Study On The Channel Assignment Problem In GSM Mobile Communication System

With the rapid increase of the multimedia mobile communication business, people's attention has already been turned to it from the traditional voice communication. The requisition on high speed data communication is becoming much more urgent. How to use the limited frequency resource effectively is a subject which is badly in need to be solved. The channel assignment is the key problem in this subject which can directly affect the performance of the overall system and its capacity.To improve the efficiency of using frequency, a hybrid channel allocation scheme is used. In this scheme, the main flow of assign channel is: search the most suitable carrier frequency, then select the best time slot of this frequency.To reduce the time spent on channel assignment, the scheme doesn't search all these usable carrier frequencies to find the best assignment result. Instead, we design the organizing and searching order carefully, ensure the channel which fulfills the condition firstly is the best assignment result. Then we can return it directly. The core of this scheme is the organizing and searching order of carrier frequencies. Bidirectional queues are used to organize channels. We put carrier frequencies orderly by comparing their keys which are calculated through their priority, existing digital service and busyness degree of voice service; then we fetch them from the queue while in allocation.Call Quality Test method is used to evaluate this scheme. The result shows that this scheme expands capacity of the system, so the expectant goal is achieved.