The design of handoff algorithms depends to a large extent on the user mobility
ID: 3853147 • Letter: T
Question
The design of handoff algorithms depends to a large extent on the user mobility pattern defined by the speed and direction of movement. For a fast moving MT, the speed is the dominant parameter in determining the cell boundary crossing. (a) Explain why, with fast moving mobiles, speed is more dominant in characterizing the use mobility pattern than direction? (b) Consider the situation in which, when the MS initiates and establishes a connection, its current location is 10 km from the cell boundary along the direction it is currently traveling. Also, the mobile is moving at a speed uniformly distributed between 40 km/hr and 60 km/hr. Calculate the mean time for the mobile to reach the cell boundary. (c) In an MAHO scheme, the mobile sends profiles containing the signal strengths received from all neighboring BSs in the same MSC. If a profile is sent every three minutes on average, what is the mean number of profiles sent before the mobile crosses the boundary?Explanation / Answer
When a mobile user travels from one area of coverage or cell to another cell within a call's duration the call should be transferred to the new cell's base station. Otherwise, the call will de dropped because the link with the current base station becomes too weak as the mobile recedes. Indeed, this ability for transference is a design matter in mobile cellular system design and is called HANDOFF.
(a). The user mobility definition defines the number of MSs APs as well how MSs move, including when and where a MS moves to and how long it stays at a waypoint. The simulation state defines the current time and the location s of all the MSs in the simulated network area. The Path Generator uses these two definitions together with the current state of the simulator to randomly select points. The path finder module then uses the path finder algorithim to generate the shortest path between the source and destination waypoints. The resulting path consist of multiple segments which are then fed to the mobility and simulator. Therefore with fast moving mobiles speed is more dominant than the direction .
(b). Distance = speed x time
so time = distance / speed
distance = 10 km
speed = (40 + 60)/2 =50 km/h
now put all the values to the fformula
time = 10 / 50 = .2 hrs = 12 mins ( convert hr into minutes by multiplying .2 with 60)
thereore mobile will take 12 mins to reach the cell boundary.