Cisco Cisco BPX 8680 8800 Series MGX-CESM-T3 E3 CESM Weißbuch
Wireless LAN Design Guide for High Density
Client Environments in Higher Education
28 © 2011 Cisco and/or its affiliates. All rights reserved.
Ceiling heights can be much higher in a college lecture hall than they would be in a normal classroom environment. A normal
ceiling height may be 8-12 feet but in a lecture hall it could be 20 feet or more. This will impact the resulting RF levels seen
at the client’s position if it is not taken into consideration in the design. Because Cisco APs centralize their RF management,
AP to AP neighbor relations will not be effected between the APs, but the APs will be closer to one another than they are to
the client and this will require some threshold tuning. Typically, an adjustment of 3-8 dB on the transmit power control (TPC)
threshold will be sufficient to increase the power to a comfortable level at the floor. This is a one-time adjustment that biases the
entire installation. Very good results can be achieved in this way. If directional antennas are used in this way, the additional gain
associated with the antenna will generally offset the path loss associated with a high ceiling, but with very high ceilings (30+ feet)
adjustments to TPC may be required, depending on the antenna chosen.
ceiling height may be 8-12 feet but in a lecture hall it could be 20 feet or more. This will impact the resulting RF levels seen
at the client’s position if it is not taken into consideration in the design. Because Cisco APs centralize their RF management,
AP to AP neighbor relations will not be effected between the APs, but the APs will be closer to one another than they are to
the client and this will require some threshold tuning. Typically, an adjustment of 3-8 dB on the transmit power control (TPC)
threshold will be sufficient to increase the power to a comfortable level at the floor. This is a one-time adjustment that biases the
entire installation. Very good results can be achieved in this way. If directional antennas are used in this way, the additional gain
associated with the antenna will generally offset the path loss associated with a high ceiling, but with very high ceilings (30+ feet)
adjustments to TPC may be required, depending on the antenna chosen.
If overhead mounting is not an option, (e.g., there is no access above the ceiling level for cables or the entire room was designed
so that nothing is on the ceiling or if there is a large skylight) there are many other mounting options.
so that nothing is on the ceiling or if there is a large skylight) there are many other mounting options.
Side Mounting
Depending on the dimensions of the room, it may be possible to cover the entire room from the sides. If the room is wider than
two cells will accommodate (assuming each cell is covering one half of the room), it will be necessary to use directional antennas
and mechanical downtilt to cover individual sections of the room for each radio. Large rooms will have aisles separating seating
sections and this space may be used to design cell overlap areas. If mechanical downtilt and directional antennas are used to
achieve this, the higher the antenna may be mounted and the larger the resulting cell will be. Good results can be achieved with
antennas mounted as low as eight feet up on the wall with 30-60 degrees of downtilt.
two cells will accommodate (assuming each cell is covering one half of the room), it will be necessary to use directional antennas
and mechanical downtilt to cover individual sections of the room for each radio. Large rooms will have aisles separating seating
sections and this space may be used to design cell overlap areas. If mechanical downtilt and directional antennas are used to
achieve this, the higher the antenna may be mounted and the larger the resulting cell will be. Good results can be achieved with
antennas mounted as low as eight feet up on the wall with 30-60 degrees of downtilt.
Front and Rear Mounting
The fronts and rear of rooms are other areas where there will generally be open space between the edge of the room and the
users. In a theater style room, look for mounting positions under or in front of the raised platform or stage and the overhead
facing out. It is possible to place APs in both locations, using the lower position on or near the floor and antennas such as the
AIR-ANT2460NP-R at 80 degrees horizontal and 75 degrees vertical to cover the first rows. (Note that two of these provide
almost a full 180 degrees of coverage and two channels of 2.4 GHz). For 5 GHz, use the AIR-ANT5160NP-R at 65 degrees
horizontal and vertical. Additional APs can be mounted near the ceiling facing back into the room using the AIR-ANT25137NP-R
at 55 degrees vertical and horizontal to cover the section behind the first rows (with 55 degrees, 3-4 channels). This pattern can
be repeated from the rear of the room and it will provide a lot of channels from the perimeter.
users. In a theater style room, look for mounting positions under or in front of the raised platform or stage and the overhead
facing out. It is possible to place APs in both locations, using the lower position on or near the floor and antennas such as the
AIR-ANT2460NP-R at 80 degrees horizontal and 75 degrees vertical to cover the first rows. (Note that two of these provide
almost a full 180 degrees of coverage and two channels of 2.4 GHz). For 5 GHz, use the AIR-ANT5160NP-R at 65 degrees
horizontal and vertical. Additional APs can be mounted near the ceiling facing back into the room using the AIR-ANT25137NP-R
at 55 degrees vertical and horizontal to cover the section behind the first rows (with 55 degrees, 3-4 channels). This pattern can
be repeated from the rear of the room and it will provide a lot of channels from the perimeter.
In Figure 14, APs have been mounted low to the floor, providing a cell that will use the users to attenuate the propagation
distance. APs have also been mounted near the ceiling using mechanical downtilt to manage the resulting cell size.
distance. APs have also been mounted near the ceiling using mechanical downtilt to manage the resulting cell size.