多用户多径长码DS-CDMA系统参数估计CRB和MCRB

多用户参数估计直接影响了多用户检测算法的性能。在多用户多径长码直接序列码分多址（DS-CDMA）系统下，首先推导出已知激活用户导频比特和扩频码时，多用户相位、时延和幅度参数联合估计的Cramer-Rao界（CRB）；然后给出了当激活用户导频比特和扩频码未知时，把激活用户扩频码看作随机变量，参数联合估计的修正CRB（MCRB）。数据仿真结果显示了导频比特长度、信噪比和激活用户个数对CRB和MCRB的影响；同时与单径长码DS-CDMA系统参数联合估计CRB和MCRB做了仿真比较。

CRB and MCRB for Parameter Estimation in Long-Code Multipath DS-CDMA Systems

The performance of muhi-user detection （MUD） algorithm is subject to multiuser parame- ter estimation directly in DS-CDMA system. The problem of estimating the phase offsets, propagation delay and amplitudes for a muhiuser asynchronous muhipath DS-CDMA system is examined. First, formulas are provided for the Cram~r-Rao bound （CRB） on the error variance of any joint muhiuser parameter estimation procedure exploiting a known training sequence. Further, this paper obtains formulas for the modified CRB （MCRB） under the assumption that the long spreading codes can be modeled as random nuisance parameters. Numerical examples showing the impact of the training length, the number of active users and signal-to-noise （SNR） on the CRB and MCRB are reported. The difference of CRB and MCRB between in muhipath and signal path long spreading code DS-CD- MA is compared through computer simulations.