"This paper mainly introduces common wireless communication technologies, including Bluetooth, Wi Fi, ZigBee, IrDA, UWB, NFC, WiMAX, RFID, GPRS, Huawei hilink protocol, mesh, thread, Z-Wave, lifi, etc.
1. Bluetooth Technology
Bluetooth technology was jointly proposed and developed by Ericsson, IBM, Intel, Nokia and Toshiba in May 1998. From the original Bluetooth v1.0 to Bluetooth V5.1, it has developed into the current situation after more than a dozen revisions.
Bluetooth technology is a short-range and low-cost wireless access technology using 2.4GHz ism public channel. It is mainly used in short-range voice and data transmission services. The working frequency band of Bluetooth device adopts the 2.4GHz ISM frequency band that can be freely used all over the world. Users can use it without application. Most countries use 79 frequency points, the carrier frequency is (2402 + k) MHz (k = 0, 1, 2... 78), and the carrier frequency interval is 1MHz. TDD time division duplex mode is adopted. The frequency hopping rate is 1600 hops / s, which makes the Bluetooth system have high enough anti-interference ability, simple equipment and superior performance. According to the different transmission power, the effective communication distance between Bluetooth devices is about 10 ~ 100m.
2、WiFi(Wireless Fidelity)
WiFi (wireless fidelity) technology is a brand of wireless network communication technology based on IEEE802.11 series standards. Its purpose is to improve the interoperability between wireless network products based on IEEE802.11 standards. It is held by Wi Fi alliance. In short, WiFi is a wireless networking technology, which used to connect computers through the network, Now it is connected by radio waves. The WiFi alliance was established in 1999. At that time, it was called wireless Ethernet Compatibility Alliance (WECA). In October 2002, it was officially renamed WiFi alliance.
The WiFi network goes from the 2.4GHz band of 802.11 to the 5GHz band of 802.11a, then to the 2.4GHz and 5GHz compatible band of 802.11n, and then to the 60GHz band of 802.11ad. After nearly ten versions of evolution, the latest 802.11ax has returned to the 2.4GHz and 5GHz compatible bands, which can reach the rate of 9.6Gbps.
WiFi covers a wide range, up to 100m, but its radio waves are easy to be disturbed and the speed is fast. Due to the use of radio waves as the transmission medium, the possibility of data packets being intercepted is high, which has also become a problem of concern to users. Now WiFi products use wed (Wired Equivalent Privacy) technology for data encryption.
3、ZigBee
ZigBee is a short distance, low power and low rate wireless access technology. ZigBee is mainly used between various electronic devices with short distance and low data transmission rate. It works in the 2.4GHz ISM band, with a rate of 10K ~ 250kbps and a transmission distance of 10 ~ 75m. The technology is close to Bluetooth, but ZigBee is simpler, slower, and lower power and cost. Its maximum speed is 250K. When it is reduced to 28K, the transmission range can be expanded to 134m and higher reliability can be obtained. In addition, it can be networked with 254 nodes. It can better support games, consumer electronics, instruments and home automation applications than Bluetooth. However, ZigBee is mostly in sleep mode, which is suitable for occasions where real-time transmission or continuous update is not required. ZigBee is an extended set of IEEE 802.15.4. The physical layer standard adopts three frequency bands: 2.4GHz and 915MHz in North America and 868mhz in Europe.
ZigBee's name comes from the communication mode used by bees to survive and develop. Bees share the location, distance and direction of newly discovered food sources by dancing zigzag shaped dance.
ZigBee alliance was established in August 2001. In the second half of 2002, Invensys, Mitsubishi, Motorola and Philips semiconductor announced to join the ZigBee alliance to develop the next generation wireless communication standard called ZigBee. So far, the alliance has about 27 member enterprises. All these companies participated in the IEEE 802.15.4 working group responsible for developing ZigBee physical and media control layer technical standards. ZigBee alliance is responsible for formulating protocols above the network layer. ZigBee protocol is simpler and more practical than Bluetooth, high-speed personal area network or 802.11x wireless LAN.
