The Study Of User Scheduling Algorithm For TD-HSPA+MU-MIMO System

In order to improve the data system capacity and reduce the transmission delay,3GPP introduces TD-HSPA+ as the evolution of TD-SCDMA system. As one of the key technologies of TD-HSPA+, MIMO technology eliminates the multipath fading of signal by imploying multiple antennas at the transmitter and receiver. MIMO technology can exponentially enhance the system capacity and spectrum efficency without increasing the bandwidth. MIMO is an essential component of TD-HSPA+ because it resoves the conflict between the large-capacity high-speed data transmission of future mobile communication system and the growing demond of spectrum.As a TDD system, the uplink and the downlink of TD-HSPA+ are allocated at the same frequency, so that the base station could obtain downlink channel impulse responses through its uplink channel estimation. Compared to SU-MIMO, MU-MIMO takes advantage of multi-user diversity gain to improve system performance. The SU-MIMO has been studied excessively, while MU-MIMO has been rarely investigated in TD-HSPA+ system. The major contribution of this work is to present MU-MIMO scheduling algorithms for TD-HSPA+ urban macro and urban micro scenarios.First of all, the pre-coding algorithms based on the SVD (Singular Value Decomposition) and BD (Block Diagonalization) are introduced, and then the traditional user scheduling algorithm and the MCS pre-processing method aiming at enhancing the initial transmission success ratio are discussed.Secondly, taking account of the shortcome of current scheduling algorithms and the impact on the MCS selection caused by SVD pre-coding and BD pre-coding, we propose a novel joint user scheduling and MCS selection algorithm. The proposed algorithm needs no additional control signaling and low user equipment. The proposed algorithm improves system throughput significantly while maintaining the satisfying success ratio of initial transmission.Finally, for the indoor MU-MIMO scenario, a novel scheduling and user pairing algorithm is proposed for TD-HSPA+ uplink. The impact of multi-stream interference between the receiving antennas and co-channel interference within the same antenna is considered in the algorithm. By accessing users into different base stations'serving user lists, the proposed algorithm can improve average throughput at the base station significantly while maintaining user fairness. It is suitable to be deployed in the practical indoor systems for its low computational complexity and no additional signaling costs.