基于循环移位码元的M进制过调制无前导短包通信方案

M-ary overmodulation based on cyclic shift symbols for pilot free short packet communication scheme

为了解决短包结构中前导训练开销过大导致传输效率低的问题,提出了一种基于循环移位码元的M进制过调制无前导短包通信方案。该方案使用循环移位码元对伪随机序列进行调制,并采用M进制过调制序列对多个码元循环移位进行二次调制。接收端利用伪随机序列良好的自相关与互相关特性,实现无前导训练的检测和同步,有效降低了短包前导训练开销。而过调制的引入在携带额外信息的同时,可有效提高码元同步性能。另外,推导了循环移位和过调制后的短包码元同步评价函数,验证了M进制过调制加载信息的可行性。仿真结果表明,在加性白高斯噪声和瑞利衰落信道下,基于循环移位码元的M进制过调制无前导短包通信方案有效提高了码元同步性能,相比于单个过调制序列,该方案额外传输了lbM bit信息。

To solve the problem of low transmission efficiency caused by the high overhead of the pilot in the short packet structure,a M-ary overmodulation based on cyclic shift symbol for pilot-free short packet communication scheme was proposed.The scheme adopted cycle code shift keying(CCSK)to modulate pseudo noise(PN)sequences,and used M-ary overmodulation sequences to perform secondary modulation on multiple CCSK symbols.The receiving end utilized the good autocorrelation and cross-correlation characteristics of PN sequences to achieve pilot-free detection and synchronization,which effectively eliminated the training overhead of short packet pilots.The introduction of overmodulation effectively improved symbol synchronization performance while carrying additional information.The synchronization evaluation function of short packet symbols after CCSK and overmodulation was derived,and the feasibility of Mary overmodulation loading information was verified.Simulation results demonstrate that under AWGN and Rayleigh fading channels,the proposed M-ary overmodulation based on cyclic shift symbols for pilot-free short packet communication scheme for pilot-free short packet communication effectively improves the symbol synchronization performance,and transmits additional lbM bit information compared to a single overmodulation sequence.