Study On Location Management In Personal Communication System

In Personal Communication System (PCS), one important thing of user's location management is to reduce the cost associated with location updating and searching. In current wireless system, such as GSM or IS-41, the location information of mobile terminal (MT) is stocked in two registers (the home location register HLR and the visiting location register VLR). For the sake of easily looking for the users when call arrives, the whole network is divided into many location areas (LA). So-called location area is the area in which MT moves around but don't need update location information in database. When MT crosses the boundary of a LA, the location information needs to be updated. A LA usually includes several cells. And its shape and size is generally fixed for all MTs, and determined by the system. Because in the future wireless communication system, a great quantity of users may move arbitrarily in a very big area (up to the whole world) and request to proceed the communication at any time. Therefore in order to quickly and accurately find the user when call arrives, it's very important how to configure the location registers (concentrated or distributed), how to divide the user location area. Obviously, too frequently location information delivering, registering, updating and querying, and too much paging service will produce great signal loading, enlarge the network system handling time, and lower the communication capacity of the network system. So how to program and optimize LA receives more and more recognition.In current wireless system, for example the GSM, the location management uses the fixed LA. So LA is same for each user. The weakness of this kind of strategy is that the size of LA is fixed determined by the total mobility and the call arrival rate, and isn't the best to each user. And that strategy can't adapt to the continuous changing of the mobility and call arrival rate.In reality, the bigger LA is, the less frequency of location updating is, and the less cost of updating is, but the bigger area for paging is. So the cost of paging increases. On the contrary, the smaller LA is, the more cost of updating is, and the less cost of paging is. Therefore, the size of LA should be configured reasonable. Because the mobility and call arrival rate of each user is not similar, and changes...