Performance of Scheduling Scheme for MU-MIMO BC System with Two-Stage Feedback

Abstract

Multi-user Multiple Input Multiple Output (MU-MIMO) broadcast channel (BC) deployed with multiple transmit antennas at the base station (BS) and multiple receive antennas at each user is considered. The channel state information (CSI) from each user is quantized at the user side and the CSI at the transmitter (CSIT) required to obtain the throughput for the system is obtained in terms of the feedback bits only. The main objective is to reduce the feedback load. Transmitter architecture is proposed based on the zero-forcing beam forming (ZFBF) semi-orthogonal user selection (SUS) algorithm. In the proposed system, a two-stage feedback scheme is used along with the SUS scheduling algorithm so as to minimize the feedback load. The Maximum expected SINR combiner (MESC) is exploited so that only a limited number of users convey their feedback. These methods efficiently eliminate users from transmission in feedback and scheduling process, resulting in optimum use of scarce resources.The selected set of users are used for finding the BER and the ergodic capacity of the system. For this the CSIT (Channel State Information) is requires to obtain throughput using the feedback bits only. The MESC (Maximum Estimated SINR combiner) is calculated for the users to convey their feedback. The analytical result shows that the BER decreases with the increase in number of antennas which helps in increasing the efficiency of the system proposed. The ergodic capacity of the system increases with an increase in the number of feedback bits thus helping in accommodating more number of users.