TopTechnical Dictionary802.11b - wireless network standard

802.11b - wireless network standard

A group of IEEE 802.11 standards define a physical layer and a MAC address of the wireless local area networks WLAN (commonly known in Poland as Wi-Fi). It includes four independent protocols (a, b, g and n). The first commonly used protocol was 802.11b.

 

The frequencies used in 802.11 are not licensed and those networks can be set up without any permits. The only limitation is the EIRP (Equivalent Isotropical Radiated Power). In Poland, EIRP must not exceed 100 mW for 2.4 GHz band and 1 W for 5.470 GHz…5.725 GHz band.

 

For 802.11b, the maximum distance can be up to approx. 50 m indoors and approx. 100 m outdoors. The bit rates for devices using this standard are up to 11 Mb/s. Any obstacles in the way of radio waves including walls, doors, glass or metal may effectively reduce the signal quality and thus the bit rate, leading to the communication issues. This standard users several algorithms to remove the interferences and prevent conflicts when using a large number of network adapters.

 

The maximum distance can be extended with directional antennas up to several kilometres. The most important factor determining the maximum distance is a direct optical visibility of the antennas and the lowest interference in the transmission path.

 

802.11b transmission band can support bit rates up to 11 Mb/s divided into 5.5 Mb/s, 2 Mb/s and 1 Mb/s if a large number of errors is detected in the transmission channel. The band can be divided into 14 channels at a constant width of 22 Mhz. In Poland, the band available for those networks is 2.4 GHz...2.4835 GHz corresponding to 13 channels.

 

Table 1. Channel numbers and corresponding frequency

 

Channel number

Low channel frequency

Mid channel frequency

High channel frequency

GHz GHz GHz
1 2.401 2.412 2.423
2 2.406 2.417 2.428
3 2.411 2.422 2.433
4 2.416 2.427 2.438
5 2.421 2.432 2.443
6 2.426 2.437 2.448
7 2.431 2.442 2.453
8 2.436 2.447 2.458
9 2.441 2.452 2.463
10 2.446 2.457 2.468
11 2.451 2.462 2.473
12 2.456 2.467 2.478
13 2.461 2.472 2.483
14 2.473 2.484 2.495

Wi-Fi Wi-Fi networks, including 802.11b are usually designed for indoor use. The wave propagation inside the buildings is relatively difficult. When designing Wi-Fi networks, all the obstacles on the propagation path must be allowed for.

 


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