WO2009139675A1

WO2009139675A1 - Generic access network (gan) registration for a mobile station

Info

Publication number: WO2009139675A1
Application number: PCT/SE2008/050552
Authority: WO
Inventors: Jari Vikberg; Rasmus Larsson; Tomas Bornefall
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2008-05-13
Filing date: 2008-05-13
Publication date: 2009-11-19

Abstract

A method of determining whether an MS (11) has left a femto cell while in idle mode, and deregistering the MS from a Generic Access Network, GAN, upon making this determination. A Femto Cell Customer Premises Equipment, Femto Cell CPE, (51) may deregister (105, 116) the MS if the MS fails to perform a periodic location update at a time ordered by the Femto Cell CPE. The Femto Cell CPE may also deregister (126) the MS if the MS fails to respond to a paging attempt originated by either the Femto Cell CPE or a GAN Controller, GANC (13). The Femto Cell CPE may also deregister (134) the MS if the GANC instructs all of the MSs in the femto cell to perform attach and detach procedures, and the MS sends a detach indication toward a core network (14). In alternative embodiments, the GANC deregisters the MS rather than the Femto Cell CPE.

Description

GENERIC ACCESS NETWORK (GAN) REGISTRATION FOR A MOBILE STATION

TECHNICAL FIELD

The present invention relates to wireless telecommunication networks.

More specifically, and without limitation, the invention is directed to a method of controlling a Generic Access Network (GAN) registration for a mobile station

(MS) by determining how long to maintain the GAN registration and to continue performing GAN Keep Alive signaling.

BACKGROUND

The Third Generation Partnership Project (3GPP) has standardized the Generic Access Network (GAN)-concept starting from 3GPP Release-6. The more precise name utilized by 3GPP is "Generic Access to A/Gb Interfaces" and this standardization was based on the Unlicensed Mobile Access (UMA) de-facto specifications. Two examples of existing solutions for enabling a Mobile Station (MS) to access a GSM Core Network (CN) are: a GAN solution and a GSM-Femto solution. FIG. 1 is a functional block diagram from 3GPP TS 43.318 illustrating an architecture of the GAN 10. GAN is specified in the 3GPP TS 43.318 and TS 44.318. A mobile station (MS) 11 connects through a WiFi access point (AP) in a generic IP access network 12. GAN provides a new Radio Access Network (RAN), and the node corresponding to the GERAN Base Station Controller is called the Generic Access Network Controller (GANC) 13. The GANC 13 includes a Security Gateway (SEGW) and connects to a GSM Core Network (CN) 14. The MS may be a dual-mode or tri-mode, dual-radio handset including for example both WiFi and 3GPP-macro radio support (GSM, WCDMA or both). The MS connects to the WiFi AP utilizing the WiFi Radio. The GAN standard defines for example how the MS can function in GAN mode and access the services provided by the GSM CN using the Up-interface 15 between the MS and the GANC. The current GAN standard may be referred to as ' 2G-GAN" or "GSM- GAN" because the standard GSM A-interface and Gb-interface are utilized between the GANC and the CN. Work is ongoing to standardize a "3G-GAN" or "WCDMA-GAN" solution. In this case, the GANC will utilize standard WCDMA interfaces such as the lu-cs and the lu-ps interfaces to connect to the CN. The resulting standard can be also called "Generic Access to Iu Interfaces" or "GAN-Iu".

FIG. 2 is a protocol diagram illustrating a circuit-switched (CS) Domain Control Plane Architecture 20 related to the GAN solution and the Up-interface 15. The GANC 13 uses normal A-interface signaling towards the Mobile Switching Center (MSC) 21. The GANC interworks the related protocols, like the Base Station System Application Part (BSSAP) 22, towards the relevant GAN-protocols, such as Generic Access - Circuit Switched Resources (GA- CSR) 23, in both directions. FIG. 3 is a signaling diagram illustrating the existing GAN registration procedure between the MS 11 and the GANC 13. This procedure is well defined, for example, in the 3GPP Technical Specifications for GAN, therefore the procedure will not be described in detail here. Of particular note is the step where the GA-RC REGISTER REQUEST message 26 is accepted by the GANC, and the GA-RC REGISTER ACCEPT message 27 is returned to the MS. This message contains values for many different timers and two of these are applicable to the present invention. The first is a timer value for the T3212 timer. This timer controls how often the MS sends periodic location update messages towards the MSC 21. The message used for this purpose is part of Mobility Management (MM) protocol and is called a LOCATION UPDATING REQUEST in which a specific location updating type field is used to indicate periodic updating. The other timer value is a value for a TU3906 timer which is also called the GAN "Keep Alive" timer. The Keep Alive timer is relatively simple and is running in the MS as long as the MS is registered with the GANC. FIG. 4 is a signaling diagram illustrating the existing GAN Keep Alive procedure between the MS 11 and the GANC 13. Every time the Keep Alive timer is triggered, the MS sends a GA-RC KEEP ALIVE message 28 to the GANC and restarts the timer. The GANC monitors the GA-RC KEEP ALIVE messages and if not received in time, the GANC can deregister the MS and release important internal resources for other MSs.

