Installation guide

Wi-Fi Location-Based Services—Design and Deployment Considerations

OL-11612-01

Deployment Best Practices

Note that WCS allows only for the adjustment of orientation in the horizontal (or azimuth) plane of the

antenna. Vertical orientation is assumed to be as indicated in the antenna pictorial shown in WCS, which

usually is vertical at 0° for omni-directional antennas and horizontal at 90° for directional and

semi-directional antennas. There is no adjustment for either electrical or mechanical down tilt.

For optimum accuracy, antennas on a floor should be installed at or near the same height throughout the

floor whenever possible. This should match the height specified for the floor when it was defined in

WCS under “Edit Floor Area”.

Site Calibration

The Cisco WCS and the location appliance are shipped with default environment models that facilitate

setup under two of the most common environments for which the product was designed. One of these

models is intended to represent a typical corporate office environment with both cubicles and drywall

offices, and the other represents an environment with drywall offices only. These models provide good

approximations of the typical path losses found in each of these environments. In many typical indoor

office installations, these pre-packaged models sufficiently represent the environment at hand, especially

when there is a need to get a location tracking system operational as quickly as possible. However, some

indoor environments may possess more attenuation than is found in a typical office environment. In

properly designed indoor installations where increased attenuation may be contributing to poor accuracy

and precision, a site calibration can in many cases help restore lost performance. When an on-site

calibration is performed, the system is provided with a better understanding of the propagation

characteristics specific to the target environment. In some cases, by using this information instead of the

default models, the degree of error between reported and observed client location can be reduced with

overall system accuracy being improved.

Calibration is actually a multi-step process that begins with defining a new calibration model via

Monitor > Maps > RF Calibration Models > Create New Model. Next, data points must be added to the

calibration model using a calibration client that is associated to the WLAN infrastructure and accessing

Monitor > Maps > RF Calibration Model > model name > Add Data Points. During the data point

collection process, the calibration client repeatedly broadcasts probe requests on all channels that are

responded to by the access points in the area. If the calibration client is a CCXv2 or greater client and

CCX Location Measurements have been enabled in the controllers, the CCXv2 calibration client

responds with probe requests on command whenever location measurement broadcasts are received.

The client repeats sending probe requests several times, giving WCS and the location appliance ample

opportunity to collect RSSI information from the controllers for input into the calibration database.

Calibration data collection should be performed after the system has been installed, basic coverage

checks are completed, and the recommended RSSI cutoff (typically -75 dB or better) to a minimum of

three (preferably four or more) access points has been verified throughout. All WLAN access points

should be in place and registered to their respective controllers with WCS and the location appliance

fully operational.

During the calibration data collection process, WCS suggests locations on the floor map where samples

should be taken (shown in Figure 49) with an indication of the degree of progress achieved thus far. The

process can be completed in one session, or the session can be stopped and returned to at a later time.