Wavelength diversity in turbulence channels for sensor networks

Wireless multimedia sensor networks (WMSN) are an emerging technology that served to ubiquitously retrieve multimedia content from the surroundings. This technology has emerged due to the availability of very sophisticated and low-cost hardware such as CMOS cameras, CPU'S, and communication transceivers. In our model, we also include an optical wireless communication (OWC) transceiver, which uses light to transmit high data rate the information. An OWC system is advantageous by comparison to RF communication systems for the following main reasons: A) it operates with low power consumption , B) the system is small and lightweight and has compact dimensions and C) its large unregulated bandwidth allows very high data rates. However one of the main challenges associated with OWC is finding ways to overcome atmospheric turbulence. Atmospheric turbulence results in rapid fluctuations in both the intensity and the phase of the received signal, which cause signal fading. Signal fading impairs the link performance severely and could lead to an increase in the BER. The conventional method to mitigate the signal fading and the increase of the BER uses spatial diversity. However, due to the size limitation of the sensors this solution is not practical. Another method is to use time diversity but this has the major disadvantage of delay of the signal reception. In this work, we propose a laboratory test bed to measure the performance of a communication system based on wavelength diversity as a function of turbulence amplitude. Wavelength diversity is a method that can mitigate the link degradation caused by atmospheric turbulence and it relies on the basic fact that the fading for different wavelengths is partly uncorrelated.