FIG. 5 is a signaling diagram illustrating the existing GAN deregistration procedure between the MS 11 and the GANC 13. When the MS is ready to leave the GAN coverage, the MS sends a GA-RC DEREGISTER message 29 to the GANC. This procedure informs the GANC that the GANC can deregister the MS and release important internal resources for other MSs.

FIG. 6 is a functional block diagram of an architecture of a GSM-Femto access network. The GSM-Femto solution provides small femto cells for the end users by having small GSM radio base stations in, for example, the user's home premises. The small radio base station is called a Femto Cell Customer Premises Equipment (CPE) 31. The Femto Cell CPE connects to the network using the proprietary Fp and Abis-over-IP interfaces. The node corresponding to the GERAN BSC is called a Femto BSC 32. No specific 3GPP standard exists for the GSM-Femto solution. One of the main differences from the GAN solution described above is that MSs do not require any changes because the standard GSM Um-interface is used between the MS and the Femto Cell CPE. The MS connects to the Femto Cell CPE as normally in GERAN. The Femto Cell CPE is then connected to the Femto BSC using the proprietary Fp and Abis-over-IP interfaces.

FIG. 7 is a protocol diagram illustrating a CS Domain Control Plane Architecture 40 related to the GSM-Femto solution of FIG. 6. The Femto BSC 32 uses normal A-interface signaling towards the MSC 21. The Femto BSC interworks the related protocols, like BSSAP 22, towards the relevant GSM- protocols such as GSM Radio Resources (GSM RR) 41 in both directions.

SUMMARY

In different embodiments, the present invention provides for the release of GAN resources more quickly and efficiently than is possible with existing systems and methods. The invention determines whether an MS has left a femto cell while in idle mode, and deregisters the MS upon making this determination.

In one embodiment, the present invention is directed to a Femto Cell Customer Premises Equipment (Femto Cell CPE) for serving a mobile station (MS) operating in a femto cell and for maintaining a Generic Access Network (GAN) registration for the MS through a GAN Controller (GANC). The Femto Cell CPE includes means for determining whether the MS has left the femto cell while in idle mode; and means for deregistering the MS with the GANC upon determining that the MS has left the femto cell while in idle mode. In another embodiment, the present invention is directed to a method of maintaining a GAN registration for an MS operating in a femto cell in a radio communication network having a Femto Cell CPE for serving the femto cell and a GANC for interfacing the Femto Cell CPE with a core network. The method includes the steps of receiving in the Femto Cell CPE, a GAN registration accept message from the GANC accepting a registration for the MS, the GAN registration accept message including a first timer value specifying a periodicity for performing periodic location updates; broadcasting the first timer value by the Femto Cell CPE in the femto cell; and determining by the Femto Cell CPE whether a periodic location update was received from the MS in accordance with the broadcast first timer value. If the periodic location update was not received from the MS in accordance with the broadcast first timer value, the Femto Cell CPE sends a GAN deregistration message to the GANC to deregister the MS with the GAN. If the periodic location update was received from the MS in accordance with the broadcast first timer value, the Femto Cell CPE sends the periodic location update to the GANC.

In another embodiment, the present invention is directed to a method in which the Femto Cell CPE modifies the first timer value received in the GAN registration accept message to define a shorter periodicity for performing periodic location updates by MSs within the femto cell. The Femto Cell CPE then broadcasts the modified first timer value in the femto cell. If a periodic location update is not received from the MS in accordance with the modified first timer value, the Femto Cell CPE sends a GAN deregistration message to the GANC to deregister the MS with the GAN. The Femto Cell CPE filters periodic location updates from the MS while the registration is active so that periodic location updates are only sent to the GANC with the periodicity specified by the first timer value received in the GAN registration accept message.

In another embodiment, the present invention is directed to a method in which the Femto Cell CPE periodically pages the MS. The Femto Cell CPE sends Keep Alive messages to the GANC as long as the MS responds to all periodic paging attempts. If the MS fails to respond to a periodic paging attempt, the Femto Cell CPE sends a GAN deregistration message to the GANC to deregister the MS with the GAN. The Femto Cell CPE may determine a paging timer value for periodically paging the MS, or the Femto Cell CPE may page the MS whenever the GANC sends a paging message directed to the MS. In another embodiment, the present invention is directed to a method in which the Femto Cell CPE receives an attach/detach indicator from the GANC indicating that MSs operating within the femto cell are to perform attach and detach procedures. The Femto Cell CPE broadcasts the attach/detach indicator in the femto cell, and if a detach indication is received from the MS, the Femto Cell CPE sends a GAN deregistration message from to the GANC to deregister the MS with the GAN.

