Opportunistic Scheduling and Beamforming for MIMO-OFDMA Downlink Systems with Reduced Feedback

TL;DR

This paper introduces a novel joint beamforming and scheduling scheme for MIMO-OFDMA downlink systems that significantly reduces feedback requirements by utilizing a channel decomposition technique, enabling efficient beamforming across all subcarriers with minimal feedback.

Contribution

The paper proposes a new joint beamforming scheme that reduces feedback by using a single beamforming matrix for all subcarriers and introduces subcarrier grouping for further feedback reduction.

Findings

Significant feedback reduction achieved compared to conventional schemes.

Effective beamforming with only one matrix for all subcarriers.

Theoretical analysis and simulations confirm scheme effectiveness.

Abstract

Opportunistic scheduling and beamforming schemes with reduced feedback are proposed for MIMO-OFDMA downlink systems. Unlike the conventional beamforming schemes in which beamforming is implemented solely by the base station (BS) in a per-subcarrier fashion, the proposed schemes take advantages of a novel channel decomposition technique to perform beamforming jointly by the BS and the mobile terminal (MT). The resulting beamforming schemes allow the BS to employ only {\em one} beamforming matrix (BFM) to form beams for {\em all} subcarriers while each MT completes the beamforming task for each subcarrier locally. Consequently, for a MIMO-OFDMA system with $Q$ subcarriers, the proposed opportunistic scheduling and beamforming schemes require only one BFM index and $Q$ supportable throughputs to be returned from each MT to the BS, in contrast to $Q$ BFM indices and $Q$ supportable throughputs required by the conventional schemes. The advantage of the proposed schemes becomes more evident when a further feedback reduction is achieved by grouping adjacent subcarriers into exclusive clusters and returning only cluster information from each MT. Theoretical analysis and computer simulation confirm the effectiveness of the proposed reduced-feedback schemes.