802. 1 1n can increase the transmission rate of WLAN from 54Mbps provided by 802.1a and 802.1/g to 300Mbps or even as high as 600Mbps.
The full name of WiFi is wireless fidelity, also known as 802. 1 1b standard. Its biggest advantage is its fast transmission speed, which can reach 1 1Mbps. In addition, it has a long effective distance and is compatible with various existing 802. 1 1 DSSS devices. Centrino technology is based on this standard, and wireless Internet access has become a reality. .
The IEEE 802. 1 1b wireless network specification is a variant of the IEEE 802. 1 1 network specification, and the maximum bandwidth is 1 Mbps, which can be adjusted to 5.5Mbps and 2Mbps in case of weak signal or interference. Its main features are: high speed and high reliability. In the open area, the communication distance can reach 305 meters, and in the closed area, the communication distance is 76 meters to 122 meters, which is convenient to integrate with the existing wired Ethernet and has lower networking cost.
WiFi——WirelessFidelity, wireless fidelity technology, like Bluetooth technology, belongs to short-distance wireless technology used in offices and homes. This technology uses a frequency band of about 2.4GHz, which is currently a wireless frequency band without a license. At present, there are two available standards, namely IEEE802. 1 1a and IEEE 802.11b. This technology is favored by manufacturers because of its own advantages.
WIFI highlights its advantages.
First, the coverage of radio waves is wide. The radio coverage based on Bluetooth technology is very small, with a radius of only about 50 feet, that is, 15 meters, while the radius of Wi-Fi can reach about 300 feet, that is, 100 meters. Needless to say, the office, the whole building can also be used. Recently, Vivato Company introduced a new type of switch. It is reported that this product can extend the communication distance of the current Wi-Fi wireless network from 300 feet (close to 100 meters) to 4 miles (about 6.5 kilometers).
Secondly, although the wireless communication quality transmitted by Wi-Fi technology is not very good, the data security performance is worse than that of Bluetooth, and the transmission quality needs to be improved, but the transmission speed is very fast, reaching 54mbps, which meets the needs of personal and social informatization.
Third, the threshold for manufacturers to enter this field is relatively low. Manufacturers only need to set up "hot spots" in crowded places such as airports, railway stations, coffee shops and libraries, and access the Internet to these places through high-speed lines. In this way, because the radio waves emitted by "hot spots" can reach the radius of tens of meters to 100 meters from the access point, users can surf the Internet at high speed as long as they enter this area with their laptops or PDA supporting wireless LAN. In other words, manufacturers do not have to spend money on network wiring access, thus saving a lot of costs.
usb wireless network card
According to the standards used by wireless network cards, the speed of WIFI is different. Among them, the highest IEEE802. 1 1b is 1 1Mbps (some manufacturers can cooperate with equipment up to 22Mbps). The IEEE802. 1 1a is 54Mbps, and the IEEE 802.1g is also 54Mbps (Netgear SuperG technology can speed up to 108Mbps, but it does not belong to 802.1/kloc).
WIFI is a wireless network composed of AP (access point) and wireless network card. AP is generally called a bridge or access point, as a bridge between traditional wired LAN and wireless LAN. Therefore, any PC equipped with wireless network card can share the resources of wired local area network or even wide area network through AP, and its working principle is equivalent to a HUB with a built-in wireless transmitter or router, while the wireless network card is a client device responsible for receiving signals transmitted by AP.
Wireless b/g indicates the model of network card, which can be divided into 802. 1 1a, 802.1/b, 802.1n according to its speed and technology.
When it comes to wireless networks, everyone has a specious feeling. Is wireless a simple connection between two computers? Don't! This is the concept of wireless in the last century. The new generation of wireless network will establish people's brand-new feeling of wireless local area network, without wiring and relatively free to use. Demand determines the development of the market. IT is rare to see any IT technology or product with such a rapid growth momentum. It is no longer a dream to surf the internet anytime and anywhere without any constraints. Among them, WiFi plays a vital role. Wi-Fi stands for "wireless fidelity" and refers to a subset of IEEE 802. 11b that is fully compatible with the 802.1standard. It adopts open 2.4GHz direct sequence spread spectrum, and the maximum data transmission rate is 1 12Mbps. The transmission rate can also be adjusted to 5 according to the signal strength. The maximum transmission range of wireless communication is 300 meters outdoors and 100 meters indoors, which is the most used transmission protocol at present. Compared with wired network, it has many advantages:
No wiring is required
Desktop wireless network card
The main advantage of WiFi is that it does not need wiring and is not limited by wiring conditions. It is very suitable for the needs of mobile office users and has a broad market prospect. At present, it has expanded from traditional special industries such as medical care, inventory control and management services to more industries, and even started to enter the fields of families and educational institutions.
