Communication modules are fundamental to IoT application terminals. IoT terminals come in a wide variety of types, differing in size, processing power, and external interfaces. Communication modules serve as the unified carrier of IoT intelligent service channels, embedded in various industry terminals to provide intelligent channel services for all sectors. In communication, communication protocols are particularly important; they refer to the rules and agreements that must be followed by both parties to complete communication or services. Moreover, the requirements for communication protocols vary significantly depending on the terminal environment.
Unlike the internet era, where TCP/IP and HTTP dominated, the Internet of Things (IoT) communication environment includes networks such as Ethernet, Wi-Fi, RFID, NFC (Near Field Communication), Zigbee, 6LoWPAN (IPv6 low-speed wireless version), Bluetooth, GSM, GPRS, GPS, 3G, and 4G. Each communication protocol has its own applicable scope. AMQP, JMS, and REST/HTTP all operate on Ethernet, the COAP protocol is specifically developed for resource-constrained devices, while DDS and MQTT have much stronger compatibility.
The Internet of Things (IoT) refers to connecting various sensors, devices, and other components via the internet to form a vast network, enabling interconnectivity between things. In achieving this, various communication protocols are widely used. This article will introduce common communication protocols in the Internet of Things.
I. MQTT
MQTT (Message Queuing Telemetry Transport) is a common protocol in Internet of Things (IoT) communication. It is a lightweight messaging protocol widely used for communication between devices and servers.
The MQTT protocol works similarly to a publish-subscribe model, allowing different devices or clients to exchange messages through a middleware called a "broker." Devices or clients can choose to subscribe to specific topics and receive messages from the broker. Simultaneously, devices or clients can publish messages to one or more specific topics, and the broker will forward these messages to all devices or clients subscribed to those topics.
Compared with other communication protocols, the MQTT protocol has the following advantages:
1. It is a lightweight protocol that consumes very little bandwidth and resources;
2. It has high reliability, ensuring message transmission and reception;
3. It supports asynchronous communication and offline messaging, allowing you to receive and send messages even when the device is offline.
Therefore, the MQTT protocol is one of the most commonly used protocols in IoT applications. It enables devices to communicate efficiently and provides a reliable and secure message passing mechanism for IoT applications.
II. CoAP
When discussing IoT communication protocols, CoAP (Constrained Application Protocol) is a very important one. CoAP is a resource-oriented protocol designed for use in constrained device and network environments to achieve low-power, low-bandwidth, and low-latency communication.
To better understand how CoAP works, you can think of it as a courier. CoAP packages the data (packages) we want to deliver into individual messages, and then sends these messages to their destination (recipient) via the internet (streets).
The CoAP protocol not only supports data transmission but also operations such as querying resource status and triggering events, making it well-suited for use in the Internet of Things (IoT). Furthermore, it has low overhead because it requires only a small amount of network resources to transmit data.
In summary, CoAP is a reliable and efficient IoT communication protocol that enables devices to communicate in low-power, low-bandwidth, and low-latency environments, and allows them to interact with other devices by querying resource status and triggering events.
III. HTTP
When we talk about communication protocols for the Internet of Things (IoT), HTTP (Hypertext Transfer Protocol) is a well-known protocol used to transmit hypertext documents over the internet. However, HTTP also plays an important role in the IoT.
The HTTP protocol not only supports data transmission but also operations such as requests, responses, and status codes. This makes it ideal for use in the Internet of Things (IoT). It is also highly flexible, supporting various data formats and communication methods, such as RESTful APIs and WebSockets.
However, using HTTP in the Internet of Things (IoT) also presents some challenges. For example, HTTP communication requires TCP connections, which can lead to excessive power consumption and latency. Furthermore, HTTP request and response headers incur additional overhead.
In summary, HTTP is a reliable and flexible IoT communication protocol that enables devices to communicate over the internet and supports various data formats and communication methods. However, when using HTTP, attention must be paid to issues such as power consumption and latency to ensure that devices can operate normally in low-power, low-bandwidth, and low-latency environments.
IV. LoRaWAN
LoRaWAN (Long Range Wide Area Network) is a wireless communication protocol specifically designed for Internet of Things (IoT) devices. It has the following characteristics:
1. Long distance: LoRaWAN can communicate over a range of several kilometers or even tens of kilometers.
2. Low power consumption: It uses low power technology, which allows the device to work continuously for several years.
3. Two-way communication: LoRaWAN supports two-way communication, which can receive data from the device and send commands to the device.
You've probably all heard about the recent "Huawei HarmonyOS" incident, which prompted many major companies in the industry to start recruiting for HarmonyOS-related positions. In fact, IoT and embedded technologies are crucial for HarmonyOS. Do you know what protocols and application scenarios are commonly used in IoT?
What are the main categories of protocol layering?
Physical layer protocols: NB-IoT, LoRa, Wi-Fi, Bluetooth, Zigbee, 4G. These all require chip module support (hardware support).
Application layer protocols: MQTT, COAP, HTTP. These require development of a server or integration with cloud platform vendors (software support).
