Optimal Rate-Diversity Tradeoff Space-Time Codes Based on Irregular Repeat-Accumulate Codes
Date Issued
2006
Date
2006
Author(s)
Chiu, Wen-Hsien
DOI
en-US
Abstract
The design of smart-greedy space-time (ST) codes for multiple-input multiple-output (MIMO) wireless systems in a variety of mobility conditions is an open problem of
great interest. Motivated by the algebraic space-time constructions of Lu and Kumar, which achieve the transmit diversity gain and permit the maximum transmission rate
possible, we propose an algebraic method for constructing optimal ST codes in the sense of achieving the rate-diversity tradeoff. We also show that our codes belong to a
class of irregular repeat-accumulate codes which can provide the potential of seizing possible temporal diversity. In this thesis, we first present new space-time codes using maximal rank-distance accumulate (MRDA) codes whose encoder consists of a repeater, an edge interleaver, a single parity-check encoder, and a simple accumulator.
Based upon their factor graph representations, we employ efficient massage-passing algorithms on the combined graph of a turbo MIMO receiver composed of an inner MIMO detector and an outer MRDA decoder. We show that for rate-1 MRDA
codes, the well-known sum-product algorithm suffices. However, it does not work for high rate MRDA codes. The convergence problems are solved by introducing the
modification of the code structure and the adaptive sum-product algorithm.
From the simulation results, more temporal diversity can be obtained in fast fading channels as the block size increases. The main difficulty in increasing the block size of MRDA codes is that the block size T is the degree of primitive polynomial such that designing codes of large T needs inevitable exhaustive search. Without a exhaustive
search for primitive polynomial with large degree, a large size scheme called cascade-interleave maximal rank-distance accumulate (CIMRDA) codes is proposed.
Furthermore, based on the binary (CI)MRDA codes, a generalized unified construction which yields ST codes over commonly used constellations such as PAM, QAM, 2k-PSK is discussed.
Subjects
時空編碼
速率分集取捨
不規則重覆累加碼
最大秩距累加碼
串接交錯式最大秩距累加碼
space-time coding
rate-diversity tradeoff
irregular repeat-accumulate code
maximal rank-distance accumulate code
cascade-interleave maximal rank-distance accumulate code
Type
thesis
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