Detailed description of Wireless LAN

Some new users are not very clear about the wireless LAN technology. What are the advantages of the wireless LAN technology? What are some related technologies and concepts?

Generally, the transmission media in computer networks rely mainly on copper or optical cables to form a wired LAN. However, in some cases, wired networks are subject to wiring restrictions: a large number of cabling and line change projects, the lines are prone to damage, and nodes in the network cannot be moved. Especially when connecting distant nodes, it is difficult, expensive, and time-consuming to build dedicated communication lines, a serious bottleneck has been formed for the rapidly expanding demand for networking. The emergence of WLAN) can solve many problems in the Wired Network.

Significant technical advantages

WLAN uses electromagnetic waves to send and receive data in the air without cable media. The data transmission rate of WLAN has now reached 11 Mbps, and the transmission distance can be as far as 20km or more. It is a supplement and extension to the wired network mode, so that the computer on the Internet can be moved, and can quickly and conveniently solve the problem of network connectivity that is not easy to implement using the wired network. Compared with wired networks, WLAN has the following advantages:

Installation is generally convenient in network construction, the longest construction period and the greatest impact on the surrounding environment is the network wiring construction project. During the construction process, it is often necessary to crack the walls and strip the cables. The biggest advantage of WLAN is to avoid or reduce the workload of network wiring. Generally, you only need to install one or more Access Point devices to establish a local network covering the entire building or area.

Flexible in wired networks, the placement of network devices is limited by the location of network information points. Once the WLAN is built, the network can be connected to any location in the signal coverage area of the wireless network.

Economic savings due to the lack of flexibility in wired networks, network planners are required to consider future development needs as much as possible, which often leads to a large number of Preset low-utilization information points. Once the development of the network exceeds the design plan, the network transformation will be performed at a high cost. However, WLAN can avoid or reduce the above situations.

Easy to expand WLAN has multiple configuration methods, and can be flexibly selected as needed. In this way, WLAN can be used for a small network with only a few users to a large network with thousands of users, and provide features that cannot be provided by wired networks such as "Roaming.

Due to its many advantages, WLAN has developed rapidly. In recent years, WLAN has been widely used in hospitals, shops, factories and schools that are not suitable for network cabling.

Broad application prospects

In China, WLAN technologies and products are still relatively new in practical application fields. However, because of its irreplaceable advantages, it will be quickly applied to scenarios requiring mobile Internet connection and inter-network roaming, it also provides powerful network support in areas where cabling is not easy and long-distance data processing nodes. Especially in some industries, WLAN will have great development opportunities:

For exhibitions and conferences on temporary occasions such as large conferences and exhibitions, WLAN allows staff to conveniently obtain computer network services, connect to the Internet, and obtain required information in a very short period of time, you can also use a mobile computer to exchange information, transmit manuscripts, and prepare reports.

Financial service banks and securities and futures trading businesses can connect institutions through wireless networks. Even if you already have a wired computer network, you still need to use the wireless computer network for backup to avoid line faults. The prices and "buy" and "sell" Information in securities and futures transactions are extremely fast and frequently changed. handheld communication devices are used to input information, quickly transmits data to the computer, quotation service system, and display board in the trading hall through a computer wireless network. administrators, brokers, and traders can quickly manage information or directly trade data using handheld communication devices, this avoids the loss of inaccurate information and time delay caused by gestures, splitters, and manual input.

Travel Service hotels use WLAN to provide timely and thoughtful services to customers anytime and anywhere. Once a registration and accounting system is established, customers can perform any activities, such as in bars, gymnasiums, entertainment halls, or restaurants, in any location within the region, you can update the accounting system through the attendant's hand-held communication terminal without waiting for the results of the complex accounting system.

The mobile office system uses WLAN in the office environment, which enables office computers to move and roaming computers within the network. Various business personnel, department heads and engineering and technical experts, as long as there are mobile terminals or laptops, whether in the office, Data room, negotiation room, you can view information and obtain information at any time through WLAN even in the dormitory. Leaders and management personnel can issue instructions, notification items, and contact businesses anywhere on the network. That is to say, mobile office can be performed anytime, anywhere.

It is foreseeable that with the popularity of Open Office and the popularity of handheld devices, there are more and more demands for mobile access and storage information, therefore, WLAN will be widely used in office, production, home and other fields. WPAN)

Concepts and technologies related to wireless LAN

In a typical WLAN environment, there are some devices that send and receive data, called AP ). Generally, an AP can connect to multiple wireless users in the range of dozens to hundreds of meters. When both wired and wireless networks are available, the AP can connect to a traditional wired network through a standard Ethernet cable as a connection point between the wireless network and the wired network. WLAN end users can access the network through wireless network interfaces.

WLAN applications have the following two types of situations:

1. Independent WLAN refers to the situation where wireless communication is used throughout the network. In this mode, you can use AP or do not use AP. When no AP is used, each user is directly connected through wireless connection. The disadvantage is that the communication distance between users is close, and the performance is poor when the number of users is large.

2. Non-independent WLAN in most cases, wireless communication is a supplement and extension of wired communication. We call this situation a non-independent WLAN. In this configuration, multiple APs are connected to the wired network through cables, so that wireless users can access all parts of the network.

Other related concepts

1. The micro-unit and wireless roaming radio waves will constantly decay during transmission, so that the AP's communication range is limited to a certain range. This range is called a microunit. When multiple APS exist in the network environment and their micro-units have a fixed range of overlap, wireless users can move across the WLAN coverage area, the wireless network adapter can automatically discover the AP with the highest signal strength nearby and send and receive data through this AP to maintain uninterrupted network connections. This is called wireless roaming.

2. Most WLAN devices use the Spread Spectrum Technology. The Spread Spectrum Technology was originally a broadband wireless communication technology used in the military communication field. The Spread Spectrum Technology can make the data complete and reliable in wireless transmission, and ensure that the data transmitted in different frequencies at the same time will not interfere with each other.

3. direct Sequence Spread Spectrum refers to the use of a High-Bit Rate Spread Spectrum to expand the signal spectrum at the transmitting end, while the same Spread Spectrum Code sequence is used at the receiving end for de-expansion, returns the expanded spread spectrum signal to the original signal.

4. the hop-Frequency Spread Spectrum Technology is completely different from the direct-order spread spectrum technology. It is another spread spectrum technology. The frequency of a hop frequency is controlled by a pseudo-random code. The frequency of a hop frequency changes according to the random pattern within the bandwidth range. The frequency of the receiver also varies randomly and remains consistent with that of the transmitter.