What are the main characteristics of each protocol in the physical layer?
1) NB-IoT and 4G
Low power consumption: NB-IoT is a low-power wide-area (LPWA) IoT technology specifically designed for battery-powered IoT devices. It employs optimized transmission mechanisms and low-power modes, enabling battery life of up to several years. 4G, on the other hand, consumes relatively more power and is typically used for applications requiring higher data rates and connection quality.
Speed and capacity: NB-IoT has a relatively low transmission speed, making it suitable for transmitting small amounts of data, such as sensor data and simple commands. 4G, on the other hand, offers higher transmission rates and capacity, capable of handling large amounts of data, and is suitable for applications requiring the transfer of large files or real-time video transmission.
Coverage: NB-IoT has an advantage in coverage, enabling wider IoT coverage areas, both indoors and outdoors. 4G networks have wider coverage, but signal strength may be weak in some remote areas or deep indoors.
Equipment cost and deployment complexity: NB-IoT is relatively inexpensive because it is designed for low-cost deployment. Its equipment modules are cheaper and deployment is relatively simple. 4G equipment is more expensive and deployment is relatively complex.
2) WIFI and Zigbee
Coverage: Wi-Fi is typically suitable for local area network (LAN) environments, including homes, offices, and public places. Its coverage is relatively wide, capable of covering large areas. Zigbee, on the other hand, is a low-power, low-data-rate wireless protocol primarily suited for personal or small-scale applications, such as smart homes and sensor networks. Its coverage is relatively small, suitable for communication between devices in close proximity.
Low power consumption: Zigbee excels in power consumption and battery life, making it particularly suitable for battery-powered IoT devices. It employs low-power modes and sleep modes to achieve extended battery life. In contrast, Wi-Fi typically requires higher power consumption and places greater demands on battery life.
Communication speed: Wi-Fi typically boasts a high data transfer rate, suitable for transmitting large amounts of data, such as audio-visual entertainment, high-definition video, and file downloads. Zigbee, on the other hand, has a lower data transfer rate, suitable for transmitting small data packets, such as sensor data and simple commands. It prioritizes low power consumption and communication stability.
Interconnectivity and Expansion: While Wi-Fi devices can typically interconnect via routers, supporting direct communication and interoperability with other Wi-Fi devices, Zigbee employs a mesh topology, enabling devices to form self-organizing networks and supporting large-scale interconnectivity and expansion.
3) LoRa WAN protocol
LoRaWAN is a low-power wide-area network protocol proposed and promoted by the LoRa Alliance. LoRa (Long Range) is a wireless communication technology characterized by long range and low power consumption. In the scenario described above, users can use LoRaWAN technology to build a network by installing LoRa-enabled modules on engineering equipment.
The LoRa relay device sends the data to a LoRa gateway located outside the tunnel with internet access. The LoRa gateway then encapsulates the data into data protocol packets (such as MQTT protocol) that can be transmitted over an IP network via TCP or UDP protocols, and then sends them to the cloud data center.
Network layer transport protocol
TCP and UDP
TCP is a connection-oriented, reliable, byte-stream-based transport layer communication protocol, while UDP is more suitable for applications with low power consumption and low reliability requirements.
Application Layer Protocols: Comparison of MQTT and COAP
1) MQTT
MQTT (Message Queuing Telemetry Transport) is an application-layer transport protocol based on TCP, employing a publish/subscribe model. Its characteristics include lightweightness, simplicity, openness, and ease of implementation, making it suitable for a wide range of application scenarios.
MQTT is widely used in many constrained environments, including machine-to-machine (M2M) communication, the Internet of Things (IoT), satellite link communication sensors, medical devices that occasionally dial, smart homes, and some miniaturized devices. Its lightweight design enables it to operate efficiently in networks and devices with bandwidth or resource constraints.
2) CoAP
CoAP (Constrained Application Protocol) is a network transport protocol built on the REST model and designed specifically for lightweight M2M communication. Since many devices in the Internet of Things (IoT) have limited memory and computing power, the traditional HTTP protocol is unsuitable for this scenario, and CoAP was developed to address this need.
From a user visibility perspective, CoAP emulates the HTTP protocol, so reading sensor data is just like making an HTTP request.
CoAP is considered a timeless technology protocol. Gartner predicts that 50 billion devices will connect to the internet in the future, requiring low-cost, low-power devices, and CoAP is designed with these needs in mind. It is designed for systems with approximately 10KB of RAM.
One of the most interesting features of CoAP is its ability to discover nodes within a network. This is extremely useful for the autonomy and self-healing of low-power wireless sensor networks. The CoAP protocol can address the scalability issues of wireless sensor networks and discover common node redundancy.
CoAP is built on top of the UDP protocol, which is the main difference compared to HTTP or MQTT. It can be faster and better at optimizing resources, but while maintaining QoS, CoAP is less reliable than HTTP and MQTT. However, for continuous streaming systems such as environmental monitoring sensor networks, a 4-byte header is a good choice.
