Cisco Cisco BPX 8680 8800 Series MGX-CESM-T3 E3 CESM Weißbuch
Wireless LAN Design Guide for High Density
Client Environments in Higher Education
29 © 2011 Cisco and/or its affiliates. All rights reserved.
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Shadows
Features in a room such as support columns or balconies can represent natural shadows within a room. Under normal
densities, such features would require an additional AP to ensure coverage for users placed in such a shadow. In a high-density
installation, these features can be used to advantage, increasing the channel reuse by designing to maximize this effect and then
filling with another channel.
densities, such features would require an additional AP to ensure coverage for users placed in such a shadow. In a high-density
installation, these features can be used to advantage, increasing the channel reuse by designing to maximize this effect and then
filling with another channel.
Under Seat Mounting
One of the optimal ways to cover a large, dense area is from underneath the users. This provides two advantages. First, the
users themselves attenuate the signals (so more APs can be accommodated with channel reuse than other more open methods
would allow). Second, this can generally provide a great way to hide APs. To do this successfully, a few experiments must be
performed to evaluate the propagation characteristics of the mounting location. Under seat or under desk mounting can provide
from 6 dB to 20 dB of attenuation to the cell, depending on the openness of the mounting options.
users themselves attenuate the signals (so more APs can be accommodated with channel reuse than other more open methods
would allow). Second, this can generally provide a great way to hide APs. To do this successfully, a few experiments must be
performed to evaluate the propagation characteristics of the mounting location. Under seat or under desk mounting can provide
from 6 dB to 20 dB of attenuation to the cell, depending on the openness of the mounting options.
It is important to note that metal chair legs and desk components will interact with the antenna of the AP and change the pattern
of the radiation. Surveying the results of placement decisions with a good tool is necessary before making permanent mounting
decisions. This can be done by selecting a representative section of the room and placing a minimum of 4 APs (even more is
better) temporarily in place. Analyzing more than one mounting option will yield comparative data that will be helpful in making a
final decision.
of the radiation. Surveying the results of placement decisions with a good tool is necessary before making permanent mounting
decisions. This can be done by selecting a representative section of the room and placing a minimum of 4 APs (even more is
better) temporarily in place. Analyzing more than one mounting option will yield comparative data that will be helpful in making a
final decision.
The solution chosen should provide decent attenuation and a usable pattern. Having shadows in this type of mounting is not
a problem and may be useful if the shadows are consistent and filled in by other cells. This may sound like considerable work
but the results can be well worth the effort. Generally, use of APs with internal antennas is recommended for this type of
installation. Experiment with the AP antennas pointed both up and down. Do not be overly concerned about the power levels;
in an empty room they will generally look very high when compared to a normal installation. As a final test, select a portion
of the room
a problem and may be useful if the shadows are consistent and filled in by other cells. This may sound like considerable work
but the results can be well worth the effort. Generally, use of APs with internal antennas is recommended for this type of
installation. Experiment with the AP antennas pointed both up and down. Do not be overly concerned about the power levels;
in an empty room they will generally look very high when compared to a normal installation. As a final test, select a portion
of the room
―perhaps 25 percent of the seating area―and measure the site with users present. This can be done using a non
production service set identifier (SSID)
to prevent attracting live users.
What we are evaluating at this stage is placement, not
user throughput. Look at CCI and the coverage pattern to evaluate the effectiveness of the design.