In another embodiment, the present invention is directed to a GANC for controlling a Femto Cell CPE serving an MS operating in a femto cell, and for maintaining a GAN registration for the MS between the Femto Cell CPE and a core network. The GANC includes means for determining whether the MS has left the femto cell while in idle mode; and means for deregistering the MS upon determining that the MS has left the femto cell while in idle mode. The GANC may send a paging instruction to the Femto Cell CPE instructing the Femto Cell CPE to page the MS, and may deregister the MS upon determining that the MS did not respond to the page. Alternatively, the GANC may sending an attach/detach indicator to the Femto Cell CPE indicating that MSs operating within the femto cell are to perform attach and detach procedures, and may deregister the MS upon detecting a detach indication sent by the MS towards the core network.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the essential features of the invention will be described in detail by showing preferred embodiments, with reference to the attached figures in which:

FIG. 1 is a functional block diagram from 3GPP TS 43.318 illustrating an architecture of the Generic Access Network (GAN); FIG. 2 is a protocol diagram illustrating a circuit-switched (CS) Domain

Control Plane Architecture related to the GAN solution of FIG. 1 ;

FIG. 3 is a signaling diagram illustrating the existing GAN registration procedure between an MS and a GANC;

FIG. 4 is a signaling diagram illustrating the existing GAN Keep Alive procedure between the MS and the GANC;

FIG. 5 is a signaling diagram illustrating the existing GAN deregistration procedure between the MS and the GANC;

FIG. 6 is a functional block diagram of an architecture of a GSM-Femto access network; FIG. 7 is a protocol diagram illustrating a CS Domain Control Plane

Architecture related to the GSM-Femto solution of FIG. 6;

FIG. 8 is a functional block diagram of an architecture of a combined GAN-GSM-Femto access network suitable for use in implementing the present invention; FIG. 9 is a protocol diagram illustrating a CS Domain Control Plane

Architecture related to the combined GAN-GSM-Femto access network of FIG. 8;

FIG. 10 is a functional block diagram of an architecture of a GAN- WCDMA-Femto access network suitable for use in implementing the present invention;

FIG. 11 is a protocol diagram illustrating a CS Domain Control Plane Architecture related to the GAN-WCDMA-Femto access network of FIG. 10; FIG. 12 is a signaling diagram illustrating two different types of GAN Registrations performed by the Femto Cell CPE towards the GANC;

FIG. 13 is a flow chart illustrating the steps of a first embodiment of the method of the present invention; FIG. 14 is a flow chart illustrating the steps of a second embodiment of the method of the present invention;

FIG. 15 is a flow chart illustrating the steps of a third embodiment of the method of the present invention;

FIG. 16 is a flow chart illustrating the steps of a fourth embodiment of the method of the present invention; and

FIG. 17 is a flow chart illustrating the steps of a fifth embodiment of the method of the present invention.

DETAILED DESCRIPTION FIG. 8 is a functional block diagram of an architecture of a combined

GAN-GSM-Femto access network 50 suitable for use in implementing the present invention. To develop an access solution with advantages over either the GAN solution or the GSM-Femto solution, one can combine the two solutions, utilizing the best properties of each. The combined solution allows existing MSs to be utilized because the Um-interface is used between the MS 11 and a modified Femto Cell CPE 51. The Femto Cell CPE in the combined solution is modified to include a GAN-client, enabling the Up-interface to be used to connect the Femto Cell CPE 51 to the GANC 13. The standardized Up- interface requires some modifications, and thus a so-called Up+interface is utilized. The GANC uses the normal GSM interfaces towards the CN 14 and the other support nodes as in the normal GAN solution.

FIG. 9 is a protocol diagram illustrating a CS Domain Control Plane Architecture 60 related to the combined GAN-GSM-Femto access network of FIG. 8. The Femto Cell CPE 51 is extended both with BSC functionality 61 and with a GAN-client 62. The BSC functionality is needed to terminate the GSM RR protocol from the MS 11 and the GAN-client is needed to interwork between GSM RR and the GA-CSR protocol. The GANC 13 then interworks between the GA-CSR and the BSSAP protocols.

FIG. 10 is a functional block diagram of an architecture of a GAN- WCDMA-Femto access network 70 suitable for use in implementing the present invention. In this case, the "GAN-Iu" interface is utilized on the network side and the air interface to the MSs is the Uu-interface. A modified Femto Cell CPE 71 is modified to include UTRAN Radio Network Controller (RNC) functionality.

