iCAR : an Integrated Cellular and Ad hoc Relaying System

The cellular concept was introduced for wireless communication to address the problem of having scarce frequency resource. It is based on the sub-division of geographical area to be covered by the network into a number of smaller areas called cells. Frequency reuse in the cells far away from each other increases system’s capacity. But at the same time, the cell boundaries prevent the channel resource of a system to be fully available for users. No access to Data Channels (or DCHs) in other cell by the mobile host (or MH) limits the channel efficiency and consequently the system capacity. In this dissertation, we propose a new wireless system architecture based on the integration of cellular and modern ad hoc relaying technologies, called iCAR. It can efficiently balance traffic loads and share channel resource between cells by using Ad hoc relaying stations (ARSs) to relay traffic from one cell to another dynamically. This not only increases the system’s capacity costeffectively, but also reduces transmission power for mobile hosts and extends system coverage. We analyze the system performance in terms of the call blocking probability and queuing delay using multi-dimensional Markov chains for the new call requests and the call dropping probability for handoff requests, and verify the analytical results via simulations. Our results show that with a limited number of ARSs and some increase in the signaling overhead (as well as hardware complexity), the call blocking/dropping probability in a congested cell as well as the overall system can be reduced. We also propose a seed-growing approach for ARS placement, and discuss the upper bound on the number of seed ARSs needed in the system. In order to quantitatively evaluate ARS placement strategies, we introduce the concept of a new performance metric called quality of (ARS) coverage (QoC) for the comparison of various ARS placement strategies, and propose three rules of thumb as guidelines for cost-effective ARS placement in iCAR. Furthermore, we propose the signaling and routing protocols for establishing QoS guaranteed connections for IP traffic in iCAR. In particular, we discuss how a relaying route between a MH and a BTS in a nearby cell can be established via ARSs, and evaluate the performance of the protocols in terms of request rejection rate and signaling overhead through simulations. In addition, we propose a novel concept called “managed mobility” and address the ARS mobility management in iCAR.