ZyXEL Communications 2WG - Manual (Page 262)

ZyWALL 2WG Support Notes
All contents copyright (c) 2006 ZyXEL Communications Corporation.
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at 11 Mbps or lower depending on range. The range at 54 Mbps is less than for 802.11b operating at 11
Mbps.
H08. What is 802.11a?
802.11a the second revision of 802.11 that operates in the unlicensed 5 GHz band and allows
transmission rates of up to 54Mbps. 802.11a uses OFDM (orthogonal frequency division multiplexing)
as opposed to FHSS or DSSS. Higher data rates are possible by combining channels. Due to higher
frequency, range is less than lower frequency systems (i.e., 802.11b and 802.11g) and can increase the
cost of the overall solution because a greater number of access points may be required. 802.11a is not
directly compatible with 802.11b or 802.11g networks. In other words, a user equipped with an 802.11b
or 802.11g radio card will not be able to interface directly to an 802.11a access point. Multi-mode NICs
will solve this problem.
H09. What is Wi-Fi?
The Wi-Fi logo signifies that a product is interoperable with wireless networking equipment from other
vendors. A Wi-Fi logo product has been tested and certified by the Wireless Ethernet Compatibility
Alliance (WECA). The Socket Wireless LAN Card is Wi-Fi certified, and that means that it will work
(interoperate) with any brand of Access Point that is also Wi-Fi certified.
H10. What types of devices use the 2.4 GHz Band?
Various spread spectrum radio communication applications use the 2.4 GHz band. This includes
WLAN systems (not necessarily of the type IEEE 802.11b), cordless phones, wireless medical
telemetry equipment and Bluetooth™ short-range wireless applications, which include connecting
printers to computers and connecting modems or hands-free kits to mobile phones.
H11. Can wireless signals pass through walls?
Transmitting through a wall is possible depending upon the material used in its construction. In general,
metals and substances with a high water content do not allow radio waves to pass through. Metals
reflect radio waves and concrete attenuates radio waves. The amount of attenuation suffered in passing
through concrete will be a function of its thickness and amount of metal re-enforcement used.
H12. What are the potential factors that may causes interference among WLAN
products?
Factors of interference:
1. Obstacles: walls, ceilings, furniture… etc.