. If circuitry ATCi 114 knows about subscriber PS_A 123, it forwards the page to the NIU under whose coverage it knows subscriber PS_A 123 to have most recently been in (for example, to interface device NIU_B 112). If circuitry ATCi 114 does not know about subscriber PS_A 123, circuitry ATCi H4 sends the page to all interface devices coupled to circuitry ATCi 114, except to the originating interface device (in this case, to interface device NIU_B 112 and interface device NIUc 113, but not to interface device NIU_A 111)- The interface device that has subscriber PS_A 123 under its coverage responds to the page. Circuitry ATCi 114 forwards the page response to the home interface device and establishes a call path between a home interface device, through circuitry ATCi 114, through a visited interface device and to subscriber PS_A 123. Authentication and alerting are also performed. An advantage of such a configuration is that a call may be delivered to subscriber PSA 123 without the home interface device, interface device NIU_A H I, explicitly knowing the location of subscriber PSA 123. In another embodiment to the invention, the home interface device keeps track of the location of each subscriber assigned to it by communication from circuitry ATC and therefore can directly page the correct radio port controller for a terminating call without having the circuitry ATC broadcast the page to all interface devices connected to it. Because the home interface device updates its database as the location is updated in the circuitry ATC, an advantage is gained that the interface device does not need to query the circuitry ATC.

0030Having the home interface device keep track of the location of each subscriber assigned to it also allows the home interface to make different routing decisions when the subscriber is out of the subscriber's home coverage area, according to one embodiment of the invention. When a single subscriber is associated with multiple directory numbers, such an approach may provide an advantage. Incoming calls associated with each of the directory numbers may be routed differently depending on instructions in the subscriber's service profile. For instance, calls associated with (directed to) the subscriber's first directory number may be routed to the subscriber's new location ("follow-me" service), calls associated with a subscriber's second directory number may be sent to voice mail, and calls associated with a subscriber's third directory number may be routed to another subscriber. When subscriber PS_A 123 wants to originate a call from the coverage area of a visited region covered by interface device NIU_B 112, subscriber PS_A 123 sends a set-up message to interface device NIU_B 112. Then NIU_B 112 recognizes that subscriber PS_A 123 is not assigned in the database of interface device NIUB 112. Call handling proceeds as in the case of registration and the call path is established between subscriber PS_A 1 3 through the interface device NIUB 112 in the visited region, through circuitry ATCi 114 and home interface device NIU_A 111. An advantage of such a configuration is that the call from subscriber PSA 123 is delivered to the network without the interface device which makes contact with subscriber PS_A 123 necessarily knowing which interface device is the home interface device for subscriber PSA 123.

0031According to one embodiment of the invention, the same messages are exchanged between the interface device and the circuitry ATC for traveling subscribers as are exchanged between the interface device and radio port controllers for a home subscriber.

0032In another embodiment of the invention, subscriber PS_A 123 is programmed with the identity of its home region or corresponding home interface device at the time the subscriber is activated for a service. The subscriber has the ability to inform the network about its home region or interface device. Upon receipt of such notification with a call set-up message, each visited region's interface device can directly forward the call to the proper home interface device through the circuitry ATC. In another embodiment to the invention, each interface device and circuitry ATC can deduce from the construction of a subscriber identifier which region or interface device the subscriber belongs to and directly forward the registration to the proper home interface device through the circuitry ATC. An example of such subscriber ID structuring is the use of prefixes unique to each interface device or region.

0033When a subscriber moves from the coverage of a radio port belonging to a first interface device to the coverage of another radio port belonging to an interface device different from the first interface device, the subscriber initiates a handover by dropping the connection to the old radio port and requesting a new connection to the new radio port. The circuitry ATC processes the set-up messages similarly to a regular originating call, with the exception that authentication steps are skipped to reduce the time to set the new handover call and with the exception that the circuitry ATC retains any parts of the existing call that are common to the handover call. Since calls enter or leave the mobile communications network through the home interface device of a subscriber even when the subscriber is located outside of the subscriber's home region, according to one embodiment of the invention, no change is needed in the billing methods of the public switched telephone network (PSTN) to which the mobile communications network connects. If an operator optionally wishes to bill differently for roaming calls, this flexibility is provided through separate call detail records which record call information such as which radio port and interface devices are involved in each call.

