Opportunistic beamforming using dumb antennas

TLDR

Diversity techniques mitigate fading by creating multiple independent signal paths across time, frequency, or space. The authors propose a scheme that induces random fading in low‑scattering or slow‑fading environments. In the downlink, multiple base‑station antennas transmit identical signals with time‑varying pseudo‑random amplitude and phase gains.

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.