Random Access in Overlapping Cells

摘要

In this paper we consider cellularnetworks in which the cells may overlapsubstantially. Such network architectures, whichare motivated by the need to increase the utilizationof the available bandwidth by reducing theseparation among cells that share the same channel,present new unexplored and fundamental problems.We begin by considering two cells whose assigneduser populations overlap spatially, and use acommon channel. Consequently, transmissionsintended for one base station can cause interferenceat the other.The interaction between such cells is bestexemplified if the protocol of access in each cell ispure random access. For Slotted Aloha, we presenta simple mathematical analysis that predictsaccurately the maximum achievable throughput.We demonstrate that an invariance (or "self- selfstabilization")stabilization") property exists that allows themaximum throughput to occur when the expectedtotal channel traffic in each cell is equal to onepacket per slot, independent of the degree of overlapof the cells. We then consider larger multi-cellnetworks and observe the same invariance propertyin our simulations. Consequently, in planar cellularnetworks there are no end effects, and coupling islimited only to adjacent overlapping cells. Thus it ispossible to evaluate random access throughput byconsidering only the local neighborhood of a cell.