Low Complexity Equalization Algorithm of OCDM Systems in Doubly-Selective Channels
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摘要: 正交Chirp复用(OCDM)是近年来提出的一种新的多载波体系，通过菲涅尔变换，获得一组正交Chirp信号，实现了CSS的最大频谱效率。该文介绍了OCDM系统的基本原理，重点研究了OCDM系统的低复杂度均衡算法。双选信道下，传统的MMSE均衡算法性能下降，提出一种基于近似带状矩阵的阻尼LSQR算法，作为求解稀疏矩阵的最小二乘迭代算法。为了缓解快速时变信道中的ICI，提出一种基于近似带状矩阵的LSQR-BDFE算法，结合判决反馈均衡，通过LSQR算法迭代计算。仿真结果表明，双选信道下，OCDM系统比OFDM系统有着更好的BER性能，所提出的LSQR-BDFE算法和带状阻尼LSQR算法，比MMSE均衡算法有着性能优势。
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关键词:
- 正交Chirp复用(OCDM) /
- 菲涅尔变换 /
- 带状阻尼LSQR算法 /
- LSQR-BDFE算法
Abstract: Orthogonal Chirp Division Multiplexing(OCDM) is a new multi-carrier system proposed in recent years. Through Fresnel transform, a set of orthogonal Chirp signals are obtained, which achieve the maximum spectral efficiency of CSS. In this paper, the basic principle of OCDM systems is introduced and the low complexity equalization algorithm of OCDM systems is studied. In doubly-selective channels, the performance of the traditional MMSE equalization algorithm declines. A Damped-LSQR algorithm is proposed based on approximate banded matrix, as a least square iterative algorithm for sparse matrix. To alleviate ICI in rapidly time-varying channels, an LSQR-BDFE algorithm is proposed based on approximate banded matrix. Combined with decision feedback equalization, LSQR algorithm is used for iterative calculation. The simulation results show that the OCDM system has better BER performance than the OFDM system under doubly-selective channels. The LSQR-BDFE algorithm and Band Damped-LSQR algorithm have performance advantages compared with the MMSE equalization algorithm. -
表 1 3种均衡算法的计算复杂度
算法 复杂度 MMSE-OP(A) $ N + 2N{\log _2}N $ BD-LSQR(B) $ NQ + \left( {i + 2} \right)N{\log _2}N $ LSQR-BDFE(C) $ N{Q^2} + \left( {i + 2} \right)N{\log _2}N $ 
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