Zhang Yiwen,Yin Qinye,Zeng Yanxing
(School of Electronics and Information Engineering,Xi'an Jiaotong University,Xi'an 710049,China)
Abstract:In multi-rate code division multiple access (CDMA) systems, the multiple access interference (MAI) results in the system performance depression and the number of the physical users in the system will reduce when using low rate detector. Focusing on these problems, the soft-decision low rate of blind space-time multi-user detection method for synchronous uplink dual-rate multicarrier (MC) CDMA systems with antenna arrays used at receiver was proposed. After letting various-rate physical users be equivalent to low rate virtual users,space-time signature vectors of the virtual users were constructed.Sequentially,these signature vectors were estimated blindly based on subspace projection algorithm to realize the multi-rate blind multi-user detection without estimating the complex scaling factors.The proposed scheme can reduce MAI and improve system capacity by introducing antenna arrays processing. Numerical simulations results demonstrate that the performance of proposed scheme is close to that of the known-channel minimum meansquare error multi-user detector and the receiving signal noise ratio with two receiving antennae will be improved about 8 dB at the bit error rate of 10-3. Although only a dual-rate system was considered were, the derivations and conclusions can be easily extended to any multi-rate system.
Keywords:multi-rate;multi-user detection;antenna arrays;subspace projection