A Systematic Evaluation of Interference Characteristics in 802.11-based Wireless Networks

Interference is a crucial factor that impacts the overall through put performance of IEEE 802.11-based wireless networks. As such, understanding interference characteristics is essential towards the optimal management and operation of these networks. In this paper, we use a conducted testbed (that allows us to completely control the signal propagation and received signal strength) to systematically evaluate the impact of interference in terms of the carrier-sensing interference and the receiver interference. Our results show that carrier-sensing interference does not conform to the often-used binary model of "either carrier-sense or nocarrier-sense", and that the sum of the normalized sending rates of nodes that can fully carrier-sense each other is greater than 1.0. In terms of receiver interference, our results show that while the interference impact on a data link's through put is approximately linear with respect to the offered load of the interferer node, its relationship with respect to the offered load of the data sender is non-linear. Our results also show that the combined interference impact of multiple interferer nodes cannot be predicted by just using independent measurements of the interference impact of individual interferer nodes. The results in this paper indicate that commonly made underlying assumptions of interference models are not valid, and consequently show the limitations of the corresponding models.