In the frequency assignment problem we are given a graph representing a wireless network and a sequence of requests, where each request is associated with a vertex. Each request has two more attributes: its arrival and departure times, and it is considered active from the time of arrival to the time of departure.
We want to assign frequencies to all requests so that at any time no two active requests associated with the same or adjacent nodes use the same frequency. The objective is to minimize the number of frequencies used.