A transmit preprocessing technique in fixed relay networks for practical multiuser transmission

Using multiple antennas at both ends of a wireless link, known as multiple-input multiple-output (MIMO) wireless, has been shown to offer significant improvements in link reliability and spectral efficiency through space-time coding and spatial multiplexing respectively. Our main objective in this contribution is to propose a novel relaying strategy that uses multiple input multiple output (MIMO) fixed relays with linear processing to support multiuser transmission in cellular networks. We apply a transmit preprocessing technique at the transmitter in order to eliminate the multiple-user interference. The fixed relays process the received signal with linear operations and forward it to multiple users. The effective channel from transmitter to the users can be modeled as a broadcast channel. This paper optimizes the relay amplification matrix and transmitted power according to achievable sum rate at the users, neglecting the direct links from the base station to the users and with certain structure of relays. The results show that the sum rate achieved by the our proposed system architecture are close to the sum rate achieved by the decode-and-forward relaying though decoding at the relay is not required.