Factory Line - Wireless LAN
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7190_en_02
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Channel 14 is approved in Japan
Figure 1-6
Frequencies and channels in IEEE 802.11b
1.3.1.1
Compatibility within the standard
In order to ensure the compatibility of devices from various manufacturers, about
40 manufacturers and a neutral independent test lab have joined together to form the WECA
(Wireless Ethernet Compatibility Alliance).
The WECA now uses the name Wi-Fi (Wireless Fidelity) to certify compatibility between
devices that use the 802.11 standard, and monitors the observance of the general standards.
1.3.1.2
Channel access
Similar to the CSMA/CD method in wired networks, in IEEE 802 the CSMA/CA (Carrier
Sense Multiple Access with Collision Avoidance) method is specified for channel access in
wireless networks. The system also checks that the medium is free before transmission is
started.
However, instead of a collision detection method (CSMA/CD), a collision avoidance method
(CSMA/CA) is used. To avoid collisions, a protocol is used, which reserves a channel for a
short period prior to a transmission and thus enables error-free transmission. This method
does not provide protection from the hidden node problem.
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