Femto-to-Femto (F2F) communication: The next evolution step in 5G wireless backhauling

The future 5G cellular networks are expected to support several-fold increase in data traffic and number of devices, and provide a very low latency and gigabit-rate data services. millimeter Wave (mmWave) communication (30–300 GHz) is proposed to be an important part of the 5G cellular networks to fulfill these requirements. With most of the high data rate demands originating from indoor User Equipments (UEs), conventional wired backhaul links prove to be a major bottleneck. Hence, mmWave wireless backhaul links are explored at Femto Base Stations (FBSs). In order to derive maximum benefit of mmWave backhaul links, efficient resource (data slots) utilization is necessary. Proper scheduling of mmWave backhaul links will help to achieve the same. In this paper, we propose a novel FBS-to-FBS (F2F) communication scheme which not only helps in offloading the data traffic from the Micro Base Station (MiBS) but also can act as a relay link for the other FBSs for routing the backhaul traffic to the MiBS. We also propose a solution to concurrently schedule mmWave wireless backhaul links to increase the resource utilization considering the coexistence of both FBS-to-MiBS (F2M) and F2F links. Our proposed solution consists of two parts — first, it determines which backhaul links can be scheduled concurrently by finding the upper bound for the interfering distance based on the alignment of different lobes of the directional antennas. Second, the transmit power is throttled to match the Quality of Service (QoS) requirements of each link aiming to further control the interference and to increase the number of concurrent transmissions. The benefits of the proposed solution are studied and compared with the Time Division Multiple Access (TDMA) and random scheduling schemes using extensive simulations.