Two Frequency Reuse Schemes in OFDMA-TDD Based Two-hop Relay Networks

Frequency reuse scheme is extremely important in multi-hop relay networks (MRNs), because some extra frequency resource should be elaborately allocated to Relay Stations (RSs). However the time and spatial reuse characteristics of RS should be taken into account in order to mitigate the co-channel interference. This paper presents two adaptive frequency reuse schemes for MRN by using different reuse patterns in different time zones of the same frame. In our schemes, reuse pattern of 1x3x1 is applied in the Relay Zone (RZ), and 1x3x3 is applied in the Access Zone (AZ). The former allows only the two RSs which are located farthest apart in one cell to share the same frequency portion; while in the latter two adjacent RSs may share the same resources. Analysis and simulation results show that both schemes improve the system throughput greatly. The comparison of coverage and throughput between the two schemes indicates that the latter scheme has better performance and an aggressive full reuse scheme could be utilized to all RSs.