A Novel MIMO Channel State Feedback Scheme and Overhead Calculation

The value of the channel state feedback becomes more significant in the upcoming 5G era due to the application of the millimeter-wave (mm-Wave) technologies in 5G. In the meantime, the feedback is challenging in the mm-Wave systems especially with massive MIMO antenna for two reasons: first, the channel states change faster at the millimeter band; second, in the massive antenna system, there are a large number of channel coefficients to report which means the feedback caused overhead will be large. Thus, optimization of the feedback system becomes necessary in the 5G era. In our optimization work, the perfect channel states are assumed to be not accessible at user equipments. Under this assumption, we propose a novel codebook-based-feedback scheme within which the differential channel information is first projected to the codebook, and then the index of the projection in the codebook is fed back. We compare the new scheme with other feedback schemes, such as analog feedback of original states and differential states. From the comparison, we analytically and numerically obtain the insight of the advantage of the proposed scheme. We can also observe that the advantage of the proposed scheme is even more significant in low-SNR conditions.