Documenting the Work
The site survey report describes the details that were
completed as part of the survey and what might need to be done in the
installation and configuration processes. When documenting the actual work,
include specific details about the following in the report:
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Analysis of the RF spectrum at the site
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AP location and mounting methods
-
Antenna type and mounting methods
-
AP configuration for RF (when applicable)
-
Coverage map for each AP
Including detailed descriptions about these items in a final
report will ensure that the details necessary for a properly installed and
easy-to-maintain WLAN are available.
Detail about the location, the type of mounting, the antennas
used, and the recommended cabling methods enhance the chances for an error-free,
easy install. Here you can use photographs to great effect (with little text
required). Use photos whenever possible.
When describing access point
(AP) locations, the site survey engineer should be as specific as possible. It
is recommended to use objects and identifiers to explain exactly where the AP is
to be located. Use a photo to identify this in the report, and label the photos
so that they correspond to the site map (see Figure 13-1).
If the AP is to be located in an aisle or hallway, specify
which aisle or hallway, and where it is located in the facility. If possible,
use some type of marking method (flagging tape or marker flags, for example) to
identify the exact location. This provides the installer with a defined location
and eliminates any question as to exactly where it goes.
Do not use as markers objects that might be temporary. If the
object has moved before the installer arrives, the installer might not be able
to find the location and might mount the equipment improperly.
Even more important than the AP location, the engineer must
specify with as much exactitude as possible where the antenna is to be located.
See the photograph in Figure 13-2.
Just stating "place the antenna on the wall above the
doorway" is not enough. The installer might not be aware of RF characteristics
and might place it behind the exit sign, so it is out of sight, thinking that
this would look better. "Place the antenna on the wall above the doorway, a foot
left of exit sign" is a better explanation. You can also use a picture to spell
out exactly what the description means (see Figure 13-2). Notice the duct tape used to temporarily
mount the antenna for the site survey. The AP and battery pack are placed above
the ceiling on the wall edge.
A detailed description of how the antenna is to be oriented
must be included. Whereas correctly positioning an antenna might seem simple to
some who have a basic understanding of RF and antennas, many others just do not
have such an understanding of proper positioning. In some cases, the installer
might have no knowledge of RF (or even networking for that matter). In one case,
a university installed APs with 2.2-dBi dipoles that both swiveled and had a
flexible 90-degree coupler. The installer assumed the energy from the antenna
was radiated out the end of the antenna, as with an LED pointer. Therefore, he
placed the antennas in a horizontal
mode, as shown in Figure 13-3, so that
the energy was "radiated out both ends." The end result was great performance on
the floors above and below, but poor performance on that floor itself.
If the antenna is omnidirectional, the engineer might mention
that the antenna is to be mounted vertically, with the cable or connector at the
top or bottom. If the antenna is directional, describe the direction in which
the antenna should be oriented. A patch antenna might be described as "facing
north" or "directed at the nursing station at the end of the hall," but unless
the installer has an understanding of that particular antenna, it might not be
installed properly. Again, a good photo can provide tremendous assistance here.
The more directional the antenna, the more important this description.
Another entry in a survey report should be parameters and
settings of an AP that can affect coverage. It is important to identify the
parameters that were used in the survey, including transmitter power levels (of
both the client and AP), data rates, channels, packet size, and thresholds. All
of these parameters can affect the overall survey results, and may or may not be
the same throughout a facility. If there is both a warehouse and an office
environment in the same site, the warehouse might only need support for a few
users, over a very wide area, with minimal bandwidth. For the warehouse,
therefore, maximum power and minimum data rates would be used. In the office
area, however, there may be a need to keep the data rate set to 11 Mbps, and the
transmit power to some lower value to stay within the user density defined in
the design.
The report should also detail the coverage of each AP and
define that coverage at desired data rates in an included diagram. Electronic
diagrams can be generated easily and make any report look more professional.
Microsoft Visio is available with templates that include items such as APs.
The report should also indicate areas where WLAN coverage is
not needed. This helps to prevent misunderstandings or the customer complaining
later that there is no coverage in an area he believes was missed, even though
the original design did not include coverage for that area. Without documenting
no-coverage areas, you cannot prove that the survey was done properly and that
the original design did not include these areas for coverage.
The report should detail the specifications for providing power
to the APs. It is not uncommon for the survey engineer to discuss the proposed
cabling runs with the site maintenance team (power and networking), including
where and how they will attach to each system. A list of the system components,
the network media type, and the network cabling methods recommended for
connecting should also be documented.
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