4、IrDA(Infrared Data Association)
IrDA (infrared data association) was established in 1993. At first, wireless devices using IrDA standard can only transmit data at the rate of 115.2kb/s within 1m, and soon develop to the rates of 4MB / s and 16MB / s. IrDA is a point-to-point communication technology using infrared. It is the first technology to realize wireless personal area network (Pan). At present, its software and hardware technology are very mature, and it is widely used in small mobile devices, such as PDA and mobile phone. In fact, every factory PDA and many mobile phones, laptops, printers and other products support IrDA.
The main advantage of IrDA is that there is no need to apply for the right to use the frequency, so the cost of infrared communication is low. It also has the characteristics of small volume, low power consumption, convenient connection and easy to use. In addition, the infrared emission angle is small and the transmission security is high. The disadvantage of IrDA is that it is a line of sight transmission. Two devices communicating with each other must be aligned and cannot be blocked by other objects. Therefore, this technology can only be used for the connection between two (not multiple) devices. Bluetooth has no such restriction and is not blocked by walls. The current research direction of IrDA is how to solve the problem of line of sight transmission and improve the data transmission rate.
5、UWB(Ultra WideBand)
Ultra wideband (UWB) is a wireless carrier communication technology. It does not use sinusoidal carrier, but uses nanosecond non sinusoidal narrow pulse to transmit data, so its spectrum range is very wide. It has great advantages in short-distance transmission (below 13m), and the maximum transmission speed can reach 1Gbps, while the traditional narrowband technology has advantages in long-distance and low-speed transmission.
UWB can transmit signals over a very wide bandwidth. The U.S. FCC stipulates that UWB occupies a bandwidth of more than 500MHz in the frequency band of 3.1 ~ 10.6GHz. UWB has developed rapidly in recent years because it can use low power consumption and low complexity transmitter / receiver to realize high-speed data transmission. It uses low-power pulses to transmit data in a very wide spectrum range without causing large interference to the conventional narrowband wireless communication system, and can make full use of spectrum resources. The high-speed data transceiver based on UWB technology has a wide range of applications.
UWB technology has the advantages of low system complexity, low power spectral density of transmitted signal, insensitive to channel fading, low interception ability and high positioning accuracy. It is especially suitable for high-speed wireless access in indoor and other dense multipath places. It is very suitable for establishing an efficient wireless local area network or wireless personal area network (WPAN).
UWB is mainly used in small-scale, high-resolution radar and image systems that can penetrate walls, ground and body. In addition, this new technology is suitable for LANs or pans with very high rate requirements (greater than 100MB / s).
The most distinctive application of UWB will be wireless personal area networks (pans) in video consumption and entertainment. The existing wireless communication methods, 802.11b and Bluetooth, are too slow to transmit video data; The 802.11a standard with 54Mb / s rate can process video data, but it is expensive. UWB may support data transmission rate of up to 110mb / s within 10m. It does not need to compress data, and can complete video data processing quickly, simply and economically. With certain compatibility and the advantages of high speed, low cost and low power consumption, UWB is more suitable for the needs of the home wireless consumer market: UWB is especially suitable for transmitting a large amount of multimedia data at high speed in a short distance and can penetrate obstacles, which makes many commercial companies regard it as a promising wireless communication technology, It is applied to family occasions such as wireless transmission of video signals from set-top box to digital TV. Of course, the future of UWB also depends on the technical development, cost, user habits and market maturity of various wireless solutions.
6、WiMAX(Worldwide Interoperability for Microwave Access)
Worldwide Interoperability for microwave access (WiMAX) is a high-speed wireless data network standard, which is mainly used in man. It was proposed by WiMAX forum and took shape in June 2001. It provides at least one mile of wireless broadband access as an alternative to cable and DSL. Make a unique choice among multiple versions and options of IEEE 802.16 standard to ensure the interoperability of products from different manufacturers. Among the three variants of 802.16 physical layer, WiMAX selects 256 carrier OFDM of 802.16-2004 version, which can assist telecom operators and Internet service providers to build the last mile of wireless network by means of wide frequency band and long transmission distance. It is quite different from IEEE 802.11 communication protocol mainly for short-distance regional transmission.
