UC Riverside

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.