Constrained interleaving for 5G wireless and optical transport networks

Abstract

The present invention provides a design framework that is used to develop new types of constrained turbo block convolutional (CTBC) codes that have higher performance than was previously attainable. The design framework is applied to design both random and deterministic constrained interleavers. Vectorizable deterministic constrained interleavers are developed and used to design parallel architectures for real time SISO decoding of CTBC codes. A new signal mapping technique called constrained interleaved coded modulation (CICM) is also developed. CICM is then used to develop rate matching, spatial modulation, and MIMO modulation subsystems to be used with CTBC codes and other types of codes. By way of example, embodiments are primarily provided for improved 5G LTE and optical transport network (OTN) communication systems.

What we claim is: 
     
         1 . A communications apparatus comprising,
 an encoder that converts a sequence of bits to an encoded bit sequence in accordance with an encoding rule, wherein the encoded bit sequence contains an integer number, K, of encoded bits, and the encoding rule has the property that, for all possible sequences of bits to be encoded, all possible low weight encoded bit sequences, i P , of weights d t ≦d≦d f  can be identified and enumerated, none of the possible low weight encoded bit sequences, i P , can have a weight less than d t , and the weights d t ≦d≦d f  correspond to Hamming distances;   a constrained interleaver configured to implement a permutation rule that permutes the K encoded bits of the encoded bit sequence to a sequence of subsets, wherein each subset contains m encoded bits;   a constellation mapper coupled to receive the sequence of subsets and configured to constellation-map the sequence of subsets to a sequence of signal constellation points in accordance with a constellation mapping rule;   wherein the permutation rule and the constellation mapping rule are jointly selected to ensure that a pre-defined target value of MSED (minimum squared Euclidian distance) is maintained for all of the possible low weight encoded bit sequences, i P , of weights d t ≦d≦d f .   
     
     
         2 . The communications apparatus of  claim 1 , wherein the sequence of subsets includes K/m number of subsets. 
     
     
         3 . The communications apparatus of  claim 2 , wherein the sequence of constellation points includes K/m number of 2 m -ary signal constellation points. 
     
     
         4 . The communications apparatus of  claim 1 , wherein the permutation rule and the constellation mapping rule are further jointly selected to ensure that a pre-defined target value of minimum symbol Hamming distance, d s , is maintained for all of the possible low weight encoded bit sequences, i P , of weights d t ≦d≦d f . 
     
     
         5 . The communications apparatus of  claim 4 , wherein the Hamming distance d f  is selected such that any possible encoded bit sequence, i P , that has a weight d>d f  will be guaranteed to have at least the pre-defined target value of MSED and the pre-defined target value of minimum symbol Hamming distance, d s . 
     
     
         6 . The communications apparatus of  claim 4 , wherein constellation mapper uses an anti-Gray coding constellation mapping rule. 
     
     
         7 . The communications apparatus of  claim 4 , wherein constellation mapper uses an RGC (Reverse Gray coding) constellation mapping rule. 
     
     
         8 . The communications apparatus of  claim 1 , wherein the Hamming distance d f  is selected such that any possible encoded bit sequence, i P , that has a weight d>d f  will be guaranteed to have at least the pre-defined target value of MSED. 
     
     
         9 . The communications apparatus of  claim 1 , wherein the constellation mapper uses an RGC (Reverse Gray coding) constellation mapping rule. 
     
     
         10 . The communications apparatus of  claim 1 , wherein constellation mapper uses an anti-Gray coding constellation mapping rule. 
     
     
         11 . The communications apparatus of  claim 1 , further comprising a spatial mapper, wherein the combination of the constellation mapper and the spatial mapper comprise a constellation and spatial mapper configured to couple the sequence of signal constellation points through a sequence of selected ones of a plurality of spatial channels in accordance with a spatial modulation rule. 
     
     
         12 . The communications apparatus of  claim 11 , wherein the sequence of selected ones of a plurality of spatial channels is selected to ensure that the pre-defined target value of MSED (minimum squared Euclidian distance) is maintained for all of the possible low weight encoded bit sequences, i P , of weights d t ≦d≦d f  that traverse the plurality of spatial channels. 
     
     
         13 . The communications apparatus of  claim 11 , wherein the each one of the plurality of spatial channels comprise an output from a different one of a set of antennas. 
     
     
         14 . The communications apparatus of  claim 11 , wherein the each one of the plurality of spatial channels comprise an path through from a different one of a set discrete-time optical filters in a bank of discrete-time optical filters. 
     
     
         15 . The communications apparatus of  claim 1 , further comprising a spatial mapper, wherein the combination of the constellation mapper and the spatial mapper comprise a constellation and spatial mapper configured to couple the sequence of signal constellation points through a plurality of spatial channels in accordance with a MIMO (multiple input multiple output) modulation rule. 
     
     
         16 . The communications apparatus of  claim 1 , wherein the encoder further comprises:
 an outer encoder that is coupled to receive the sequence of bits and to produce therefrom a sequence of outer-encoded bits in accordance with member of the group consisting of a block code, a finite-length convolutional code and an LDPC (low density parity check) code;   a second constrained interleaver that is coupled to receive the sequence of outer-encoded bits and is operable to produce a permuted sequence of outer encoded bits subject to one or more constraints that ensure that none of the possible low weight encoded bit sequences, i P , can have a weight less than d t ;   an inner coder that is coupled to receive the permuted sequence of outer encoded bits and to produce a sequence of inner-encoded bits in accordance with an inner code that is a recursive convolutional code;   wherein encoded bit sequence corresponds to the sequence of inner-encoded bits.   
     
     
         17 . The communications apparatus of  claim 16 , wherein the one or more constraints include at least one SRCI (single row constrained interleaving) constraint. 
     
     
         18 . The communications apparatus of  claim 17 , wherein the SRCI constraint is a member of the group consisting of a CI-3 constraint and a CI-4 constraint. 
     
     
         19 . The communications apparatus of  claim 18 , wherein the one or more constraints further include a vectorization constraint and the second constrained interleaver is a contention free deterministic constrained interleaver. 
     
     
         20 . The communications apparatus of  claim 1 , wherein the encoder is configured to encode in accordance with a CTBC (constrained turbo block convolutional) code. 
     
     
         21 . The communications apparatus of  claim 1 , wherein the encoder is configured to encode in accordance with a block code. 
     
     
         22 . The communications apparatus of  claim 1 , wherein the encoder is configured to encode in accordance with a convolutional code. 
     
     
         23 . The communications apparatus of  claim 1 , wherein the encoder is configured to encode in accordance with a turbo code for which all possible low weight encoded bit sequences, i P , of weights d t ≦d≦d f  can be identified and enumerated. 
     
     
         24 . The communications apparatus of  claim 1 , wherein the encoder is configured to encode in accordance with an LDPC code for which all possible low weight encoded bit sequences, i P , of weights d t ≦d≦d f  can be identified and enumerated.