Performance Evaluation of Heterogeneous Wireless Networks with Location Distribution and Migration of User Equipments

In this paper, we present a performance evaluation scenario of heterogeneous wireless networks based on overlays of new/existing radio access technologies. The aim is to study the effects of deploying the new network (e.g. 4G or 3G) co sited with the existing network (e.g. 2G), while old equipments with their compatibility to only the existing but not the new networks are gradually replaced by those user equipments (UEs) that work with both the existing and new networks. Our system model allows the data traffic offered from new UEs to choose the new network first and overflow to the existing network if the link in the new network is saturated. Analytical and simulation results, surprisingly, show that the decreased (increased) percentage of existing (new) UEs, while the capacity of new and existing networks as well as the total number of UEs are still unchanged, may lead to degraded quality of service (QoS) on both the new and existing networks if insufficient traffic management is given during the migration. This QoS degradation is found when UE and site location distributions do not match in case of the spatially uniform placement of sites with the normally distributed UE locations. The finding thus shows the importance with the load balancing of not only the new platform being migrated to, but also the old existing platform being migrated from.