Relay-enhanced Cellular Performance of OFDMA-TDD System for Mobile Wireless Broadband Services

Multi-hop relay (MR) and repeater are useful means of improving system throughput and coverage in the cellular mobile packet access system, as carrier-to-interference ratio can be improved with deploying them in the heavily shadowed region. In this paper, we investigate the bandwidth efficiency and the associated service outage performance for the different relay scenarios, using the system level simulation for a cellular OFDMA-TDD system. It is demonstrated that a capacity gain by an optical repeater which has a simple amplify-and-forwarding capability only could be minimal due to co-channel interference from all repeaters in the neighbor cells, even though they are usually useful for warranting the outage performance with a multiple order of combining gain, especially in the destructive area, e.g., edge of sub-cell coverage. Meanwhile, multi-hop relays are shown to increase the average system capacity (almost doubling the system throughput) by fully reusing the frequency in every relay station, while improving the per-user data rate in the cell edges or heavily shadowed areas.