Spectral Efficiency Maximization for Massive MIMO Uplink With Intra-Cell Pilot Reuse

Massive multiple-input multiple-output (mMIMO) and spatial multiplexing of devices are crucial technologies to support massive connectivity. As the number of users increases, it becomes impossible to assign unique orthogonal pilot sequences to each device, making the necessary channel state estimation challenging. Hence, intra-cell pilot reuse becomes necessary. In this letter, we propose a novel method for determining the optimal pilot length that maximizes spectral efficiency (SE) in mMIMO networks with pilot reuse. To that end, we develop an approximated expression for the signal-to-interference-plus-noise ratio, which is a function of the pilot length. The proposed method achieves accurate SE for different degrees of channel correlation and block length. This allows for efficient evaluation of the SE for different pilot lengths, without having to resort to lengthy network simulations.