Efficient Algorithms for Channel Assignment in a Cellular Network
During recent years, the world is experiencing almost an exponential growth in the demand for various mobile communication services. On the other hand, the available bandwidth for such communication is very much limited. As a result, efficient utilization of bandwidth for mobile communication has become more and more critical. When a mobile cellular network is designed, each cell of the network is assigned a set of channels to provide services to the individual calls of the cell. The task of assigning frequency channels to the cells satisfying some frequency separation constraints with a view to avoiding channel interference and using as small bandwidth as possible is known as the channel assignment problem. Three types of interference are generally taken into consideration in the form of constraints: i) co-channel constraint, due to which the same channel is not allowed to be assigned to certain pairs of cells simultaneously, ii) adjacent channel constraint, for which adjacent channels are not allowed to be assigned to certain pairs of cells simultaneously, and iii) co-site constraint, which implies that any pair of channels assigned to the same cell must be separated by a certain number. In its most general form, the channel assignment problem (CAP) is equivalent to the generalized graph-coloring problem which is a well-known NPcomplete problem.