Method and apparatus for interleaving\within a communication system
View Patent ↗A method and apparatus for interleaving within a communication system is provided herein. More particularly parameters for a convolutional turbo code interleaver are provided, and interleaving takes place utilizing the new parameters. The new parameters generate interleavers that have the correct turbo code behaviors of improving performance with increasing block size and an error floor well below a block error rate of 10 −4 . Furthermore, the parameters have no implementation impact. Interleaving in accordance with the preferred embodiment of the present invention can achieve a block error rate of 10 −4 at a signal-to-noise ratio that is at least 0.5 dB, and in some cases up to 1.3 dB, smaller than that which can be achieved with the code using the existing parameters.
1. A method for an interleaver within an encoder to encode information bits, the method comprising the steps of:
the interleaver grouping the information bits into couples (A 0 ,B 0 ), (A 1 ,B 1 ), (A 2 ,B 2 ), (A 3 ,B 3 ), . . . , (AN−1,BN−1);
the encoder performing the steps of:
encoding (A 0 ,B 0 ), (A 1 ,B 1 ), (A 2 ,B 2 ), (A 3 ,B 3 ), . . . , (AN−1,BN−1) in a first encoder;
switching alternate couples to produce (A 0 ,B 0 ), (B 1 ,A 1 ), (A 2 ,B 2 ), . . . , (BN−1, AN−1)=u 1 ( 0 ), u 1 ( 1 ), u 1 ( 2 ), u 1 ( 3 ), . . . , u 1 (N−1);
mapping the couples of sequence u 1 onto an address j of an interleaved sequence, where a function P(j) provides the address of the couple of the sequence u 1 that shall be mapped onto the address j of the interleaved sequence, wherein u 2 ( j )=u 1 (P(j))=[u 1 (P( 0 )), u 1 (P( 1 )), u 1 (P( 2 )), u 1 (P( 3 )), . . . , u 1 (P(N−1))], and wherein for j=0, . . . , N−1
switch j mod 4:
case 0: P(j)=(P 0 j+1)mod N
case 1: P(j)=(P 0 j+1+N/2+P 1 )mod N
case 2: P(j)=(P 0 j/+1+P 2 )mod N
case 3: P(j)=(P 0 j+1+N/2+P 3 )mod N;
encoding u 2 in a second encoder;
transmitting the encoded u 1 and/or u 2 ; and
where values for N, P 0 , P 1 , P 2 , and P 3 take the form
Data block
size (bytes)
N
P 0
P 1
P 2
P 3
120
480
53
62
12
2
240
960
43
64
300
824
360
1440
43
720
360
540
480
1920
31
8
24
16
600
2400
53
66
24
2
and wherein (A 0 ,B 0 ), (A 1 ,B 1 ), (A 2 ,B 2 ), (A 3 ,B 3 ), . . . , (AN−1,BN−1) are information couples, N is an integer, and P( 0 ) . . . P(N−1) are functions that provide the address of the couples.
2. The method of claim 1 further comprising the step of:
having a transmitter transmitting the encoded u 1 .
3. The method of claim 1 further comprising the step of:
having a transmitter transmitting the encoded u 2 .
4. The method of claim 1 further comprising the step of:
having a transmitter transmitting the couples;
having the transmitter transmitting the encoded u 1 ; and
having the transmitter transmitting the encoded u 2 .
5. An apparatus comprising:
grouping circuitry outputting information bits into couples (A 0 ,B 0 ), (A 1 ,B 1 ), (A 2 ,B 2 ), (A 3 ,B 3 ), . . . , (AN−1,BN−1);
first encoding circuitry receiving the couples and encoding (A 0 ,B 0 ), (A 1 ,B 1 ), (A 2 ,B 2 ), (A 3 ,B 3 ), . . . , (AN−1,BN−1);
an interleaver switching alternate couples to produce (A 0 ,B 0 ), (B 1 ,A 1 ), (A 2 ,B 2 ), . . . , (BN−1, AN−1)=u 1 ( 0 ), u 1 ( 1 ), u 1 ( 2 ), u 1 ( 3 ), . . . , u 1 (N−1) and mapping the couples of sequence u 1 onto an address j of an interleaved sequence, where a function P(j) provides the address of the couple of the sequence u 1 that shall be mapped onto the address j of the interleaved sequence, wherein u 2 ( j )=u 1 (P(j))=[u 1 (P( 0 )), u 1 (P( 1 )), u 1 (P( 2 )), u 1 (P( 3 )), . . . , u 1 (P(N−1))] and wherein for j=0, . . . , N−1
switch j mod 4:
case 0: P(j)=(P 0 j+1)mod N
case 1: P(j)=(P 0 j+1+N/2+P 1 )mod N
case 2: P(j)=(P 0 j+1+P 2 )mod N
case 3: P(j)=(P 0 j+1+N/2+P 3 )mod N;
a second encoder, receiving u 2 and encoding u 2 ;
transmitting the encoded u 1 and/or u 2 ; and
where values for N, P 0 , P 1 , P 2 , and P 3 take the form
Data block
size (bytes)
N
P 0
P 1
P 2
P 3
120
480
53
62
12
2
240
960
43
64
300
824
360
1440
43
720
360
540
480
1920
31
8
24
16
600
2400
53
66
24
2
and wherein (A 0 ,B 0 ), (A 1 ,B 1 ), (A 2 ,B 2 ), (A 3 ,B 3 ), . . . , (AN−1,BN−1) are information couples, N is an integer, and P( 0 ) . . . P(N−1) are functions that provide the address of the couples.
6. The apparatus of claim 5 further comprising:
a transmitter transmitting the encoded u 1 .
7. The apparatus of claim 5 further comprising:
a transmitter transmitting the encoded u 2 .
8. The apparatus of claim 5 further comprising:
a transmitter transmitting the encoded u 1 , u 2 , and the couples.