Safety and health care department
IEEE802. 1 1 stipulates that the transmission power shall not exceed 100 MW, and the actual transmission power is about 60~70 MW. What kind of concept is this? The transmitting power of the mobile phone is about 200 MW to 1 W, and the handheld walkie-talkie is as high as 5 W. Unlike the mobile phone, it is absolutely safe to directly contact the human body and use wireless networks.
Simple forming method
Generally speaking, the basic equipment for building a wireless network is wireless network card and AP, so that network resources can be shared with the existing wired architecture in a wireless way, and the construction cost and complicated process are far lower than those of the traditional wired network. If it's just a point-to-point network of several computers, you don't need an AP, just equip each computer with a wireless network card. AP is the abbreviation of AccessPoint, which is generally translated as "wireless access node" or "bridge". It mainly acts as a bridge between wireless workstation and wired LAN in MAC of media access control layer. With AP, wireless workstations can connect to the network quickly and conveniently, just like hubs in general wired networks. Especially for the use of broadband, WiFi has more advantages. After the wired broadband network (ADSL, local area network, etc.). ) to the AP, you can install a wireless network card in your computer. It is enough for ordinary families to have an AP. Even after the user's block is authorized, you can surf the Internet in a * * * way without adding a port.
Long distance work
Although the working distance of wireless WiFi is not large, the real working distance of 802. 1 1b can reach more than 100 meters under the condition of complete network construction, which solves the problems of data error correction and error code when moving at high speed, and well solves the problems of handover and security authentication between WiFi devices and devices and base stations.
WIFI mobile phone
main feature
Although there is only one call mode, single-mode WiFi mobile phone is favored by enterprises and groups because of its own characteristics. Its main features are:
(1): The call is clear and timely;
(2): Because of the network session, the call cost is low;
(3): strong flexibility, and the group can talk anytime and anywhere;
(4): No wiring is required.
(5): Simple equipment
Main classification
At present, WiFi mobile phones on the market are divided into "single mode WiFi mobile phones" and "dual mode WiFi mobile phones".
Dual-mode WIFI mobile phone refers to a mobile phone with WIFI communication mode and another communication mode (GSM, etc.). ). Dual-mode WIFI mobile phones are common in the market and suitable for personal use, but the call quality is not very clear and the call delay is long.
Domestic and international situation
At present, this technology has been very popular abroad, while domestic companies engaged in research and development of this technology are mainly concentrated in Shenzhen. In a real sense, domestic WI-FI mobile phone manufacturers will encounter many technical bottlenecks when producing WI-FI mobile phones, and many technologies still need to be completed through cooperation with foreign operators.
Only Shenzhen Roukete Technology Co., Ltd. can independently develop and complete the production of mobile phones. At present, most of the popular WI-FI mobile phones in the domestic market come from foreign brands. But making video calls is really enough. At present, only Shenzhen Roucaute WI-FI mobile phone has broken through this technology. And realize the trinity, GSM+Eden+Wifi V2IP. The real Roucaute WI-FI mobile phone is the first high-end WI-FI mobile phone developed and designed by China people themselves.
At present, the WI-FI network has been concerned and recognized by the national government, and the country has allowed the opening of WI-FI networks. Therefore, WI-FI mobile phone will become a well-known communication product in a short time, and will win the favor of consumers and major enterprises with low price and wide use.
HomeRF working group was established in 1997, and is led by American Home Radio Frequency Committee. Its main task is to establish an interoperable voice and data communication network for home users. HomeRF standard integrates voice and data transmission technology, and the working frequency band is 2.4GHz, and the data transmission rate reaches100 mbit/s. WLAN security mainly considers access control and encryption technology.
HomeRF is a synthesis and improvement of existing wireless communication standards: TCP/IP transmission protocol in IEEE802. 1 1 specification is adopted for data communication; When voice communication is carried out, the digital enhanced cordless communication standard is adopted. However, this standard is not compatible with 802. 1 1b, and occupies the same 2.4GHz band as 802.1/b and Bluetooth, so its application scope will be greatly limited, and it is more used in home networks.
Remarks: RF is the abbreviation of radio frequency, indicating the electromagnetic frequency that can be radiated into space, and the frequency range is 300 kHz-30 GHz. Radio frequency is abbreviated as RF current, which is the abbreviation of high frequency AC electromagnetic wave. Alternating current that changes less than 1000 times per second is called low-frequency current, and that that changes more than 10000 times is called high-frequency current, and radio frequency is such high-frequency current. Cable TV system adopts radio frequency transmission mode.