What are the most common "wireless communication (data) transmission technologies" currently?

In recent years, with the development of electronic technology and computer technology, wireless communication technology has flourished, and various wireless data transmission standards have emerged. They each have their own advantages and disadvantages and different application scenarios. This article analyzes and compares the currently used types of wireless communications for your reference.

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1. Wireless communication (data) transmission method and technical principle

Wireless communication is a communication method that uses the characteristics of electromagnetic wave signals propagating in free space to exchange information. Wireless communication technology has many advantages. It is low-cost and does not require the establishment of physical lines, let alone a large number of manpower to lay cables. Moreover, wireless communication technology is not restricted by industrial environments, has a strong ability to resist environmental changes, and is easier to diagnose faults. Compared with the setting and maintenance of traditional wired communications, wireless network maintenance can be completed through remote diagnosis, which is more convenient; it has strong scalability. When the network needs to be expanded, wireless communication does not require expansion wiring; it has strong flexibility. Wireless networks are not restricted by environmental terrain, etc., and when the use environment changes, wireless networks only need to make few adjustments to adapt to the requirements of the new environment.

Common wireless communication (data) transmission methods and technologies are divided into two types: "short-range wireless communication technology" and "long-range wireless transmission technology".

1. Short-range wireless communication technology

Short (near) distance wireless communication technology refers to the communication between two parties through the use of radio waves to transmit data, and the transmission distance is within a relatively short range. Its application range is very wide. In recent years, the short-range wireless communication standards that are widely used and have good development prospects include: Zig-Bee, Bluetooth, wireless broadband (Wi-Fi), ultra-wideband (UWB) and near field communication (NFC).

(1) Zig-Bee

Zig-Bee is a short-distance, low-power wireless communication technology based on the IEEE802.15.4 standard. Zig-Bee originated from the communication method of bee colonies. Since bees (Bee) rely on flying and "buzzing" (Zig) to shake their wings to determine the direction, location and distance of food sources with their companions, they form a communication network for the bee colony. Its characteristics are short distance, and its usual transmission distance is 10-100m; low power consumption, in low-power standby mode, 2 No. 5 dry batteries can support a terminal to work for 6-24 months, or even longer; its cost, Zig-Bee is free of protocol fees, and the chip price is cheap; low rate, Zig-Bee usually works at a lower rate of 20-250kbps; short delay, Zig-Bee has a faster response speed, etc. It is mainly suitable for home and building control, industrial field automation control, agricultural information collection and control, public place information detection and control, smart tags and other fields, and can be embedded in various devices.

(2) Bluetooth

It can realize point-to-point or point-to-multipoint wireless data and voice transmission within a radius of 10 meters, and its data transmission bandwidth can reach 1Mbps. The communication medium is electromagnetic waves with a frequency between 2.402GHz and 2.480GHz. Bluetooth technology can be widely used in various data and voice devices in local area networks, such as PCs, dial-up networks, laptops, printers, fax machines, digital cameras, mobile phones and high-quality headphones, etc., to realize communication between various devices anytime and anywhere.

Bluetooth technology is widely used in wireless office environments, automotive industry, information appliances, medical equipment, school education, factory automation control and other fields. The main problems of Bluetooth at present are the high chip size and price; and weak anti-interference ability.

(3) Wireless broadband (Wi-Fi)

It is a wireless LAN access technology based on the 802.11 protocol. The outstanding advantage of (Wi-Fi) technology is that it has a wider LAN coverage range, and its coverage radius can reach about 100 meters. Compared with Bluetooth technology, (Wi-Fi) has a wider coverage range; the transmission speed is very fast, and its transmission speed can reach 11mbps (802.11b) or 54mbps (802.11.a), which is suitable for high-speed data transmission business; no wiring is required, and it is not restricted by wiring conditions, which is very suitable for the needs of mobile office users. In some crowded places, such as railway stations, bus stations, shopping malls, airports, libraries, campuses, etc., "hotspots" are set up, and the Internet can be connected to the above places through high-speed lines. Users only need to place terminal devices that support wireless networks in the area to access the Internet at high speed; it is healthy and safe. The transmission power of products with WiFi function does not exceed 100 milliwatts, and the actual transmission power is about 60-70 milliwatts. Compared with communication equipment such as mobile phones and handheld walkie-talkies, WiFi products have less radiation.

