Hot-spot traffic relief in cellular systems

The authors show by analysis of mathematical models that combining channel borrowing with a coordinated sectoring or overlaying 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 blocking requirements of 1% channel borrowing with cell sectoring can increase the traffic load in the hot-spot cell from 47 Erlangs to 63 Erlangs, whereas 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 the cell overlaying arrangement. Under the technical assumptions, probability of an additional handoff for the sectorized arrangements is found to be about half of that for the cell overlaying arrangement