FIG. 11 is a protocol diagram illustrating a CS Domain Control Plane Architecture 80 related to the WCDMA-Femto access network of FIG. 10. As noted, the modified Femto Cell CPE 71 is modified to include UTRAN RNC functionality in the Radio Resource Control (RRC) 81 , Radio Link Control (RLC) 82, and Media Access Control (MAC) 83 layers.

Since the present invention relates to the GAN Keep Alive signaling, the areas related are now described for the GAN-GSM-Femto access network 50 of FIG. 8 (the same description applies also for the GAN-WCDMA-Femto access network 70 of FIG. 10). In this case, the Femto Cell CPE 51 contains the logic needed to implement the Up-interface towards the GANC 13.

FIG. 12 is a signaling diagram illustrating two different types of GAN Registrations performed by the Femto Cell CPE 51 towards the GANC 13. The two types of registrations are called CPE GAN Registration and MS GAN Registration. The CPE GAN Registration is performed when the Femto Cell CPE 51 is powered on and the associated femto cell is created. After the Femto Cell CPE 51 sends a (CPE) GA-RC REGISTER REQUEST message 91 to the GANC 13, the GANC returns a (CPE) GA-RC REGISTER ACCEPT message 92 with GAN system information needed by the Femto Cell CPE. Note that this signaling sequence shows only the case in which the GANC accepts the MS GAN Registration since this is the only outcome relevant to the present invention. The Femto Cell CPE stays registered in the GANC and performs the GAN Keep Alive signaling at 93 as described above in relation to FIG. 4. The MS GAN Registration is performed by the Femto Cell CPE 51 when it detects that an MS 11 is trying to access the femto cell. This normally happens when the MS performs a Location Updating procedure via the femto cell because the femto cell has a different Location Area Identifier (LAI) compared to macro cells in the area. After the Femto Cell CPE 51 sends a (MS) GA-RC REGISTER REQUEST message 96 to the GANC 13, the GANC returns a (MS) GA-RC REGISTER ACCEPT message 97 with GAN system information. This means that the MS stays registered with the GANC and the Femto Cell CPE performs the GAN Keep Alive signaling at 98 for the MS registration.

A problem with this solution, however, is that the Femto Cell CPE 51 has no knowledge of when an MS 11 in idle mode is leaving the femto cell. This means that there is no indication that the Femto Cell CPE should perform GAN deregistration for the MS and/or how long the Femto Cell CPE should continue to perform the GAN Keep Alive signaling for the MS.

The present invention provides a solution to this problem by having the Femto Cell CPE 51 utilize other existing signaling mechanisms in a novel way to determine how long the Femto Cell CPE should maintain the GAN registration for the MS and/or how long the Femto Cell CPE should continue to perform the GAN Keep Alive signaling for the MS. These mechanisms include:

(a) periodic location update signaling;

(b) enhanced periodic location update signaling;

(c) paging to find out that an MS is still in the femto cell; (d) detach indication; and

(e) unsuccessful paging.

FIG. 13 is a flow chart illustrating the steps of a first embodiment of the method of the present invention. In this embodiment, the Femto Cell CPE 51 utilizes periodic location update signaling to determine how long the Femto Cell CPE should maintain the GAN registration for the MS and/or how long the Femto Cell CPE should continue to perform the GAN Keep Alive signaling for the MS 11. At step 101 , the Femto Cell CPE receives the T3212 timer value and the TU3906 timer value in a (CPE) GA-RC REGISTER ACCEPT message 92 from the GANC 13 (see FIG. 12). At step 102, the Femto Cell CPE broadcasts the T3212 timer value unmodified in the system information that the Femto Cell CPE broadcasts in the femto cell. This means that any MS camped in the femto cell knows how often the MSC 21 expects the MS to perform the periodic location update signaling. Thus, at step 103, the MS 11 begins transmitting periodic location update message with the T3212 periodicity.

The Femto Cell CPE 51 uses the knowledge of the T3212 value to find out how long it should maintain a MS GAN Registration. Thus, at step 104, the Femto Cell CPE determines whether an expected periodic location update message is received from the MS 11. If not, the method moves to step 105 where the Femto Cell CPE sends a GAN Deregistration message to the GANC 13. If the periodic location update message is received from the MS, the method moves to step 106 where the Femto Cell CPE sends GAN Keep Alive messages to the GANC with TU3906 periodicity. At step 107, the Femto Cell CPE forwards the location update messages to the MSC with T3212 periodicity (i.e. as received from the MS).

