Summary
As the number of Internet of Things devices continues to increase, the communication or connection between these devices has become an important subject for consideration.
Communication is very common and critical to the Internet of Things. Whether it is short-range wireless transmission technology or mobile communication technology, it affects the development of the Internet of Things.
In communication, the communication protocol is especially important, and it is the rules and conventions that the two entities must follow to complete the communication or service.
Application scenarios of IoT communication protocol
This article introduces several available IoT communication protocols, which have different performance, data rate, coverage, power and memory, and each protocol has
Have their own advantages and more or less disadvantages. Some of these communication protocols are only suitable for small household appliances, while others can be used in large-scale smart cities.
City project.
IoT communication protocols are divided into two categories:
-
One type is access protocol: generally responsible for networking and communication between devices in the subnet
-
One is the communication protocol: it is mainly the device communication protocol running on the traditional Internet TCP/IP protocol, which is responsible for the data exchange and communication of the device through the Internet.
One, physical layer, data link layer protocol
1. Long-distance cellular communication
(1) 2G/3G/4G communication protocol
Refers 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 consumes only 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 : Scenario applications brought by the NB-IoT network include smart parking, smart fire protection, smart water services, 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 reduction, increased system capacity and large-scale device connections.
Application scenarios : AR/VR, car networking, smart manufacturing, smart energy, wireless medical care, wireless home entertainment, networked drones, ultra-high-definition/panoramic live broadcast, personal AI assistance, smart cities.
2. Long-distance non-cellular communication
（1）WiFi
Due to the rapid popularity 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 directly access the Internet. **Compared to ZigBee, the smart home solution using Wifi protocol eliminates the need for additional gateways.
The Bluetooth protocol 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 will undoubtedly reveal the application potential of commercial WiFi.
（2）ZigBee
ZigBee is a low-speed and short-distance wireless communication protocol, and a highly reliable wireless data transmission network.
The main features are low speed, low power consumption, low cost, support for a large number of online nodes, support for multiple online topologies, low complexity, fast, reliable, and safe.
ZigBee technology is a new type of technology. It has appeared recently. It mainly relies on wireless network for transmission. It can connect wirelessly at short distances. It belongs to wireless
Network communication technology.
The innate advantages of ZigBee technology have made 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.
Applications.
（3）LoRa
LoRa™ (LongRange, long distance) is a modulation technology that provides a longer communication distance compared with similar technologies.
LoRa gateways, smoke detectors, water monitoring, infrared detection, positioning, power strips and other widely used IoT products.
As a narrowband wireless technology, LoRa uses the time difference of arrival to achieve geographic positioning.
LoRa positioning application scenarios : smart city and traffic monitoring, metering and logistics, agricultural positioning monitoring.
3. Near field communication
（1）RFID
Radio Frequency Identification (RFID) is the abbreviation of Radio Frequency Identification.
The principle is 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 application scenarios : animal chip, car chip anti-theft device, access control, parking lot control, production line automation, material management
Rationale.
The complete RFID system consists of three parts: Reader, Tag and data management system.
（2）NFC
The Chinese full name of NFC 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 is an increasingly popular variety in our daily lives.
Electronic products provide a very safe and fast communication method. The "near field" in the Chinese name of NFC refers to radio waves near the electromagnetic field.
Application scenarios : Used in access control, attendance, visitors, conference sign-in, patrol 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 low-cost short-range wireless connections to establish communication for fixed and mobile devices
A special short-range wireless technology connection for the environment.
Bluetooth can exchange information wirelessly among many devices including mobile phones, PDAs, wireless headsets, notebook computers, and related peripherals.
Using "Bluetooth" technology can effectively simplify the communication between mobile communication terminal devices, and also successfully simplify the communication between the device and the Internet.
As a result, data transmission becomes more rapid and efficient, which broadens the way for wireless communication.
4. Wired communication
（1）USB
USB, which is the abbreviation of English Universal Serial Bus (Universal Serial Bus), is an external bus standard used to regulate the connection and
communication. It is an interface technology applied in the PC field.
(2) Serial communication protocol
The serial communication protocol is to specify the content of the data packet, which includes the start bit, body data, check bit and stop bit. Both parties need to agree on a consistent data packet
The format can normally send and receive data. In serial communication, commonly used protocols include RS-232, RS-422 and RS-485.
Serial communication refers to a communication method in which data is transmitted bit by bit between peripherals and computers.
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) contain two RS-232 serial ports. Notebooks usually use USB-serial modules for serial communication, which is also instrumental equipment.
Prepare commonly used communication protocols.
(3) Ethernet
Ethernet is a computer local area network technology.
The IEEE 802.3 standard organized by the IEEE establishes the technical standard for Ethernet, which specifies the content of the physical layer connection, electronic signal and media access layer protocol.
（4）MBus
MBus remote meter reading system (symphonic mbus) is a European standard 2-wire two bus, mainly used for consumption measuring instruments such as heat meters and water meters.
2. Network layer and transmission protocol
1 、 IPv 4
The fourth edition of the Internet Communication Protocol is the fourth revision in the development of the Internet Protocol and the first widely deployed version of this protocol. IPv4 is interconnection
The core of the Internet and the most widely used version of the Internet Protocol
2、IPv6
In the sixth version of the Internet Protocol, the biggest problem with IPv4 is the limited network address resources, which severely restricts the application and development of the Internet.
The use of IPv6 not only solves the problem of the number of network address resources, but also solves the barriers for multiple access devices to connect to the Internet
3、TCP
Transmission Control Protocol (TCP) is a connection-oriented, reliable, byte stream-based transport layer communication protocol.
