Capacity and cross-layer design of wireless ad hoc networks

The focus of this thesis is on the establishment of theoretical lower and upper bounds on the traffic-carrying capabilities of wireless ad hoc networks. This theoretical investigation brings forward good design principles, therefore a part of the thesis is devoted to the design of wireless ad hoc networks based on these principles.; We first define and study capacity regions for networks with an arbitrary number of nodes and topology. These regions describe the set of achievable rate combinations between all source-destination pairs in the network under various transmission strategies, such as variable-rate transmission, single hop or multihop routing, power control and successive interference cancellation. With slight modifications, the developed formulation can handle node mobility and time-varying flat fading channels.; We next investigate the performance and interaction of various protocols lying in different layers of the OSI protocol stack. Our approach is to compare the actual performance of wireless networks with theoretical upper bounds, as determined by the capacity region formulation of the first part. In particular, we study the routing protocol, the queuing discipline, the power control algorithm and the medium access control protocol. Our study culminates in the introduction of two medium access control protocols: the Progressive Back Off Algorithm (PBOA), which performs medium access jointly with power control, and the Progressive Ramp Up Algorithm ( PRUA), which sacrifices energy efficiency in order to achieve higher throughputs.; We conclude by studying wireless ad hoc networks with a large number of nodes. We first concentrate on a network of n immobile nodes, with n randomly created source-destination node pairs. We develop a scheme under which, in the presence of a general model of fading, the network can provide each pair with a traffic rate λ₁( n) = $K1n-12logn-32$. Next, we extend our formulation to study the effects of mobility. We develop a scheme under which each of the nodes can send data to a randomly chosen destination with a rate λ₂(n) = $K2nd-12logn-52$, provided that nodes are willing to tolerate packet delays smaller than a d_max(n) < K₃nd, where 0 < d < 1.