低轨道卫星随机接入系统中多用户检测算法

Multi-user detection algorithm in the LEO satellite random access system

针对快速时变信道导致低轨道卫星随机接入中多用户检测性能恶化的问题,提出了克服大多普勒频移的多用户检测算法.算法采用基扩展模型建模各用户的信道,通过最大似然法联合求解各用户的基系数,接着利用基系数拟合出各用户信道,然后重构所有干扰用户分组并进行干扰消除,最后对干扰消除后的剩余信号进行译码.利用译码比特及各用户训练块和已检测用户数据重复进行信道估计及干扰消除,以提高用户分组的检测概率.仿真结果表明,该算法相对已有算法在误包率、信道估计均方误差及吞吐量性能方面均有明显提升.算法能够有效的工作于具有较高信噪比及大多普勒频移的低轨道卫星多用户场景.

The performance of multi-user detection in the low earthorbit satellite random access system deteriorates seriously over rapidly time-varying channels.To solve this problem,a multi-user detection algorithm is proposed to overcome the large Doppler frequency shift.The algorithm uses the basis expansion model for modeling the channel of each user and the basis coefficients of each user are jointly solved by the maximum likelihood method.Then,the channel of each user is fitted by the basis coefficients.After that,all interference packets are reconstructed and eliminated.Finally,the residual signals after interference cancellation are decoded.To improve the detection probability of the user's packets,the channll estimation and interference cancellation are repeated using the decoded bits,each users training blocks and the detected user data.Simulation results show that,compared with the existing algorithm,the algorithm has significantly improved the performance of the packet error rate,channel estimation mean square error and throughput.The algorithm can work efficiently in low earth orbit satellite multi-user scenarios,which have a high signal noise ratio and a large Doppler frequency shift.