For example, if the CPE GAN Registration returns a T3212 value indicating one hour and a TU3906 value indicating five minutes, then the Femto Cell CPE 51 broadcasts the T3212 value unmodified in the femto cell system information. This means that all the MSs camping in the femto cell will perform periodic location updates with the periodicity of one hour. The Femto Cell CPE maintains the MS GAN registration by sending the GAN Keep Alive messages to the GANC every five minutes as long as the MS 11 is performing the periodic location updates. The Femto Cell CPE forwards the location update messages to the MSC every hour when they are received from the MS.

This solution is relatively simple to implement, and the Femto Cell CPE can supervise that the MS is sending the periodic location updates to the MSC. As long as these are happening with the T3212 periodicity, the Femto Cell CPE maintains the GAN registration for that MS.

FIG. 14 is a flow chart illustrating the steps of a second embodiment of the method of the present invention. This embodiment, referred to as enhanced periodic location update signaling is an enhancement of the first embodiment shown in FIG. 13. The enhancement is a technique for more quickly notifying the GANC 13 when the MS 11 has left the femto cell. Note that in the example provided for the first embodiment, the Femto Cell CPE 51 may not recognize that the MS has left the femto cell for up to an hour after the MS has left due to the lengthy T3212 timer value.

In the second embodiment, the Femto Cell CPE 51 modifies the T3212 timer value received in the CPE GAN Registration before broadcasting the timer value in the system information broadcast in the femto cell. Thus, at step 111 , the Femto Cell CPE receives the T3212 timer value and the TU3906 timer value in the (CPE) GA-RC REGISTER ACCEPT message 92 from the GANC 13 (see FIG. 12). At step 112, the Femto Cell CPE modifies (i.e., shortens) the T3212 timer value, and at step 113 broadcasts the modified T3212 timer value in the system information that the Femto Cell CPE broadcasts in the femto cell. At step 114, the MS 11 begins transmitting periodic location update message with the modified T3212 periodicity. At step 115, the Femto Cell CPE determines whether an expected periodic location update message is received from the MS 11. If not, the method moves to step 116 where the Femto Cell CPE sends a GAN Deregistration message to the GANC 13. If the periodic location update message is received from the MS, the method moves to step 117 where the Femto Cell CPE sends GAN Keep Alive messages to the GANC with TU3906 periodicity.

Thus, any MS 11 camping in the femto cell will perform the location update signaling more often than requested by the MSC 21. To minimize the unnecessary periodic location update signaling towards the MSC, the Femto Cell CPE filters out some of the periodic location updates performed by the MS and at step 118 only passes through the periodic location updates with the periodicity indicated by the unmodified T3212 timer in the CPE GAN Registration. For example, if the CPE GAN Registration returns the T3212 value indicating one hour and a TU3906 value indicating five minutes, then the Femto Cell CPE may modify the T3212 value to twenty minutes in the broadcast femto cell system information. As a result, all of the MSs in the femto cell perform periodic location updates with the periodicity of twenty minutes. The Femto Cell CPE maintains the MS GAN registration by sending the GAN Keep Alive messages to the GANC every five minutes as long as the MS is performing the periodic location updates with the periodicity of twenty minutes. Additionally, the Femto Cell CPE only forwards every third periodic location update message towards the MSC via the GANC.

FIG. 15 is a flow chart illustrating the steps of a third embodiment of the method of the present invention. This embodiment can be used by the Femto Cell CPE 51 to check that an MS 11 is still camping on the femto cell. At step 121 , the Femto Cell CPE receives the T3212 timer value and the TU3906 timer value in the (CPE) GA-RC REGISTER ACCEPT message 92 from the GANC 13 (see FIG. 12). At step 122, the Femto Cell CPE broadcasts the T3212 timer value in the system information that the Femto Cell CPE broadcasts in the femto cell. At step 123. the Femto Cell CPE determines an internal timer value (for example based on the received T3212 or TU3906 timer values) that is referred to herein as the T_Check_MS timer. The Femto Cell CPE starts this timer when it creates the GAN Registration for an MS. The timer may be reset if the MS creates any traffic in the femto cell. At step 124, the Femto Cell CPE pages the MS associated with the T_Check_MS timer whenever the timer expires. At step 125, the Femto Cell CPE determines whether the MS responded to the paging. The Femto Cell CPE may detect that the MS responded to the paging, for example, utilizing a Channel Request message with an establishment cause indicating "Paging Response". If the MS does not respond to the paging, the method moves to step 126 where the Femto Cell CPE performs deregistration of the MS towards the GANC. If the MS responded to the paging, the method moves to step 127 where the Femto Cell CPE releases the established signaling connection towards the MS and restarts the T_Check_MS timer. At step 128, the Femto Cell CPE sends GAN Keep Alive messages to the GANC with TU3906 periodicity. At step 129, the Femto Cell CPE forwards location update messages to the MSC with T3212 periodicity. The T3212 and TU3906 handling and the related procedures can be performed as normally in this embodiment. It is also possible to combine this embodiment with the embodiments shown in FIGS. 13 or 14.

