Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter Guide De Conception
3-5
Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 3 WLAN Radio Frequency Design Considerations
RF Basics
The new additional 11 channels are for indoor/outdoor use. To use the 11 new channels, however, radios
must comply with two features that are part of the 802.11h specification: TPC and DFS. DFS is required
to avoid radar that operates in this frequency range, but it can also be used for other purposes, such as
dynamic frequency planning. 802.11h has been supported since Cisco Unified Wireless Network
Software Release 3.1.
must comply with two features that are part of the 802.11h specification: TPC and DFS. DFS is required
to avoid radar that operates in this frequency range, but it can also be used for other purposes, such as
dynamic frequency planning. 802.11h has been supported since Cisco Unified Wireless Network
Software Release 3.1.
DFS dynamically instructs a transmitter to switch to another channel whenever a particular condition
(such as the presence of a radar signal) is met. Before transmitting, the DFS mechanism of a device
monitors its available operating spectrum, listening for a radar signal. If a signal is detected, the channel
associated with the radar signal is vacated or flagged as unavailable for use by the transmitter. The
transmitting device continuously monitors the environment for the presence of radar, both prior to and
during operation. Portions of the 5 GHz band are allocated to radar systems, which allows WLANs to
avoid interference with incumbent radar users in instances where they are collocated.
(such as the presence of a radar signal) is met. Before transmitting, the DFS mechanism of a device
monitors its available operating spectrum, listening for a radar signal. If a signal is detected, the channel
associated with the radar signal is vacated or flagged as unavailable for use by the transmitter. The
transmitting device continuously monitors the environment for the presence of radar, both prior to and
during operation. Portions of the 5 GHz band are allocated to radar systems, which allows WLANs to
avoid interference with incumbent radar users in instances where they are collocated.
TPC allows the AP to negotiate power levels with a WLAN client during that association process. The
AP can inform that WLAN client of the range of allowable transmit power to be used with that AP, and
may reject clients unable to meet those levels. The WLAN client is able to adjust its transmit power level
within the range specified in the TPC negotiations. This ensures that interference from the WLAN is
minimized and allows the WLAN client to optimize battery life.
AP can inform that WLAN client of the range of allowable transmit power to be used with that AP, and
may reject clients unable to meet those levels. The WLAN client is able to adjust its transmit power level
within the range specified in the TPC negotiations. This ensures that interference from the WLAN is
minimized and allows the WLAN client to optimize battery life.
For more information on FCC regulation updates, see the following URL:
shows the standard 802.11a frequencies.
shows the specific frequency bands and channel numbers for a few specific regulatory
domains.
Table 3-3
Operating Frequency Range for 802.11a
Channel
ID
ID
36
40
44
48
52
56
60
64
100
104
108
112
116
120
124
128
132
136
140
149
153
157
161
Center
Freq.
MHz
Freq.
MHz
5180
5200
5220
5240
5260
5280
5300
5320
5500
5520
5540
5560
5580
5600
5620
5640
5660
5680
5700
5745
5765
5785
5805
Band
UNII-1
UNII-2
UNNII-3
Table 3-4
Additional Frequency Bands and Channel Numbers for Other Regulatory Domains
Regulatory Domain
Frequency Band
Channel Number
Center Frequency
Japan
U-NII lower bands
36
40
44
48
5.180
5.200
5.220
5.240
Singapore
U-NII lower band
36
40
44
48
5.180
5.200
5.220
5.240