Channel and Interference Analysis for Wireless Sensor Networks

This paper presents preliminary investigations of the short range (~10 cm) narrowband wireless channel appropriate to specks operating in the 2.4 GHz ISM band. Path loss measurements have been made in the laboratory using rectaxial antennas at 2.45 GHz. The transmitted signal is an unmodulated carrier and the receiver is a spectrum analyzer. Characterization of signal power variations are important for system design and so path loss and fading models have been derived. The paper presents a comprehensive narrowband channel model (including interference due to neighboring nodes) for application to asynchronous short-range wireless networks. Medium access is assumed to be CSMA based and SIR will therefore depend on inhibition distance and antenna characteristics. Aggregated interference due to neighboring nodes has been calculated. Finally, cumulative SIR values have been used to construct link budgets and bit error rates.