(4) Ultra-wideband (UWB)

UWB is a carrier-free communication technology that uses non-sinusoidal narrow pulses in the nanosecond to picosecond range to transmit data. Its transmission distance is usually within 10M. Using a bandwidth of more than 1GHz, the communication speed can reach hundreds of megabits/s. The operating frequency band of UWB ranges from 3.1GHz to 10.6GHz, and the minimum operating bandwidth is 500MHz.

Its main features are: high transmission rate; low transmission power, low power consumption; strong confidentiality; UWB communication uses time-modulated sequence, which can resist multipath fading; UWB requires few RF and microwave devices, which can reduce the complexity of the system. Due to the high bandwidth occupied by the UWB system, the UWB system may interfere with other existing wireless communication systems. UWB is mainly used in high-resolution "small range" radar and imaging systems that can penetrate obstacles such as walls and the ground.

This device can be used to check for defects in concrete and asphalt structures of buildings, bridges, roads and other projects, locate faults in underground cables and other pipelines, and can also be used for disease diagnosis. In addition, it is also very useful in the fields of rescue, public security prevention, fire fighting, medical treatment, medical image processing, etc.

(5) NFC

NFC is a new short-range wireless communication technology with an operating frequency of 13.56MHz. It is developed from the 13.56MHz radio frequency identification (RFID) technology. It is the same frequency used by the currently popular contactless smart card ISO14443, which provides a convenient communication method for all consumer electronic products. NFC uses amplitude shift keying (ASK) modulation, and its data transmission rate is generally 106kbit/s and 424kbit/s. The main advantages of NFC are: short distance, high bandwidth, low energy consumption, and compatibility with contactless smart card technology. It has broad application value in access control, public transportation, mobile payment and other fields.

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NFC application scenarios can be basically divided into the following five categories:

• A contact-pass, mainly used in conference admission, traffic checkpoints, access control and event tickets;
• B contact-confirmation/payment, mainly used in mobile wallets, mobile and public transportation payment, etc.;
• C-contact-connect, this application can realize point-to-point data transmission between two NFC-enabled devices;
• D-touch-browse, users can use NFC mobile phones to understand and use the functions and services provided by the system;
• E-Download-Contact, through a terminal device with NFC function, uses the GPRS/CDMA network to receive or download relevant information for functions such as access control or payment.

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2. Long-distance wireless transmission technology

Long-distance wireless transmission technology: Currently, the wireless communication technologies widely used in remote areas include GPRS/CDMA, digital radio, spread spectrum microwave, wireless bridge, satellite communication, shortwave communication technology, etc. It is mainly used in remote areas or areas where it is not suitable to lay lines, such as coal mines, offshore, polluted or harsh environmental areas, etc.

(1) GPRS/CDMA wireless communication technology:

GPRS (General Packet Radio Service) is a wireless packet switching technology based on the GSM communication system developed and operated by China Mobile. It is a technology between the second generation and the third generation, usually called 2.5G. It is a wireless transmission method developed using the concept of "packet switching". Packet switching encapsulates data into many independent packets, and then transmits these packets one by one. It is a bit similar to sending a parcel. Its advantage is that it will only occupy bandwidth when there is data to be transmitted, and it is priced by the amount of data, which effectively improves the utilization rate of the network. The GPRS network supports both circuit-type data and packet-switched data, so that the GPRS network can be easily connected to the Internet. Compared with the original GSM network's circuit-switched data transmission method, GRRS's packet switching technology has the advantages of real-time online "pay-as-you-go" high-speed transmission.

CDMA (the abbreviation of Code Division Multiple Access) is a new wireless communication system based on code division technology and multiple access technology operated by China Telecom. Its principle is based on spread spectrum technology.

(2) Digital radio communication:

Digital radio is the abbreviation of digital wireless data transmission radio. It is a wireless data transmission radio that uses digital signal processing, digital modulation and demodulation, and has functions such as forward error correction and equalization soft decision. The working frequency of digital radio mostly uses the 220--240MHz or 400--470MHz frequency band. It has the advantages of digital and voice compatibility, good real-time data transmission, dedicated data transmission channel, one-time investment, no operating fee, suitable for harsh environments, and good stability. The effective coverage radius of digital radio is about tens of kilometers, which can cover a city or a certain area. Digital radio usually provides a standard RS-232 data interface, which can be directly connected to computers, data collectors, RTUs, PLCs, data terminals, GPS receivers, digital cameras, etc. It has been widely used in various industries, including aerospace, railways, electricity, petroleum, meteorology, earthquake and other industries. It has also made great progress and development in the fields of SCADA such as remote control, telemetry, shaking letters, and remote sensing.

