Руководство По Проектированию для Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter
9-4
Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 9 VoWLAN Design Recommendations
Channel Utilization
Figure 9-2
Typical Office Channel Utilization for 2.4 GHz and 5 GHz
Before the installation of the Cisco Unified Wireless Network, a site can be tested for channel
interference and utilization with tools from AirMagnet, Wild Packets, Cognio, and others. The Wireless
Control System (WCS) AP On-Demand Statistics Display report provides a spectrum review of the
following:
Control System (WCS) AP On-Demand Statistics Display report provides a spectrum review of the
following:
•
Noise by channel
•
Interference by channel
•
Client count versus RSSI
•
Client count versus SNR
•
Channel radar detection versus time
Dynamic Frequency Selection (DFS) and 802.11h Requirements of the APs
The Federal Communications Commission (FCC) of the United States, the European
Telecommunications Standards Institute (ETSI), and other regulatory agencies have requirements
regarding the use of radio frequencies. Portions of the 5 GHz band have been and are currently being
used for radar, such as weather radar. Although most 5 GHz radar systems generally use higher
frequencies with shorter wavelengths, there are still systems in place that overlap with some Wi-Fi
UNII-2 bands. In 2006, the FCC opened the frequencies in the 5470–5725 MHz range to unlicensed use.
With these additional frequencies came a requirement to maintaining an “interference-free” AP
configuration. The AP must constantly monitor for radar pulses (typically from military, satellite, and
weather stations), and must automatically switch to a “clean” channel if radar is detected.
Telecommunications Standards Institute (ETSI), and other regulatory agencies have requirements
regarding the use of radio frequencies. Portions of the 5 GHz band have been and are currently being
used for radar, such as weather radar. Although most 5 GHz radar systems generally use higher
frequencies with shorter wavelengths, there are still systems in place that overlap with some Wi-Fi
UNII-2 bands. In 2006, the FCC opened the frequencies in the 5470–5725 MHz range to unlicensed use.
With these additional frequencies came a requirement to maintaining an “interference-free” AP
configuration. The AP must constantly monitor for radar pulses (typically from military, satellite, and
weather stations), and must automatically switch to a “clean” channel if radar is detected.
When radar is detected, the system must do the following:
220351
2.4 GHz Band – 1%
5 GHz Band – Less than a 0.25%