Iterative Detected Sphere Packing Modulated OFDM: An EXIT Chart Perspective

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Description/Abstract

A novel iteratively detected Sphere Packing (SP) modulation aided Orthogonal Frequency Division Multiplexing (OFDM) scheme is proposed, which we refer to as the SPOFDM arrangement. The advocated SP-OFDM system outperforms conventional OFDMdispensing with SP. As its upperbound performance limit, the Discrete Input Continuous Output Memoryless Channel (DCMC) capacity of this system is formulated. In order to maximize the DCMC channel capacity, a SP-to- OFDM-sub-carrier mapper (SPTSCM) is contrived, which is capable of providing an approximately 0.3bit/s/Hz DCMC capacity benefit, by employing a variety of different SPTSCM arrangements. Additionally, the proposed SP-OFDM scheme exhibits a DCMC capacity advantage of 0.8bit/s/Hz over the conventional equivalent-throughput Gray Mapping (GM) and Anti-Gray Mapping (AGM) based QPSK-OFDM schemes. Furthermore, the performance of the SP-OFDM system can be improved by serially concatenated convolutional coding relying on iterative extrinsic information exchange between the SP-symbol-to-bit demapper and the channel decoder. Explicitly, the proposed turbo-detected SP-OFDM scheme exhibits an approximately Eb/N0 = 3dB and Eb/N0 = 4.5dB gain at a Bit Error Ratio (BER) of 10?4 over the equivalent throughput turbo-detected GM based QPSK-OFDM scheme and AGM QPSK-OFDM scheme, respectively. EXtrinsic Information Transfer (EXIT) charts are employed for analyzing the achievable convergence behaviour.