LDPC Code Aided Phase Ambiguity Resolution for QPSK signals Affected by a Frequency Offset
Date
2007
Authors
Karuppasami, S.
Cowley, W.G.
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Conference paper
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Proceedings of the 2007 AusCTW: Australian Communications Workshop, 2007, pp.47-50
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8th Australian communication theory workshop (5 Feb 2007 - 7 Feb 2007 : University of Adelaide, South Australia)
Abstract
Low-density parity-check (LDPC) codes provide capacity approaching performances with very long codes in a coherent channel. However, as the block length increases, their performance becomes worse with residual frequency offsets. Residual frequency offsets can be tackled with sub-block decoding and LDPC code-aided phase ambiguity resolution for binary phase-shift keying (BPSK) signals. Sub-block decoding is a practical technique where phase estimation/correction are done over every sub-block in a codeword. In this paper, we extend the concept of LDPC code-aided phase ambiguity resolution to Quadrature phase-shift keying(QPSK) modulated signals through a mapping/demapping technique. Bit-error rate (BER) simulations show that the phase ambiguity algorithm along with sub-block decoding tackle small frequency offsets with a negligible loss. We further show with the help of EXIT charts that LDPC code distributions performing close to capacity and also aiding phase ambiguity resolution can be constructed.
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Copyright 2007 IEEE