The hottest WLAN standard ieee80211b standard brie

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Brief analysis of IEEE 802.11b standard for wireless local area network

in the past, wireless local area network developed slowly and was difficult to popularize and apply, mainly due to low transmission rate, high cost, limited product series, and many products are not compatible with each other. For example, in the past, the rate of wireless local area network was only 1 ~ 2mb/s, and many applications were designed based on 10mb/s Ethernet rate, which limited the application types of wireless products. For the rapid growth of data services and multimedia services, the key to the progress of wireless local area network lies in the formulation of new high-speed standards and the emergence of 10mb/s or even higher rate products based on this standard. IEEE 802.11b fundamentally changes the design and application status of wireless local area network, meets the needs of people to achieve uninterrupted mobile office in a certain area, and creates a free space for us

■ introduction to 802.11b standard

ieee 802.11b wireless local area network has a maximum bandwidth of 11Mbps, which is five times faster than the IEEE 802.11 standard just approved two years ago, expanding the application field of wireless local area network. In addition, 5.5mbps, 2 Mbps and 1 Mbps bandwidths can also be used according to the actual situation. The actual working speed is about 5mb/s, which is almost at the same level as the ordinary 10Base-T specification wired local area network. As an internal facility of the company, it can basically meet the use requirements. IEEE 802.11b uses the open 2.4GB band, which can be used without application. It can not only be used as a supplement to the wired network, but also can be grouped independently, so that the network users can get rid of the shackles of the line and realize the real mobile application

ieee 802.11b wireless local area network is very similar to the familiar principle of IEEE 802.3 Ethernet, which uses carrier sense to control the transmission of information in the network. The difference is that csma/cd (carrier sense/collision detection) is used in Ethernet × 25mm × 2=1250mm2=12.5cm2;) Technology, all workstations on the network listen to whether there is information sent in the network, and send their own information when the network is found to be idle. Like answering, only one workstation can grab the right to speak, while the rest of the workstations need to continue to wait. If more than two workstations send messages at the same time, conflicts will occur in the network. After the conflict, these conflicting messages will be lost, and each workstation will continue to seize the right to speak. 802.11b wireless local area network introduces conflict avoidance technology, which can avoid the occurrence of conflicts in the network and greatly improve the network efficiency

ieee 802.11b advantages

function advantages

speed 2.4GHz direct sequence spread spectrum radio provides a maximum data transmission rate of 11Mbps, without linear propagation

dynamic rate conversion. When the RF condition becomes worse, reduce the data transmission rate to 5.5mbps 2Mbps and 1Mbps

range of use 802.11b supports a range of 100 meters (300 meters outdoors; 100 meters at most in an office environment)

reliability connection protocols and packet confirmation similar to Ethernet provide reliable data transmission and effective use of network bandwidth

interoperability unlike previous standards, 802.11b only allows one standard signal transmission technology. WECA will certify the interoperability of products

power management 802.11b network interface card can be switched to sleep mode, and the access point will buffer the information to the customer, extending the battery life of notebook computers

roaming support allows seamless connection between access points when users move between buildings or company departments

load balanced 802.11b NIC to change the access point connected to it, To improve performance (for example, when the current access point traffic is crowded, or sends low-quality signals)

scalability up to three access points can be positioned in the effective use range at the same time to support hundreds of users

simultaneous voice and data support

Security built-in authentication and encryption

■ the basic operation mode of 802.11b

the operation mode of 802.11b is basically divided into two types: point-to-point mode and basic mode, As shown in Figure 1. Point to point mode refers to the communication mode between wireless card and wireless card. As long as the PC is plugged in with a wireless card, it can connect with another PC with a wireless card. For small wireless networks, it is a convenient connection method, which can connect up to 256 PCs. The basic mode refers to the communication mode when the wireless network scale is expanded or the wireless and wired networks coexist, which is the most commonly used mode of 802.11b. At this time, the PC with the wireless card needs to be connected with another PC by the access point. The access point is responsible for frequency band management, roaming and other command work. One access point can connect 1024 PCs (wireless cards) at most. When wireless network nodes are expanded, the network access speed will slow down with the expansion of the range and the increase of nodes. At this time, adding access points can effectively control and manage the bandwidth and frequency band. When wireless networks need to be interconnected with wired networks, or wireless network nodes need to connect and access wired resources and servers, access points can be used as a bridge between wireless and wired

