Mixed media cellular systems

A voiceldata cellular system is studied in this work. Analytical methods are used based on generating functions techniques. An extended simulation analysis it was also carried out, defining the main performance parameters and their impact on system behaviour. The limits or analytical study are investigated and solutions through simulation methods are proposed. 1. INTRQDUCTION UTURE communication networks are expected to handle a variety of data traffic types, including digital voice, facsimile, video, file transfer and interactive information services. These services will be offered not only by stationary terininals but also by land mobile terminals which will be totally integrated into tlie public cominunications networks. Cellular mobile networks have been studied extensively last years. Frequency assignmelit techniques, cliaimel access models, transmission quality, standards for interfacing with the wired network as well as traffic management are some of the topics gained attention. Especially, referring to the last topic, a mathematical model has been developed [1]-[3] adequate Tor lrafFic analysis of mobile coniniunications systems. The important parameters of voice coiiimunication systems, i.e. blocking probability of new calls, handoff requirement probability, forced termination probability e.t.c, have been stated as functions of the system state probabilities. The cases of vehicular as well as portablc terminals havc becn covered. But as far as we know there is no analysis for mixed media cellular systems -voice, data, videowhich will be widely used in the near future. In this work, we extend the mathematical model of [l] for the purpose of studying a voice-data cellular system. In the second section the mathematical model is presented and the main performance parameters are evaluated. Simulation analysis is carried out and results are presented in the third section. Conclusion and suggestions for fbrther analysis are finally staled. 11. M~THEMATICAI, MODEL A. SYSTEM DESCFXPTION Without loss of generality we concentrate on the study of a highway cellular system, Fig. 1, where the base stations are installed at the center of rectangular cells of length L. Paper approved by tlie Editor for Random Access and Distributed Communications Systems of the IEEE Cotnmutiications Society. Manuscript received April 4, 1992; revised June 15, 1992. F-N. Pavlidou is with the Dept. of Electrical Engineering, Aristotle University of Tliessaloniki, Greece. This paper was presented in part at the 2 lth IEEE C o n m Theoiy Workshop, Rhodes, Greece, June, 199 1. IEEE Log Number 9400975. 0090-6778/94$04 Frequencies in successive cells are different to each other so we do not deal with interference effects. We assume IWO streams -voice calls and data packetsof Poisson arrivals originated at each cell with rates Anv and A, and average service durations and 14% The two processes being independent, a cumulative service time can be defined by the wellknown hyperexponential formula = i / p = U p v + U p p . At each cell we have also arrivals of handoff calls and packets, assumed Poisson with rates A , and A P ~ . The system rule is described in Fig.2, where in each ,cell there are C-Ch channels available for new calls and packets, C channels available for handoff calls and packets and an infinite queue. If there is no free channel after a handoff requirement a call is forced into termination while a packet i s placed in the queue in FIFO order. New packets that do not succeed to get a channel in the cell of their arrival are blocked and cleared from the system. Once they have got a channel they remain in the system, possibly transferred from one queue to another, till they finish their service.