1. A method of providing Dynamic Channel Assignment (DCA) for at least a part of an overlay macrocellular system to facilitate the coexistence of at least one autonomous underlay microcellular system, comprising the steps of excluding a predetermined number of channels from one or more macrocells of the overlay system which overlap one or more cells of the underlay system, where E.sub.i is the set of channels to be excluded from a macrocell i of the overlay system, allocating the excluded predetermined number of channels for use by the underlay system or allowing those channels to be scanned and seized by an independent underlay system, and wherein the predetermined number of channels to be excluded from the one or more macrocells of the overlay system is selected so as to deterministically meet only one of a group of requirements including (1) satisfying both equations 1 (EQ 1) and 2 (EQ 2), and (2) violating EQ 1 and satisfying EQ 2; where ##EQU22## where N.sub.min is the minimum number of channels available for the underlay system, where P is the set of cells that causes interference to the underlay system, and ##EQU23## where .PHI. is the null set and where .OMEGA. is a set of macrocells belonging to a universal cluster, the universal cluster being the minimal set of clustered macrocells with no common exclusion channels.