In the figure above, clients farther away are on the air more (sending longer, slower rate packets). The 2.4
–
GHz
channels (channel 1) will typically propagate farther than 5
–
GHz so often the 2.4
–
GHz radio is redundant
and in some cases is even turned off. So now the AP is covering a single 5
–
GHz cell in a Macro or large cell
mode.
Using FRA, you can either automatically enable an additional 5
–
GHz cell using Radio Resource Management
or you can manually decide that you would like to turn the XOR radio from its default 2.4
–
GHz to an additional
5
–
GHz cell.
Figure 29: Enabling the FRA XOR radio as a dual 5 GHz AP creating Micro (yellow) and Macro (green cell)
By optimizing the FRA to enable the access point to have two 5
–
GHz radios, this solves the problem of too
much 2.4
–
GHz coverage while creating two completely RF diverse 5
–
GHz cells. This not only doubles the
air time available to the 5
–
GHz clients, it also optimizes the client throughput by keeping like clients together
for better spectrum efficiency.
Now instead of 60% channel utilization with the clients in near field competing for airtime from the slower
farther away clients, like clients are now grouped with similar data rate characteristics.
Net result, channel utilization is now reduced to 20% on channel 36 and 24% on channel 108.
Currently both Macro (green) and Micro (yellow) cells use the same SSID by design; later releases will likely
allow for different SSIDs.
Cisco Aironet Series 2800/3800 Access Point Deployment Guide
28
Client Roaming in a Micro and Macro Cell
Understanding Macro and Micro Cells
