UAV-Enabled Cellular User Offloading With SIC Based Interference Handling

In dynamic hotspot scenarios, unserved users from the hotspots of the overloaded gNBs can be offloaded to the neighbouring underloaded gNBs by using Unmanned Aerial Vehicles (UAVs) as relays. However, it may lead to co-channel interference as the same frequencies are used by every gNB. Therefore, unlicensed bands are leveraged for communication between the offloaded users and the UAVs in the state-of-the-art. It leads to contention with other users that use unlicensed bands and reduces the efficiency of spectral usage. To avoid the usage of unlicensed bands, we propose an offloading solution where Successive Interference Cancellation (SIC) is used to handle the co-channel interference. The proposed solution can be used for both cell-centred and cell-edge hotspot scenarios. New challenges arise when a multi-gNB and multi-hotspot scenario is considered, such as determining the load re-distribution strategy, determining the number and locations of the UAVs, detecting the hotspots across the coverage area of multiple gNBs, and determining the user offloading strategy that makes SIC feasible. Therefore, we formulate the problem for multi-gNB and multi-hotspot scenario to minimize the total cost of Service Level Agreement (SLA) violations, by jointly optimizing the load redistribution, number and locations of the UAVs, power levels of the gNBs and UAVs, bandwidth allocation and user offloading strategy. We also propose an efficient heuristic solution to the formulated problem and demonstrate its effectiveness through extensive numerical simulations. The numerical simulations show that the proposed solution achieves up to 55.39% fewer SLA violations and up to 37.91% less total SLA violation cost compared to the baseline.