Resource Allocation in Energy Efficient Hybrid FSO/mmW Fronthaul: A Differential Evolution Approach

In 5G access network, a hybrid free space optic (FSO)/millimeter-wave (mmW) system is a promising fronthaul solution for dense urban area. In the hybrid FSO/mmW system, mmW in-band self-fronthaul is more efficient because the spectrum of radio access and fronthaul are allocated in the same radio band. However, it incurs inefficient usage of spectrum and transmission power. The allocation of resource blocks and power for user access and fronthaul transmission should consider dynamic weather conditions to improve energy efficiency of system. In this paper, we consider the downlink of 5G fronthaul. An intelligent resource reuse and allocation algorithm based on the constrained differential evolution is proposed to maximize the energy efficiency. The spectrum of mmW is partitioned into two parts, one for resource blocks in radio access, the other for data transmission over fronthaul. Also, transmission power in access and fronthaul are jointly considered to improve the energy efficiency. Simulation results show a considerable benefit on energy efficiency for different weather conditions compared with traditional water-filling baseline algorithm.