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.