1. IoT communication protocols are divided into two categories
1. Access protocol: generally responsible for networking and communication between devices in the subnet
2. Communication protocol: It is mainly a device communication protocol running on the traditional Internet TCP/IP protocol, which is responsible for data exchange and communication of devices through the Internet.
2. Physical layer, data link layer protocol
1. Long-distance cellular communication
(1) 2G/3G/4G communication protocols refer to the second, third and fourth generation mobile communication system protocols respectively.
(2)NB-IoT
Narrow Band Internet of Things (NB-IoT) has become an important branch of the Internet of Everything. NB-IoT is built on a cellular network and only consumes about 180kHz of bandwidth. It can be directly deployed on a GSM network, UMTS network or LTE network to reduce deployment costs and achieve smooth upgrades. NB-IoT focuses on the Low Power Wide Coverage (LPWA) Internet of Things (IoT) market and is an emerging technology that can be widely used worldwide. It has the characteristics of wide coverage, multiple connections, fast speed, low cost, low power consumption, and excellent architecture.
Application scenarios: The scenario applications brought by NB-IoT networks include smart parking, smart fire protection, smart water, smart street lights, shared bicycles, and smart home appliances.
(3)5G
The fifth generation mobile communication technology is the latest generation of cellular mobile communication technology. The performance goals of 5G are high data rates, reduced latency, energy savings, cost reductions, increased system capacity, and large-scale device connectivity.
Application scenarios: AR/VR, Internet of Vehicles, smart manufacturing, smart energy, wireless medical care, wireless home entertainment, networked drones, ultra-high-definition/panoramic live broadcast, personal AI assistance, and smart cities.
2. Long-distance non- cellular communication
(1)WiFi
Due to the rapid popularization of home WiFi routers and smart phones in the past few years, WiFi protocols have also been widely used in the field of smart homes. The biggest advantage of the WiFi protocol is that it can be directly connected to the Internet. Compared with ZigBee, the smart home solution using the Wifi protocol eliminates an additional gateway, and compared with the Bluetooth protocol, it eliminates the dependence on mobile terminals such as mobile phones.
The coverage of commercial WiFi in public places such as urban public transportation and shopping malls reveals the application potential of commercial WiFi in scenarios.
(2)ZigBee
ZigBee is a wireless communication protocol for low-speed short-distance transmission. It is a highly reliable wireless data transmission network. Its main features are low speed, low power consumption, low cost, supporting a large number of online nodes, supporting multiple online topologies, and low complexity. , fast, reliable and safe. ZigBee technology is a new type of technology, it appears recently, mainly rely on wireless network for transmission, it can carry out wireless connection at close range, it belongs to wireless network communication technology.
The inherent advantages of ZigBee technology make it gradually become a mainstream technology in the Internet of Things industry, and it has been widely used in industry, agriculture, smart home and other fields.
(3)LoRa
LoRa™ (LongRange, Long Range) is a modulation technology that provides a longer communication distance than similar technologies. IoT products are widely used in LoRa gateways, smoke detectors, water monitoring, infrared detection, positioning, and power strips. As a narrowband wireless technology, LoRa uses time difference of arrival for geolocation. Application scenarios of LoRa positioning: smart city and traffic monitoring, metering and logistics, agricultural positioning monitoring.
3. Short distance communication
(1)RFID
Radio Frequency Identification (RFID) is the abbreviation of Radio Frequency Identification. The principle is to conduct non-contact data communication between the reader and the tag to achieve the purpose of identifying the target. RFID has a wide range of applications, typical applications include animal chips, car chip anti-theft devices, access control, parking lot control, production line automation, and material management. A complete RFID system consists of three parts: Reader, Tag and data management system.
(2)NFC
The full name of NFC in Chinese is Near Field Communication Technology. NFC is developed on the basis of non-contact radio frequency identification (RFID) technology combined with wireless interconnection technology. It provides a very safe and fast communication method for various electronic products that are becoming more and more popular in our daily life. The "near field" in the Chinese name of NFC refers to radio waves that are close to the electromagnetic field.
Application Scenarios: Applied in access control, attendance, visitors, meeting sign-in, patrolling and other fields. NFC has functions such as human-computer interaction and machine-to-machine interaction.
(3)Bluetooth
Bluetooth technology is an open global specification for wireless data and voice communication. It is based on a low-cost short-range wireless connection and a special short-range wireless technology connection for establishing a communication environment for fixed and mobile devices.
Bluetooth enables wireless information exchange between many devices including mobile phones, PDAs, wireless headsets, notebook computers, and related peripherals. The use of "Bluetooth" technology can effectively simplify the communication between mobile communication terminal equipment, and can also successfully simplify the communication between equipment and the Internet, so that data transmission becomes faster and more efficient, and broadens the road for wireless communication.
4. Wired communication
(1)USB
USB, the abbreviation of Universal Serial Bus (Universal Serial Bus) in English, is an external bus standard used to regulate the connection and communication between computers and external devices. It is an interface technology applied in the PC field.
