Beam Division Multiple Access Transmission for Massive MIMO Communications

TLDR

We study multicarrier multiuser MIMO systems with a base station that has an asymptotically large number of antennas. The authors propose a beam division multiple access (BDMA) scheme that serves multiple users via distinct beams. They model a fully correlated channel in the beam domain, derive a closed‑form upper bound on ergodic sum‑rate, establish statistical‑CSIT optimality conditions, and design optimal Zadoff‑Chu pilots for BDMA. The BDMA approach decomposes MU‑MIMO into single‑user channels, reducing channel‑estimation overhead and transceiver complexity, and simulations confirm near‑optimal performance and pilot‑sequence benefits.

Abstract

We study multicarrier multiuser multiple-input multiple-output (MU-MIMO) systems, in which the base station employs an asymptotically large number of antennas. We analyze a fully correlated channel matrix and provide a beam domain channel model, where the channel gains are independent of sub-carriers. For this model, we first derive a closed-form upper bound on the achievable ergodic sum-rate, based on which, we develop asymptotically necessary and sufficient conditions for optimal downlink transmission that require only statistical channel state information at the transmitter. Furthermore, we propose a beam division multiple access (BDMA) transmission scheme that simultaneously serves multiple users via different beams. By selecting users within non-overlapping beams, the MU-MIMO channels can be equivalently decomposed into multiple single-user MIMO channels; this scheme significantly reduces the overhead of channel estimation, as well as, the processing complexity at transceivers. For BDMA transmission, we work out an optimal pilot design criterion to minimize the mean square error (MSE) and provide optimal pilot sequences by utilizing the Zadoff-Chu sequences. Simulations demonstrate the near-optimal performance of BDMA transmission and the advantages of the proposed pilot sequences.