Publication
Opportunistic AP Selection in Cell-Free Massive MIMO-OFDM Systems
Wei Jiang; Hans Dieter Schotten
In: 2022 IEEE 95th Vehicular Technology Conference. IEEE Vehicular Technology Conference (VTC-2022), June 19-22, Helsinki, Finland, IEEE, 6/2022.
Abstract
Exploiting the degree of freedom enabled by OFDM transmission in cell-free massive MIMO, we propose an opportunistic transmission scheme in this paper. The key idea is to orthogonally assign frequency-domain resources to users, and then each user is only served by its near APs through opportunistic selection. In contrast, the far APs are deactivated to avoid wasting power over their channels with severe propagation losses. As a side effect, the small number of active APs per subcarrier enables the use of downlink pilots so that the user can perform coherent detection with estimated channel realizations. As corroborated by numerical results, opportunistic selection and downlink pilots bring a significant performance boost in terms of both power and spectral efficiencies.