0034FIG. 2 is a block diagram illustrating circuitry acting as a proxy for radio ports belonging to other interface devices for terminating calls, according to an embodiment of the invention. Thus, this shows that circuitry ATC may act logically like another radio port controller coupled to an interface device. For example, here interface device NIU_A 211 is coupled to radio port controller RPC_AI 212 and radio port controller RPC_A2214. Circuitry ATC 216 routes calls to respective interface devices (not shown) thus logically allowing access through interface device NIU _A 211 to radio port controllers RPC_{C 1}221 , RPC _C2 223, RPC _Bi 217, and RPC_B2219. Thus, subscriber PS _A 230, whose home interface device is interface device NIU _A 211, is provided access to PSTN 210 via remote radio ports serving a region outside of subscriber's PS_A 230 home region. Thus, logically, the ATC 216 circuitry makes radio ports 222, 224, 218, and 220, which serve a remote region, appear like local radio ports coupled to home interface device NIUA 211 •

0035FIG. 3 is a block diagram illustrating circuitry acting as a proxy for network ports for a first interface for calls originating from mobile subscribers assigned to another region, according to an embodiment of the invention. An originating call is placed from subscriber PS_A 320, currently located in the region of network interface NIU_B 317. This call is received by a radio port among radio ports 319, which are coupled to radio port controller RPCBI 318. Radio port controller RPC BI 318 is coupled to interface device NIU_B 317, which is coupled to PSTN 310. However, the call is routed through an ATC to interface device NIUA 311 through which the call is then routed to the PSTN 310. Thus, a virtual connection exists from interface device NIU_B 317 into a portion of the PSTN to which interface device NIU_A 311 is coupled. This is shown in the figure as the connection between interface device NIU_B 317 and PSTN 316. Similarly, connection is provided virtually from interface device NIUc 323 to PSTN 310. This connection takes place physically through a connection between interface device NIUc 323 and interface device NIUA 11. However logically, it is as if there is a connection between interface device NIUc 323 at the portion of the PSTN to which interface device NIU_A 311 is connected. This is shown here as a connection between interface device NIUc 323 and PSTN 324.

0036FIG. 4 is a flow diagram of the location registration process, according to an embodiment of the invention. Fig. 4 has various lines representing communication with the following entities: PSTN 410, NIU_A411, NIU_B412, NIUc 413, RPC_BI 414, RPC_B2415, ATC 416, and PS_A417. First a registration message is received by a radio port and forwarded to the radio port controller. As shown here, location registration 418 is sent from subscriber PS_A 417 to radio port RPC_BI 414. In this case, subscriber PS_A 417 is located in the coverage area of radio port controller RPC_BI 414, which is not the home location of subscriber PSA 417. Radio port controller RPCB_I 414 sends a message to its respective interface device, interface device NIU_B 412 (line 419). Interface device NIU_B 412 does not recognize subscriber PSA 417. Thus interface NIUB 412 sends a message to the circuitry ATC 416 (line 420).

0037Assuming that ATC 416 has not yet stored PS_A 417 in its database, then ATC 416 queries other interface devices to determine the home location for subscriber PSA 417 (lines 421 and 422, which are sent to interface device 411 NIU_A and interface device NIUc 413, but not interface device NIU_B 412). In this example, subscriber PS_A 417 belongs to interface device NIU_A

0038411. Thus, interface device NIU_A 411 responds (authorization request 423). ATC 416 forwards this response to interface device NIUB 412. Interface device NIU_B 412 then sends the authorization request 428 to interface device NIU_B

0039412. An authorization response is sent back (429) from interface device NIU_B 412 to circuitry ATC 416. The authorization response is then sent from circuitry ATC 416 back to interface device NIU_A 411. Interface device NIU_A 411 determines whether the subscriber PS_A 417 should be authenticated, and can then make future determinations based on this authentication.

