A spectrum allocation scheme for adjacent channel interference mitigation in relay backhaul link in coexisting FDD and TDD systems

In wireless communications, when multiple radio access networks operate in adjacent frequency bands, there is the potential for adjacent channel interference (ACI). In this paper, we investigate the ACI problem in coexisting frequency division duplex and time division duplex systems. Inserting a guard band (GB) is a straightforward way to avoid the performance degradation due to ACI; however, this method sacrifices spectrum efficiency. To overcome this shortcoming, we propose a novel frequency spectrum allocation scheme to mitigate the ACI. The proposed scheme effectively avoids the ACI from base stations to relay nodes. We verify the effectiveness in a 3G Long Term Evolution-Advanced network coexistence scenario for the 2.6-GHz band. Numerical results show that the proposed scheme significantly improves the performance by avoiding the interference even compared to the GB scheme, and greatly improves the efficiency in the spectrum resource utilization.