Method for a general near optimal turbo code trellis termination
A method of terminating two or more constituent encoders of a turbo encoder employing a turbo code, comprising the step of: generating tail input bits at each of two or more constituent encoders, including deriving the tail input bits from each of the two or more constituent encoders separately from a contents of shift registers within each of the two or more constituent encoders, after an encoding of information bits by the two or more constituent encoders; puncturing one or more tail output bits such that 1/R output tail bits are transmitted for each of a plurality of trellis branches, wherein R is a turbo code rate employed by the turbo encoder during an information bit transmission. In yet another variation, the step of puncturing the tail output bits further comprises the step of: transmitting, during trellis termination, the tail output bits, only if they are sent from an output branch of one of the two or more constituent encoders that are used during information bit transmission.
1. A method for turbo encoding, the method comprising:
encoding information bits to generate output bits at least a first (X) output branch, a second (Y 0 ) output branch, a third (X′) output branch, and a fourth (Y′ 0 ) output branch;
selectively transmitting encoded bits from the first, second, third and fourth output branches according to at least one code rate (R);
determining tail output bits based on the at least one code rate (R); and
transmitting the tail output bits.
2. The method of claim 1 , wherein (R) comprises a plurality of code rates.
3. The method of claim 1 , wherein the tail output bits are based on last shift register state values after encoding all of the information bits.
4. The method of claim 1 , wherein the tail output bits are selectively transmitted based on the at least one code rate (R).
5. The method of claim 1 , further comprising generating output bits at a fifth (Y 1 ) output branch and a sixth (Y′ 1 ) output branch.
6. The method of claim 1 , wherein the output bits from the third (X′) output branch and the fourth (Y′ 0 ) output branch are from interleaved information bits.
7. The method of claim 1 , wherein the tail output bits are pre-determined in association with the shift register state values.
8. The method of claim 1 , wherein one or more of the tail output bits is punctured as follows:
R
½
X(t)
111 000
Y 0 (t)
111 000
Y 1 (t)
000 000
X'(t)
000 111
Y' 0 (t)
000 111
Y' 1 (t)
000 000
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
9. The method of claim 1 , wherein one or more of the tail output bits is punctured as follows:
R
1/3
X(t)
111 000
Repeat
Y 0 (t)
111 000
Y 1 (t)
000 000
X'(t)
000 111
Repeat
Y' 0 (t)
000 111
Y' 1 (t)
000 000
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
10. The method of claim 1 , wherein one or more of the tail output bits is punctured as follows:
R
1/4
X(t)
111 000
Repeat
Y 0 (t)
111 000
Y 1 (t)
111 000
X'(t)
000 111
Repeat
Y' 0 (t)
000 111
Y' 1 (t)
000 111
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
11. The method of claim 1 , wherein the code rate (R) comprises one of ½, ⅓ and ¼.
12. The method of claim 5 , wherein one or more of the tail output bits is punctured as follows:
R
½
1/3
1/4
X(t)
111 000
111 000
111 000
Repeat
Repeat
Y 0 (t)
111 000
111 000
111 000
Y 1 (t)
000 000
000 000
111 000
X'(t)
000 111
000 111
000 111
Repeat
Repeat
Y' 0 (t)
000 111
000 111
000 111
Y' 1 (t)
000 000
000 000
000 111
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
13. A communication system for use in wireless communication, the communication system comprising:
an encoder comprising shift registers and encoding information bits to generate output bits at at least a first (X) output branch, a second (Y 0 ) output branch, a third (X′) output branch, and a fourth (Y′ 0 ) output branch and to selectively transmit encoded bits from the first, second, third and fourth output branches according to at least one code rate (R); and
an interleaver connected to the encoder and interleaving the information bits,
wherein the tail output bits are determined based on the at least one code rate (R) and transmitted.
14. The communication system of claim 13 , wherein the tail output bits are based on last shift register state values after encoding all of the information bits.
15. The communication system of claim 13 , wherein the tail output bits are selectively transmitted based on the at least one code rate (R).
16. The communication system of claim 13 , further comprising generating output bits at a fifth (Y 1 ) output branch and a sixth (Y′ 1 ) output branch.
17. The communication system of claim 13 , wherein the output bits from the third (X′) output branch and the fourth (Y′ 0 ) output branch are from interleaved information bits.
18. The communication system of claim 13 , wherein the code rate (R) comprises one of ½, ⅓ and ¼.
19. The communication system of claim 13 , wherein the tail output bits are pre-determined in association with the shift register state values.
20. The communication system of claim 13 , wherein one or more of the tail output bits is punctured as follows:
R
½
X(t)
111 000
Y 0 (t)
111 000
Y 1 (t)
000 000
X'(t)
000 111
Y' 0 (t)
000 111
Y' 1 (t)
000 000
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
21. The communication system of claim 13 , wherein one or more of the tail output bits is punctured as follows:
R
1/3
X(t)
111 000
Repeat
Y 0 (t)
111 000
Y 1 (t)
000 000
X'(t)
000 111
Repeat
Y' 0 (t)
000 111
Y' 1 (t)
000 000
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
22. The communication system of claim 13 , wherein one or more of the tail output bits is punctured as follows:
R
¼
X(t)
111 000
Repeat
Y 0 (t)
111 000
Y 1 (t)
111 000
X'(t)
000 111
Repeat
Y' 0 (t)
000 111
Y' 1 (t)
000 111
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.
23. The communication system of claim 13 , wherein (R) comprises a plurality of code rates.
24. The communication system of claim 23 , wherein one or more of the tail output bits is punctured as follows:
R
½
1/3
1/4
X(t)
111 000
111 000
111 000
Repeat
Repeat
Y 0 (t)
111 000
111 000
111 000
Y 1 (t)
000 000
000 000
111 000
X'(t)
000 111
000 111
000 111
Repeat
Repeat
Y' 0 (t)
000 111
000 111
000 111
Y' 1 (t)
000 000
000 000
000 111
wherein “0” indicates a punctured bit and “1” indicates a transmitted bit.