Channel assignment schemes and traffic capacities of mobile radio systems

In this paper, we examine the spectrum efficiency of various land mobile radio system approaches in terms of traffic capacity for a given number of channels. Spectrum Efficiency can also be described in terms of Communication Capacity of the system per unit bandwidth. To determine the number of users a system can support for a given grade of service, both aspects (traffic handling and communication) should be considered simultaneously. In the first part of this paper we examine the traffic capacity of cellular mobile radio systems with different channel assignment schemes. It is shown that cellular systems are superior to trunked systems with moderate frequency reuse but not without frequency reuse. However, with use of effective channel assignment schemes, cellular system's performance is close to that of trunked systems even without frequency reuse. Adaptive channel assignment schemes are examined. Adaptive shcemes are based on the fact that traffic intensity of the arrival process varies slowly with time. Therefore, channels can be assigned to take the maximum advantage of the random nature of the arrival process and the frequency reuse at a given time. Traffic capacity of the mobile radio system is examined which uses the same set of channels to service the different classes of users. One such example is the mobile radio system which provides voice-telephone and dispatch service on the same channels. Arrival process is assumed to be Poisson for both telephone and dispatch calls with different arrival rates. Service rates are also different for the telephone and dispatch calls. Blocked telephone calls are cleared from the system and blocked dispatch calls are delayed. Another example is a mobile radio system which services different classes of users with different service times and grades of service.