Load Balancing Techniques Based on Antenna Tilt and Handover Timing Control

Due to the recent mobile traffic explosion, especially in hotspots where a lot of traffic is generated in a limited space, an imbalance in the traffic load among cells occurs. Such traffic load imbalance requires the deployment of many base stations (BSs) in the hotspots. This results in the inefficient operation of cellular systems. In order to overcome this problem, load balancing techniques have been studied. There are two main approaches. One is based on antenna tilt control (TiLt-control-based Load Balancing: TL-LB) and the other is based on handover (HO) timing control (HandOver-timing-control-based Load Balancing: HO-LB). These techniques have been studied separately; however, a detailed comparison of the two techniques has not been reported so far. This paper numerically compares TL-LB and HO-LB in terms of not only the amount of user equipment (UE) distribution to neighboring cells, but also the degradation of Signal to Interference plus Noise Power Ratio (SINR), HO performance, and the change in the number of UEs in each cell. Numerical results show that TL-LB is superior to HO-LB in terms of the amount of UE distribution, SINR, and HO performance. With TL-LB, about 65% of UEs in a cell are distributed to neighboring cells with little degradation of SINR and HO performance. In contrast, with HO-LB, no more than 43% of UEs can be distributed to neighboring cells at the expense of 5th percentile SINR degradation of 21 dB and significant degradation in HO performance. The results also show that TL-LB is inferior to HO-LB in terms of the change in the number of UEs in each cell. However, this disadvantage of TL-LB can be overcome by appropriate cooperation control with neighboring cells. It can be concluded that TL-LB with appropriate cooperation control is much more effective than HO-LB as a load balancing technique.