Approximating EXIT Characteristics of Soft Demodulators in OFDM BICM-ID Systems for Time Variant Frequency Selective Fading Channels

Orthogonal Frequency Division Multiplexing (OFDM) in combination with Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is known to provide very good BER performance: While OFDM decomposes a frequency selective broadband transmission channel causing intersymbol interference (ISI) into narrow band flat fading subchannels, the iterative BICM-ID scheme enables demodulation and decoding of the transmitted data at nearly optimum Bit Error Rates (BERs). To provide a stopping criterion for the iterative process, the Extrinsic Information Transfer (EXIT) chart is an efficient tool. For the use in time-varying ISI environments however it is impossible to provide EXIT characteristics of the Soft Demodulator (SDM) as these change with the channel. In this paper we describe a simple but effective and accurate method for constructing SDM characteristics for ISI environments based on a limited set of SDM characteristics prerecorded under AWGN conditions.

[1]  A. Glavieux,et al.  Near Shannon limit error-correcting coding and decoding: Turbo-codes. 1 , 1993, Proceedings of ICC '93 - IEEE International Conference on Communications.

[2]  Ieee Microwave Theory,et al.  IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions , 2007 .

[3]  Stephan ten Brink,et al.  Extrinsic information transfer functions: model and erasure channel properties , 2004, IEEE Transactions on Information Theory.

[4]  Stephan ten Brink,et al.  Convergence behavior of iteratively decoded parallel concatenated codes , 2001, IEEE Trans. Commun..

[5]  Xiaodong Li,et al.  Bit-interleaved coded modulation with iterative decoding , 1997, IEEE Communications Letters.

[6]  M. Lamarca,et al.  Bit loading and power allocation for BICM-ID with convolutional codes , 2007, 2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications.

[7]  Xiaodong Li,et al.  Bit-interleaved coded modulation with iterative decoding and 8 PSK signaling , 2002, IEEE Trans. Commun..

[8]  Peter Vary,et al.  PSK versus QAM for iterative decoding of bit-interleaved coded modulation , 2004, IEEE Global Telecommunications Conference, 2004. GLOBECOM '04..

[9]  H.H. Nguyen,et al.  Bit-Interleaved Coded Modulation With Iterative Decoding in Impulsive Noise , 2007, IEEE Transactions on Power Delivery.

[10]  S. Brink.  Convergence of iterative decoding , 1999 .

[11]  Michael Tuchler,et al.  EXIT charts of irregular codes , 2002 .

[12]  Gerhard Bauch,et al.  Optimization of symbol mappings for bit-interleaved coded Modulation with iterative decoding , 2003, IEEE Communications Letters.

[13]  Stephan ten Brink,et al.  Designing Iterative Decoding Schemes with the Extrinsic Information Transfer Chart , 2001 .

[14]  T. Clevorn,et al.  EXIT Chart Analysis of Non-Regular Signal Constellation Sets for BICM-ID , 2004 .