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In this paper, we investigate the channel assignment problem, that is, the problem of assigning channels (codes) to the cells of a cellular radio network so as to avoid interference and minimize the number of channels used. The problem is formulated as a generalization of the graph coloring problem. We consider the saturation degree heuristic, first proposed as a technique for solving the graph coloring problem, which was already successfully used for code assignment in packet radio networks. We give a new, version of this heuristic technique for cellular radio networks, called randomized saturation degree (RSD), based on node ordering and randomization. Furthermore, we improve the solution given by RSD by means of a local search technique. Experimental results show the effectiveness of the heuristic both in terms of solution quality and computing times. Index Terms--Cellular network, channel assignment problem (CAP), graph coloring, heuristic, local search.