Internet of Things Protocols
With the continuous increase of the number of IoT devices, the communication or connection between these devices has become an important thinking topic. 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, communication protocol is particularly important, which is the rule and agreement that both entities must follow to complete communication or service.
This paper introduces several available Internet of Things communication protocols, which have different performance, data rate, coverage, power and memory, and each protocol has its own advantages and more or less disadvantages. Some of these communication protocols are only suitable for small household appliances, while others can be used for large smart city projects. IoT communication protocols are divided into two categories:
One is access protocol, which is generally responsible for networking and communication between devices in the subnet
One is the communication protocol: mainly the device communication protocol running on the traditional Internet TCP/IP protocol, which is responsible for the data exchange and communication of devices through the Internet.
one
Physical layer and data link layer protocols
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 Internet of Everything. The NB IoT is built on the cellular network and consumes only about 180kHz bandwidth. It can be directly deployed on the GSM network, UMTS network or LTE network to reduce deployment costs and achieve smooth upgrading. NB IoT, focusing on the Low Power Wide Coverage (LPWA) Internet of Things (IoT) market, 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 scenario: The scenario applications brought by NB IoT network include intelligent parking, intelligent fire protection, intelligent water affairs, intelligent street lamps, shared bicycles, intelligent appliances, etc.
（3）5G
The fifth generation mobile communication technology is the latest generation of cellular mobile communication technology. The performance goal of 5G is to achieve high data rate, reduce latency, save energy, reduce cost, improve system capacity and connect large-scale equipment.
Application scenarios: AR/VR, Internet of Vehicles, intelligent manufacturing, smart energy, wireless medical, wireless home entertainment, networked UAV, ultra-high definition/panoramic live broadcast, personal AI assistance, and smart city.
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 home. The biggest advantage of WiFi protocol is that it can directly access the Internet. Compared with ZigBee, the smart home solution using Wifi protocol eliminates the need for additional gateways and the need for mobile terminals such as mobile phones compared with Bluetooth protocol.
The coverage of commercial WiFi in urban public transport, shopping malls and other public places shows the potential of commercial WiFi scene applications.
（2）ZigBee
ZigBee is a low speed short distance wireless communication protocol and a highly reliable wireless data transmission network. Its main features are low speed, low power consumption, low cost, support for a large number of network nodes, support for multiple network topologies, low complexity, fast, reliable and safe. ZigBee technology is a new type of technology. It has recently emerged, mainly relying on wireless networks for transmission. It can connect wirelessly in a short distance and belongs to wireless network communication technology.
ZigBee technology has become a mainstream technology in the Internet of Things industry due to its inherent advantages, and has been widely used in industry, agriculture, smart home and other fields.
（3）LoRa
LoRa ™ (LongRange) is a modulation technology that provides a longer communication distance than similar technologies. LoRa gateway, smoke detector, water monitoring, infrared detection, positioning, row and plug and other products are widely used in the Internet of Things. As a narrowband wireless technology, LoRa uses time difference of arrival to achieve geographical positioning. Application scenarios of LoRa positioning: smart city and traffic monitoring, metering and logistics, and agricultural positioning monitoring.
3. Short range communication
（1）RFID
Radio Frequency Identification (RFID) is an abbreviation for Radio Frequency Identification. Its principle is non-contact data communication between readers and tags to achieve the goal of identification. RFID is widely used, including animal chips, car chip anti-theft devices, access control, parking lot control, production line automation, and material management. The complete RFID system consists of three parts: Reader, Tag and data management system.
（2）NFC
The full Chinese 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 provides a very safe and fast communication mode for various electronic products that are increasingly popular in our daily life. The "near field" in the Chinese name of NFC refers to the radio wave near the electromagnetic field.
Application scenario: It is used in the fields of access control, attendance, visitors, meeting sign in, patrol, etc. NFC has human-computer interaction, machine interaction and other functions.
（3）Bluetooth
Bluetooth technology is an open global specification for wireless data and voice communication. It is a special short-range wireless technology connection based on low-cost short-range wireless connection to establish communication environment for fixed and mobile devices.
Bluetooth can exchange wireless information among many devices, including mobile phones, PDAs, wireless headsets, laptops, and related peripherals. The use of "Bluetooth" technology can effectively simplify the communication between mobile communication terminal devices, and also can successfully simplify the communication between devices and the Internet, so that data transmission becomes more rapid and efficient, and broaden the road for wireless communication.
4. Wired communication
（1）USB
USB, the abbreviation of Universal Serial Bus, 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
Serial communication protocol refers to the specification that specifies the content of the data packet, including the start bit, main data, check bit and stop bit. Both parties need to agree on a consistent packet format in order to send and receive data normally. In serial communication, the commonly used protocols include RS-232, RS-422 and RS-485.
Serial communication refers to a communication mode in which data is transmitted bit by bit through data lines between peripherals and computers. This communication mode uses fewer data lines, which can save communication cost in long-distance communication, but its transmission speed is lower than that of parallel transmission. Most computers (excluding laptops) include two RS-232 serial ports. Serial communication is also a common communication protocol for instruments and equipment.
