Shakhar Smorodinsky

We prove that any collection of n discs in which each one intersects at most k others, can be colored with at most O(log³ k) colors so that for each point p in the union of all discs there is at least one disc in the collection containing p whose color differs from that of all other members of the collection that contain p. This is motivated by a problem on frequency assignment in cellular networks, and improves the best previously known upper bound of O(log n) when k is much smaller than n.