Performance study of wireless sensor networks in aquaculture environments

Abstract

Multipath fading effect is a common problem of electromagnetic wave or signal propagation. For WSN (Wireless Sensor Networks) system, the effect is able to degrade the system by contributing to the problem of packet rejection, packet loss and shortening the network lifetime. The existence and level of the effect is totally depend on the conditions of the communication system environment. To solve the problem of the effect, a signal propagation study must be conducted in the environment where the system will be implemented. The objectives of this research is to study the signal propagation characteristics of WSN devices and the devices physical position that influence signal propagation characteristics, to verify suitable analysis tools (Packet Error Rate, average received power, standard deviation, goodness of fit χ² test and Rice K ) for signal propagation study, to study the signal propagation of WSN devices in aquaculture environments with focusing on multipath fading effect issue, to minimise multipath fading effect by using the method of controlling time interval between packets transmission and to study the feasibility of WSN system to be implemented in aquaculture environments. The first experiment was conducted at an open outdoor area (sports arena). The experiment was conducted by placing the nodes in different positions (vertical, horizontal and low) at different distances (10 – 40 m) between nodes. The result shows the vertical position has the best performance in all analysis. The average received power curve is monotonic and it can be modeled by second order of polynomial equation. From this equation, the maximum range of communication is estimated at 70 m. The second experiment was conducted at an indoor aquaculture environment (fish hatchery). In this environment, the multipath fading effect is found at low level where the standard deviation analysis shows Tank 3 has high variation of data and the Rice K analysis shows the direct component of Tank 9 is not monotone. After sending packets at 100 ms, the effect has been minimised with the variation of data is become low for Tank 3 and the direct component of Tank 12 is become monotone. The third experiment was conducted at an outdoor aquaculture environment (fish pond). This experiment found that the effect at this environment is at high level, where the PER value for side D is more than 1%. After sending packets at 50 ms, the effect can be minimised with the PER value of Side D become less than 1%. This research concludes that the multipath fading effect is exist in aquaculture environment. By using combination of PER, average RSSI, standard deviation, χ² test and Rice K analysis tools is able to analyse the multipath fading effect. This effect can be minimised by controlling time interval between packets transmission. From this research is obtained that WSN is feasible to operate in aquaculture environment.