Modeling Environmental Effects on Directionality in Wireless Networks ; CU-CS-1044-08

As the demand for wireless networks grows, the research community continues to seek methods for improving network performance. On method for improving network throughput involves using directional antennas to increase signal gain and/or decrease interference. The physical-layer models used in current networking simulators only minimally address the interaction of directional antennas and radio propagation. This paper compares the models found in popular simulation tools with measurements taken across a variety of links in multiple environments. We find that the effects of antenna direction are significantly different from the models used by the common wireless network simulators. We propose a parametric model which better captures the effects of different propagation environments on directional antenna systems; we also show that the derived models are sensitive to both the direction of signal gain and the environment in which the antenna is used. Equally important, we demonstrate how researchers can use inexpensive equipment to record data for their own environments. Although we use sensitive vector signal analyzers in our measurements, we show that using commodity wireless networking cards produces effectively equivalent models. We believe that a combination of the specific model we propose and the process by which we gather data to derive that model will influence the simulated performance of wireless network protocols that rely on directional antennas, providing a more realistic assessment of those protocols. We also offer some general guidance for researchers attempting to use directional antennas to modify a wireless network topology or reduce interference.