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Variable Length L DPC Codes for 45 GHz

The Variable LDPC codes define a J-by-L base matrix for improved communication channel adaptation in 45GHz indoor mmWave scenarios. This proposal aims to enhance receiver adaptation capability through different code rates and lengths, maintaining compatibility with existing coding schemes. Performance comparisons with different modulation schemes and code rates are provided, showcasing the benefits of using long codes over short codes. The proposed scheme offers improved decoding and encoding efficiency without the need for additional hardware resources. Implementation complexity, buffer sizes, and throughput considerations are discussed, highlighting the advantages of the Variable LDPC scheme for 45GHz communication applications.

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Variable Length L DPC Codes for 45 GHz

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  1. Variable Length LDPC Codes for 45GHz Authors: • Date: 2015-05-19

  2. A QC-LDPC is defined by a J-by-L base matrixand the size of sub-matrices, p. A J-by-L base matrix has the following representation. (0<=i<J, 0<=i<L) represents a p-by-p sub-matrix: 0 represents an identity matrix; -1 represents a zero matrix; other non-zero less-than-p values represent circulant permutation matrices. Quasi-cyclic low density parity check codes

  3. LDPC codes proposed in [1] has been adopted by draft standard. Compared to other semi-static wireless channels, indoor mmw communication channel has more variations because of rich reflections/scattering and moving objects. It is desirable for receiver to have more adaptation to channel variation. Besides code rate, code length provides another dimension of coding gain change, thus improves the receiver’s adaptation capability to channel variations It is desirable to be compatible to existing coding scheme and minimize the added complexity. Considerations

  4. Same base matrices proposed by ZTE in [1]. Four code rates are 1/2, 5/8, 3/4and 13/16. Rate 1/2： Rate 5/8： LDPC Base matrices (1)

  5. Rate 3/4： Rate 13/16： LDPC Base Matrices (2)

  6. Based on the sets of base matrices by [1], code length change is achieved by changing p , the sub-matrix size. p=42 maintains the same set of 672 long LDPC codes proposed by ZTE. (672 , 366), (672 , 420), (672 , 504)and (672, 546) codes p=126 introduces a set of LDPC codes with code length of 2016. (2016, 1008), (2016, 1260), (2016, 1512) and (2016, 1638) codes 1-bit signaling field to indicate the code length Variable LDPC code length

  7. QPSK modulation and AWGN Performance of rate ½ codes (1)

  8. 16QAM modulation and AWGN Performance of rate ½ codes (2)

  9. 64QAM modulation and AWGN Performance of rate ½ codes (3)

  10. Performance of rate 5/8 codes(1) • QPSK modulation and AWGN

  11. Performance of rate 5/8 codes(2) • 16QAM modulation and AWGN

  12. Performance of rate 5/8 codes(3) • 64QAM modulation and AWGN

  13. Performance of rate 3/4 codes(1) • QPSK modulation and AWGN

  14. Performance of rate 3/4 codes(2) • 16QAM modulation and AWGN

  15. Performance of rate 3/4 codes(3) • 64QAM modulation and AWGN

  16. Performance of rate 13/16 codes(1) • QPSK modulation and AWGN

  17. Performance of rate 13/16 codes(2) • 16QAM modulation and AWGN

  18. Performance of rate 13/16 codes(3) • 64QAM modulation and AWGN

  19. All benefits from base matrices proposed in [1] are maintained. Improved performance of 0.1dB ~ 0.8dB achieved by longer codes compared to short codes. This also means finer coding gain grids for finer ACM adaptation. The short codes and long codes can share the same encoder and decoder. For decoder, larger value of p implies possible higher parallel processing, thus higher throughput, although at the expense of more logic and memory in ASIC implementation. Benefits of proposed scheme

  20. Encoding, compared to the short codes in [1] For long codes, buffer size needs to be tripled. Because the base matrices are the same, logic resources won't be increased if tripling of latency is tolerable, or logic resouces need to be tripled to maintain the same latency. Decoding, compared to the short codes in [1] For long codes, buffer size needs to be tripled. For layered decoding, logic resources for variable and check node processing won't be increased if throughput keeps the same. However, the shifting network complexity will increase. For full parallel implementation, the logic resources will be tripled. Complexity

  21. Conclusion • Variable LDPC code length is proposed to improved performance and channel adaptation capability. • Compatible to existing LDPC codes [1] adopted by the standard draft. • No need to add new encoder and decoder

  22. References [1]. LDPC Coding for 45GHz(11-14-0807-01-00aj). Proposal of IEEE802.11aj(45G).

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