Performance Of Multiuser MIMO Systems Research Articles

Scheduling for Multi-User Multi-Input Multi-Output Wireless Networks with Priorities and Deadlines

The spectral efficiency of wireless networks can be significantly improved by exploiting spatial multiplexing techniques known as multi-user MIMO. These techniques enable the allocation of multiple users to the same time-frequency block, thus reducing the interference between users. There is ample evidence that user groupings can have a significant impact on the performance of spatial multiplexing. The situation is even more complex when the data packets have priority and deadlines for delivery. Hence, combining packet queue management and beamforming would considerably enhance the overall system performance. In this paper, we propose a combination of beamforming and scheduling to improve the overall performance of multi-user MIMO systems in realistic conditions where data packets have both priority and deadlines beyond which they become obsolete. This method dubbed Reward Per Second (RPS), combines advanced matrix factorization at the physical layer with recently-developed queue management techniques. We demonstrate the merits of the this technique compared to other state-of-the-art scheduling methods through simulations.

Analysis of the performance of multiuser MIMO systems with user scheduling over Nakagami- [formula omitted] fading channels

A performance analysis of user scheduling schemes for multiuser MIMO systems exploiting the multiuser and antenna diversities over Nakagami- m fading channels is presented. We consider different scheduling schemes including absolute SNR-based scheduling, and normalized SNR-based scheduling schemes for both heterogeneous and homogeneous wireless networks. We derive closed-form expressions for the average spectral efficiency, average bit error rate (BER), and outage probability of the system under study for each scheduling scheme. Using the results obtained from the closed-form analytical expressions, we compare the presented schemes and show their significant advantages.

Feedback Reduction in Uplink MIMO OFDM Systems by Chunk Optimization

The performance of multiuser MIMO systems can be significantly increased by channel aware scheduling and signal processing at the transmitters based on channel state information. In the multiple-antenna uplink multi-carrier scenario, the base station decides centrally on the optimal signal processing and spectral power allocation as well as scheduling. An interesting challenge is the reduction of the overhead in order to inform the mobiles about their transmit strategies. In this work, we propose to reduce the feedback by chunk processing and quantization. We maximize the weighted sum rate of a MIMO OFDM MAC under individual power constraints and chunk size constraints. An efficient iterative algorithm is developed and convergence proved. The feedback overhead as a function of the chunk size is considered in the rate computation and the optimal chunk size is determined by numerical simulations for various channel models. Finally, the issues of finite modulation and coding schemes as well as quantization of the preceding matrices are addressed.