In an alternative variant of this embodiment, the GANC sends a paging instruction to the Femto Cell CPE instructing the Femto Cell CPE to page a given MS. The GANC sends the instruction to the Femto Cell CPE where the

GANC believes that the MS is located. If there is no response to this paging, the GANC may deregister the MS.

FIG. 16 is a flow chart illustrating the steps of a fourth embodiment of the method of the present invention. In this embodiment, the Femto Cell CPE 51 indicates in the system information (ATT-bit) that attach and detach procedures shall be performed by the MSs in the femto cell. The GAN System Information in the (CPE) GA-RC REGISTER ACCEPT message 92 (FIG. 12) includes this ATT-information and may also indicate whether the Femto Cell CPE is to forward detach signaling to the core network. At step 131 , the Femto Cell CPE registers the MS 11 with the GANC 13. At step 132, the Femto Cell CPE broadcasts an ATT-bit in the system information indicating that MSs are to perform attach and detach procedures in the femto cell. This means that any MS being powered off is to inform the Femto Cell CPE that it is detaching. At step 133, the Femto Cell CPE determines whether a detach indication has been received from the MS 11. If so, the method moves to step 134 where the Femto Cell CPE performs deregistration of the MS towards the GANC. If a detach indication is not received, the method moves to step 135 where the Femto Cell CPE continues to send GAN Keep Alive messages to the GANC with TU3906 periodicity. At step 136, the Femto Cell CPE forwards location update messages to the MSC with T3212 periodicity.

In an alternative variant of this embodiment, the GANC 13 detects the ' Detach indication" sent by the MS towards the core network. Once detected, the GANC may deregister the MS. FIG. 17 is a flow chart illustrating the steps of a fifth embodiment of the method of the present invention. In this embodiment, the Femto Cell CPE 51 utilizes unsuccessful paging as an indication to perform deregistration of the MS 11 towards the GANC 13. At step 141 , the Femto Cell CPE registers the MS with the GANC. At step 142, the Femto Cell CPE receives a paging message from the GANC (for example on a TCP connection) related to the MS GAN Registration. At step 143, the Femto Cell CPE pages the MS, and at step 144 determines whether the MS responded to the paging request. If no response is received, the Femto Cell CPE determines at step 145 whether the MS is creating any traffic. If not, the Femto Cell CPE deregisters the MS towards the GANC at step 146.

If a paging response was received at step 144, or the Femto Cell CPE 51 determines that the MS 11 is creating traffic at 145, then the method moves to step 147 135 where the Femto Cell CPE continues to send GAN Keep Alive messages to the GANC with TU3906 periodicity. At step 148, the Femto Cell CPE forwards location update messages to the MSC with T3212 periodicity.

In the manner described, the present invention provides for the release of GAN resources more quickly and efficiently than is possible with existing systems and methods.

Although preferred embodiments of the present invention have been illustrated in the accompanying drawings and described in the foregoing Detailed Description, it is understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the scope of the invention. For example, although the exemplary embodiments described herein utilized the GAN-GSM-Femto access network of FIGS. 8 and 9, the invention may also be implemented utilizing the GAN-WCDMA-Femto access network of FIGS. 10 and 11. The specification contemplates any and all modifications that fall within the scope of the invention defined by the following claims.

Claims

CLAIMS:

1. A method of maintaining a Generic Access Network, GAN, registration for a mobile station, MS, operating in a femto cell in a radio communication network having a Femto Cell Customer Premises Equipment, Femto Cell CPE, for serving the femto cell and a GAN Controller, GANC, for interfacing the Femto Cell CPE with a core network, said method comprising the steps of: receiving in the Femto Cell CPE, a GAN registration accept message from the GANC accepting a registration for the MS, said GAN registration accept message including a first timer value specifying a periodicity for performing periodic location updates; broadcasting the first timer value by the Femto Cell CPE in the femto cell; determining by the Femto Cell CPE whether a periodic location update was received from the MS in accordance with the broadcast first timer value; if the periodic location update was not received from the MS in accordance with the broadcast first timer value, sending a GAN deregistration message from the Femto Cell CPE to the GANC to deregister the MS with the GAN; and if the periodic location update was received from the MS in accordance with the broadcast first timer value, sending the periodic location update from the Femto Cell CPE to the GANC.

