无线网络与移动计算 Wireless Network and Mobile Computing

Overview

In this course, we mainly studied three types of wireless networks:

• 无线个域网 WPAN

• 无线局域网 WLAN

• 无线广域网 WWAN

  In fact, there is also a wireless metropolitan area network WMAN, but we have not studied in depth. The main difference between the networks is the coverage:

一、无线个域网 WPAN

​ 个域网(Personal Area Network, PAN)是一种范围较小的计算机网络，其通信范围只有几米。WPAN即采用无线连接的个域网。WPAN可以实现个人终端设备的互联，组建个人信息网络。

​ Personal Area Network (PAN) is a small computer network with a communication range of only a few meters. WPAN is a personal area network that uses wireless connections. WPAN can realize the interconnection of personal terminal equipment and build a personal information network.

1、 Key Technologies of WPAN

​ The key technologies of WPAN include UWB, Bluetooth, ZigBee, etc.

• UWB: Ultra Wide Band, Ultra-high-speed, short-distance wireless access technology. High transmission rate and low power consumption.
• Bluetooth: Widely used short-range communication technology. Work in the 2.4GHz frequency band.
• ZigBee: Compared with Bluetooth, the transmission rate is lower, but the transmission distance is longer than Bluetooth, about 10 to 100 meters.

2、WPAN application examples

​ Use ZigBee technology to build WPAN in the supermarket to connect the data of all electronic scales and minimize the impact of electronic scale failures.

二、无线局域网 WLAN

​ WLAN，Wireless Local Area Network. Its coverage is about 100 meters. When it comes to WLAN, we have to mention the IEEE 802.11 standard.

1、IEEE 802.11 Standard

​ IEEE 802.11 is a WLAN communication standard, which defines the Media Access Control (MAC) layer and the physical layer. We usually refer to the 802.11ac standard as Wi-Fi 5 and the 802.11ax standard as Wi-Fi 6. The maximum transmission rate of Wi-Fi 6 can reach 9.6 Gbps.

2、The relationship between WLAN and Wi-Fi

​ WLAN is a concept, and Wi-Fi is a technology to realize the concept.

三、无线广域网 WWAN

​ WWAN can provide a wide range of wireless access, and it emphasizes fast mobility. Typical WWAN includes GSM, 4G, 5G, etc. Its transmission rate is lower than that of WLAN. The communication standard of WWAN is IEEE 802.20

1、IEEE 802.20 Standard

​ The operating frequency of 802.20 is less than 3.5GHz. At the physical layer, its core technology is Orthogonal Frequency Division Multiplexing (OFDM) and multiple input multiple input technology MIMO.

​ The IEEE 802.20 standard has high mobility and low latency.

2、Application of WWAN

​ For example, in the power industry, WWAN is used to connect substations, power plants, and power bureaus that are distributed in different regions.

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