Distributed sensing of spectrum occupancy and interference in outdoor 2.4 GHz Wi-Fi networks
Salim A. Hanna, John Sydor · 2012
A spectrum monitoring campaign was launched in an outdoor urban radio environment to investigate the potential deployment of Cognitive Radio (CR) Wi-Fi networks in the 2.4 GHz ISM band. The campaign used a CR learning platform with 4, 8, and 16 sensors. This paper presents Wi-Fi spectrum occupancy and interference behaviour based on the outcome of one of the measurements using 16 GPS-synchronized sensors. At detection thresholds Td≥ -62dBm, long-term spectrum holes were dominant on all Wi-Fi channels. However, at Tdrdof management packets were beacons, and more than 1/2 of data packets were data-reserved and null (no data). We also noted, at Td≤ -82dBm, a large number of Wi-Fi users more than can be attributed to the immediate surroundings of sensors, but a small set of them was dominant producing the bulk of spectrum occupancy and interference. In addition, at least 25% of these users were detected only once over the 5.5 hours measurement time span. The measurements showed spatial variations of the Wi-Fi environment over a small sensing area (21m-by-45m). We noted considerable non-homogeneity in the distribution of Wi-Fi interference at Td≥ -62dBm, but some non-homogeneity at Td≤ -82dBm. We also noted significant correlated fluctuations of received signal strength and non-reciprocal links over short distances between sensors.