This paper investigates an attempt to improve reliability in two-way communication through the bi-directional use of spatial resources when time selectivity exists and instantaneous channel information is not available at the transmitter. The system, which uses spatial resources bi-directionally and employs beamforming, is called a ‘bi-directional beamforming (BBF)’ system. The use of full bandwidth and the reciprocity between time and frequency allow the BBF system to reduce the symbol duration. Focusing on this reduction in symbol duration, we propose a transmit antenna-switched receive diversity for BBF (TAS-BBF) scheme designed to improve reliability in time selective environments. The resulting TAS-BBF scheme with N antennas can achieve diversity order of 2(N−1) in fast fading environments without channel state information at the transmitter, whereas conventional schemes are only able to achieve a diversity order of N in this environment.
['Dongkyu Kim', 'Hyungsik Ju', 'Seokjung Kim', 'Haesoon Lee', 'Daesik Hong']
Transmit antenna-switched receive diversity for bi-directional beamforming in two-way communications