(2) Serial communication protocol
The serial port communication protocol refers to the relevant specifications that stipulate the content of the data packet, which includes the start bit, main data, check bit and stop bit. The two parties need to agree on a consistent data packet format to send and receive data normally. In serial communication, commonly used protocols include RS-232, RS-422 and RS-485.
Serial port communication refers to a communication method that transmits data bit by bit through the data line between the peripheral device and the computer. This communication method uses fewer data lines, which can save communication costs in long-distance communication, but its transmission speed is lower than parallel transmission. Most computers (not including notebooks) include two RS-232 serial ports. Serial communication is also a commonly used communication protocol for instrumentation equipment.
(3) Ethernet
Ethernet is a computer local area network technology. The IEEE 802.3 standard of the IEEE organization has established the technical standard of Ethernet, which stipulates the content of the connection, electronic signal and medium access layer protocol including the physical layer.
(4)MBus
MBus remote meter reading system (symphonic mbus), is a European standard 2-wire bus, mainly used for consumption measuring instruments such as heat meters and water meters.
3. Network layer, transport protocol
1、IPv 4
Internet Communications Protocol Version 4 is the fourth revision in the development of the Internet Protocol and the first widely deployed version of the protocol. IPv4 is the heart of the Internet and the most widely used version of the Internet Protocol
2、IPv6
Internet protocol version 6, because the biggest problem with IPv4 is the limited network address resources, which seriously restricts the application and development of the Internet. The use of IPv6 can not only solve the problem of the number of network address resources, but also solve the obstacles of connecting various access devices to the Internet
3、TCP
Transmission Control Protocol (TCP, Transmission Control Protocol) is a connection-oriented, reliable, byte stream-based transport layer communication protocol. TCP was designed to accommodate a layered protocol hierarchy supporting multiple network applications. TCP is used to provide reliable communication services between pairs of processes in host computers connected to different but interconnected computer communication networks. TCP assumes that it can obtain simple, possibly unreliable, datagram service from lower-level protocols.
4、LoRa
LoRa is a low power local area network wireless standard. Its biggest feature is that it can transmit farther than other wireless methods under the same power consumption conditions, realizing the unity of low power consumption and long distance. It expands the distance of traditional wireless radio frequency communication by 3-5 at the same power consumption times.
5 、LoRaWAN
The LoRaWAN protocol is a Low Power Wide Area Network (LPWAN) communication protocol running on LORA. The LoRaWAN specification is open, so anyone can set up and operate a LoRa network.
6、6LoWPAN
6LoWPAN is a low-speed wireless personal area network standard based on IPv6, that is, IPv6 over IEEE 802.15.4. 6LoWPAN allows only smaller devices with very limited processing power to establish communication using one of the Internet protocols, IPv6. It features low cost, short range, low memory usage, and low bitrate.
4. Application Layer Protocol
1. MQTT protocol
MQTT (Message Queue Telemetry Transport), translated into Chinese, is a telemetry transmission protocol, which mainly provides two message modes of subscription/publishing, which is more simple, lightweight, and easy to use, especially suitable for restricted environments (low bandwidth, network High latency, unstable network communication) message distribution, which belongs to a standard transmission protocol of the Internet of Things (Internet of Things).
In many cases, including constrained environments such as machine-to-machine (M2M) communication and the Internet of Things (IoT). It is used extensively in sensors communicating via satellite links, medical devices that occasionally dial, smart homes, and some miniaturized devices.
2. MQTT-SN protocol
The MQTT-SN (MQTT for Sensor Network) protocol is the sensor version of the MQTT protocol. Although the MQTT protocol is a lightweight application layer protocol, the MQTT protocol runs on top of the TCP protocol stack. The TCP protocol is not suitable for some devices with very limited computing power and power, such as sensors. MQTT-SN runs on the UDP protocol, while retaining most of the signaling and features of the MQTT protocol, such as subscription and publishing.
3. CoAP protocol
CoAP (Constrained Application Protocol) is a Web-like protocol in the Internet of Things world, suitable for small low-power sensors, switches, valves and similar components that need to be remotely controlled or monitored over a standard Internet network, and the server does not support the type Can not respond.
4. REST/HTTP protocol
RESTful is a resource-based software architectural style. The so-called resource is an entity on the network, or a specific piece of information on the network. A picture, a song is a resource. RESTful API is an implementation based on the HTTP protocol. (HTTP is an application layer protocol, characterized by simplicity and speed). An application or design that meets the Rest specification is RESTful, and an API designed according to the Rest specification is called a RESTful API. HTTP is based on the client/server model and is connection-oriented (built on top of TCP).
5. DDS protocol
DDS (Data Distribution Service) distributed real-time data distribution service middleware protocol, it is "TCP/IP" in the distributed real-time network, used to solve the network protocol interconnection in the real-time network, its role is equivalent to "bus on the bus ".
