Existing legacy 802.11 systems experience an unacceptable long
interruption of the link layer connection during handover. This
is due to the time spent in the required scanning phase.
Protocol mechanisms which are currently developed in the 802.11
standardization body provide means to exchange information regarding
the existance of neighboring accesspoints and their location. In
combination with the mobile users trajectory, this information can
be used to:
- reduce the time spent in scanning as this procedure may be limited
to those frequecies on which neighboring access points are well
known to operate on
- reduce the total number of hanodvers and thus the time spent
for handover as mobile termininals may select the access point
as a next communication parter which is known to be located along
the mobile's trajectory.
This project aims to quantifiy the performance improvement regarding
the scanning behavior which can be achieved using upcoming standardized
protocol mechanisms by means of simulation.
In order to fascilita the project's work, the 802.11 simulation
model in OPNET was enhanced within a previous project. In now includes
- Transmission of location information by the access point in
the advertised beacons or pilot frames.
- Alternative algorithms to decide to which access point a mobile
should connect during a handover, i.e.
- first access point found during the scanning process
- access point with the strongest RSSI (radio-signal-srength-indicator)
- access point which is the closes to the estimated mobile's