On the Design of Interleavers for BICM Transmission

Conference: European Wireless 2008 - 14th European Wireless Conference
06/22/2008 - 06/25/2008 at Prague, Czech Republic

Proceedings: European Wireless 2008

Pages: 7Language: englishTyp: PDF

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Alvarado, Alex; Agrell, Erik; Svensson, Arne (Department of Signals and Systems, Communication Systems Group, Chalmers University of Technology, Gothenburg, Sweden)
Szczecinski, Leszek (INRS-EMT, University of Quebec, Montreal, Canada)

In this paper we design interleavers for bitinterleaved coded modulation (BICM) based on popular convolutional codes and quadrature amplitude modulation with Gray mapping. We analyze the so-called modular interleavers where the outputs of the convolutional encoder are appropriately matched with the input bits of the modulator. To quantify the achievable improvements we develop bounds on the coded BER using the multidimensional weight distribution spectrum of a code together with an equivalent QAM channel model. Based on these bounds, we show that the assignment of the encoder’s output to the bit positions in the symbol significantly affects the system performance. The analytical developments are contrasted with numerical simulations. The improvements obtained through the proposed approach do not change the receiver’s complexity and, depending on the system’s parameters (rate, modulation, code’s memory), they may be up to 1.7 dB!