分段限速设计改善导频辅助调制系统频谱效率的研究

本文提出了一种分段限速的传输方式、用以改善频率选择性块衰落信道中导频辅助调制OFDM系统的频谱效率,具体设计为:发射机将一个OFDM数据块分为若干组、每组的传输速率限定为它能够达到的输入与输出之间互信息的下界;接收机将当前组的符号判决后用作下一组附加的导频符号,附加导频符号的增多将提高信道估计质量,并最终改善系统频谱效率.理论上讲,在每组信息符号足够多的情况下,只要传输速率不大于互信息下界,信道编码可以保证该组误符号率的极限为零.文中以这一极限为前提,推导了分段限速设计能够达到的频谱效率.理论分析及其数值结果表明:与传统导频辅助调制OFDM系统相比,分段限速设计能够实现更高的频谱效率.

A Design for Increasing Spectral Efficiency of PSAM-OFDM System Based on Segmented Effective Transmission Rate

This paper presents a design for increasing spectral efficiency of Pilot Symbol Assisted Modulation(PSAM)-Orthogonal Frequency Division Multiplexing(OFDM) system by the use of segmented data rate transmission in the frequency-selective block fading channel model.In the proposed scheme,the transmitter divides the information-bearing tones of a block into several segments,each of which uses the data rate limited by its lower bound of the mutual information.The receiver detects current segments and uses the detected symbols as the addition pilots for next segment.With the number of the pilot symbols increases,quality of each channel estimate is improved and,consequently,the spectral efficiency of the system can be increased.It is reasonable to assume that the limit of symbol error rate is zero when each segment contains large number of symbols.Under this assumption,we derived the lower bound of the spectral efficiency.The numerical results show the spectral efficiency gain over the conventional design.