Shifting the MIMO Paradigm

TLDR

Multi‑user MIMO networks enable joint optimization of antenna combining and resource allocation, providing robustness to multipath, compact antenna spacing, and diversity/multiplexing gains without multiple antennas at user terminals, yet achieving these gains requires base‑station knowledge of user channel coefficients, limiting practical use to TDD or low‑mobility scenarios. The authors aim to combine MU‑MIMO with opportunistic scheduling to reduce feedback load. They implement this by integrating MU‑MIMO with opportunistic scheduling, thereby decreasing the need for extensive channel state information at the base station. The scheduler’s success is strongly dependent on traffic patterns and quality‑of‑service requirements.

Abstract

Multi-user MIMO (MU-MIMO) networks reveal the unique opportunities arising from a joint optimization of antenna combining techniques with resource allocation protocols. Furthermore, it brings robustness with respect to multipath richness, allowing for compact antenna spacing at the BS and, crucially, yielding the diversity and multiplexing gains without the need for multiple antenna user terminals. To realize these gains, however, the BS should be informed with the user's channel coefficients, which may limit practical application to TDD or low-mobility settings. To circumvent this problem and reduce feedback load, combining MU-MIMO with opportunistic scheduling seems a promising direction. The success for this type of scheduler is strongly traffic and QoS-dependent, however.