When applying internet of things (IoT) to the agriculture domain, Machine-to-Machine (M2M) communications are a central key, empowering ubiquitous and independent communications amongst numerous gadgets without any human interference. In this way, necessities such as productivity, versatility, low-cost equipment and low-power utilization are expected from this kind of communications. The demand for these necessities varies according to the various application scenarios, which has driven to the development of endless number of conventions, standards, communication stacks and models, each one addressing specific issues or applications. Some of the technologies like:
LPWAN Technologies - Demand for low power communications has led to increase in the use of Low-Power Wide-Area Network (LPWAN). The LPWAN technologies can be used like some of the short-range communication technologies by positioning them between cellular networks and operating them in the license free band of the spectrum, thus, potentially covering the communication ranges similar to a cellular cell. The data rates are also like the short-range communication solutions which are adequate for many IoT solutions. Some examples are Sigfox, Long Range (LoRa) WAN, NarrowBand-IoT (NB-IoT) and LTE-M.
Sigfox is a centralized and low-throughput wireless communication system which is efficient energy-wise but provides limited capacity, smaller coverage area, insufficient bandwidth and prohibits localization.
LoRa is a Wireless Wide Area Network specification designed to minimize energy consumption and provide long range communications. It provides a reasonable bandwidth, permits RSSI-based localization and can be used as a private network. The only disadvantage of LoRa is its poor performance due to low data accuracy for wide range applications and its cost in case it is considered for each animal sensor.
NB-IOT and LTE-M, part of 3GPP Long-Term Evolution(LTE), have been developed for M2M ad IoT applications. Despite its advantages of high bandwidth provision and potentially low power consumption, it depends on a public communication infrastructure which is not available in rural areas. Moreover, the need for paying fees to the telecom operator arises thus making the exploration costs intolerable.
Non-IP Protocols - There are several applications that also resort to non-IP solutions like ZigBee and BLE for optimized use of resources, processes and communications.
ZigBee is based on IEEE 802.15.4 standard for the Physical and MAC layers with its higher layers defined by the ZigBee Alliance. It provides a framework for low-power wireless communication. Nonetheless, IEEE 802.15.4 poses specific limitations when considered for TDMA applications.
BLE is an upgraded version of the classic Bluetooth, allowing 10-fold higher communication ranges, lower radio power and lower latencies. In addition to its significant reduction in power consumption and increased range, the application of star and mesh topologies remains significantly limited.