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User identification detector based on power of R technique

The subspace-based user identification detector (UID) is undoubtedly an efficient method identifying the active user in the synchronous or asynchronous code division multiple access (CDMA) systems. However the subspace-based UID needs to estimate the number of active users, inaccurate estimation results in the significant performance degradation. In fact, such estimation is practically difficult in multipath channels. To avoid the inaccurate estimation of active user's number and corresponding performance degradation, we propose a novel POR-based UID that adopts the power of R (POR) technique being proposed by Xu and Wang and MUSIC (multiple signal classification) method. The new detector does not require the estimation of active users' number, therefore obtains lower false alarm probability than the subspace-based UID in multipath channels. However, from our analysis, increasing the order m of POR technique does not improve the performance of POR-based UID. Therefore, when m is one, the performance of new detector is maximal.