Adaptive Method to Estimate Link Budget Parameters in Wireless Networks

Localization is crucial for sensor nodes to functionally operate in a sensor network. It becomes more challenging when the nodes are mobile in an area where the GPS coverage is unreliable. The transmission path between the transmitter and the receivers defines the way the signal propagates and therefore the resulting received signal strength. Most sensor nodes use the measured Received Signal Strength Indicator (RSSI) to calculate the received power and estimate their distance from neighboring nodes using free space FRISS equation. However, in practice, the separation between the transmitter and the receiver can be obstructed which make the free space model impractical. A more accurate propagation model to estimate the distance between two nodes can used if the Path loss exponent for the obstructed path is known. Another challenge is that the RSSI measurements are noisy which also affects the accuracy of estimating the distance. Accordingly, we propose in this work, a method for estimating the Path loss exponent n taking the Nosie into consideration. The solution assumes the existence of a few beacons that know their locations and the locations of other beacons deployed in the area to estimate the Path loss exponent n and the noise standard deviation and share them with the mobile nodes to become aware of the propagation model in the area and be able to accurately estimate their locations and distances from each other’s. The paper introduces the basic mathematical background and the localization algorithm assuming Gaussian noise.