Is handoff traffic really Poissonian?

A one-moment model for grade of service evaluation in cellular mobile networks is developed. Traffic flows are modelled as a function of fresh traffic and users' movement. A model of a single flow is proposed at first, then it is generalized for the whole network. An iterative relaxation algorithm following the Erlang fixed-point approximation is used to produce numerical results. From the usual assumptions such as Poissonian fresh call arrivals and exponential call holding times it is proven that handoff traffic is Poissonian only in a nonblocking environment. Since this assumption is common in the literature with reference to a blocking environment, we examine its validity under such circumstances. Network grade of service is evaluated by using the Erlang fixed-point approximation as if handoff traffic were Poissonian although it is smooth due to blocking. The performance of the presented model is given in comparison to the solution of the exact Markov chain formulation for an isolated traffic stream or the results of simulations run to evaluate blocking of the whole network. A perfect agreement between exact and approximate analytical results is shown.