■ typical solution of 802.11b

802.11b wireless local area network is especially suitable for small office environments and home networks because of its convenience and scalability. In the indoor environment, there can be different typical solutions for different actual situations

peer to peer solution

peer to peer solution is the simplest application solution. As long as you install a wireless card on each computer, you can access each other. If you need to connect with the wired network, you can install another wired card for one of the computers, and the rest of the computers in the wireless use this computer as data: turn off after the experiment, and access the wired network or shared printers and other devices

but peer-to-peer solution is a point-to-point solution. Computers in the network can only transfer information to each other one-to-one, and cannot access multiple points at the same time. If you want to realize the interworking function like wired local area, you must use access points

single access point solution

access points are equivalent to hubs in wired networks. The wireless access point can connect the surrounding wireless network terminals to form a star network structure, and connect with the wired network through the 10Base-T port, so that the entire wireless terminal can access the resources of the wired network and access the Internet through the router

802.11b application

functional advantages

areas where wiring is difficult or wiring costs are high (such as historic buildings, buildings with asbestos, and classrooms) Providing network services in

flexible workgroups reduce the total cost of ownership for workspaces that often make network configuration changes

networked conference room users can make network connections when moving from one conference room to another to obtain the latest information, And they can communicate with each other when making decisions.

the rapid installation and compatible software of special network field consultants and small working groups can improve work efficiency.

subsidiary networks provide networks for remote or sales offices that are easy to install, use and maintain.

Department wide network migration animation game function enables enterprises to establish easy-to-use wireless networks that can cover all departments.

generally speaking, 802.11b allows the use of any existing application or network service running on a wired network

multi access point solution

when the network scale is large and exceeds the coverage radius of a single access point, multiple access points can be used to connect with the wired network respectively, so as to form a multi access point wireless network with the wired network as the backbone. All wireless terminals can access the network through the nearest access point to access the resources of the whole network, so as to break through the limitation of the wireless coverage radius

wireless relay solution

wireless access device has another purpose, that is, it acts as an extension of wired network. For example, in the factory workshop, the workshop has a network interface to connect wires, and many information points in the workshop have high network wiring costs due to their long distance, and some information points cannot be wired due to the poor surrounding environment. Since the distribution range of these information points exceeds the coverage radius of a single access point, we can use two access points to realize wireless relay to expand the coverage of the wireless network

wireless redundancy solution

for application environments that require high network reliability, such as finance, securities, etc., once the access point fails, the entire wireless network will be paralyzed, which will bring great losses. Therefore, two access points can be placed in the same location, so as to realize the wireless redundant backup scheme

multi cell roaming working mode

when deploying wireless networks in a building or in a large plane, multiple access points can be arranged to form a set of microcellular systems, which is very similar to mobile microcellular systems. Microcellular system allows a user to roam freely in the coverage area of different access points. With the change of location, the signal will be automatically switched from one of these access points with less market competition to another access point. The whole roaming process is transparent to users. Although the access points providing connection services have been switched, the services to users will not be interrupted

■ the application prospect of 802.11b

the early 802.11b wireless local area network technology has achieved success in vertical market applications, such as production, inventory control and retail outlets. In 1999, it has achieved sales of US $400million. With the substantial improvement of 802.11b performance price ratio, a new horizontal market application will be launched in full swing. Enterprises will be able to use wireless local area as an extension of their limited local area. This application will enable them to connect with company applications and network peripherals in an all-round way, thus greatly improving employees' work efficiency in mobile. Wireless local area technology will first be applied to conference halls and department offices of enterprises. With its in-depth use, it will eventually be applied to every corner of the company. Small businesses and home users will also use wireless LAN instead of wired network, so as to obtain the savings in "wireless" installation and maintenance provided by wireless LAN

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