Cooperative Frequency Reuse for the Downlink of Cellular Systems

We propose a space time coded cooperative diversity protocol that achieves improved quality of service for the mobile users in cellular systems. The protocol, called cooperative frequency reuse, exploits the cellular frequency reuse concept to create spatial diversity among neighboring base stations. After transmitting their individual signals in the channel reuse protected frequency subchannels in the first time frame, the base stations divide their transmit power between the relayed signals from the neighboring base stations and the signals intended for their own users. We discuss the performance of the proposed cooperation strategy by evaluating the fractional power allocations that lead to the best performance in terms of achievable sum rate and probability of outage. We use simulations to show that the proposed strategy, in the presence of full channel state information at the transmitter, yields considerable improvement over traditional direct transmission frequency reuse schemes.