Руководство По Проектированию для Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter
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Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 3 WLAN Radio Frequency Design Considerations
Radio Resource Management (Auto-RF)
Radio Resource Management (Auto-RF)
) the processing of 802.11 data and management protocols and access point capabilities is
distributed between a lightweight access point and a centralized WLAN controller. More specifically,
time-sensitive activities, such as probe response and MAC layer encryption, are handled at the access
point. All other functions are sent to the controller, where system-wide visibility is required.
time-sensitive activities, such as probe response and MAC layer encryption, are handled at the access
point. All other functions are sent to the controller, where system-wide visibility is required.
Real-time RF management of a WLAN network requires system-wide visibility and is implemented at
the controller level. The controller learns about the necessary information for an effective RF
channel/power plan via information forwarded by the APs in the RF network group.
the controller level. The controller learns about the necessary information for an effective RF
channel/power plan via information forwarded by the APs in the RF network group.
Note
An RF network group (or RF group) is not the same as a mobility group. A mobility group defines a
mobility domain of 1–25 controllers in which a client would not be required to change IP address during
a roaming event. This is accomplished by building Ethernet over IP tunnels for forwarding client data
from an “anchor” controller to the “foreign” controller handling the new AP servicing the client.
mobility domain of 1–25 controllers in which a client would not be required to change IP address during
a roaming event. This is accomplished by building Ethernet over IP tunnels for forwarding client data
from an “anchor” controller to the “foreign” controller handling the new AP servicing the client.
Radio Resource Management (RRM), also known as Auto-RF, can adjust the channel (dynamic channel
assignment) and power (dynamic transmit power control) to maintain the RF coverage area. It adjusts
the power level of the AP to maintain a baseline signal strength with neighboring APs at -65 dBm
(configurable) (See
assignment) and power (dynamic transmit power control) to maintain the RF coverage area. It adjusts
the power level of the AP to maintain a baseline signal strength with neighboring APs at -65 dBm
(configurable) (See
). It adjusts the channel of the AP when
it notices nearby interference sources on the channel on which the AP is currently located. It continues
to optimize the RF coverage for the best reception and throughput for the wireless network.
to optimize the RF coverage for the best reception and throughput for the wireless network.
Note
The transmit power control and dynamic frequency management performed by RRM are not the TPC
and DFS required for operation in the UNII-2 bands that are defined in 802.11h.
and DFS required for operation in the UNII-2 bands that are defined in 802.11h.
RRM understands that the RF environment is not static. As different RF affecting variables change
(people in the room, amount of devices stored in the facility, leaves on trees for outside deployment,
interference from different RF sources, and so on), the RF coverage adjusts to these variables and
changes with them. Because these variables change continuously, monitoring for the RF coverage and
adjusting it periodically is necessary.
(people in the room, amount of devices stored in the facility, leaves on trees for outside deployment,
interference from different RF sources, and so on), the RF coverage adjusts to these variables and
changes with them. Because these variables change continuously, monitoring for the RF coverage and
adjusting it periodically is necessary.
WLC software Release 4.185 introduced significant number of enhancements to Radio Resource
Management (Auto-RF). For details on the changes and operation, see the following URL:
Management (Auto-RF). For details on the changes and operation, see the following URL:
.
Overview of Auto-RF Operation
Each controller is configured with an RF network group name (called RF Network Name under the WLC
Controller -> General menu). In each RF group (if Group Mode is enabled), the controllers elect a leader
and form an RF domain. The function of the leader is to collect the network-wide neighbor information
from a group of controllers and do the channel/power computation for an optimal system-wide map. If
Group Mode is not enabled, the controllers run computations based only on the neighbor data gathered
from the APs connected via LWAPP, trying to optimize the signal to -70 dBm between APs.
Controller -> General menu). In each RF group (if Group Mode is enabled), the controllers elect a leader
and form an RF domain. The function of the leader is to collect the network-wide neighbor information
from a group of controllers and do the channel/power computation for an optimal system-wide map. If
Group Mode is not enabled, the controllers run computations based only on the neighbor data gathered
from the APs connected via LWAPP, trying to optimize the signal to -70 dBm between APs.
The APs transmit Radio Resource Management (RRM) neighbor packets at full power at regular
intervals. These messages contain a field that is a hash of the RF group name, BSSID, and time stamp.
The APs accept only RRM neighbor packets sent with this RF network name.
intervals. These messages contain a field that is a hash of the RF group name, BSSID, and time stamp.
The APs accept only RRM neighbor packets sent with this RF network name.