Speed Based Optimal Power Division in Small Cell Networks

Small cell networks promise to boost the capacity and provide good QoS (Quality of Service) to cell edge users. However they pose serious challenges, especially in the case of high speed unidirectional (e.g., users traveling on highways or in metros) users, in the form of frequent handovers. The extent of the handover losses depends greatly upon the speed of the user and we showed in our previous paper that optimal cell size increases with speed. Thus in scenarios with diverse users (speeds spanning over large ranges), it would be inefficient to serve all of them using common cell radius and it is practically infeasible to design different cell sizes for different speeds. We alternatively propose to allocate power to an user based on its speed. Higher power virtually increases the cell size. We provide an optimal power division, optimal for busy probability (which optimizes an appropriate QoS that considers handover losses), for any given power budget and cell size. We further establish the need for higher power budgets for larger cell sizes, which we called as beta+ power scaling (beta is path-loss factor). We finally obtain optimal cell size, after beta+ scaling and optimal power division.