Improved Pilot Designs for Enhancing Connectivity in Multicarrier Massive MIMO Systems

This letter proposes improved pilot designs to enhance the connectivity of multicarrier massive MIMO systems. Exploiting the fact that orthogonal frequency-division multiplexing (OFDM) training symbols end with zero samples, the proposed pilot designs reduce pilot overhead by truncating the zero samples and/or intentionally using them for a guard interval without affecting the channel estimation quality. The proposed designs allow a massive MIMO system either to serve more users with a fixed amount of training time, or requires less training time for a fixed number of users. Numerical results obtained for a cell-free massive MIMO system (as an application use case) demonstrate significant improvements in connectivity and spectral efficiency by the proposed designs over the conventional designs.