6. AMQP protocol
AMQP, or Advanced Message Queuing Protocol, is an application layer standard advanced message queuing protocol that provides unified messaging services. It is an open standard for application layer protocols and is designed for message-oriented middleware. The client and message middleware based on this protocol can transmit messages, and it is not limited by different client/middleware products, different development languages and other conditions. Implementations in Erlang include RabbitMQ, etc.
7. XMPP protocol
XMPP is a protocol based on XML, a subset of the standard general-purpose markup language, which inherits the flexible development in the XML environment. Therefore, XMPP-based applications have super scalability. The extended XMPP can deal with users' needs by sending extended information, and build applications such as content publishing systems and address-based services on top of XMPP.
8. LwM2M protocol
The LwM2M (Lightweight Machine-To-Machine) protocol is a set of lightweight protocols for the Internet of Things defined by the Open Mobile Alliance (OMA). It uses a RESTful interface to provide device access, management and communication functions, and is also suitable for devices with relatively tight resources. The architecture of the LwM2M protocol is shown in Figure 2-4. The underlying layer of the LwM2M protocol uses the CoAP protocol to transmit data and signaling. In the architecture of the LwM2M protocol, the CoAP protocol can run on UDP or SMS (short message), and implement secure data transmission through DTLS (Datagram Transport Layer Security).
5. Comparison of some communication protocols
1. Comparison between NB-IoT protocol and LoRa protocol
First, the frequency band. LoRa works in the unlicensed frequency band below 1GHz, and there is no need to pay extra for the application. The frequency band below 1GHz used by NB-IoT and cellular communication is authorized by 2113, which requires a fee.
Second, battery life. LoRa modules have unique characteristics in handling interference, network overlap, scalability, etc., but they cannot provide the same quality of service as cellular protocols. Due to the consideration of service quality, NB-IoT cannot provide the same battery life as LoRa.
Third, equipment costs. For terminal nodes, the LoRa protocol is simpler and easier to develop than NB-IoT, and it is more applicable and compatible with microprocessors. At the same time, LoRa modules with low cost and relatively mature technology can already be found in the market, and there will be upgraded versions coming out one after another.
Fourth, network coverage and deployment schedule. The NB-IoT standard was announced in 2016. In addition to network deployment, the corresponding commercialization and establishment of the industrial chain still need more time and effort to explore. The entire industrial chain of LoRa is relatively mature, and the products are also in a state of "ready to be released". At the same time, many countries around the world are conducting or have completed nationwide network deployment.
2. Comparison of Bluetooth, WiFi, and ZigBee protocols
At present, the advantage of WiFi is that it is widely used and has been popularized to thousands of households; the advantage of ZigBee is low power consumption and self-organizing network; the advantage of UWB carrier-free wireless communication technology is the transmission rate; the advantage of Bluetooth is simple networking. However, these three technologies also have their own shortcomings, and none of them can fully meet all the requirements of smart home.
The emergence of Bluetooth technology makes short-distance wireless communication possible, but its protocol is more complex, high power consumption, and high cost are not suitable for industrial control and home networks that require low cost and low power consumption. In particular, the biggest obstacle of Bluetooth is the limited transmission range, the general effective range is about 10 meters, weak anti-interference ability, information security issues and other issues are also the main factors restricting its further development and large-scale application.
WiFi is also a short-distance wireless transmission technology, which can access wireless signals at any time, has strong mobility, and is more suitable for applications in office and home environments. Of course, WiFi also has a fatal flaw. Since WiFi uses radio frequency technology, it sends and receives data through the air, and uses radio waves to transmit data signals, which is relatively susceptible to external interference.
ZigBee is an internationally accepted wireless communication technology. Each of its network ports can access more than 65,000 ports at most, which is suitable for use in many fields such as home, industry, and agriculture, while Bluetooth and WiFi network terminals can only access 10 ports. port, obviously can not meet family needs. ZigBee also has the advantages of low power consumption and low cost.
3. Comparison of MQTT protocol and CoAP protocol
MQTT is a many-to-many communication protocol used to transmit messages between different clients through an intermediate agent, decouple producers and consumers, and let the agent decide the route and copy the message by making the client publish. Although MQTT supports some persistence, it is best used as a real-time data communication bus.
CoAP is primarily a point-to-point protocol for transferring state information between a client and a server. While supporting observation resources, CoAP is best suited to a stateful transfer model, not entirely event-based.
The MQTT client establishes a long-lived TCP connection, which usually indicates no problem. Both the CoAP client and server send and receive UDP packets. In a NAT environment, tunneling or port forwarding can be used to allow CoAP, or like LWM2M, the device may first Initialize the frontend connection.
MQTT does not provide support for message type tags or other metadata to help clients understand. MQTT messages can be used for any purpose, but all clients must know the format of the data upwards to allow communication. CoAP, in contrast, provides built-in support for content negotiation and Discovery, which allows devices to probe each other to find ways to exchange data.
6. Comparison of various networking technologies
At present, mainstream networking technologies can be compared in terms of transmission distance, scale, power consumption, and cost, as shown in the figure below, and you can choose a suitable networking method according to your own project application scenarios.