(3) Spread spectrum microwave communication:

Spread spectrum communication, or spread spectrum communication technology, refers to a communication technology in which the bandwidth of the signal used to transmit information is much larger than the bandwidth of the information itself. It was first used in military communications. The basic principle of its transmission is to modulate the transmitted information with a pseudo-random code sequence (spread spectrum code). The rate of the pseudo-random code is much larger than the rate of transmitting information. At this time, the bandwidth occupied by the transmitted signal is much larger than the bandwidth required by the information itself, thus achieving spectrum expansion. At the same time, the radio power spectrum density emitted into space is also greatly reduced. At the receiving end, the same spread spectrum code is used for correlation demodulation and information data recovery! Its main features are: strong anti-noise ability; strong anti-interference ability; strong anti-fading ability; strong anti-multipath interference ability; easy multimedia communication networking; good security communication ability; no interference with other similar systems, etc. It also has the characteristics of long transmission distance and wide coverage, which is particularly suitable for field networking applications.

(4) Wireless Bridge:

Wireless bridge is the product of the combination of wireless radio frequency technology and traditional wired bridge technology. Wireless bridge is designed for point-to-point network interconnection using wireless (microwave) for long-distance data transmission. It is a storage and forwarding device that realizes LAN interconnection at the link layer. It can be used for long-distance (up to 50Km) and high-speed (up to 100M bps) wireless networking between fixed digital devices and other fixed digital devices. Both spread spectrum microwave and wireless bridge technology can be used to transmit large data signal transmission services such as video surveillance that have very high bandwidth requirements.

(5) Satellite communications:

Satellite communication refers to a technology that uses artificial satellites as relay stations to forward radio signals, thereby achieving communication between multiple ground stations. It is the inheritance and development of ground microwave communication. Satellite communication systems usually consist of two parts, namely the satellite end and the ground end. The satellite end is in the air and is mainly used to amplify the signals sent by the ground station and then forward them to other ground stations. The ground station is mainly used to control and track satellites and to connect the ground communication system to the satellite communication system.

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Satellites can be divided into synchronous satellites and asynchronous satellites. The direction and period of a synchronous satellite's movement in the air are the same as the direction and period of the Earth's rotation. From any position on the ground, the satellite appears stationary. The operating period of an asynchronous satellite is greater or less than the Earth's operating period, and the height and "inclination" of its orbit can be adjusted as needed.

The characteristics of satellite communication are: wide coverage, wide working frequency band, good communication quality, no geographical restrictions, and cost independent of communication distance. It is mainly used in international communication, domestic communication, military communication, mobile communication, radio and television, etc. The main disadvantage of satellite communication is that the communication has a certain delay. For example, when making a satellite call, you cannot hear the other party's reply immediately. The main reason is that the transmission distance of satellite communication is long, and the transmission of radio waves in the air has a certain delay.

(6) Shortwave communication:

According to the classification of the International Radio Consultative Committee, shortwave refers to electromagnetic waves with a wavelength of 100m-10m and a frequency of 3MHZ-30MHZ. Shortwave communication refers to radio communication using shortwave, also known as high frequency (HF) communication. Shortwave communication can be divided into ground wave propagation and sky wave propagation. The attenuation of ground wave propagation increases with the increase of operating frequency. Under the same ground conditions, the higher the frequency, the greater the attenuation. The use of ground waves is only suitable for short-distance communication, and its operating frequency is generally selected below 5MHZ. Ground wave propagation is less affected by weather and is relatively stable. The channel parameters basically do not change with time, so the channel can be regarded as a constant parameter channel. Sky wave propagation is a way for radio waves to be reflected by the ionosphere for long-distance communication. The obliquely projected electromagnetic waves can be transmitted to the ground thousands of kilometers away after being reflected by the ionosphere. The propagation loss of sky waves is much smaller than that of ground waves. After multiple reflections between the ground and the ionosphere, they can reach extremely far places. Therefore, sky waves can be used for global communication. Sky wave propagation is extremely unstable due to the serious influence of ionospheric changes and multipath propagation, and its channel parameters change dramatically over time, so it is called a variable parameter channel. The characteristics of shortwave communication are: low construction and maintenance costs, short cycle, simple equipment, easy circuit scheduling, strong anti-destruction ability, narrow frequency band, small communication capacity, and poor stability of sky wave channel signal transmission.

