Opportunistic beamforming using dumb antennas

Abstract

An important means to cope with fading in wireless channels is the use of diversity. Diversity can be obtained over time (interleaving of coded bits), frequency (combining of multipaths in CDMA systems) and space (multiple antennas). The basic idea is to improve performance by creating several independent signal paths between the transmitter and the receiver. In this paper, we propose a scheme that induces random fading when the environment has little scattering and/or the fading is slow. We focus on the downlink of a cellular system. We use multiple antennas at the base-station to transmit the same signal from each antenna modulated by a gain whose phase and magnitude is changing in time in a controlled but pseudo random fashion.