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WIRELESS COMMUNICATION


share common data rate options; however, the prior exhibits lower sensitivities on average.


Figure 3 plots the data rates versus the link budget values; a link budget* is the difference between a power output and a sensitivity value. Radio engineers fit these values with path loss models that account for signal losses due to terrain contours, environment, propagation medium, etc. to estimate communication ranges between two devices. A higher link budget value represents a better range. Hence, throughput is not the only parameter of interest when comparing protocols; parameters like sensitivity and link budget values are critical factors as they demonstrate unique radio characteristics offered by different protocols.


What needs to be considered when evaluating available wireless technologies in order to pick out the best one(s)?


Last but not least, having the right power strategy for smart irrigation devices/equipment is essential. Figure 4 plots the sensitivity versus the current consumptions of different modules. There are several observations: 1) It usually takes more power to transmit than to receive; 2) LoRa, Bluetooth and Zigbee modules normally consume less energy than Wi-Fi and cellular modules; and 3) cellular modules have the highest power consumption. Hence, if a grower intends to use a 1,000-milliampere battery to deploy a device, low-power modules (Bluetooth and LoRa) will last months with proper schedule configurations, while power-hungry Wi-Fi and cellular modules drain the battery in hours.


This brings out the core idea behind selecting suitable modules or protocols: An ideal protocol should offer highly sensitive radio (thus more consistent data reception and longer range), a low power consumption and a high throughput. However, finding one protocol that fits all use cases is not feasible. Instead, whether it is for actual deployment or evaluating a new technology, selecting the suitable wireless devices/equipment is about considering different technical parameters, finding the right balance to tailor practical needs and, finally, making informed and judicious decisions.


* Author’s note: This definition is not rigorous. In radio planning, engineers need to account for factors like antenna characteristics, cable losses, etc. as well.


Yang Wang is a PhD candidate under James Krogmeier, PhD, and  


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Spring 2020 | Irrigation TODAY 25


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