Performance bounds for bit -interleaved coded modulation with application to multiuser coded OFDM

Krishna-Kamal Sayana, Purdue University


In our work, we develop a general approach to compute union bounds for higher order modulated BICM systems on fading channels. Suggested approaches for fading channels consider infinite depth interleaving to obtain a simplified memoryless bit-channel model. However; the assumption of asymptotically large coding length cannot be applied to all scenarios. On the other hand, concatenated codes employ a finite interleaver. In our work, we develop a new error event description assuming an ideal model for the modulator. In the second part of the thesis, the above approach is applied to analyze a coded multiplexing scheme for resource allocation in OFDM multiuser systems. This scheme does not rely on reverse link feedback, and obtains higher diversity on frequency selective fading channels, by spreading each user's data over the complete set of subcarriers with coding and interleaving. We present an information theoretic approach to study the asymptotic performance of asynchronous and adaptive incremental redundancy schemes extending the work by Caire and Tuninetti. Specifically, we outline a more general coding and decoding scheme incorporating variable transmission time intervals (TTI) and rate adaptation, and prove the corresponding coding theorems. The theorems can be seen as an extension of well known channel coding theorems to a HARQ scenario. We obtain conditions for successful transmission as a function of the channel conditions and the choice of the rate sequence over retransmissions. The analysis demonstrates that asynchronism and adaptivity are highly desirable features that greatly enhance the performance of HARQ in combination with scheduling.




Gelfand, Purdue University.

Subject Area

Electrical engineering

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