Methods and apparatus for fast synchronization using quasi-cyclic low-density parity-check (QC-LDPC) codes
For use in a wireless communication network, a transmitter is configured to encode information. The transmitter includes a cyclic redundancy check (CRC) encoder configured to encode a physical broadcast channel (PBCH) message using a cyclic redundancy check. The transmitter also includes a timing dependent cyclic shift block configured to encode information in the PBCH message. The transmitter further includes a quasi-cyclic low-density parity-check (QC-LDPC) encoder configured to encode the PBCH message using a QC-LDPC.
1. For use in a wireless network, a transmitter configured to encode information, the transmitter comprising:
a cyclic redundancy check (CRC) encoder configured to encode a physical broadcast channel (PBCH) message using a cyclic redundancy check;
a timing dependent cyclic shift block configured to encode information in the PBCH message; and
a quasi-cyclic low-density parity-check (QC-LDPC) encoder configured to encode the PBCH message using a QC-LDPC code.
2. The transmitter of claim 1 , wherein the timing dependent cyclic shift block is configured to encode the information in the PBCH message by cyclically shifting a plurality of bits in the PBCH message a predetermined number of times, the predetermined number corresponding to a value of the information in the PBCH message.
3. The transmitter of claim 2 , wherein the PBCH message is divided into m b sections, each section having a same number of bits, and wherein the timing dependent cyclic shift block cyclically shifts using m b -sectionized cyclically shifting.
4. The transmitter of claim 3 , wherein the timing dependent cyclic shift block m b -sectionized cyclically shifts a predetermined number of times.
5. The transmitter of claim 2 , wherein the value of the information in the PBCH message is determined from a final two bits of a system frame number (SFN) of a frame.
6. The transmitter of claim 5 , wherein the information in the PBCH message comprises frame timing information.
7. The transmitter of claim 1 , wherein the timing dependent cyclic shift block encodes the information in the PBCH message and then the QC-LDPC encoder encodes the PBCH message using the QC-LDPC code.
8. The transmitter of claim 1 , wherein the QC-LDPC encoder encodes the PBCH message using the QC-LDPC code before the timing dependent cyclic shift block encodes the information in the PBCH message.
9. The transmitter of claim 1 , wherein the information in the PBCH message is encoded such that the information can be detected by a receiver either after or before QC-LDPC decoding of the PBCH message.
10. For use in a wireless network, a method of encoding information at a transmitter, the method comprising:
encoding a physical broadcast channel (PBCH) message using a cyclic redundancy check (CRC);
encoding information in the PBCH message; and
encoding the PBCH message using a quasi-cyclic low-density parity-check (QC-LDPC) code.
11. The method of claim 10 , wherein encoding the information in the PBCH message comprises cyclically shifting a plurality of bits in the PBCH message a predetermined number of times, the predetermined number corresponding to a value of the information in the PBCH message.
12. The method of claim 11 , wherein the PBCH message is divided into m b sections, each section having a same number of bits, and wherein cyclically shifting comprises m b -sectionized cyclically shifting.
13. The method of claim 12 , wherein m b -sectionized cyclically shifting comprises m b -sectionized cyclically shifting a predetermined number of times.
14. The method of claim 10 , wherein the value of the information in the PBCH message is determined from a final two bits of a system frame number (SFN) of a frame.
15. The method of claim 14 , wherein the information in the PBCH message comprises frame timing information.
16. The method of claim 10 , wherein the encoding of the information in the PBCH message is performed before the encoding of the PBCH message using the QC-LDPC code.
17. The method of claim 10 , wherein the encoding of the PBCH message using the QC-LDPC code is performed before the encoding of the information in the PBCH message.
18. The method of claim 10 , wherein the information in the PBCH message is encoded such that the information can be detected by a receiver either after or before QC-LDPC decoding of the PBCH message.
19. For use in a wireless communication network, a method of detecting frame timing at a receiver, the method comprising:
receiving code symbols of a physical broadcast channel (PBCH) in a message;
decoding the received code symbols using a quasi-cyclic low-density parity-check (QC-LDPC) code;
examining the QC-LDPC-decoded symbols for a cyclic redundancy check (CRC);
m b -sectionized cyclically shifting the QC-LDPC-decoded symbols; and
determining a current frame number based on a number of times the QC-LDPC-decoded symbols are cyclically shifted.
20. The method of claim 19 , further comprising:
soft combining the received code symbols of a current frame with the received code symbols of at least one previous frame.
21. The method of claim 20 , further comprising:
repeating the examining, m b -sectionized cyclically shifting, and soft combining steps until a CRC check is established.
22. The method of claim 19 , wherein m b -sectionized cyclically shifting comprises m b -sectionized cyclically shifting a predetermined number of times.