One of the major problems experienced by wireless multi-hop networks is the intermittent network connectivity, which is a consequence of fluctuating link quality due to signal fading.

Antenna array technology has been proposed to alleviate the problem of signal fading,

and it provides significant performance increase on a single link. However, translating this link-level performance increase to an end-to-end gain in multi-hop networks is not straightforward; a cross-layer design is necessary to efficiently facilitate this translation. In this dissertation, we present cross-layer design approaches for providing end-to-end performance increase in multi-hop networks using antenna arrays. Each approach is designed to utilize a special capability with antenna arrays.

Using antenna arrays, nodes can increase the signal strength in a specific direction;

i.e., perform directional communications. Using directional communications in a multi-hop network requires nodes to periodically update the directions of their neighbors, which introduces an overhead. We propose topology control algorithms that enable the use of directional communications in multi-hop networks with bounded overhead. The bounds provided by

our Low Degree Spanner (LDS) and Distributed LDS (D-LDS) algorithms are near-optimal.

Space-Time Block Coding (STBC) with antenna arrays (referred to as MIMO-STBC) offers significant robustness to fading without an overhead at the higher layers.

Robust MIMO-STBC links can also provide performance improvements at the higher layers

by the design of proper protocols. Such a design necessitates an accurate representation of the MIMO-STBC link behavior. To date, simplistic representations have been used. We design an accurate representation of MIMO-STBC communications, which we show to have a high fidelity to the MIMO-STBC communications in practice.

Antenna arrays also facilitate the spatial multiplexing of signals, allowing a node to transmit and receive multiple signals simultaneously. In a multi-hop network, spatial multiplexing enables receptions from multiple concurrent transmitters. However, such a reception is successful only if

both the number and the strength of concurrent transmissions is controlled by a higher-layer mechanism. We design topology control algorithms for activating a maximal number of communications simultaneously, while ensuring that every communication is successful with high probability.

Traditional MAC and routing protocols, which are primarily designed for homogeneous networks wherein all nodes transmit with the same power, suffer performance degradations when employed in power heterogeneous networks. The observed degradations are due to link asymmetry, which arises as high power nodes that do not sense the transmissions of low power nodes can potentially initiate transmissions that interfere with the low power communications. Link layer asymmetry in power heterogeneous networks not only disrupts the functioning of the routing protocol in use, but also results in unfairness in medium access. In this paper, we develop a cross-layer framework to effectively address the link asymmetry problem at both the MAC and the routing layers. At the MAC layer, the framework intelligently propagates low power control messages to the higher power nodes, so as to preclude them from initiating transmissions while there are low power communications in progress within their sensing range. At the routing layer, the framework facilitates the efficient use of unidirectional links. We perform extensive simulations to study the performance of our proposed framework in various settings, and show that the overall throughput in power heterogeneous networks is enhanced by as much as 25% over traditional layered approaches. In addition, we show that our schemes are also beneficial in power homogeneous settings, as they reduce the extent of false link failures that arise when the IEEE 802.11 MAC protocol is used. In summary, our framework offers a simple yet effective and viable approach for medium access control and for supporting routing in power heterogeneous ad hoc networks.