0040FIG. 5 is a block diagram of an originating call process, according to an embodiment of the invention. Here it is assumed that subscriber PS_A 517 is already registered at the particular location and that the circuitry ATC knows that subscriber PS_A 517 belongs to interface device NIU_A 511. Subscriber PS_A 517 is located in the coverage area of interface device NIUB 512. Thus, subscriber PSA 517 sends a set-up request 518 to radio port controller RPC_BI 514. This request is forwarded to interface device NIU_B 512 (line 519). Interface device NIUB 512 signals circuitry ATC's 516 (line 520). Because circuitry ATC 516 knows that subscriber PSA 517 belongs to interface device NIU_A 511, circuitry ATC 516 signals interface device NIU_A 511. Interface device NIU_A 511 makes an authorization request (line 522) to circuitry ATC 516. In response, circuitry ATC 516 forwards the request to interface device NIU_B 512 (line 523), and interface device NIU_B 512 forwards the request to radio port controller RPC_{B I} 514, which forwards the message to subscriber PSA 517 (line 525). An authentication response is returned from subscriber 517 to radio port controller RPC_BI 514 (line 525), and this result is forwarded to interface device NIU_B 512 (line 527), and to circuitry ATC 516 (line 528) and back to interface device NIU_A 511 (line 529). If the authentication result is good, then NIU_A 511 makes a set-up request to the PSTN 510 (line 530). A connect response is received from PSTN 510 to interface device NIU_A 511 (connect line 531). The PSTN makes necessary set-up in order to connect the message back.

0041The connect message is then forwarded to circuitry ATC 516 from interface device NIUA 511 (line 532). This response is forwarded from circuitry ATC 516 to interface device NIU_B 512 (line 533) and subsequently to radio port controller RPC_Bι 514 and on to subscriber PS_A 517 (lines 534 and 535). A communications connection is then set up between subscriber PSA 517 and PSTN 510. The communications path includes subscriber PS_A 517, radio port controller RPC_{B I} 514, interface device NIU_B 512, circuitry ACT 516, interface device NIUA 511, and PSTN 510. In this way, a call path is established between a subscriber (PSA 517) and the public-switched telephone network (PSTN 510) by way of the subscriber's home interface device (NIU_A 511).

0042FIG. 6 is a flow diagram of a terminating call process, according to an embodiment of the invention. Shown here is communication between entities: public switched to telephone network PSTN 610, interface device NIUA 611, interface device NIUB 612, interface device NIUc 613, radio port controller RPC_BI 614, radio port controller RPC_B2 615, circuitry ATC 616, radio port controller RPC_AI 617, radio port controller RPCA2 618, and subscriber PS_A 619. When a call originates from PSTN 610, its set-up request is sent from PSTN 610 to interface device NIU_A 611 (set-up 620). This set-up request is made to interface device NIUA 611 because that interface device is the home interface device for subscriber PS_A 619. Interface device NIU_A 611 sends a setup request to the radio port controllers coupled to interface device NIU_A 11 (radio port controller RPC_A, radio port controller RPCAI 617, and radio port controller RPC_A2 618, via set-up request 622 and 623). A set-up request is also sent to ATC 616 (set-up 621). This set-up 621 is sent to ATC 616 because

0043ATC 616 looks to interface device NIU_A 611 like another radio port controller. Circuitry ATC 616 sends a set-up request to interface device NIU_B 612 (line 624). Interface device NIU_B 612 sends the set-up request to radio port controllers located in the areas of interface device NIU_B 612 (radio port controller RPCBI 614 and radio port controller RPCβ₂615, lines 625 and 626). A page is then made by radio port controller RPC_BI 614 (page 627 from radio port controller RPC_BI 614 to subscriber PS_A 619). Subscriber PS_A 619 responds to radio port controller RPCBI 614 (page response 628).

0044The response is forwarded to the local interface device (line 629 to interface device NIU_B 612) and on the circuitry ATC 616 (line 630). Response is forwarded to the home interface device (line 631 from ATC 616 to interface device NIU_A 611)- Interface device NIU_A 611 responds with an authorization authentication request 650 to circuitry ATC 616. Circuitry ATC 616 forwards the authentication request to interface device NIU_B 612 (line 632), which forwards the request (line 633) to radio port controller RPCBI 614. Radio port controller RPC_BI 614 forwards the request to subscriber PS_A 616 (authentication request 634). Subscriber PSA 619 provides an authentication response 635 to radio port controller RPC_BI 614, which forwards the result (636 to interface device NIU_B 612). The result is additionally forwarded to circuitry ATC 616, and along to interface device NIUA 11. The interface device NIUA 611 responds with an alert 640 to circuitry ATC 616. The alert is forwarded to the interface located near the subscriber, interface NIU_B 612 (line 641) and is additionally forwarded to radio port controller RPC_BI 614 (line 642), and further to subscriber PS_A 619 (alert 643). The alert causes the subscribers device to ring, for example. The subscriber answers (line 644). This answer is forwarded from radio port controller RPC_BI 614 and on to the local interface device NIU_B 612 (line 645), and on to circuitry ATC 616 (box 646), and on to the home interface device NIUA 611 (line 647). A connect message is returned to the public switched network PSTN 610 (connect 648).

