An Efficient Location Area Design Scheme to Minimize Registration Signalling Traffic in Wireless Systems
One of the main problems in mobile computing is the tracking of the current location of the users (mobiles). When a connection needs to be established for a particular user, the network has to determine the user’s exact location within the cell granularity. Location management involves two operations: The operation of informing the network about the current location of the mobile user is known as location registration, and the operation of determining the location of the mobile user is called terminal paging.
Mobility tracking expends the limited resources of the wireless network. Beside the bandwidth used for registration and terminal paging, power is also consumed from portable devices. Frequent signalling may also result in degradation of Quality of Service, due to interferences. Therefore, the goal of location management is to minimize the signalling traffic.
Current networks use location area (LA)-based management techniques. The coverage area is partitioned into a number of LAs, each containing a group of cells. While a mobile is moving from one LA to another, it reports its new LA by a registration process. An LA may static or dynamic. A static LA consists of a group of cells that are permanently assigned to that LA, and is fixed for all mobiles. On the other hand, dynamic LAs are created for each mobile during a registration process based on mobility and call patterns of the user. Although signalling traffic can be reduced by using dynamic LAs they impose higher computation and separate data storage of LAs for each mobile. As a result, most of the current cellular systems use static LAs.
Two main factors affecting the signalling traffic are the number of cells in an LA and the cell-partitioning technique. When the number of cells in an LA is high, the registration traffic decreases, but the paging traffic increases. On the other hand, for smaller LAs, the registration traffic increases, but the paging traffic decreases. The cell-partitioning technique is also very important. If the LAs are designed such that the inter-LA mobile traffic is reduced, the registration traffic decreases for the same LA size.
In this study, we propose a new static location area design scheme named ETB-LAD (Enhanced TB-LAD), which is an enhancement on previously published Traffic-based location area design (TB-LAD) technique. In TB-LAD technique, the intercell traffic prediction and traffic-based cell grouping schemes are used consecutively to partition the cells into LAs. The neighbour cells with higher intercell traffic are assigned to the same LAs, to decrease the inter-LA movements of mobiles. But in this technique the proper number of cells in a LA is not determined.
Our ETB-LAD scheme differs significantly from the TB-LAD scheme by explicitly taking into account the number of cells in an LA. The intercell traffic predictions are used by the traffic-based cell grouping scheme to group cells into LAs and also to determine the proper number of cells in an LA. The LAs, in which the neighbour cells have higher intercell traffic, may include more cells than the LAs, where the intercell traffic is low. We try to increment the intra-LA movements of mobiles in order to decrement the inter-LA movements, which create registration traffic.