15.1 Introduction

Multiaccess schemes are used to provide resources for establishing calls. Since spectrum is a scarce resource and can be directly related to capacity, efficiency enables the spectrum to handle a large number of calls. In order to make a call, either a physical channel served by a circuit switch or a virtual channel served by a packet switch is needed. A call can be defined as a voice call or a data transmission, a short-message call or a long-message call. Therefore, the evaluation of the capacity for each multiple-access scheme is very different. The calculation of capacity should be stated as, "The calculation of channels (or calls) in a cell served at the same time (simultaneously) by one multiple-access scheme."

For example, one paging channel can serve 80,000 tone-only pagers in one hour. But at any instant, only one pager can be served. We still consider the paging channel one channel per cell or per base station. Based on this definition, the spectrum used for physical or virtual channels makes no difference in finding radio capacity from different multiple-access schemes.