0045The call is then established between the PSTN 610 and subscriber PSA 619 via the subscriber's home interface device NIU_A 611. The path includes PSTN 610, interface device NIU_A 611, circuitry ATC 616, interface device NIU_B 612, radio port controller RPC_BI 614 and subscriber PS_A 619 (communication in progress line 649).

0046FIG. 7 is a flow diagram of an interface handover process, according to an embodiment of the invention. First a connection is established between subscriber PS_A 719 and PSTN 710 via subscriber's home interface device

0047NIUA 711 and the interface device that serves the region in which the subscriber is currently located, NIU_B 712. Later the subscriber PS_A 719 moves from the coverage area of interface device NIU_B 712 and into the coverage area of interface device NIUc 713. A disconnect signal is sent from subscriber PS_A 719 to radio port controller RPC_BI 714, which is covered by interface device NIU_B 712 (disconnect line 721). A set-up signal is sent from subscriber PS_A 719 to radio port controller NIUci 717, which serves the region in which the subscriber is now located (set-up line (hand-over) 722). Radio port controller NIUc ι 717 forwards this set-up request to the local interface device NIUc 713 (line 723). This request is then forwarded to circuitry ATC 716

0048(line 724). A connect request is sent to the now local interface device NIUc 713 (line 725) from circuitry ATC 716. Now a release can be sent from circuitry ATC 716 to the old local interface device NIU_B 712. A connect request is then sent from the new interface device NIUc 713 (connect 727) to the local radio port controller RPC_d 717 (connect 727). Authentication, according to one embodiment of the invention is not performed at this point. FIG. 8 is a block diagram illustrating the circuitry that routes calls configured as regional circuitry interconnected centrally, according to an embodiment of the invention. Regional ATC R-ATCi 811 is coupled to interface devices that are located geographically closer to circuitry R-ATCi 811 (NIU_D 714, NIU_E 715, and NIU_F 716). Another regional circuitry R-ATC₂ 812 located in another geographic area is coupled to interface devices geographically close to it (NIU_A 817, NIU_B 818, and NIU_C 819). The circuitry is coupled via a connecting device 813, which couples R-ATCc 811 and R- ATCi 812. The various interface devices are coupled to the PSTN 810. The regional circuits (R-ATCi 811 and R-ATC₂ 812 are located geographically close to the interface devices that they service. Alternatively, the circuits are coupled to interface devices that are likely to have traffic between them.

0049FIG. 9 is a block diagram illustrating expanded circuitry for routing calls connected by a local or distributed control bus, according to an embodiment of the invention. The particular circuitry that is used to interconnect interface devices may have physical limits in terms of numbers of interconnections it can support, or other limitations. Therefore multiple such circuits may be combined as shown. Here, ATC block 911 is used to couple interface device NIU_A 912 and interface device NIU_D 913 and other interface devices between them, which are couple to the PSTN 910. The circuitry ATC block 911 is comprised of S- ATC 914, which is responsible for signaling and expansion circuits E-ATCj 915 and E-ATC₂ 916. The bearer capability of the ATC block 911 is expanded by connecting multiple expansion ATCs (E-ATC) between interface devices. The expansion ATCs are under control of the signaling ATC (S-ATC) over a common bus 917. Individual interface devices connect to one or more expansion ATCs and the signaling ATC. The signaling ATC coordinates time slot arrangements between each interface device and one or more of the expansion ATCs.

