Study On Channel Assignment Strategy For Cellular Mobile Telecommunication System

The tremendous growth of mobile users'population coupled with the increasing requirements of voice and data service from subscribers, which result to the limited radio spectrum become more and more scarce. How to improve the utilization of radio spectrum, as an important factor, has restricted the development of mobile communications. It can be resolved by making good use of channel assignment techniques. Since 1970s, channel assignment for cellular mobile telecommunication system has been a hot and difficult. Now still many issues are worth studying.In several classic channel assignment strategies, although fixed channel assignment (FCA) is easy and simple, it can not deal with hot issues. Dynamic channel assignment (DCA) and hybrid channel assignment (HCA) can trick the changes of traffic, but without using other optimization measures, the system has lower call blocking rate only when the traffic is fewer. Besides, it has higher complexity of its implementation. Therefore, some new channel assignment strategies were presented. Such as Channel Borrowing Strategy (CBS), Guard Channel Strategy (GCS), Queue Strategy (QS) and so on. Based on moveable boundary framework, this paper presents two new channel assignment strategies, a channel assignment strategy combining guard channel and queuing, and a guard channel strategy with preemptive priority in cellular system.In the first strategy, the strategy provided guard channel for data call to reduce blocking probability of data call. Meanwhile, voice call queuing strategy was adopted to restrain voice call blockage deterioration caused by guard channel strategy. To further improve the system performance, impatient customers were introduced. And a queue system with impatient customers was given.In the second strategy, guard channels are provided for new voice calls and handoff voice calls to reduce the blocking probability. To further improve the voice traffic of the system, voice calls carry preemptive priority and can preempt data channels. Meanwhile, new voice guard channels can be occupied by handoff voice calls. Buffers are provided for data calls to reduce the data blocking probability.Then, Markov chain analysis models are established using the knowledge on stochastic processes and queuing theory, the performance of the system is inspected by the theory analysis and simulated by the MATLAB software. Theoretical analysis and simulation result show that the proposed strategies can lower blocking probabilities and improve system performance.