To satisfy the high data demands in future cellular networks, an ultra-densification approach is introduced to shrink the coverage of base station (BS) and improve the frequency reuse. In an ultra-densification approach, small cells such as relay node (RN), micro, pico and femto base stations (BSs) are deployed to the network of macro cells in the same geographic region, forming HetNet. HetNets introduce some notable challenges like inter-cell-interference-coordination (ICIC), mobility management and backhaul provisioning. In this paper, we investigate the performance of the hard handover (HHO) in 5G HetNets. The performance metrics are the total number of handovers and the outage probability. Simulation results show that the average outage probability is decreased in HetNet scenario compared the macro only scenario. However, this improvement comes at the expense of increase number of handovers.

Heterogeneous network (HetNet) is an attractive solution for future cellular networks with high data rate and coverage requirements. In HetNets, small cells such as micro cells, pico cells, femto cells and relay node (RN) are added to the network of macro cells in the same region. A large number of low power RNs produces new cell edges with significant intra-cell and inter-cell interferences. In the uplink (UL) scenarios of timedivision based HetNets with RN, the user equipment (UE) desired signal may be interfered by the transmissions of the co-channel UEs during the first time slot and by the transmissions of the cochannel UEs or RNs during the second time slot. The interference caused by the RNs may significantly degrade the UE signal. UL transmission power control (PC) is essential for mitigating interference and, as a result, enhancing the cell edge and overall system performance. This research proposes a PC algorithm in order to mitigate the UL interference in 5g relay-based HetNets. This research also investigates the UL performance of HetNets when PC is applied at the RNs. Simulation results indicate that UL PC at the RNs greatly reduces average interference and improves average UL signal-to-interference-plus-noise ratio (SINR) and average UL end-to-end throughput compared to the situation in which UL PC is not implemented.