Zone based downlink frequency planning scheme in relay enhanced cellular systems

A novel zone based downlink frequency planning scheme in relay enhanced cellular systems is proposed in this paper. There are two basic frequency planning methods for relay nodes in one cell: spectrum sharing which can avoid intra-cell interference between relay nodes to improve channel quality; spectrum reusing which can increase amount of available channels for each relay node. Neither of these two methods can achieve the best spectral efficiency by oneself. In the zone based downlink frequency planning scheme, the multiple relay nodes within one cell are partitioned into several zones according to the transmission data rate demand of each relay node and the intracell interference information between relay nodes. Frequency resource is shared between relay nodes in the same zone and reused between different zones. Heuristic algorithm is proposed to solve the problem of zone partition optimization. Simulation results show that the proposed frequency planning method can improve relay users´ signal to interference plus noise ratio (SINR) efficiently and obtain superior spectral efficiency compared to traditional methods.