Circuit-switched fallback (CSFB) call setup utilizing multiple RF receive chains

1. A method for circuit-switched fallback (CSFB) in a wireless communication system comprising:

initiating a CSFB process;

sending an extended service request (ESR) message on a packet-switched network;

monitoring for receipt of an ESR response on the packet-switched network using a first radio frequency (RF) receive chain;

in parallel with monitoring for receipt of the ESR response, acquiring an initial circuit-switched network using a second RF receive chain;

starting an ESR timer when sending the ESR message; and

detecting whether the ESR timer expires before the ESR response is received.

2. The method of claim 1 , wherein acquiring the initial circuit-switched network includes:

tuning the second RF receive chain to a frequency; and

receiving system information block (SIB) messages for the initial circuit-switched network.

3. The method of claim 2 , wherein the frequency is selected from a neighbor list for the packet-switched network.

4. The method of claim 1 , further comprising:

if the ESR timer expires before the ESR response is received, starting a voice call using the initial circuit-switched network; and

if the ESR response is received before the ESR timer expires, detecting whether the initial circuit-switched network matches an ESR-response-indicated circuit-switched network.

5. The method of claim 4 , further comprising:

if the initial circuit-switched network matches the ESR-response-indicated circuit-switched network, starting the voice call using the initial circuit-switched network; and

if the initial circuit-switched network does not match the ESR-response-indicated circuit-switched network, acquiring the ESR-response-indicated circuit-switched network for the voice call.

6. An apparatus for circuit-switched fallback (CSFB) in a wireless communication system comprising:

a first radio frequency (RF) receive chain for receiving a circuit-switched voice call page on a packet-switched network;

RF transmitter circuitry for sending an extended service request (ESR) message on the packet-switched network;

a processor configured to:

monitor for receipt of an ESR response on the packet-switched network using the first radio frequency (RF) receive chain;

acquire an initial circuit-switched network using a second RF receive chain simultaneously with monitoring for receipt of the ESR responses

start an ESR timer at sending the ESR message; and

detect whether the ESR timer expires before the ESR response is received.

7. The apparatus of claim 6 , wherein the processor is further configured to:

tune the second RF receive chain to a frequency selected from a neighbor list for the packet-switched network; and

receive system information block (SIB) messages for the initial circuit-switched network using the tuned second RF receive chain.

8. The apparatus of claim 7 , wherein the processor is further configured to:

if the ESR timer expires before the ESR response is received, start a voice call using the initial circuit-switched network.

9. The apparatus of claim 7 , wherein the processor is further configured to:

if the ESR response is received before the ESR timer expires, detect whether the initial circuit-switched network matches an ESR-response-indicated circuit-switched network.

10. The apparatus of claim 9 , wherein the processor is further configured to:

if the initial circuit-switched network matches the ESR-response-indicated circuit-switched network, start a voice call using the initial circuit-switched network.

11. The apparatus of claim 9 , wherein the processor is further configured to:

if the initial circuit-switched network does not match the ESR-response-indicated circuit-switched network, acquire the ESR-response-indicated circuit-switched network for a voice call.

12. A computer-program storage apparatus for circuit-switched fallback (CSFB) in a wireless communication system comprising a memory having one or more software modules stored thereon, the one or more software modules being executable by one or more processors and the one or more software modules comprising:

code for sending an extended service request (ESR) message on a packet-switched network;

code for starting an ESR timer when sending the ESR message;

code for detecting whether the ESR timer expires before the ESR response is received;

code for monitoring for receipt of an ESR response on the packet-switched network using a first radio frequency (RF) receive chain; and

code for acquiring an initial circuit-switched network using a second RF receive chain and in parallel with monitoring for receipt of the ESR response.

13. The computer-program storage apparatus of claim 12 , wherein the code for acquiring the initial circuit-switched network includes:

code for tuning the second RF receive chain to a frequency; and

code for receiving system information block (SIB) messages for the initial circuit-switched network.

14. The computer-program storage apparatus of claim 13 wherein the frequency is selected from a neighbor list for the packet-switched network.

15. The computer-program storage apparatus of claim 14 , wherein the one or more software modules further comprise:

code for starting a voice call using the initial circuit-switched network if the ESR timer expires before the ESR response is received.

16. The computer-program storage apparatus of claim 14 , wherein the one or more software modules further comprise:

code for detecting whether the initial circuit-switched network matches an ESR-response-indicated circuit-switched network-if the ESR response is received before the ESR timer expires.

17. The computer-program storage apparatus of claim 16 , wherein the one or more software modules further comprise:

code for starting a voice call using the initial circuit-switched network if the initial circuit-switched network matches the ESR-response-indicated circuit-switched network; and

code for acquiring the ESR-response-indicated circuit-switched network for the voice call if the initial circuit-switched network does not match the ESR-response-indicated circuit-witched network.