(3) Ethernet
Ethernet is a computer LAN technology. The IEEE 802.3 standard organized by IEEE establishes the technical standard of Ethernet, which specifies the connection of physical layer, electronic signal and media access layer protocol.
（4）MBus
MBus remote meter reading system (synchronous MBus) is a 2-wire two bus of European standard, which is mainly used to consume measuring instruments such as heat meter and water meter series.
two
Network layer, transmission protocol
1、IPv 4
The fourth version of the Internet Communication Protocol is the fourth revised version in the development process of the Internet Protocol and the first widely deployed version of the protocol. IPv4 is the core of the Internet and the most widely used version of the Internet protocol
2、IPv6
Internet Protocol Version 6, because the biggest problem of 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 obstacle of multiple access devices connecting to the Internet
3、TCP
Transmission Control Protocol (TCP) is a connection oriented, reliable and byte stream based transport layer communication protocol. TCP is designed to adapt to the hierarchical protocol hierarchy supporting multi network applications. Paired processes in host computers connected to different but interconnected computer communication networks rely on TCP to provide reliable communication services. TCP assumes that it can obtain simple, 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 a telemetry transmission protocol. It mainly provides two message modes of subscription/release, which are simpler, lighter, and easier to use. It is particularly suitable for message distribution in restricted environments (low bandwidth, high network latency, and unstable network communication). It is a standard transmission protocol of the Internet of Things.
In many cases, including limited environments, such as machine to machine (M2M) communications and the Internet of Things (IoT). It has been widely used in communication sensors via satellite links, medical devices that occasionally dial, smart homes, and some miniaturized devices.
2. CoAP Agreement
CoAP (Constrained Application Protocol) is a kind of Web like protocol in the Internet of Things world, which is applicable to small low-power sensors, switches, valves and similar components that need to be remotely controlled or monitored through standard Internet networks. 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 information on the network. A picture and a song are all resources. RESTful API is an implementation based on HTTP protocol. (HTTP is an application layer protocol, characterized by simplicity and speed.).
Applications or designs that meet the Rest specification are RESTful. APIs designed according to the Rest specification are called RESTful APIs
4. DDS protocol
DDS (Data Distribution Service) distributed real-time data distribution service middleware protocol, which is the "TCP/IP" in the distributed real-time network, is used to solve the network protocol interconnection in the real-time network, and its role is equivalent to the "bus on the bus".
5. AMQP protocol
AMQP, namely Advanced Message Queuing Protocol, is an application layer standard advanced message queue protocol that provides unified message services. It is an open standard of application layer protocols and is designed for message oriented middleware. The client and message oriented middleware based on this protocol can transfer messages, and are not limited by different products and development languages of the client/middleware. The implementation in Erlang includes RabbitMQ, etc.
6. XMPP protocol
XMPP is a subset XML protocol based on standard general markup language, which inherits the flexible development in XML environment. Therefore, the application based on XMPP has strong scalability. The extended XMPP can handle the needs of users by sending extended information, and establish applications such as content publishing systems and address based services at the top of XMPP.
four
Comparison of some communication protocols
1. Comparison between NB IoT protocol and LoRa protocol
First, frequency band. LoRa works in the unlicensed frequency band below 1GHz, and there is no need to pay extra for application. NB IoT and cellular communication use the frequency band below 1GHz, which is 2113 licensed, and there is a charge.
Second, battery life. LoRa module has unique characteristics in handling interference, network 5261 overlap, scalability, etc., but it cannot provide the same quality of service as cellular protocol 4102. NB IoT cannot provide the same battery life as LoRa due to the consideration of service quality.
Third, equipment cost. For the terminal node, LoRa protocol is simpler and easier to develop than NB IoT, and 1653 has better applicability and compatibility for microprocessors. At the same time, LoRa modules with low cost and relatively mature technology can already be found in the market, and upgrading versions will come out one after another.
Fourth, network coverage and deployment schedule. The NB IoT standard was released in 2016. In addition to the network deployment, the corresponding commercialization and the establishment of the industrial chain still need more time and effort to explore. The whole industrial chain of LoRa is relatively mature, and its products are in a state of "readiness". At the same time, many countries around the world are conducting or have completed national 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; ZigBee's advantages are low power consumption and ad hoc network; The advantage of UWB carrier free wireless communication technology is the transmission rate; The advantages of Bluetooth are 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, high cost and so on. In particular, the biggest obstacle of Bluetooth is its limited transmission range, which is generally about 10 meters. The weak anti-interference ability and information security problems are also the main factors restricting its further development and large-scale application.
WiFi is also a short-range wireless transmission technology, which can access wireless signals at any time. With strong mobility, it is more suitable for use in office and home environments. Of course, WiFi also has a fatal disadvantage. Because WiFi uses radio frequency technology to send and receive data through air and transmit data signals using radio waves, it is relatively vulnerable to external interference.
ZigBee is an internationally accepted wireless communication technology. Each of its network ports can access more than 65000 ports at most, which is suitable for home, industry, agriculture and other fields. Bluetooth and WiFi network terminals can only access 10 ports, which obviously cannot meet the needs of families. ZigBee also has the advantages of low power consumption and low cost.
3. Comparison between MQTT protocol and CoAP protocol
MQTT is used for many to many communication protocol