2. The method as recited in claim 1 , wherein the registration accept message from the GANC also includes a second timer value specifying a periodicity for sending Keep Alive messages from the Femto Cell CPE to the GANC during the time that the GAN registration is active, and the method further comprises, when the periodic location update was received from the MS in accordance with the broadcast first timer value, the step of sending Keep Alive messages from the Femto Cell CPE to the GANC with the periodicity specified by the second timer value.

3. A method of maintaining a Generic Access Network, GAN, registration for a mobile station, MS, operating in a femto cell in a radio communication network having a Femto Cell Customer Premises Equipment, Femto Cell CPE, for serving the femto cell and a GAN Controller, GANC, for interfacing the Femto Cell CPE with a core network, said method comprising the steps of: receiving in the Femto Cell CPE, a GAN registration accept message from the GANC accepting a registration for the MS, said GAN registration accept message including a first timer value specifying a periodicity for reporting periodic location updates to the GANC; modifying the first timer value to define a shorter periodicity for performing periodic location updates by MSs within the femto cell; broadcasting the modified first timer value by the Femto Cell CPE in the femto cell; determining by the Femto Cell CPE whether a periodic location update was received from the MS in accordance with the modified first timer value; if the periodic location update was not received from the MS in accordance with the modified first timer value, sending a GAN deregistration message from the Femto Cell CPE to the GANC to deregister the MS with the GAN; and if the periodic location update was received from the MS in accordance with the modified first timer value, filtering periodic location updates from the

MS so that the Femto Cell CPE only sends periodic location updates to the

GANC with the periodicity specified by the first timer value received in the GAN registration accept message.

4. The method as recited in claim 3, wherein the registration accept message from the GANC also includes a second timer value specifying a periodicity for sending Keep Alive messages from the Femto Cell CPE to the GANC during the time that the GAN registration is active, and the method further comprises, when the periodic location update was received from the MS in accordance with the modified first timer value, the step of sending Keep Alive messages from the Femto Cell CPE to the GANC with the periodicity specified by the second timer value.

5. A method of maintaining a Generic Access Network, GAN, registration for a mobile station, MS, operating in a femto cell in a radio communication network having a Femto Cell Customer Premises Equipment,

Femto Cell CPE, for serving the femto cell and a GAN Controller, GANC, for interfacing the Femto Cell CPE with a core network, said method comprising the steps of: receiving in the Femto Cell CPE, a GAN registration accept message from the GANC accepting a registration for the MS; periodically paging the MS by the Femto Cell CPE; sending Keep Alive messages from the Femto Cell CPE to the GANC as long as the MS responds to all periodic paging attempts; and sending a GAN deregistration message from the Femto Cell CPE to the

GANC to deregister the MS with the GAN if the MS fails to respond to a periodic paging attempt.

6. The method as recited in claim 5, wherein the GAN registration accept message from the GANC includes a first timer value specifying a periodicity for reporting periodic location updates to the GANC, and the method further comprises the steps of: broadcasting the first timer value by the Femto Cell CPE in the femto cell; determining by the Femto Cell CPE whether a periodic location update was received from the MS in accordance with the broadcast first timer value; and if the periodic location update was not received from the MS in accordance with the broadcast first timer value, sending the GAN deregistration message from the Femto Cell CPE to the GANC to deregister the MS with the GAN.

7. The method as recited in claim 6, wherein the GAN registration accept message from the GANC also includes a second timer value specifying a periodicity for sending Keep Alive messages from the Femto Cell CPE to the GANC during the time that the GAN registration is active, and the step of sending Keep Alive messages includes sending Keep Alive messages to the GANC with the periodicity specified by the second timer value.

8. The method as recited in claim 6, wherein the Femto Cell CPE determines a paging time period for periodically paging the MS, said paging time period being shorter than the first timer value received in the GAN registration accept message.

9. The method as recited in claim 5, further comprising: receiving in the Femto Cell CPE, a paging message for the MS from the GANC; paging the MS by the Femto Cell CPE in response to receiving the paging message from the GANC; and sending a GAN deregistration message from the Femto Cell CPE to the GANC to deregister the MS with the GAN if the MS fails to respond to the paging message from the GANC.

10. The method as recited in claim 5, wherein the step of sending a GAN deregistration message from the Femto Cell CPE to the GANC also includes: determining whether the MS is creating any traffic if the MS fails to respond to a periodic paging attempt; and sending the GAN deregistration message from the Femto Cell CPE to the GANC only if the MS is not creating any traffic and the MS failed to respond to the periodic paging attempt.

