Link adaptation with distributed Jacobi eigenbeamforming for MIMO systems

Abstract

This work presents a transmission strategy for closed-loop MIMO systems, where compact feedback messages meant for transmit weight adaptation are also used to convey basic link adaptation requests that can improve the link reliability or the data throughput without additional feedback overhead. The proposed link adaptation varies the number of orthogonal transmit beams and the symbol modulation employed on each beam. The simulation study focuses in a system with four transmit and two receive antennas, with constant data rate and two different underlying beamforming schemes: a recently proposed Jacobi beamformer, and a Grassmanian codebook approach. It is shown that both schemes can obtain an improvement of around 1 dB in bit error probability (BEP) performance, in slowly fading and spatially uncorrelated channels, compared to the case where both beams are used all the time. The application of the proposed technique to other precoding algorithms is briefly discussed.