Seven short-range wireless communication technologies

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1.Wi-Fi

In theory, the user is located in a certain area around the access point, but if it is blocked by the wall, the effective transmission distance in the building will be smaller than the outdoor. WiFi technology is mainly used for SOHO, shopping centers, airports, home wireless networks, airports, hotels, other public hot spots and other buildings and places that are not convenient to install cables, saving a lot of cable laying costs.

2.Bluetooth

无线数据和语音通信的开放式全球规范。蓝牙技术的应用是在固定或移动设备之间的通信环境中建立一个通用的短距离无线接口。其传输频段为全球通用的2.4GHz ISM频段。提供1Mbps的传输速率和10m的传输距离。缺点：芯片尺寸和价格难以下降，抗干扰性不强，传输距离太短，信息安全问题。

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3.ZigBee

This is mainly used for short distance between various electronic devices, data transmission speed is not high. The name ZigBee comes from the way that bees communicate for survival and development. Bees dance tortuously, sharing the location, distance and direction of newly discovered food. ZigBee can be said to be a brother of the same Bluetooth family. This family uses the 2.4GHz band and frequency hopping technology. But ZigBee is simpler than Bluetooth, low speed, low power consumption and low cost. The basic rate is 250kb / s.When it is reduced to 28kb / s, the transmission range can be extended to 134m, and higher reliability can be obtained. It can also connect to 254 nodes and networks. It supports games, home appliances, devices and home automation applications better than Bluetooth.

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4.IrDA

IrDA是一种利用红外线的点对点通信技术，是最早实现无线个域网（PAN）的技术。目前其软硬件技术已经非常成熟，在PDA、手机、笔记本电脑、打印机等小型移动设备上都支持IrDA。

优点：无需申请使用权，红外通信成本低，体积小，功耗低，连接方便，移动通信简单易用，红外辐射角小，传输安全性高。

Disadvantages : This technique can only be used for connections between two ( non-multiple ) devices. Bluetooth technology does not have this limitation, so IrDA 's current research direction is to solve the problem of line-of-sight transmission and improve the speed of data transmission.

5.NFC

Short-range wireless communication technology standards such as RFID ( contactless radio frequency identification ) promoted by Philips, Nokia and Sony. Unlike RFID, NFC uses bidirectional identification and connection. The action is in the frequency range of 13.56 MHz and the distance is 20 cm. NFC was originally just a combination of remote control identification and network technology, but now it has gradually developed into a wireless connection technology.

NFC solves the problem of storing multiple passwords and ensures data security by combining all identification applications and services on one device. Using NFC, wireless interconnection can be achieved between multiple devices ( such as digital cameras, PDAs, set-top boxes, computers, mobile phones, etc. ), and data and services can be exchanged. Similarly, to build a Wi-Fi series of wireless networks, you need devices with multiple computers, printers, and other wireless cards. Some technical experts are also required to complete this work. After setting NFC on the access point, if two of them are closed, it can communicate much easier than setting Wi-Fi connection.

6.UWB

Wireless carrier communication technology. UWB can transmit signals with a very wide bandwidth because it uses nanosecond non-sinusoidal narrow pulses rather than sinusoidal carriers to transmit data. The United States FCC regulations, so accounted for a large spectrum. UWB has a frequency band of more than 500MHz in the 3.1 to 10.6GHz band.

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UWB has developed rapidly in recent years because it can use low-power, low-complexity transceivers to achieve high-speed data transmission. By using low-power pulses, data can be transmitted over a very wide spectrum and spectrum resources can be utilized without causing significant interference to traditional narrowband wireless communication systems. High-speed data transceivers based on UWB technology have a wide range of uses.

7.SIM

At present, the RFID technology integrated with mobile phones is mainly NFC ( short-range communication ), SIMpass ( dual-interface SIM card ) and RF-SIM ( mobile smart card for short-range wireless communication ) technology.

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Ele_insect

Zigbee是IEEE 802.15.4协议的代名词。根据这个协议规定的技术是一种短距离、低功耗的无线通信技术。