# Energy-Efficient Wireless Communication Strategy for Precision Agriculture Irrigation Control
## 5 Conclusions and Future Works  
We described and evaluated the design and implementation of self-triggered control algorithms to communicate soil moisture measurements in a closed-loop agriculture  
Figure 10: The estimated spent energy for the sensor nodes and water consumption for each irrigation area.  
irrigation process against the traditional fixed-periodical sampling approach. First, a specific model for a pecan crop irrigation system was identified and validated. Then, four sampling strategies were evaluated simultaneously in the experimental pecan field. Two self-triggered periodical sampling algorithms were implemented, considering the state variables to determine the next sampling instant.  
One algorithm selected the sampling period based on the estimated measured error, while the other used a Lyapunov function to trigger the communication event. The other two implemented strategies used periodical sampling with low and high fixed communication rates. The experimental results showed that the self-triggered approaches provided higher efficiency in communication messages, thus, implying a significant reduction of energy consumption--a critical parameter for battery-powered wireless nodes. Both self-triggered strategies achieved the control performance objectives regarding water consumption and precision irrigation. This approach demonstrates that the sampling strategy to measure and communicate only when relevant provides an efficient communication mechanism in terms of energy while still achieving the control objectives.  
In future works, the implementation of self-triggered techniques in wireless sensor networks can be extended to other agriculture and environmental applications where specific model-based processes can be properly identified to achieve an energy-efficient communication strategy. The triggering conditions for the algorithms can be refined to guarantee optimal performance under specific evaluation parameters. Finally, self-triggered control strategies can be compared with other energy-efficient sampling rate adaptation techniques within the precision agriculture domain.  
Conceptualization, C.L., A.F.-C. and A.A.-G.; methodology, C.L., A.F.-C., A.A.-G., L.C.F.-H. and L.O.; software, C.L. and A.A.-G.; validation, C.L., A.F.-C., A.A.-G., L.C.F.-H. and L.O.; formal analysis, C.L. and L.O.; investigation, C.L., A.F.-C., A.A.-G. and L.C.F.-H.; writing--original draft preparation, C.L. and A.A.-G.; writing--review and editing, C.L., A.F.-C., A.A.-G., L.C.F.-H. and L.O.; supervision, C.L. and A.F.-C.; project administration, C.L. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors would like to thank the Sensors and Devices Research Group from the School of Engineering and Sciences of Tecnologico de Monterrey for the support given to develop this work.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} ETC & Event-triggered control \\ ETO & Reference evapotranspiration \\ FAO & Food and Agriculture Organization \\ FC & Field capacity \\ MAD & Maximum allowable depletion \\ PWP & Permanent wilting point \\ RF & Radio frequency \\ STC & Self-triggered control \\ VWC & Volumetric water content \\ WSN & Wireless sensor network \\ \end{tabular}