How MQTT-SN achieves low-cost and efficient transmission of IoT

Many IoT projects fail due to unpredictable costs. One of the main factors is communication efficiency. It is necessary to communicate more efficiently and conveniently. At the same time, as the network scales, cost is also an important factor. As the number of devices increases, the overall operating cost also increases, including not only the cost of the hardware itself, but also the cost of data transmission, power supply, and data.

These factors combined create a problem that, if not addressed during the definition phase of an IoT project, can spiral out of control, leading to further increases in data volume and power consumption costs as the network grows.

Clear benefits and unclear costs

There are many benefits to digital transformation and the adoption of the Internet of Things, including greater business intelligence, process improvements, lower equipment maintenance costs, and even new ways to generate revenue. Many companies have already realized these benefits, so the trend of growth will continue. Gartner predicts that by 2020, the total installed base of IoT devices worldwide will reach 20.4 billion, and the total spending on terminals and services will reach $3.4 trillion.

While the benefits of IoT may be clear, the costs associated with deployment and subsequent operation are complex. Every device deployed carries with it a significant amount of costs, some of which, like the cost of the hardware itself, are relatively predictable, but when it comes to operational costs, seemingly minor factors like the amount of data transferred and the power used can become major issues when scaling to hundreds or even thousands of devices.

The increasing complexity and fragmentation of the IoT ecosystem further exacerbates the above problems. Regardless of the application, there are many different ways to collect data from devices and push instructions to them, each of which brings different challenges and different costs.

Cost-effective expansion using MQTT-SN

One of the biggest costs facing large-scale IoT is the cost of the data transmission itself. With thousands of devices and millions of messages per year, the cost of each communication needs to be small. This is also related to the amount of power used to communicate the data. For these reasons, data must be transmitted as little as possible and only sent when needed.

By reducing the amount of data transmitted, the cost per device and subsequently the total cost of operation can be reduced. This can be addressed in part by processing data at the edge of the network and transmitting data only when it is needed; however, the amount of data that needs to be sent can still be an issue, especially where long-range wireless networks are involved.

Another way to solve the data problem is to choose a messaging standard that inherently generates small messages. There are various messaging protocols available for IoT, and their suitability varies depending on the application.

For example, popular IoT protocols such as DDS (Data Distribution Service) and XMPP (Extensible Messaging and Presence Protocol) may be useful for sending large amounts of data where processing power and data are abundant, but they are not suitable for use in large-scale deployments due to the large message volumes and heavy processing.

Introduction to MQTT

MQTT is a lightweight machine-to-machine (M2M) messaging protocol that is well suited for large networks, especially when network bandwidth is limited, due to its small code footprint and small message size. MQTT can also help reduce the layers of technology and integration. It does this by eliminating the need to convert data between different components and the need to use third-party middleware for communication between devices and IoT platforms.

MQTT works on a publish and subscribe basis, which means that instead of devices and applications communicating directly with each other on the network, they publish to a topic, and then any device that subscribes to that topic will receive the published message. The system can easily implement one-to-many or many-to-one messaging. MQTT also has built-in QoS (Quality of Service) to ensure that important messages always reach where they are needed, enhancing network reliability.

Advantages of MQTT-SN

MQTT-SN is a variant of MQTT, designed specifically for wireless sensor networks with scale in mind. MQTT based on TCP is still too heavy for some sensors, which may only have a few dozen bytes of memory and cannot run the TCP protocol. MQTT-SN optimizes MQTT appropriately for memory-constrained microprocessors so that it can run on such processors. The standard further improves the efficiency of data transmission and power consumption. The increased efficiency includes shortened topic IDs, which reduce the size of topic IDs by converting them from strings to two-byte aliases, thereby reducing message sizes.

The smaller topic IDs can be achieved through the addition of a "register" function that allows a client to register an alias with the gateway for forwarding messages. In addition to this, the shorter topic IDs can be programmed into devices and gateways to ensure that both entities already know the ID without the need for registration, reducing the need for additional control messages.

MQTT-SN also has a keep-alive process that allows devices to go to sleep when not needed and receive any information waiting for them when they wake up.

u-blox’s MQTT Anywhere uses MQTT-SN to keep IoT communication and connectivity costs low.