采用上行SCMA系统的新型导频结构及信道估计方法

New pilot structure and channel estimation for uplink SCMA system

针对在上行稀疏码分多址接入(sparse code multiple access,SCMA)系统中,如果按照多用户共享相同资源的复用形式进行导频结构的设计,会导致正确估计每个用户的信道信息存在较大困难的问题,提出一种适合于上行SCMA系统的新型导频结构.通过导频间隔和导频位置的合理设计,保证不同用户在不同的子载波上发送各自的导频,在接收端使用最小二乘法(least square,LS)和线性最小均方误差法(linear minimum mean square error,LMMSE)对导频进行信道估计,最后,通过Cubic内插得到完整的信道估计值.仿真结果表明,基于LS算法的该导频结构更好地平衡了误码率性能和系统复杂度,减少了系统导频开销,并且运算量明显降低.

In uplink sparse code multiple access(SCMA)system,if the pilot structure is designed according to this multiplexing form of multiuser sharing the same resources,it will make it difficult to properly estimate each user’s channel information.To solve this problem,a new pilot structure suitable for uplink SCMA system is proposed through a reasonable design of pilot interval and pilot position,which can ensure that different users send their pilot on different subcarriers.Then the least square(LS)algorithm and linear minimum mean square error(LMMSE)algorithm are used to estimate the channel state information of pilots at the receiver.Finally,the complete channel estimation value is obtained through Cubic interpolation.Simulation results show that the pilot structure that uses LS algorithm better balances the bit error rate performance and system complexity,which reduces the system pilot overhead,and significantly reduces the amount of calculation.