Training and Feedback for Two-Stage Angles Estimation of mmWave Systems

In this paper, we consider the allocation of training time and feedback bits of a two-stage angle estimation scheme for a hybrid mmWave system that has limited feedback rate. In a two-stage estimation scheme, the total training time and feedback bits are allocated to the two stages. Due to finite feedback rate, the AoDs are quantized before they are fed back to the transmitter. The AoD estimates available to the transmitter contain both quantization and angle estimation errors. The allocation of training time affects the estimation accuracy of the two stages while the allocation of feed-back bits affect the quantization errors of the two stages. We derive the overall error and show that the training vectors should be equally allocated to the two stages in the useful case of high feedback rate. Simulations show that high resolution estimates can be achieved using the proposed allocation.