CHAPTER
4-3
Site Survey Guide for Deploying Cisco 7920 IP Phones
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Conducting a WIPT Survey
This chapter describes specific steps for performing a site survey for WIPT.
How To Survey for the WIPT
Cisco recommends that the first step of a survey is to work with administrators at the local site to
determine the requirements of the RF network. Determine what the coverage areas are or will become.
Determine the number of RF network users by location in the site. If the site already has an active RF
network, learn the site’s radio frequencies, equipment locations, and equipment characteristics. Next, do
a complete scan for RF signals throughout the site. Determine the levels of RF at the site, and verify that
the information you’ve been given about the locations of RF devices is correct. Report your findings to
the site administrators.
Cisco recommends that the next step is to find on the drawings the locations of the existing RF devices.
Use the drawings to estimate the cells based on the requirements for 7920 call capacities and cell design.
Plan the antennas needed and transmit powers required for the access points within the site. When
surveying with an existing WLAN, plan for the areas to be filled in and for changes to existing data rate
and transmit power settings. Plan on possible changes to antenna types. At a multi-floor site, plan the
survey of the coverage for the floor above and below. When doing a manual survey, record the cell edges
of the current floor and then use your survey tool on other floors to measure and record the signal levels.
When doing an automated survey, include the access point on the floors above and below in the
walk-through survey.
When you survey a site without an installed 802.11 network, plan to use two or three access points to
measure cell coverage and cell overlap. The cell edge for the 7920 at the 11-Mbps data rate is -67 dBm.
The signal strength at the edge of that cell needs to be 19 dB weaker than the signal from the next cell
on the same channel. That means at the -67 dBm edge of the cell, the next cell on the same channel
should measure -86 dBm, as shown in Figure 4-1.
