A USRP based UHF Wireless Sensor Node and Fusion Centre for Aquaponics System Monitoring

Tremendous rise in smart and sustainable agricultural systems such as the Aquaponics, demand continuous system monitoring for predictive analytics and timely control. Many such monitoring systems have been developed in the literature using microcontrollers, which transmit the sensed data to cloud using off-the-shelf components. However, these do not exploit underutilized Ultra High Frequency (UHF) transmission bands and have fixed carrier frequency, transmit and receive signal processing chains. Contrarily, this paper discusses the development of a wireless sensor node and fusion centre at the underutilized 470 MHz UHF band, using microcontroller and programmable Universal Software Radio Peripheral (USRP) modules, for temperature and pH monitoring of a smart aquaponics system. Analog data frame comprising temperature and pH values is acquired, digitized using 32-bit Pulse Code Modulation (PCM) and a frame header is added. The frame is then transmitted to a remote fusion center using 470 MHz carrier, where the received symbols are decoded to retrieve the analog frame. Average Bit Error Rate (BER) of the wireless link is obtained as 0.003 at a receiver gain of 20 dB. Hence, reduced frame loss/improved link reliability is ensured by repeated transmissions. The sensor node transmits each analog frame 50 times, while the fusion center is programmed to collect 20 successive frames. At the fusion center, these 20 frames are pre-processed to estimate the actual analog frame. The developed monitoring system acquired temperature and pH time series data for a total duration of 12 hours with 1 minute sampling period.