Automated Monitoring of Launching Girder Operations Using Wireless Sensor Network

Variation of RSSI (Received Signal Strength Indicator) with distance is shown in Figure 1, Consistent with the results reported in the literature(Piyare et al. 2013). RSSI decreases with distance from the coordinator. However, the reduction in strength if plotted logarithmically will not result in a linear relationship with distance as expected. This is in conformation with (Parameswaran et al. 2009)wherein it was observed that even in ideal scenarios RSSI does not give a consistent behavior. The fluctuations at distances from 40 to 60 m in 10 bytes and 30 bytes can be correlated with reflection and multipath phenomena due to end walls and presence of electromagnetic interference from equipment such as Wi-Fi routers. This is also supported by the findings of Bae et al (2013)10 and Piyare et al (2013)29. Despite the observations that RSSI fluctuated from the theoretical expectation, all the values lie above the threshold of XBee requirements, which is -102dBm (http://www.digi.com/pdf/ds_XBeemultipointmodules.pdf [Accessed 10th January 2015]) Therefore, it can be concluded that the current wireless sensor network has enough signal strength to support data transmission in the range specified.

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