Multi-beam multiplexing using multiuser diversity and random beams in wireless systems

In this paper, we propose a new multiple-access transmission scheme that can simultaneously achieve both diversity and multiplexing gain in the multi-user domain, by using multiple random beams. Multiple beams are generated so that the users encounter multiple channels at the same rime, enabling the use of multi-user diversity through each channel. Since the transmit power is spilt into multiple channels, the signal-to-noise power ratio (SNR) of each channel is reduced in proportion to the number of beams. However, multiple beams are generated so that the multiplexing gain is much larger than the decrease of SNR, increasing the overall system capacity. The proposed scheme works well in both Rician and Rayleigh fading channels regardless of the channel correlation, providing the maximum capacity in multiuser and multi-antenna systems in practice. The proposed scheme is applicable to both MIMO and MISO systems, enabling the use of receivers with flexible antenna structure.