IoT Technologies for Irrigation Water Management

 

IoT Technologies for Irrigation Water Management

Studies show there is a potential for water savings of over 50% with sensor-based irrigation scheduling methods. Informed irrigation decisions require real-time data from networks of soil and weather sensors at desired resolution and a reasonable cost. Wireless sensor networks can collect data on plants in a lot of detail in areas of the field that behave differently.

This need for wireless sensors and actuators has propelled the development of Internet of Things (IoT) solutions, particularly Low-Power Wide-Area Networking (LPWAN). Essentially, IoT in agriculture means enabling wireless communication and data transfer to management systems for analysis, allowing for enhanced farming practices, especially in irrigation and resource management. LPWAN technologies are specifically designed to connect low-cost, low-power sensors to cloud-based services, a crucial feature for agricultural settings where sensors must transmit small data packets over vast areas while relying on long-lasting battery power.

However, the rapid proliferation of wireless and IoT connectivity solutions presents a challenge: which LPWAN technology best suits specific agricultural applications? This article aims to address this question by exploring the role of IoT in modern agriculture, the key challenges and limitations to its widespread adoption, and the practical implementation scenarios available.

Specifically, we will delve into the various IoT implementation approaches, from simple sensor-to-Wi-Fi setups to complex, vendor-managed or network operator-provided LPWAN infrastructures. This includes examining the strengths and limitations of technologies like LoRaWAN, LTE Cat-M1, NB-IoT, and others, considering factors such as data rates, cost, network coverage, and power consumption. We will further analyze how these technologies fit into diverse agricultural needs, from basic monitoring to advanced control systems.

Understanding the nuances of each IoT solution is vital for growers and consultants. While the potential for improved irrigation and resource management through IoT is undeniable, factors like cost, connectivity, and infrastructure considerations remain significant hurdles. As the IoT market matures, the integration of robust sensor technology with reliable and cost-effective communication networks will be key to unlocking its full potential in agriculture. This article will also touch on the future of agricultural IoT, including the ongoing evolution of these technologies and the anticipated shifts in market dynamics.

IoT Implementation Scenarios

The following are scenarios for implementing IoT:

  1. buying a sensor that is going to connect to a wireless network that you own (i.e., customer supplied like Wi-Fi, Bluetooth),

  2. buying the infrastructure or at least pieces of it to install onsite (i.e., vendor managed LPWAN such as LoRaWAN, Symphony Link), and

  3. relying on the infrastructure from a network operator LPWAN (e.g., LTE Cat-M1, NB-IOT, Sigfox, Ingenu, LoRWAN).

This is how cellular network operators or cellular IoT works. LPWAN technology fits well into agricultural settings where sensors need to send small data over a wide area while relying on batteries for many years. This distinguishes LPWAN from Bluetooth, ZigBee, or traditional cellular networks with limited range and higher power requirements. However, like any emerging technology, certain limitations still exist with LPWAN.

IoT Strengths and Limitations

The average data rate in cellular IoT can be 20 times faster than LoRa or Symphony Link, making it ideal for applications that require higher data rates. LTE Cat-M1 (aka LTE-M), for example, is like a Ferrari in terms of speed compared to other IoT technologies. At the same time, sensor data usage is the most important driver of the cost in using cellular IoT. Individual sensor subscription fee in cellular IoT may add up and make it very expensive where many sensors are needed. This means using existing wireless technologies like traditional cellular or ZigBee to complement LPWAN.

One-to-many architecture is a common approach with respect to wireless communication and can help save the most money. Existing wireless technologies like Bluetooth LE, WiFi or ZigBee can be exploited to collect in-field data. In this case, data could be transmitted in-and-out of the field through existing communication infrastructure like a traditional cellular network (e.g., 3G, 4G) or LAN. Alternatively, private or public LPWAN solutions such as LoRaWAN gateways or cellular IoT can be used to push data to the cloud. Combination of Bluetooth, radio or WiFi with cellular IoT means you will have fewer bills to pay. It is anticipated that, with more integrations, the IoT market will mature, and costs will drop further.

Many of LPWAN technologies currently have a very limited network coverage in the U.S. LTE Cat-M1 by far has the largest coverage. Ingenu, which is a legacy technology, Sigfox and NB-IOT have very limited U.S. coverage. Some private companies are currently using subscription-free, crowd-funded LoRaWAN networks to provide service to U.S. growers: however, with a very limited network footprint. Currently, cellular IoT does not perform well in rural areas without strong cellular data coverage.

LoRaWAN is ideal for monitoring applications where sensors need to send data only a couple of times per day with very high battery life at very low cost. Cellular IoT, on the other hand, works best for agricultural applications where sensors are required to send data more frequently and irrigation valves need to be turned on/off. Low-Power Wide-Area Networking (LPWAN) technologies need gateways or base stations for functioning. The gateway uploads data to a cloud server through traditional cellular networks like 4G.

Symphony Link has an architecture very similar to LoRaWAN with higher degree of reliability appropriate for industrial applications. The power budget of LTE Cat-M1 9 (a network operator LPWAN) is 30% higher per bit than technologies like SigFox or LoRaWAN, which means more expensive batteries are required. Some IoT technologies like LoRa and SigFox only support uplink suited for monitoring while cellular IoT allows for both monitoring and control. LTE-M is a better option for agricultural weather and soil moisture sensor applications where more data usage is expected.

NB-IoT is more popular in EU and China and LTE Cat-M1 in the U.S. and Japan. T-Mobile deployed an NB-IoT network in the U.S. recently, following a pilot project in Las Vegas. Verizon and AT&T launched LTE Cat-M1 networks a couple of years ago and their IoT-specific data plans are available for purchase. Verizon and AT&T IoT networks cover a much greater area than LoRa or Sigfox.

An IoT device can be connected to AT&T’s network for close to $1.00 per month, and to Verizon’s for as low as $2 per month for 1MB of data. A typical sensor message generally falls into 10-200 bytes range. With the overhead associated with protocols to send the data to the cloud, this may reach to 1KB. This can be used as a general guide to determine how much data to buy from a network operator.

What the Future Holds

Many startup companies are currently focused on the software aspect of IoT, and their products lack the sensor technology. The main problem they have is that developing good sensors is hard. Most of these companies will fail before batteries of their sensors die. Few will survive or prevail in the very competitive IoT market. Larger companies who own sensor technologies are more concerned with the compatibility and interoperability of these IoT technologies and will be hesitant to adopt them until they have a clear picture. It is going to take time to see both IoT and accurate plant and soil sensors in one package in the agriculture market.

With the rapid growth of IoT in other areas, there will be an opportunity to evaluate different IoT technologies before adopting them in agriculture. As a company, you may be forced to choose specific IoT technology. Growers and consultants should not worry about what solution is employed to transfer data from their field to the cloud and to their computer or smart phones, as long as quality data is collected and costs and services are reasonable. Currently, some companies are using traditional cellular networks. It is highly likely that they will finally switch to cellular IoT like LTE Cat-M1. This, however, may potentially increase the costs in some designs due to the higher cost of cellular IoT data plans.

Citation

Osroosh, Y., Adhikari, D., 2018. Using the Power of IoT to Improve Irrigation Water Management. Irrigation Today, April: 6-7.

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