I. Introduction
In cellular mobile communications, since the given frequency spectrum is limited, how to effectively make use of the spectrum to achieve optimum system capacity at some minimum quality of service, is of paramount importance. The conventional way of allocating channels is called fixed channel assignment (FCA) [1]. In FCA, a set of nominal channels is assigned to each cell on a semi-permanent basis. FCA is a very simple radio resource management strategy, however, it is not able to adapt to the uneven and time-varying traffic nature. Dynamic channel assignment (DCA) is a good approach to overcome such disadvantage. In DCA, all channels are potentially available in all cells, i.e., any channel can be used by any cell as long as the co-channel interference remains acceptable [2]. Clique packing [3] is considered as a model of an idealized DCA method that can provide the lower bound of blocking probability for any practical DCA.