WiMAX can provide many kinds of application services, including last mile wireless broadband access, hotspot, mobile communication return line and high-speed connection between enterprises for commercial purposes. Products that pass the WiMAX conformance test can create wireless connections to each other and send internet packet data. Conceptually, it is similar to WiFi. WiMAX has faster transmission rate and larger transmission range and distance. It is simply understood as a "big WiFi".
The upgraded version of WiMAX wireless man advanced (IEEE 802.16m) is one of the two 4G standards.
7、NFC(NFC(Near Field Communication)
NFC (near field communication) is a short-range wireless communication technology standard similar to RFID (non-contact radio frequency identification) promoted by Philips, Nokia and Sony. Different from RFID, NFC adopts two-way identification and connection. It operates in the frequency range of 13.56MHz within a distance of 20cm. NFC was originally just the combination of remote control identification and network technology, but now it has developed into wireless connection technology. It can quickly and automatically establish a wireless network and provide a "virtual connection" for cellular devices, Bluetooth devices and Wi Fi devices, so that electronic devices can communicate in a short distance. The short-distance interaction of NFC greatly simplifies the whole authentication and recognition process, makes the mutual access between electronic devices more direct, safer and clearer, and eliminates all kinds of electronic noise. NFC helps solve the problem of memorizing multiple passwords by combining all identification applications and services on a single device, and also ensures the security of data. With NFC, the wireless interconnection between multiple devices such as digital cameras, PDAs, set-top boxes, computers, mobile phones, etc., and the exchange of data or services with each other will be possible. In addition, NFC can "accelerate" other types of wireless communication (such as Wi Fi and Bluetooth) to achieve faster and longer distance data transmission. Each electronic device has its own special application menu, and NFC can create a fast and secure connection without selecting from the menus of many interfaces. Different from the well-known short-range wireless communication standards such as Bluetooth, the operating distance of NFC is further shortened, and there is no need for corresponding encryption devices like Bluetooth. Similarly, building Wi Fi family wireless networks requires multiple computers, printers and other devices with wireless network cards. In addition, professionals with certain skills are required to be competent for this job. After the NFC is placed in the access point, communication can be realized as long as two of them are close, which is much easier than configuring Wi Fi connection.
NFC has three types of applications: one is device connection. In addition to WLAN, NFC can also simplify Bluetooth connection. For example, if a laptop user wants to surf the Internet at the airport, he only needs to approach a Wi Fi hotspot. Second, real-time reservation. For example, a specific chip is pasted behind the poster or exhibition information. You can obtain detailed information by using a mobile phone or PDA with NFC protocol, or buy tickets online immediately with a credit card. Moreover, these chips do not require independent energy. Third, mobile commerce. Philips Mifare technology supports several large transportation systems in the world and provides customers with visa card and other services in the banking industry. Sony's felica contactless smart card technology products have a very high market share in Hong Kong, Shenzhen, Singapore and Japan, and are mainly used in transportation and financial institutions. In short, this new technology is rewriting the rules of the game of wireless network connection, but the goal of NFC is not to completely replace other wireless technologies such as Bluetooth and Wi Fi, but to complement each other in different occasions and fields.
8、RFID(Radio Frequency Identification)
Radio frequency identification (RFID) is the abbreviation of radio frequency identification., RFID is a new automatic identification technology developed in the 1980s. RFID is a technology that uses RF signals to realize contactless information transmission through spatial coupling (alternating magnetic field or electromagnetic field) and achieves the purpose of identification through the transmitted information.
RFID is a simple wireless system. The complete RFID system consists of reader, tag and data management system.
RFID radio frequency identification is a non-contact automatic identification technology. It automatically identifies the target object and obtains relevant data through radio frequency signals. The identification work does not need manual intervention and can work in various harsh environments
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