HOT-SPOT TRAFFIC RELIEF IN CELLULAR-SYSTEMS

During the operation of a cellular system, unexpected growth of traffic may develop in various cells and create local traffic congestions. Channel borrowing, at least in a ''semi-dynamic'' way, is known to be a viable solution to alleviate congestions. In this paper, we show by analysis of mathematical models that combining channel borrowing with a coordinated sectoring or overlying scheme provides effective ways to handle hot-spots in the system. Blocking probabilities with these arrangements are derived, and the Dynamic Sharing with Bias (DSB) rule is suggested for increasing the trunking efficiency. A simple handoff model is formulated and analyzed for comparing the probabilities of additional handoffs due to sectoring and overlaying of cells. With the nominal allocation of 60 channels per cell and a donor cell having a load of 30 Erlangs, numerical results show that at a blocking requirement of 1 percent, the traffic load in the hot-spot cell can be increased from 47 to 63 Erlangs with the use of the channel borrowing with the cell sectoring scheme; while with the use of the DSB rule, the load can be increased further to 71 Erlangs. A slightly higher load can be carried in the hot-spot cell with the use of cell overlaying arrangement.