联合子载波抑制-机会网络编码的OFDM数据广播方法

Joint Subcarriers Suppression and Opportunistic Network Coding for OFDM Data Broadcasting

正交频分复用(Orthogonal freqency division multiplexing,OFDM)技术通过采用多个子载波在不同的子带上传输信息来有效对抗频率选择性衰落。但不同子载波信道质量不同,其中信道质量较差的子载波会产生较大的误码率,从而导致整个系统性能下降。将信道质量较差的子载波抑制不用即可解决该问题。本文提出了一种适用于OFDM数据广播系统的联合子载波抑制-机会网络编码方法(Joint subcarriers suppression and opportunistic network coding,JSSONC),即将子载波抑制技术与网络编码(Network coding,NC)技术联合使用。基站抑制信道质量较差的子载波,仅采用信道质量较好的子载波进行数据包的广播与重传。在此基础上,结合机会网络编码,进一步减少重传数据包数量。仿真结果表明,与传统OFDM广播系统相比,本文提出的JSSONC方法降低了每一个数据包平均传输次数(Average transmission times of every data package,ATT-E),从而大大提高了系统传输效率。

Orthogonal frequency division multiplexing （OFDM） could efficiently tackle the problem of fre- quency-selective fading By adopting multiple subcarriers to Be transmitted upon different suBbands. Sub- carriers with weak channel qualities suffer severe symbol＇errors, which limits the overall system per- formance. Suppressing subcarriers with bad channel qualities would solve the problem. Here, a joint subearriers suppression and opportunistic network coding （JSSONC） scheme is proposed for OFDM data broadcasting systems, where subcarriers suppression technique is combined with network coding （NC） technique. By using JSSONC, the base station suppresses the subcarriers being in bad channel conditions. Consequently, retransmission packets used to recover lost packets are produced by adopting net- work coding to reduce further the number of transmissions. Simulation results show that the proposed JSSONC in OFDM data broadcasting systems reduces the average transmission times of every data pack- age （ATT-E）, compared with the traditional OFDM broadcasting systems, thus improving the system transmission efficiency.