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2. Comparison between various mainstream wireless communication technologies

Currently popular wireless communication technologies include: RFID, GPRS, Bluetooth, Wi-Fi, IrDA, UWB, Zig-Bee and NFC.

1. RFID

RFID is a simple wireless system with only two basic components, which is used to control, detect and track objects. The system consists of an interrogator and many transponders.

• Transponder: It consists of an antenna, a coupling element and a chip. Generally, a tag is used as a transponder. Each tag has a unique electronic code and is attached to an object to identify the target object.
• Reader: A device consisting of an antenna, a coupling element, and a chip that reads (and sometimes writes) tag information. It can be designed as a handheld RFID
• Application software system: It is application layer software, which mainly processes the collected data further and makes it available for people to use.

2. GPRS

The following figure is a typical GPRS system structure diagram. Through the monitoring center connected to the Internet, it can support some relatively complex applications. In addition, it supports a variety of communication methods, allowing users to monitor actual application points anytime and anywhere in a variety of communication methods. This solution can also allow the monitoring center to communicate with multiple GPRS modules at the same time, thereby monitoring multiple work sites.

3. Bluetooth

The Bluetooth system consists of a radio unit, a link controller, a link manager, and a support unit that provides interface functions to the host.

The Bluetooth wireless unit is a microwave frequency hopping spread spectrum communication system. Data and voice information are grouped in designated time slots and designated hopping frequencies for transmission and reception. The frequency hopping sequence is determined by the master device address, and channel connections are established by paging and querying. The link controller (baseband controller) includes the hardware part of the baseband digital signal processing and completes the baseband protocol and other underlying link procedures. The link manager (LM) software implements the establishment, verification, link configuration and its protocol of the link. The link manager can discover other link managers and establish communication links through the connection management protocol LMP. The link manager implements the above functions through the services provided by the link controller.

4. Wi-Fi

The design of Wi-Fi solution is relatively simple compared with other solutions. It only needs to control the Wi-Fi module through MCU, communicate with the mainboard through CAN bus, and then transmit the information to the Internet through the Wi-Fi module. It connects to the server, and then the server processes the data.

5. IrDA

Infrared communication mainly consists of three parts:

• Transmitter part: The information sources of existing infrared wireless digital communication systems include voice, data, images, etc.
• Channel part: Their functions are: shaping, filtering, field of view transformation, frequency band division, etc.
• Terminal part: The terminal part of the infrared wireless digital communication system includes light receiving part, sampling, filtering, judgment, quantization, equalization and decoding.

6. UWB

UWB (UltraWideband) is a carrier-free communication technology that uses non-sinusoidal narrow pulses from nanoseconds to picoseconds to transmit data. By transmitting extremely low-power signals over a wider spectrum, UWB can achieve data transmission rates of hundreds of Mbit/s to several Gbit/s within a range of about 10 meters.

7. Zig-Bee

Technology is a short-distance, low-complexity, low-power, low-rate, low-cost two-way wireless communication technology. It is mainly used for data transmission between various electronic devices with short distance, low power consumption and low transmission rate, as well as typical applications with periodic data, intermittent data and low response time data transmission.

8. NFC

Like RFID, NFC information is transmitted through electromagnetic induction coupling in the radio frequency part of the spectrum, but there are still big differences between the two. First, NFC is a wireless connection technology that provides easy, secure and fast communication, and its transmission range is smaller than RFID. Second, NFC is compatible with existing contactless smart card technology and has become an official standard supported by more and more major manufacturers. Third, NFC is also a short-range connection protocol that provides easy, secure, fast and automatic communication between various devices. Compared with other connection methods in the wireless world, NFC is a close-range private communication method.

Comparison table of mainstream wireless communication technologies

Applicable frequency bands, modulation methods, maximum ranges, data rates and application areas of various wireless communication technologies. The relationship between the range and data rate of these wireless communication technologies. The higher the data rate, the shorter the range. Network technology can be used to extend the range while still maintaining the data rate.