WiFi Site Survey
Introduction
Site surveys are critical for the proper deployment of a WiFi network. For installations in new construction environments
it is not possible to conduct a physical site survey so desktop surveys have to be carried out in order to provide
a basis for a WiFi network design. In these circumstances it is necessary to carry out a full physical survey
after completion in order to amend the design and installation in accordance with the final environment.
The process of surveying a site needs to begin with determining the client's requirements. On the basis of this
you can begin to place access points on a floorplan taking into consideration the materials and nature of the
environment. Then the access points need to be installed and made operational and at this point the
performance need to be verified and remediation taken place to ensure that the initial requirements
are met by the completed installation.
Assess Requirements
A series of questions need to be asked of the client in order to provide the specification for the solution performance.
These questions are as follows:
- What floorplans are available?
- What materials are the used in the construction of the walls and floors?
- What type of devices are going to use the network?
- What type of NICs and supplicants are being used?
- What are the number of clients and how dense are they?
- What is the pattern of usage e.g. peaks and troughs
- Will voice be used over the WiFi network?
- Will asset tracking be used?
- Will users be on the move whilst using the network?
- What tools are suitable in order to help plan access point location? e.g. floorplan
planning mode features, report generation. These tools should give information such as:
- Signal strength
- Signal-to-Noise ratio
- Channel interference
- Data rate
- Loss rate
- Retry rate
- What radios are to be used e.g. 802.11b/g, 802.11a or 802.11n?
- What are the bandwidth throughput requirement?
- Do clients need to roam between access points seamlessly?
- What type of antennae are being used?
- What percentage of coverage holes are acceptable e.g. 2-10%?
Large areas may have different characteristics depending on where you are in that area. In such circumstances it
is a good idea to divide up the area in to smaller coverage areas and treat them separately. Typical problem areas
are as follows:
- Filing cabinet rooms
- Reinforced stairwell areas
- Kitchen areas, metal divides, microwave ovens etc.
- Lift shafts
- Lab areas
- Retail distribution and manufacturing centres with robots and metal rails
Guidelines
The maximum power output of an Access Point (AP) is 100mW, however you do not want to design the network to run
at this power for coverage. It is better to plan for coverage at a lower power output e.g. 50mW so that
if an AP fails surrounding APs can have their power outputs increased to fill in the coverage hole.
APs need to be positioned away from load-bearing or solid concrete walls, preferably as central as possible. APs
can be placed above light dry walls to serve two rooms at once. Conference rooms ideally need an AP centrally placed
and powered so that it can be exclusively for the use of the occupants without disturbing users in surrounding
desk areas.
It is good rule of thumb to have smaller, overlapping cells running at lower powers. With non-overlapping
channels this increases the chance of greater data throughput. If APs are too close together however, then
this could cause interference between client devices because clients tend to transmit at normal power anyway.
Performing the Survey
when performing the survey you will need an AP with the appropriate antennae for the site. You will need to be able to
configure the AP power and radios and you will need to have the AP mounted on a stand that can be extended to
the correct height for the installation.
Survey Report
The survey report should include the following information:
- Purpose of the facility
- Floorplans showing AP locations, covergae areas and non-coverage areas
- AP height
- Radios used
- Status of the site i.e. is it still under construction or fully operational
- Date of the survey
- Describe AP locations accurately
- Type of antennae
- Orientation of antennae
- Describe tools used in the survey
- Describe the settings used for the survey
- Describe the coverage of each AP
- Gain the customer's signature
- Cable runs
- Mounting positions of antennae
- Future expansion capability
- Photographs of AP locations
- Comms room locations
- Equipment list
- Customer contact details
- Surveyor's contact details
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