Cisco 1004-CH - 1004 Enet/ISDN/Bri Rter Handbuch für den Einsatz - Seite 27
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Deployment
Professional Site Survey
Generally, the professional site survey involves temporarily placing one or more Cisco 1000 series
lightweight access points and then measuring the resulting coverage(s). Based on the results of these
measurements, Cisco 1000 series lightweight access points are relocated and/or reoriented to achieve
complete coverage of the target space without unnecessary coverage overlap or coverage holes between
Cisco 1000 series lightweight access points. This approach is appropriate given the following
deployment requirements:
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During the Professional Site Survey, one or two access points are placed at or near one end of a building.
Their coverage is measured and the access points are relocated and reoriented as necessary to ensure that
this end of the building is completely covered. When measurements confirm that this is true, a second
or third access point is added so its coverage area somewhat overlaps the coverage area of the first access
point(s). (Generally, 10 to 15 percent coverage overlap is considered appropriate.) Its coverage is
measured to ensure that its overlap with the first access point(s) is appropriate and to determine the
coverage in the rest of the building. This process continues, adding a third or fourth access point and so
on. This process continues until all areas of the building are covered.
The professional site survey allows the designer to provide full seamless coverage; however, the Radio
Resource Management (RRM) ensures that the channel assignments and transmit power levels are
optimized for the Cisco WLAN Solution coverage area, freeing the site survey professional from having
to fine-tune these variables.
Other variables designers may include static transmit power level, geometric pattern used for access
point placement, and the antenna type (omnidirectional, wide beam directional, or narrow-beam
directional). Some designers like to have the flexibility to select antenna types most suited to specific
buildings.
Designers may differ in the criteria they use to determine coverage area. Some prefer to use signal
strength (RSSI), some prefer signal-to-noise ratio (SNR), and others prefer to use some indication of
throughput, such as packet retry rate. These measurements are normally made using site survey software
provided by a wireless LAN manufacturer, running on a PC or PDA. They may also be made using one
of the handheld measurement tools currently available, such as Air Magnet or Berkeley Varitronics. The
measurement tools are usually selected based on their ability to measure the desired variable, RSSI,
SNR, or packet retry rates.
RF Prediction with Optional Site Survey
RF prediction consists of importing the floor plans of the coverage area into a Computer Aided Design
system in which a user can place access points, draw in the walls of the building and assign RF
characteristics to the walls. Depending on the confidence level of the estimates made for the building RF
characteristics and the cost of filling in potential coverage holes after deployment, an optional site survey
may be appropriate to verify assumptions. This approach is appropriate given the following deployment
requirements:
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78-17279-01
Full Coverage with 0% coverage holes
The RF characteristics of the building vary throughout the coverage area
The building type is not typical (Arena, Convention Center, Stock Exchange)
Full Coverage with 2 to 10% coverage holes
The RF characteristics of the building vary throughout the coverage area
The building type is not typical (Arena, Convention Center, Stock Exchange)
Deployment Guide: Cisco Aironet 1000 Series Lightweight Access Points
Determining Deployment Strategy
9