Ap, Channel, And Domain Relationships - Cisco 7925G - Unified Wireless IP Phone VoIP Administration Manual

Understanding WLAN Standards and Technologies
•
Table 2-3
standard.
Table 2-3
Item
Data Rates
Non-overlapping
Channels
Wireless
Modulation

AP, Channel, and Domain Relationships

APs transmit and receive RF signals over channels within the 2.4 GHz or 5.1 to 5.8 GHz frequency band.
To provide a stable wireless environment and reduce channel interference, you must specify
non-overlapping channels for each AP. The recommended channels for 802.11b and 802.11g in North
America are 1, 6, and 11.
Regulatory domains determine the number of channels that wireless communications can use within the
frequency band.
regulatory domains. The Cisco Unified Wireless IP Phone 7925G uses the fourth domain for all other
regions in the world. Wireless LANs in the rest of the world use 802.11d to identify band ranges and
channels.
In a non controller-based wireless network, it is recommended that you statically configure channels for
Note
each AP. If your wireless network uses a controller, use the Auto-RF feature with minimal voice
disruption.
The AP coverage area depends on its type of antenna and transmission power. The AP coverage range
is from 500 to 1000 feet with effective isotropic radiated power (EIRP) output that scales at 1, 5, 20, and
50 mW. To provide effective coverage, APs need a range overlap of approximately 20 percent to allow
uninterrupted connections as phone users roam from one AP to another.
Wireless networks use a service set identifier (SSID). The SSID differentiates one WLAN from another,
so all APs and all devices attempting to connect to a specific WLAN must use the same SSID. The SSID
groups user devices and associates the group with the APs.
For more information about wireless network components and design, refer to the Overview: Cisco
Unified Wireless Network at
http://www.cisco.com/en/US/solutions/ns175/networking_solutions_products_genericcontent0900aecd
80529a5f.html.
For more information about APs, see the
Cisco Unified Wireless IP Phone 7925G Administration Guide for Cisco Unified Communications Manager 7.0(1)
2-6
Orthogonal Frequency Division Multiplexing (OFDM)—Transmits signals by using RF. OFDM is
a physical–layer encoding technology that breaks one high-speed data carrier into several
lower-speed carriers to transmit in parallel across the RF spectrum. OFDM, when used with 802.11g
and 802.11a, can support data rates as high as 54 Mbps.
provides a comparison of data rates, number of channels, and modulation technologies by
Data Rates, Number of Channels, and Modulation Technologies by IEEE Standard
802.11b
1, 2, 5.5, 11 Mbps
3 (Japan uses 4)
DSSS
Table 2-1 lists the frequency ranges, operating channels, and product numbers for four
Chapter 2
802.11g
6, 9, 12, 18, 24, 36, 48, 54
Mbps
3 (Japan uses 4)
DSSS, ODFM
"VoIP WLAN Configuration" section on page
Overview of the VoIP Wireless Network
802.11a
6, 9, 12, 18, 24, 36, 48, 54
Mbps
Up to 23
ODFM
2-21.
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