Reconfiguration of carrier assignment in cellular networks

We consider the problem of updating nominal carrier assignments in cellular networks, which dymamically operate with channel borrowing and reassignmen ts, to match the time-varying offered traffic demands encountered on these systems. Assuming an existing assignment of nominal carriers and the new re quirements in each cell, we formulate the problem of obtaining a new assign ment such that the number of carriers required to meet the total traffic de mand as well as the number of different assignments between the old and the new allocation are minimized. We introduce two approaches to obtain this n ew assignment. One approach treats the two objectives independently and is applicable to problems with cochannel interference constraints only. This a pproach produces a new assignment optimized with respect to the first goal, and then rearranges the frequencies of this new allocation so that the num ber of different assignments with respect to the previous allocation is min imum. A second approach aims at satisfying both goals at the same time and is applicable to problems with any type of interference constraints. The ma in advantage of this approach is the introduction of a single window parame ter which can control the assignments produced, by favoring one goal at the expense of the other. We study several transition scenarios in macrocellul ar and microcellular environments, and show that in the majority of cases t hese objectives are conflicting, and that reconfiguration strongly depends on the amount of change of the traffic requirements.