0050FIG. 10 is a block diagram illustrating circuitry that routes calls implemented in a mesh configuration, according to an embodiment of the invention. Mesh of circuits 1011, which routes calls between interfaces, comprises M-ATC 1012, M-ATC 1013, and M-ATC 1014. Such circuits 1012, 1013, and 1014 are interconnected in a mesh fashion whereby one circuit is coupled to more than one other circuit. Here, for example, circuit M-ATC 1012 is coupled to both circuit M-ATC 1013 and circuit M-ATC 1014. Circuit M- ATC 1014 is also coupled to circuit M-ATC 1013. An advantage of such a configuration is that a failure of a single circuit ATC may merely reduce the grade of service but does not necessarily destroy connectivity among the interface devices. Circuits 1011 may be advantageously partitioned based on roaming statistics between interface devices with adjacent coverage areas. For example, subscribers may typically roam between interface device NIU 1020, interface device NIU 1019, interface device NIU 1021 , and interface device

0051NIU 1022. For this reason, the regional circuits R-ATC 1018 and R-ATC 1017 may be coupled to the same circuit in the mesh, circuit M-ATC 1012. The association between interface devices and regional circuits may be determined based on typical roaming patterns. For example, subscribers may typically roam between interface devices NIU 1020 and NIU 1019. For this reason, for example, such interface devices may be coupled to a single regional circuit R- ATC 1018.

0052Under one embodiment of the invention, calls with a subscriber located outside of the subscriber's home region may be routed via the PSTN to the interface device that serves in the subscriber's home region. Then, the call is routed from the interface device that serves the subscriber's home region back into the PSTN. The routing from the equipment serving visited region to the home region's interface device takes place via connections in the PSTN 1110 without specifically billing the subscriber for such connections. Here interface devices NIUA 1111, NIUB 1112, and NIUc 1113 are coupled by a control bus 1114, which is coupled to a circuit 1115. Calls with subscribers located in their home regions are routed between respective interface devices serving the home region and the PSTN 1110. Calls with a subscriber located outside of the subscriber's home region are routed through an interface device serving the region outside of the home region into the PSTN 1110 to the interface device serving the subscriber's home region, and then back into the PSTN 1110. The routing of calls with roaming subscribers through the PSTN to the home interface takes place through a different type of routing than routing of a typical call directly to a subscriber. In one example, the routing takes place by way of a set of routing numbers reserved for routing roaming calls or other calls other than typical calls directly with subscribers. The routing numbers may be assigned in advance or may be dynamically allocated and released out of a pool of roaming numbers. Such allocation out of a pool of numbers may be made based on desired grade of service for the roaming calls. For a related discussion, see U.S. Pat. No. 5,353,340 by Kunz, which is incorporated herein by reference.

0053Circuitry 1115 (which may be referred to as a network ATC) may coordinate the assignment, release, and dissemination of such PSTN routing numbers among the interface devices. Circuitry 1115 may determine the home region or home interface device of a subscriber located outside of the subscriber's home region. Signaling information for such processes may be transferred over a control bus 1114, into the interface devices and circuitry 1115.

0054For an example of operation of such an approach, consider a case in which a subscriber is located outside of the subscriber's home region. For example, a subscriber has a home region associated with interface device NIU_A 1111, and the subscriber is currently located in an area covered by interface device NIUc 1113. Interface device NIUc 1113 recognizes that the subscriber is a roaming subscriber. By way of an interface, shown here as roaming gateway 1118, the bearer channel for the subscriber includes a path with connection 1124 from visited interface NIU_C 1113 into the PSTN 1110 via connection 1125 and to the home interface device NIU_A 1111 via connection 1120. The path also includes the connection 1119 from the home interface 1111 into PSTN 1110. The path through the PSTN 1125 takes place via a special assigned number, rather than a number associated with the particular subscriber. In this way, a roaming subscriber's call is routed from the visited interface device through the PSTN to the home interface device and back into the PSTN. Roaming gateway 1116 of interface device NIU_A 1111 is coupled to the PSTN by connection 1120, which represents a special connection for the purpose of routing roaming calls through the PSTN to the home interface device. Similarly, roaming gateway 1117 of interface device NIU_B 1112 is coupled via line 1122 to PSTN 1110, and roaming gateway 1118, which is located in interface device NIU_B 113 is coupled to PSTN 1110 via connection 1124. Connections 1125, 1126, and 1127 connect the respective roaming gateways for routing roaming calls back to their respective home interfaces through which they are routed back into the PSTN 1110. Another embodiment of the invention is directed to a communications system and set of interfaces adapted to be coupled to a cable network. The cable network may comprise, in one example, a cable television network. The cable television network may comprise a coax network, a fiber network, or a hybrid fiber and coax network. Circuitry coupled to the interfaces routes transmissions of information to selected interfaces from among the set of interfaces adapted to be coupled to the network.

0055The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to limit the invention to the precise forms disclosed. Many modifications and equivalent arrangements will be apparent.