TCP is designed to adapt to the layered protocol hierarchy that supports multiple network applications. Between a pair of processes in a host computer connected to a different but interconnected computer communication network
Rely on TCP to provide reliable communication services. TCP assumes that it can obtain simple and possibly unreliable datagram services from lower-level protocols.
4、6LoWPAN
6LoWPAN is a low-speed wireless personal area network standard based on IPv6, namely IPv6 over IEEE 802.15.4.
Three, application layer protocol
1. MQTT protocol
MQTT (Message Queue Telemetry Transport), translated into Chinese, is the telemetry transmission protocol. It mainly provides two message modes: subscription/publishing. It is simpler, lighter, and easy to use. It is especially suitable for restricted environments (low bandwidth, network The distribution of messages with high latency and unstable network communication is a standard transmission protocol of the Internet of Thing.
In many cases, including restricted environments, such as machine-to-machine (M2M) communication and the Internet of Things (IoT). It is, through the satellite link communication sensor
It has been widely used in medical devices, smart home appliances, and some miniaturized devices.
2. CoAP protocol
CoAP (Constrained Application Protocol) is a web-like protocol in the world of Internet of Things. It is suitable for remote
Small low-power sensors, switches, valves and similar components for remote control or monitoring, the server may not respond to unsupported types.
**
**
3. REST/HTTP protocol
RESTful is a resource-based software architecture style. The so-called resource is an entity on the network, or a specific piece of information on the network.
A picture and a song are 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.
4. DDS protocol
DDS (Data Distribution Service) distributed real-time data distribution service middleware protocol, it is the "TCP/IP" in the distributed real-time network, used to
solve the network protocol interconnection in the real-time network, and its function is equivalent to "the bus on the bus ".
5. 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.
Clients and message middleware based on this protocol can transmit messages without being restricted by different client/middleware products, different development languages and other conditions.
Implementations in Erlang include RabbitMQ and so on.
6. XMPP protocol
XMPP is a protocol based on XML, a subset of the standard general-purpose markup language, which inherits the flexibility of development in the XML environment. Therefore, XMPP-based
The application has super scalability. After expansion, XMPP can handle user needs by sending expanded information, and build on top of XMPP.
Establish applications such as content publishing systems and address-based services.
4. Comparison of some communication protocols
1. Comparison of NB-IoT protocol and LoRa protocol
First, the frequency band. LoRa works in unlicensed frequency bands below 1GHz, and there is no additional charge for application. NB-IoT and cellular communications use frequencies below 1GHz.
The segment is authorized by 2113 and is charged.
Second, battery life. The LoRa module has unique characteristics in dealing with interference, network 5261 overlap, scalability, etc., but it cannot provide cellular
4102 The same service quality as the agreement. NB-IoT cannot provide the same battery life as LoRa due to the consideration of service quality.
Third, equipment cost. For terminal nodes, LoRa protocol is simpler than NB-IoT, easier to develop, and 1653 is more applicable and compatible with microprocessors.
it is good. At the same time, the low-cost, relatively mature LoRa module 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 the establishment of the industrial chain also need
Longer time and effort to explore. LoRa’s entire industrial chain is relatively mature, and the products are in a state of “ready to be released”. At the same time, there are many
The country is currently or has completed nationwide network deployment.
2. Comparison of Bluetooth, WiFi and ZigBee protocols
currently,The advantage of WiFi is that it is widely used and has spread to thousands of households; the advantage of ZigBee is low power consumption and self-organizing network; the advantage of UWB 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 homes.
(1) The emergence of Bluetooth technology makes short-distance wireless communication possible, but its characteristics such as complex protocols, high power consumption, and high cost are not suitable for low cost requirements.
This, low-power industrial control and home network. In particular, the biggest obstacle of Bluetooth is the limited transmission range. Generally, the effective range is about 10 meters.
Weakness and information security issues are also the main factors restricting its further development and large-scale application.
(2) WiFi is also a short-distance wireless transmission technology, which can access wireless signals at any time. It has strong mobility and is more suitable for applications in office and home environments.
use. Of course, WiFi also has a fatal flaw. Because WiFi uses radio frequency technology, it sends and receives data through the air, and uses radio waves to transmit data information.
Number, it is more susceptible to external interference.
(3) ZigBee is an internationally accepted wireless communication technology, each of its network ports can be connected to more than 65,000 ports at most, suitable for household, industry, agriculture, etc.
It is used in many fields, but Bluetooth and WiFi network terminals can only access 10 ports, which obviously cannot meet the needs of families. ZigBee also has low power consumption and low cost advantages.
3. Comparison of MQTT protocol and CoAP protocol
(1). MQTT is a many-to-many communication protocol used to transfer messages between different clients through an intermediate agent, decoupling producers and consumers, by making the client
Publish, let the agent decide to route and copy the message. Although MQTT supports some persistence, it is best used as a real-time data communication bus.
(2) CoAP is mainly a point-to-point protocol used to transfer status information between the client and the server. Although it supports observation resources, CoAP is best suited for status
The state transmission model is not entirely based on events.
(3) The MQTT client establishes a long TCP connection, which usually means that there is no problem. Both the CoAP client and the server send and receive UDP packets. In the NAT ring
In the environment, tunnel or port forwarding can be used to allow CoAP, or like LWM2M, the device may first initialize the front-end connection.
(4) MQTT does not provide support for message type marking or other metadata to help clients understand. MQTT messages can be used for any purpose, but all customers
The end must know the upstream data format to allow communication, CoAP, on the contrary, provide built-in support for content negotiation and discovery, allowing devices to detect each other to find communication
The way to change data.
Both protocols have their own advantages and disadvantages, and choosing the right one depends on your application.