Method for accessing a service unavailable through a network cell

Abstract

A method performed by user equipment (UE) includes receiving a request to access a service unavailable through a first network cell associated with the UE, and receiving a message from an access device associated with the first network cell, wherein the message identifies a plurality of second network cells providing the service.

1 . A method performed by user equipment (UE), comprising:
 sending a request to access a service via a first network cell associated with the UE, said first network cell part of a first network, the first network having a first radio access technology; and   receiving a message responsive to the request from an access device associated with the first network, the message identifying a plurality of second network cells capable of providing the service, said second network cells having a second radio access technology.   
     
     
         2 . The method of  claim 1 , wherein the service is circuit-switched voice. 
     
     
         3 . The method of  claim 1 , wherein the service is not provided by the first network cell. 
     
     
         4 . The method of  claim 1  wherein the request to access the service is a Non-Access Stratum (NAS) extended service request message. 
     
     
         5 . The method of  claim 1 , wherein the UE does not support a protocol under which the first network cell provides the service. 
     
     
         6 . The method of  claim 1 , further comprising:
 receiving user input in response to which the UE performs the sending of the request to access the service.   
     
     
         7 . The method of  claim 1 , further comprising:
 receiving a paging message from the first network cell in response to which the UE performs the sending of the request to access the service.   
     
     
         8 . The method of  claim 1 , wherein the message contains system information of the plurality of second network cells. 
     
     
         9 . The method of  claim 1 , wherein the message identifies location areas of the plurality of second network cells. 
     
     
         10 . The method of  claim 9 , further comprising:
 comparing a location area in which the UE is registered with the location areas of the plurality of second network cells; and   selecting one of the plurality of second network cells belonging to the same location area as the location area in which the UE is registered.   
     
     
         11 . The method of  claim 1 , further comprising receiving system information of the plurality of second network cells identified in the message. 
     
     
         12 . The method of  claim 11 , wherein the system information identifies location areas of the plurality of second network cells, the method further comprising:
 comparing a location area (LA) in which the UE is registered with the location areas of the plurality of second network cells; and   selecting one of the plurality of second network cells based on the comparison.   
     
     
         13 . The method of  claim 12 , wherein the selecting comprises selecting one of the plurality of second network cells belonging to the same location area as the location area in which the UE is registered. 
     
     
         14 . The method of  claim 1 , wherein the message directs the UE to connect to one of the plurality of second network cells. 
     
     
         15 . The method of  claim 1 , wherein the message directs the UE to switch from the first network cell associated with the first radio access technology to a second network cell associated with the second radio access technology. 
     
     
         16 . The method of  claim 1 , wherein the message directs the UE to release a connection with the access device. 
     
     
         17 . The method of  claim 16  wherein the message is a RRC Connection Release message. 
     
     
         18 . The method of  claim 1  wherein the first radio access technology is evolved universal terrestrial radio access, E-UTRA, and
 the access device is an evolved node B (eNB) associated with the first network cell. 
 
     
     
         19 . The method of  claim 14 , wherein the plurality of second network cells are in one of a universal terrestrial radio access network (UTRAN), a global system for mobile communications (GSM) network, an evolution-data optimized (EV-DO) network, a 3GSM network, a digital enhanced cordless (DECT) network, a digital AMPS (IS-136/TDMA) network, an integrated digital enhanced network (iDEN), a universal mobile telecommunications system (UMTS), an enhanced data rates for GSM evolution (EDGE) network, a general packet radio service (GPRS) network, and a GPRS/EDGE radio access network (GERAN). 
     
     
         20 . A non-transitory computer-readable storage medium containing instructions that when executed by a processor of a user equipment (UE) perform a method, comprising:
 sending a request to access a service via a first network cell associated with the UE, said first network cell part of a first network, the first network having a first radio access technology; and   receiving a message responsive to the request from an access device associated with the first network, the message identifying a plurality of second network cells capable of providing the service, said second network cells having a second radio access technology.