Wireless Coverage. TANDBERG FieldView

Chapter 3 TANDBERG FieldView Administrator Guide

Wireless Coverage

Range achievable over the 802.11b/g WLAN interface can vary from hundreds of meters under near ideal conditions down to much shorter distances under challenging conditions. Coverage area can vary dramatically depending on a variety of factors, including:

• Topography

• Walls, dividers, windows, ceilings, floors, etc.

• Radio-reflective materials (may cause attenuation and/or multi-path reflections)

• Interference and noise

• Access point and antenna mounting location

• Antenna type and orientation

• TANDBERG FieldView Device orientation

• Network traffic

• Number of connected devices

Fig. 3-2 Wireless Coverage Map (Aerial

View).

Effect of Topography on Coverage

Fig. 3-2 shows an aerial view of a simple floor plan with a single access point

(denoted as AP). The dark blue shaded area indicates the coverage pattern that the access point provides for this site. The building’s walls and dividers act as attenuators for the signal, shaping the coverage pattern as shown.

Signal to Noise Ratio

Achievable range is directly related to the quality of the signal received by the TANDBERG FieldView Device. The quality is a factor of the radio signal strength, which is affected by attenuators such as the topographic features listed above and the air itself, and the interference and noise level.

As the noise level approaches the level of the desired received signal, the quality will suffer. To increase usable range, noise must be kept to a minimum and signal strength must be used to overcome the remaining noise level (there is always some level of background noise). The usual measure of signal quality is Signal-to–Noise Ratio (SNR) which is illustrated in Fig. 3-3 with a simplified signal.

The TANDBERG FieldView Device provides received signal strength and

SNR information that can be used to assist with range determination and troubleshoot problems. A more rigorous method of ensuring proper coverage across a facility is done using a site survey, as discussed in the section

Site

Survey

.

Fig. 3-3 Signal to Noise Ratio (SNR).

Other Factors Affecting Coverage

Range further depends on the configuration of the video and audio settings. In general, higher bit rate settings will lower the range achieved before noticeable artifacts occur.

In practice, range will vary widely with the factors discussed. The TANDBERG

FieldView Device has been tested and found to work satisfactorily at a distance of over 200 meters with a 1 Mbps video stream under near-ideal conditions

(outdoors, line of sight, no obstructions, access point mounted at 8 feet, no nearby 2.4 GHz interference sources). At the other extreme, combinations of interference and topographic factors can limit range to a fraction of the ideal.

Coverage problems can usually be resolved by assuring proper access point placement and/or adding additional access points.

Fig. 3-4 Wireless Cell Layout.

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