High-performance and secure wireless networking through unified cellular and ad-hoc networks

Ubiquitous Internet access calls for high-performance wireless networking. However, due to the fundamental tradeoff between data rate and communication range, none of the existing wireless technologies meets mobile users' demands for both high data rate and ubiquitous coverage. Nevertheless, the coverage of IEEE 802.11 WLANs in public areas is limited due to the short communication range and slow infrastructure deployment. As a result, both networks will co-exist in the foreseeable future and mobile devices will possess both wireless interfaces for connectivity in different scenarios.; The key contribution of this dissertation is to achieve high-performance wireless networking for mobile users by leveraging the coverage ubiquity of the 3G WWAN and the popularity of ad-hoc communication capable IEEE 802.11 interfaces. Our approach is to enable cross-interface awareness so that mobile user's 3G and IEEE 802.11 interfaces work together to optimize the performance of each other. To this end, we propose a novel network architecture, Unified Cellular and Ad-Hoc Network (UCAN). UCAN networks inherit the ubiquitous coverage of the 3G infrastructure, thus providing availability assurance required by most commercial network applications. UCAN also maximizes users' throughput by relaying the traffic destined to users with low data-rate 3G connections via users with high data-rate 3G connections, through their IEEE 802.11 interfaces in ad-hoc mode.; The following challenges have to be addressed to enable the opportunistic use of IEEE 802.11 ad-hoc networks and 3G WWANs: (1) Highly dynamic 3G channel quality and IEEE 802.11 network topology. The discovery of users with high data rate 3G connections and the maintenance of the routes to reach such users in an IEEE 802.11 network have to be adaptive to these system dynamics. (2) Resource constraint of mobile devices. Mobile devices may be battery-powered, and users are usually selfish in sharing the computing and/or communication resources of their mobile devices. Incentives must be provided to users for the proper operation of ULAN networks. (3) Location-dependent wireless channel contention and channel reuse. Explicit channel access coordination among competing nodes in an IEEE 802.11 network is needed to achieve packet-level fair channel access for throughput and delay assurance of the relayed 3G traffic. (4) Fragile network access control. In UCAN 3G base stations control the access to the ad-hoc networks. However, wireless communication is prone to environmental noise, interferences, and/or malicious jamming. The centralized certification service offered by the 3G infrastructure may not be always available. Robust network access control with intermittent 3G connections is therefore necessary.; In this dissertation, we address these challenges through analysis, algorithm design, and protocol implementation. (Abstract shortened by UMI.)...