Mitigation of Performance Degradation by Impulsive Noise in LDPC Coded OFDM System

In the paper, LDPC (low-density parity-check) coded OFDM system applicable for impulsive noise channel, such as powerline channel (PLC) will be presented. Performance degradation in the proposed system over impulsive noise channel is mitigated using a simple estimator based on the Gaussian approximation with estimated channel information (ECI) and a signal level limiter. At first, it will be shown that the performance of a conventional LDPC coded OFDM system is seriously degraded due to the imperfection of estimating the initial LLRs (log likelihood ratios) of sum-product decoder over impulsive noise channels and hard evaluation of the initial LLRs from the decentralized noise samples by OFDM demodulator. Thereafter, to overcome the problems, the system using the simple estimator and the received signal level limiter is proposed. Simulation results show that the proposed system has much better performance than that of conventional systems. For the verification, Monte Carlo simulation is applied

[1]  Robert G. Gallager,et al.  Low-density parity-check codes , 1962, IRE Trans. Inf. Theory.

[2]  David Middleton,et al.  Statistical-Physical Models of Electromagnetic Interference , 1977, IEEE Transactions on Electromagnetic Compatibility.

[3]  Robert Michael Tanner,et al.  A recursive approach to low complexity codes , 1981, IEEE Trans. Inf. Theory.

[4]  Noga Alon,et al.  A linear time erasure-resilient code with nearly optimal recovery , 1996, IEEE Trans. Inf. Theory.

[5]  Radford M. Neal,et al.  Near Shannon limit performance of low density parity check codes , 1996 .

[6]  D.J.C. MacKay,et al.  Good error-correcting codes based on very sparse matrices , 1997, Proceedings of IEEE International Symposium on Information Theory.

[7]  T. Richardson,et al.  Design of provably good low-density parity check codes , 2000, 2000 IEEE International Symposium on Information Theory (Cat. No.00CH37060).

[8]  Rüdiger L. Urbanke,et al.  Design of capacity-approaching irregular low-density parity-check codes , 2001, IEEE Trans. Inf. Theory.

[9]  Tomoaki Ohtsuki,et al.  Low-density parity-check (LDPC) coded OFDM systems , 2001, IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211).

[10]  Jan L. Fan,et al.  Constrained coding and soft iterative decoding , 2001, Proceedings 2001 IEEE Information Theory Workshop (Cat. No.01EX494).

[11]  Sae-Young Chung,et al.  On the design of low-density parity-check codes within 0.0045 dB of the Shannon limit , 2001, IEEE Communications Letters.

[12]  Rüdiger L. Urbanke,et al.  The capacity of low-density parity-check codes under message-passing decoding , 2001, IEEE Trans. Inf. Theory.

[13]  Wei Yu,et al.  Low-density parity-check coding for impulse noise correction on power-line channels , 2005, International Symposium on Power Line Communications and Its Applications, 2005..

[14]  S. Denno,et al.  A decoding for low density parity check codes over impulsive noise channels , 2005, International Symposium on Power Line Communications and Its Applications, 2005..

[15]  Q.H. Spencer.  Short-block LDPC codes for a low-frequency power-line communications system , 2005, International Symposium on Power Line Communications and Its Applications, 2005..