Design of Low-density parity-check (LDPC) codes for high order constellations Conference Paper uri icon


  • Multilevel coding (MLC) with multistage decoding (MSD) is known to achieve capacity for coded modulation schemes. However, as MSD is not very practical due to delay constraints, MLC with parallel independent decoding (PID) of the component levels is more popular. Also, even though MLC with MSD is optimal asymptotically in the length of the code, in the finite-length case, it can have a component code of length only 1/m (for 2m-PAM or 2 2m-QAM) times the code-length of an equivalent bit-interleaved coded modulation (BICM) scheme. Using codes like LDPC codes and turbo codes, whose performance improves with length as component codes in MLC with MSD or PID, will be disadvantageous as opposed to a BICM scheme. Therefore, in this paper, we propose a simple design of LDPC codes which combines the good properties of MLC and BICM schemes with Gray-mapped PAM constellations and one-shot demodulation. Through simulations, we show that it performs better than MLC/PID for short-medium lengths, which is required for most applications, on AWGN and block-fading channels. Since 2m-PAM represents one quadrature component of 22m-QAM, the optimization holds true for QAM too. In general, this idea can be extended to other modulation schemes like 2 m-PSK very easily. 2004 IEEE.

name of conference

  • IEEE Global Telecommunications Conference, 2004. GLOBECOM '04.

published proceedings


altmetric score

  • 6

author list (cited authors)

  • Sankar, H., Sindhushayana, N., & Narayanan, K. R.

citation count

  • 29

complete list of authors

  • Sankar, H||Sindhushayana, N||Narayanan, KR

publication date

  • January 2004