In this thesis, techniques are considered in order to avoid unnecessary handover in both static and mobile networks. Toward this goal, the work is divided into two major parts. In the first half, handover in static networks specifically WiMAX femtocells is looked. The second half covers handover in a special class of mobile ad hoc network named as a vehicular ad hoc network (VANET).
It is known that addition of femtocells provides services in shadowed areas of the WiMAX macrocell and enhances the cell coverage. This also relieves traffic from the macrocell network, reduces infrastructure cost for the network operator, increases the network capacity, and provides needed quality of service (QoS) in an indoor environment. However, it is rather difficult in to support network performance under
different mobility patterns and dynamic network conditions using conventional handover methods. Unnecessary handovers pose serious problems since they may cause reduction in the user’s QoS level and the effective system capacity. An appropriate call admission control is introduced and a resource management scheme is proposed that significantly reduces unnecessary handovers. Simulation results are shown to validate our performance predictions.
A vehicular ad-hoc network is a dynamic network that changes its topology frequently due to the mobility of vehicles. Providing safety information, traffic conditions, traffic monitoring, and route updates and therefore services available in nearby area become difficult, especially when the vehicle density is low. Vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communication can be used to achieve such goals as described above. However, V2I communication has comparatively a longer delay as compared to V2V communication, as V2I depends on uplink, downlink and intra-infrastructure rates. If a message is not delivered on time because of the longer delays, it may become useless especially safety and emergency message. Herein, a hybrid model is proposed that makes judiciously use of both V2V and V2I schemes; therefore it will increase the message efficiency and could reduce the data propagation delays. Handover technique for hybrid model has also been examined. ‘Highway’ model traffic is simulated for estimating propagation delay at different vehicle speeds and traffic densities. The simulation results show that when the traffic density is small, it is better for the vehicles to handover data to the infrastructure and when the traffic density is high, it is advised to send data using the V2V scheme.