Relay-assisted downlink transmissions to support increased data rates for single antenna users

In this paper, we exploit cooperation between mobile stations and transmissions scheduling in a wireless network to enhance the downlink data rates to multiple single antenna users. The objective is to increase the number of multiplexed signals within a channel use close to what is offered in interference alignment approaches without incurring the corresponding system complexity. Specifically, we divide the communication process into two stages. In the first stage, the transmitter with multiple antennas using time division multiplexing sends to different users in their allocated time slots a number of messages equal to the number of transmit antennas in a MISO frame. In the next stage, every user and its assigned relays form an independent network, and relays using an amplify-and-forward scheme aid the recovery of messages by the user solving linear system of equations. All of these subnetworks utilize the available channel concurrently producing an acceptable level of multiple access interference (MAI) where the MAI is controlled using a clustering technique tailored to location of users and potential relays. Simulation results are provided demonstrating the capacity improvements in the proposed scheme and showing good performance in a low SNR region of operation.