Enhanced opportunistic beamforming

Abstract

Opportunistic beamforming was recently proposed to exploit multiuser diversity in cellular wireless communication systems. The basic idea is to use multiple 'dumb' transmit antennas at the base station to deliberately induce channel fluctuations that mimic those due to multi-path and Doppler. These fluctuations can be exploited by a smart scheduler to improve system throughput. Practical considerations can limit the rate of the induced channel fluctuations, therefore resulting in performance penalty for delay sensitive traffic such as voice. In this paper, we propose an enhancement of this technique that uses opportunistic beamforming on multiple 'pipes' to overcome this shortcoming and yield additional performance improvement by combining selection diversity and multiuser diversity. The simplicity of this technique and the resulting performance benefits point to the potential value in thinking of cellular wireless systems from an asynchronous packet-data perspective rather than adopting the conventional circuit approach.