1 1. A method of maintaining a Generic Access Network, GAN, registration for a mobile station, MS, operating in a femto cell in a radio communication network having a Femto Cell Customer Premises Equipment, Femto Cell CPE, for serving the femto cell and a GAN Controller, GANC, for interfacing the Femto Cell CPE with a core network, said method comprising the steps of: receiving in the Femto Cell CPE, a GAN registration accept message from the GANC accepting a registration for the MS, said GAN registration accept message including an attach/detach indicator indicating that MSs operating within the femto cell are to perform attach and detach procedures; broadcasting the attach/detach indicator by the Femto Cell CPE in the femto cell; receiving by the Femto Cell CPE, a detach indication from the MS; and sending a GAN deregistration message from the Femto Cell CPE to the GANC to deregister the MS with the GAN upon receiving the detach indication from the MS.

12. The method as recited in claim 11 , wherein the GAN registration accept message from the GANC also includes a second timer value specifying a periodicity for sending Keep Alive messages from the Femto Cell CPE to the GANC during the time that the GAN registration is active, and the method further comprises sending Keep Alive messages from the Femto Cell CPE to the GANC with the periodicity specified by the second timer value as long as a detach indication is not received from the MS.

13. The method as recited in claim 12, wherein the GAN registration accept message from the GANC also includes a first timer value specifying a periodicity for reporting periodic location updates to the GANC, and the method further comprises the steps of: broadcasting the first timer value by the Femto Cell CPE in the femto cell; determining by the Femto Cell CPE whether a periodic location update was received from the MS in accordance with the broadcast first timer value; and if the periodic location update was not received from the MS in accordance with the broadcast first timer value, sending the GAN deregistration message from the Femto Cell CPE to the GANC to deregister the MS with the GAN.

14. A Femto Cell Customer Premises Equipment, Femto Cell CPE, for serving a mobile station, MS, operating in a femto cell and for maintaining a Generic Access Network, GAN, registration for the MS through a GAN Controller, GANC, said Femto Cell CPE comprising: means for determining whether the MS has left the femto cell while in idle mode; and means for deregistering the MS with the GANC upon determining that the MS has left the femto cell while in idle mode.

15. The Femto Cell CPE as recited in claim 14, wherein the means for determining whether the MS has left the femto cell while in idle mode includes means for determining that the MS failed to send a periodic location update in accordance with a first timer value broadcast in the femto cell by the Femto Cell CPE.

16. The Femto Cell CPE as recited in claim 15, wherein the first timer value is a location update timer value received by the Femto Cell CPE in a GAN registration accept message from the GANC.

17. The Femto Cell CPE as recited in claim 15, wherein the first timer value is shorter than a location update timer value received by the Femto Cell CPE in a GAN registration accept message from the GANC.

18. The Femto Cell CPE as recited in claim 14, wherein the means for determining whether the MS has left the femto cell while in idle mode includes: means for periodically paging the MS by the Femto Cell CPE; and means for determining that the MS has left the femto cell while in idle mode whenever the MS fails to respond to a paging attempt.

19. The Femto Cell CPE as recited in claim 18, wherein the means for determining whether the MS has left the femto cell while in idle mode also includes means for determining that the MS is not creating any traffic.

20. The Femto Cell CPE as recited in claim 14, wherein the means for determining whether the MS has left the femto cell while in idle mode includes: means for receiving a paging message for the MS from the GANC; means for paging the MS in response to receiving the paging message from the GANC; and means for determining that the MS has left the femto cell while in idle mode whenever the MS fails to respond to a paging attempt from the GANC.

21. The Femto Cell CPE as recited in claim 14, wherein the means for determining whether the MS has left the femto cell while in idle mode includes: means for receiving a GAN registration accept message from the GANC accepting a registration for the MS₁ said GAN registration accept message including an attach/detach indicator indicating that MSs operating within the femto cell are to perform attach and detach procedures; means for broadcasting the attach/detach indicator in the femto cell; and means for receiving a detach indication from the MS.

22. A Generic Access Network Controller, GANC, for controlling a Femto Cell Customer Premises Equipment, Femto Cell CPE, serving a mobile station, MS, operating in a femto cell and for maintaining a GAN registration for the MS between the Femto Cell CPE and a core network, said GANC comprising: means for determining whether the MS has left the femto cell while in idle mode; and means for deregistering the MS upon determining that the MS has left the femto cell while in idle mode.

23. The GANC as recited in claim 22, wherein the means for determining whether the MS has left the femto cell while in idle mode includes: means for sending a paging instruction to the Femto Cell CPE instructing the Femto Cell CPE to page the MS; and means for determining whether the MS responded to the page.

24. The GANC as recited in claim 22, wherein the means for determining whether the MS has left the femto cell while in idle mode includes: means for sending an attach/detach indicator to the Femto Cell CPE indicating that MSs operating within the femto cell are to perform attach and detach procedures; and means for detecting a detach indication sent by the MS towards the core network.