无线网络
概述
无线网络是使用无线电做为其载波或者物理层的电话或者计算机网络
Types
Wireless LAN
One type of wireless network is a WLAN or Wireless Local Area Network. Similar to other wireless devices, it uses radio instead of wires to transmit data back and forth between computers on the same network.
Wi-Fi: Wi-Fi is a commonly used wireless network in computer systems which enable connection to the internet or other machines that have Wi-Fi functionalities. Wi-Fi networks broadcast radio waves that can be picked up by Wi-Fi receivers that are attached to different computers or mobile phones.
Fixed Wireless Data: Fixed wireless data is a type of wireless data network that can be used to connect two or more buildings together in order to extend or share the network bandwidth without physically wiring the buildings together.
Wireless MAN
A type of wireless network that connects several Wireless LANs.
WiMAX: WiMAX is the term used to refer to wireless MANs.
Mobile devices networks
Global System for Mobile Communications (GSM): The GSM network is divided into three major systems which are :the switching system, the base station system, and the operation and support system (Global System for Mobile Communication (GSM)). The cell phone connects to the base system station which then connects to the operation and support station; it then connects to the switching station where the call is transferred where it needs to go (Global System for Mobile Communication (GSM)). This is used for cellular phones, is the most common standard and is used for a majority of cellular providers.[3]
Personal Communications Service (PCS): PCS is a radio band that can be used by mobile phones in North America. Sprint happened to be the first service to set up a PCS.
D-AMPS: D-AMPS, which stands for Digital Advanced Mobile Phone Service, is an upgraded version of AMPS but it is being phased out due to advancement in technology. The newer GSM networks are replacing the older system.
Uses
Wireless networks have had a significant impact on the world as far back as World War II. Through the use of wireless networks, information could be sent overseas or behind enemy lines easily and quickly and more reliably. Since then wireless networks have continued to develop and its uses have significantly grown. Cellular phones are part of huge wireless network systems. People use these phones daily to communicate with one another. Sending information over seas is possible through wireless network systems using satellites and other signals to communicate across the world. Emergency services such as the police department utilize wireless networks to communicate important information quickly. People and businesses use wireless networks to send and share data quickly whether it be in a small office building or across the world.[4]
Another important use for wireless networks is as an inexpensive and rapid way to be connected to the Internet in countries and regions where the telecom infrastructure is poor or there is a lack of resources, like most developing countries.
Compatibility issues also arise when dealing with wireless networks. Different components not made by the same company may not work together, or might require extra work to fix compatibility issues. Wireless networks are typically slower than those that are directly connected through an Ethernet cable.
A wireless network is more vulnerable because anyone can try to break into a network broadcasting a signal. Many networks offer WEP - Wired Equivalent Privacy - security systems which have been found to be vulnerable to intrusion. Though WEP does block some intruders, the security problems have caused some businesses to stick with wired networks until security can be improved. Another type of security for wireless networks is WPA - Wi-Fi Protected Access. WPA provides more security to wireless networks than a WEP security set up. The use of firewalls will help with security breaches which can help to fix security problems in some wireless networks that are more vulnerable.
Environmental concerns and health hazard
In recent time there are increased concerns and research linking usage of wireless communications with poor concentration, memory loss, nausea, premature senility and even cancer.[5] Questions of safety have been raised, citing that long term exposure to electromagnetic radiation of the sort emitted by wireless networks may someday prove to be dangerous.[6]
网络类型 |
技术名称 |
覆盖范围 |
带宽速度 |
上网方式 |
移动能力 |
||||||
WPAN |
蓝牙、Wireless USB… |
10M |
间接 |
||||||||
WLAN |
WiFi 802.11b |
100M |
11M,WiFi 802.11g 54M,WiFi 802.11a 54M,802.11n (MIMO) 300M |
间接 |
室内移动 |
||||||
WMAN |
WiMAX 802.16d |
10KM |
70M |
间接 |
小范围 |
||||||
WiMAX 802.16e |
70M |
城内移动 |
|||||||||
WWAN |
GPRS(2.5G) |
广域覆盖 |
20~40K |
直接 |
广域移动 |
||||||
*WCDMA(3G) 384K/128K CDMA2000(3G) 153.6K/153.6K WCDMA+HSDPA(3.5G) 14.4M/384K WCDMA+HSDPA+HSUPA(3.75G) 上行5.76M 3G LTE 100M/50M
参见
[无线通信] 无线通信技术的热点与发展趋势