摘要
正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)是应用于高速率无线传输的一项有效技术。标准的OFDM系统的时频格是方形的,因此当信道在格点频率附近存在深度衰落时,未编码的OFDM系统面临着严重的符号恢复问题。为克服上述问题,在符号复用之前,可采用频谱利用率较高的Lattice编码。本文推导了针对衰落信道的编码优化性能指标、相应的编码设计标准,并提供了代数设计方法和实例。数值仿真结果验证了Lattice编码的OFDM系统相对于未编码系统有着更好的抗频率选择性衰落性能。
OFDM has gained considerable interest as an efficient technology for high-date-data transmission over wireless channels. Standard OFDM systems are associated with a rectangular grid in the time-frequency plane, when the channel has nulls close to or on the FFT grid, uncoded OFDM faces serious symbol recovery problems. As a spectral efficient method to ameliorate the problem, we perform Lattice coding before the symbols are multiplexed. We provide performance criteria for fading channel and show how to build efficient lattice codes with algebraic method. Numerical simulations confirm that Lattice coded OFDM systems outperform ordinary OFDM systems with regard to robustness against frequency selective fading.
出处
《信息与电子工程》
2007年第5期329-333,共5页
information and electronic engineering
