Abstract: The limited feedback in multiuser MultipleInput MultipleOutput (MUMIMO) systems is addressed in this paper. In order to reduce the feedback overhead in the uplink channel, we analyze the relation between user’s feedback bits and rate, deduce the optimal solution for adaptive limited feedback, and propose a suboptimal feedback scheme which is more practical. In this scheme, users choose the feedback bits according to both their channel gains and the average gain of the system. Users with high SNR are assigned with more feedback bits than the lowSNR users so as to improve the feedback efficiency. Simulation results and analysis show that the proposed scheme is easytoimplement and can enhance the throughput with no additional feedback overhead.

Key words: multipleinput multipleoutput (MIMO), multiuser, limited feedback, adaptive