Wireless communication system

Abstract

Methods and apparatus for communicating circuit switched voice data with a first cellular radio access network (RAN) and communicating voice over Internet protocol (VoIP) packets using session initiation protocol (SIP) with a second cellular RAN. The second cellular RAN does not support circuit switched voice communication.

What is claimed is: 
     
         1 . A user equipment comprising:
 a receiver;   a transmitter; and   a processor; and   wherein the receiver, the transmitter, and the processor are configured to cause the user equipment:   to transmit and receive circuit switched voice data with a first cellular radio access network (RAN);   to transmit and receive voice over Internet protocol (VoIP) packets using session initiation protocol (SIP) with a second cellular RAN; and   to process the VoIP packets using an AMR type codec,   wherein the second cellular RAN does not support circuit switched voice communication.   
     
     
         2 . The user equipment of  claim 1 , wherein the second cellular radio access network is IP based. 
     
     
         3 . The user equipment of  claim 1 , wherein the receiver, the transmitter, and the processor are configured to cause the user equipment to use an AMR type codec to produce voice data and to process the produced voice data to produce the VoIP packets. 
     
     
         4 . The user equipment of  claim 1 , wherein the AMR type codec is used to recover a voice signal. 
     
     
         5 . The user equipment of  claim 1 , wherein the receiver, the transmitter, and the processor are configured to cause the user equipment to send the VoIP packets to an IP gateway associated with the second radio access network. 
     
     
         6 . A method for use in a user equipment, the method comprising:
 transmitting and receiving circuit switched voice data with a first cellular radio access network (RAN);   transmitting and receiving voice over Internet protocol (VoIP) packets using session initiation protocol (SIP) with a second cellular RAN; and   processing the VoIP packets using an AMR type codec,   wherein the second cellular RAN does not support circuit switched voice communication.   
     
     
         7 . The method of  claim 6 , wherein the second cellular RAN is IP based. 
     
     
         8 . The method of  claim 6 , further comprising using an AMR type codec to produce voice data and processing the produced voice data to produce the VoIP packets. 
     
     
         9 . The method of  claim 6 , wherein the AMR type codec is used to recover a voice signal. 
     
     
         10 . The method of  claim 6 , further comprising sending the VoIP packets to an IP gateway associated with the second radio access network.