The Myth of Spatial Reuse with Directional Antennas in Indoor Wireless Networks

Sriram Lakshmanan1, Karthikeyan Sundaresan2, Sampath Rangarajan2, and Raghupathy Sivakumar1
1GNAN Research Group
School of Electrical and Computer Engineering
Georgia Institute of Technology
2NEC Labs. America
Princeton, NJ

The 11th Passive and Active Measurement Conference (PAM 2010), Zurich, Switzerland, April 7-9th, 2010.


Interference among co-channel users is a fundamental prob- lem in wireless networks, which prevents nearby links from operating concurrently. Directional antennas allow the radiation patterns of wire- less transmitters to be shaped to form directed beams. Conventionally, such beams are assumed to improve the spatial reuse (i.e. concurrency) in indoor wireless networks. In this paper, we use experiments in an indoor office setting of Wifi Access points equipped with directional antennas, to study their potential for interference mitigation and spatial reuse. In contrast to conventional wisdom, we observe that the interference mit- igation benefits of directional antennas are minimal. On analyzing our experimental traces we observe that directional links do not reduce inter- ference to nearby links due to the lack of signal confinement due to indoor multipath fading. We then use the insights derived from our study to de- velop an alternative approach that provides better interference reduction in indoor networks compared to directional links.

Presentation: [pdf (1784KB)]      Full Paper: [pdf (203KB)]