| Wireless ad hoc networking enables communications between terminals in the absence of or as a supplement to a centralized infrastructure, often using multiple hops to relay messages to their destinations. Benefits include the capability for on-demand networking, power efficiency and extended coverage. Prior work in ad hoc networks has emphasized the use of fixed signaling schemes and the development of routing protocols that disregard physical laver channel conditions. This dissertation presents a framework for the analysis of cross-layer channel-adaptive techniques that exploit the inherent diversity of multihop ad hoc networks. Specifically, adaptive modulation, adaptive routing and adaptive cooperative coding are considered.; First, an existing model for the distribution of the interference in slotted, random access, packet radio networks using DS/CDMA and coherent modulation is extended to account for two-dimensional constellations. The alpha-stable interference distribution is validated by simulation and applied to the analysis of adaptive modulation and channel-adaptive routing. Performance is evaluated in terms of the network's information efficiency, a progress-related measure that incorporates link throughput and number of hops, and closed-form expressions are obtained for special cases of interest. A four-fold increase in information efficiency is observed from the joint use of adaptive routing, which selects a link with favorable channel conditions, and adaptive modulation, which maximizes the throughput on that link. Most of this benefit is still available under certain limitations, such as imperfect channel state information and limited route diversity. In addition, implementation strategies for realizing the adaptive routing gain are proposed for position-based as well as position-blind networks.; Spatial diversity gain in multihop networks is also investigated in the context of cooperative transmission for the relay channel. In particular, an analysis of cooperative coding shows that the adaptive choice of a relay can reduce power consumption by half. Furthermore, an examination of the trade-off between spatial and temporal diversity gain in the presence of mobility demonstrates that the gain due to spatial diversity can be considerable even in moderately mobile environments.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat. |
