基于分段混合调制的导频辅助块传输技术研究

在导频与数据时分复接的块传输系统中,无保护间隔系统具有最佳的数据传输效率,但工作在多径信道下时,该系统接收信号中导频和数据边缘混叠,接收机需要额外的干扰消除操作以精确分离二者。实际干扰消除算法都会存在一定误差,这种误差会降低信道估计算法的精度,进一步影响整个数据块的解调及解码,最后导致系统误码性能下降。该文提出一种分段混合调制方式：数据块中,可能与导频发生混叠的前后两端数据符号采用低阶调制;而中部依然采用高阶调制。仿真结果表明,在典型大延时多径信道下,分段混合调制系统误码性能明显优于传统无保护间隔的时分导频辅助块传输系统。

A Novel Hybrid Modulation Scheme for PUot-assisted Block Transmission Technology

When PABT (Pilot-Assisted Block Transmission) signal is transmitted over severe multipath channels, consecutive pilot block and data block may partially overlap each other. If no guard interval is inserted between them, a process to cancel the mutual interference is usually adopted in the receiver. But this process, as well as channel equalization, may suffer severe performance degradation when channel estimation is not so reliable. A hybrid modulation scheme is proposed in this paper, in which the overlapped part in data block is modulated using lower order constellation, while the other part keeps using higher order constellation. Its advantage in BER performance and robustness over conventional PABT schemes is demonstrated with simulation in some multipath channels with large delay spread.