Call Blocking versus Hando Blocking inCellular

In cellular networks, blocking occurs when a base station has no free channel to allocate to a mobile user. One distinguishes between two kinds of blocking, the rst is called new call blocking and refers to blocking of new calls, the second is called handoo blocking and refers to blocking of ongoing calls due to the mobility of the users. In this paper, we rst provide explicit analytic expressions for the two kinds of blocking probabilities in two asymptotic regimes, i.e., for very slow mobile users and for very fast mobile users, and show the fundamental diierences between these blocking probabilities. Next, an approximation is introduced in order to capture the system behavior for moderate mobility. The approximation is based on the idea of isolating a set of cells and having a simplifying assumption regarding the handoo traac into this set of cells, while keeping the exact behavior of the traac between cells in the set. It is shown that a group of 3 cells is enough to capture the diierence between the blocking probabilities of handoo call attempts and new call attempts. 1 { Introduction Future wireless networks will provide ubiquitous communication services to a large number of mobile users ((Sch94], Cox95], PGH95]). The design of such networks is based on a cellular architecture ((Lee89], Goo90], CiS88], Cal88], Ste89]) that allows eecient use of the limited available spectrum. The cellular architecture consists of a backbone network with xed base stations interconnected through a xed network (usually wired), and of mobile units that communicate with the base stations via wireless links. The geographic area within which mobile units can communicate with a particular base station is referred to a cell. Neighboring cells overlap with each other, thus ensuring continuity of communications when the users move from one cell to another. The mobile units communicate with each other, as well as with other networks, through the base stations and