Feedback rate allocation of precoder and bit loading for MIMO systems with limited feedback

In this paper we consider feedback rate allocation for MIMO systems with limited feedback of both bit loading and precoder. Allocation of feedback rate is an essential problem when there are two or more kinds of feedback information. We address this issue by analyzing the performance loss due to quantization of precoder and bit loading. We first derive the increase in transmission power when precoder is quantized, and then the additional penalty when bit loading is also quantized. The analysis allows us to find the optimal feedback rate allocation that minimizes the power penalty. Simulations show that the system with proper feedback rate allocation can achieve a very good performance compared with systems that do not consider the feedback of precoder and bit loading jointly.