一种卫星SCMA系统接收机同步算法

A receiver synchronization algorithm for satellite SCMA system

SCMA技术通过资源过载能够实现大规模用户的并发接入,非常适合物联网应用,但是SCMA解调性能受定时误差和载波频差影响较大。对此,文中通过基于导频的两阶段频差估计算法和ML相位偏差估计算法,实现大频差下的高精度频、相偏估计;通过SCMA和LDPC联合迭代,利用发送数据实现高精度定时误差估计。仿真结果表明,在AWGN信道下,载波同步算法采用优化的帧结构后可以获得距理想性能不到0.25dB的优异性能,定时同步算法在1次迭代下获得了距理想性能仅0.2dB的性能,在3次迭代下获得了与理想性能一致的优异性能,能适应大频差、高动态的卫星信道环境。

SCMA technology can realize the concurrent access for large-scale users through information overload,which is very suitable for the application of Internet of things.However,the demodulation performance of SCMA is greatly affected by timing error and carrier offset difference.Therefore,in this paper,on the basis of two-stage frequency difference estimation algorithm based on pilot carrier and ML phase offset estimation algorithm,high-precision frequency and phase offset estimation can be realized under large frequency offset.Through the simultaneous iteration of SCMA and LDPC,high precision timing error estimation is realized by using sent data.The simulation results show that in AWGN channel,the carrier synchronization algorithm with optimized frame structure can achieve excellent performance,which is less than 0.25dB compared with the ideal performance.However the timing synchronization algorithm only achieves 0.2db from the ideal performance in one iteration,and in three iterations the result is finally consistent with the ideal performance,which can adapt to the highly dynamic satellite channel environment with large frequency offset.