Supporting quality of service (QoS) in overlaid wireless networks

In this dissertation, we explore the techniques that may be used in the third-generation (3G) network to improve the system QoS. Specifically, we emphasize on the overlaid network architecture. We first survey the major research on the homogeneous overlaid cellular networks (hierarchical networks), i.e., the overlaid cellular networks with the same operating systems in different tiers. We then exploit the performance improvement in a macrocell/microcell homogeneous network with different handoff-priority queuing strategies. In this research, we build an analytical model to analyze queuing handoff in a tiered cellular network; we also show different queuing strategies in the tiered network as well as their performance. Later, we study the mobility management in the hierarchical network. In this work, we examine the delay and cost of a new location update/paging scheme, called two-step paging scheme, in the macrocell/microcell network. Using the feature that a mobile unit in the tiered cellular network can receive signals from different tiers, the two-step paging scheme maintains low paging delay at a low location update/paging cost. We also conduct research on the network with heterogeneous hierarchy, i.e., the overlaid network with different operating systems in the different tiers. We add an ad-hoc overlay network on a cellular network and examine the network performance when using multi-hop connections. Load in a hot cell is diverted to its neighboring cold cells through some special channels, called forwarding channels. We investigate two research directions in such an overlaid network: (1) the call-blocking probability study; and (2) the average packet delay study. We find that this new scheme achieves lower call-blocking probability and lower delay.