Random beamforming OFDMA for future generation cellular communication systems

Abstract

This paper presents a downlink performance analysis of a Layered Random Beamforming (LRB) - MIMO-OFDMA Physical Layer (PHY) as applicable to future generation wireless communication systems. OFDMA is a popular multiple access candidate for future generation cellular communication systems which facilitates multi-user diversity by enabling multiple access in the frequency domain. Random Beamforming (RB) is a method which enables the exploitation of spatial multi-user diversity gain and a spatial multiplexing capacity gain. Unlike a conventional beamforming system, an RB system only requires effective signal to noise ratios (ESNR) as feedback and thus has potentially much lower feedback requirements than a system which requires feedback of more detailed channel information. The Layered method (LRB) enables the spatial multiplex of data transmitted simultaneously to different destinations. As a result it is able to offer a further spatial multi-user diversity gain, referred to here as layer multi-user diversity gain to distinguish from that achieved by the RB technique. An LRB-OFDMA system is thus able to achieve the rich benefits of spatial multiplexing capacity gain in combination with spatial, layer and spectral multi-user diversity gains. In this paper, the design of both RB-OFDMA and LRB-OFDMA systems are proposed and the performance of the system is evaluated by software simulation using various statistical channel models