Spatio-temporal characteristics of link quality in wireless sensor networks

Modeling the link quality is essential in achieving and maintaining stable communication and minimizing energy consumption by controlling packet transmissions across a wireless sensor network. The quality of the communication links is a function of many variables including location, distance, direction and time. In this paper, we investigate the statistical channel models for spatial and temporal characteristics of link quality in different environments. These investigations are based on three metrics: received signal strength indicator (RSSI), packet loss rate (PLR) and link quality index (LQI). Statistical models are offered for all three parameters for both indoor and outdoor cases. The best distributions modeling PLR, LQI and RSSI at a certain distance are exponential, Weibull and normal respectively. The best fit for the parameters of these distributions are the same functions but with different constants for indoor and outdoor environments. Moreover, the correlations in different directions have normal distributions for all three metrics with absolute means and variances less than 0.4. The variations of the link characteristics over time on the other hand depends on the average quality of the link which should be taken into account in the design of upper layers. The temporal correlation of a link is modeled by using a sinusoidal function the parameters of which depend on the quality of the link. This is the first work to perform a detailed quantification of time and space dependencies on the link quality by using statistical models.