Differential feedback in MIMO communications : performance with delay and real channel measurements

This work studies the performance of our recently proposed differential feedback scheme for multi-input-multi-output (MIMO) communication systems using real channel measurement data. The algorithm is applied to the channel correlation matrix exploiting geodesic curves and the intrinsic geometry of positive definite Hermitian matrices. The performance of this and a conventional non-differential feedback scheme are evaluated using real data and channel measurements obtained with the Eurecom MIMO OpenAir Sounder (EMOS). Additionally, the impact of having a delay in the feedback link is also studied in terms of a loss of performance in the communication through several simulations. The results show that the differential feedback strategy performs much better than the non-differential strategies in low mobility channels, while in high mobility channels the performance is similar. A delay in the feedback channel affects specially high mobility channels while having a negligible impact in the slow-varying cases.