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access point is seen. Once this is complete and it is determined that adjusting this value is required, begin with
a value of Ÿ1 dBm for the Transmit Power Control algorithm. Use this CLI parameter:
config advanced 802.11b tx−power−thresh −71
Allow the network to work through this adjustment with a minimum of 30 minutes to an hour before you
observe any changes. Once the network is given a sufficient amount of time, walk the site using the same
survey tool and badges again. Observe the same roaming characteristics and access point power. The goal
here is to attempt to have the badges roam at or before the next access point to get the best possible signal to
noise ratio.
How do I know if the tranmit power is too hot or too cold?
Determining whether you have your transmit power threshold too high or too low requires a good
understanding of your environment. If you have walked your entire deployment area (where you
expect your Vocera badges to function), you should know where your access points are located as
well as experience the roaming behavior of the badge.
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What do I do if my transmit power is too hot?
The Vocera Badge roams based solely on the signal strength rather than signal quality. If the Vocera
Badge does not roam after it passes several access points while engaged in the welcome tutorial or the
test tone, the badge is considered to be sticky. If this behavior is indicative of the entire campus
deployment area, then your transmit power threshold is too hot and should be backed down. If only
one or two isolated areas show this behavior and the rest of the deployment area shows more idealistic
roaming characteristics this is not an indication that your network is running too hot.
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What do I do if my transmit power is too cold?
The default transmit threshold should almost never provide you a deployment area where your
network runs too cold. If the transmit power threshold is adjusted down, and walking the halls with
the Vocera Badge provides you with an environment where the badge roams well, but loses
connectivity and/or dead/spotty coverage, then your network might have been tuned too low. If this is
not characteristic of your entire network but isolated to one or two areas, then it is more indicative of
a coverage hole rather than a network−wide problem.
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Isolated Behavior
If you find that in one or two areas, the badge sticks to an access point rather than roaming in an
idealistic manner, examine this area.
How is this area different from the rest of the campus?♦
If this/these areas are near building exits or areas under construction, could coverage hole
detection be forcing these access points to raise the power?
♦
Look at the WLC log file and access point neighbor lists to help determine why such an
anomaly could occur.
♦
If you find that in one or more isolated areas, the badge experiences dead or spotty coverage, then you
need to examine these areas separately.
Is this area near an elevator shaft, radiology, or a break room?♦
These areas might be better suited by the installation or better placement of an access point to
allow for better voice coverage.
♦
In both cases, it is always advisable to understand that you are working in an unlicensed radio
spectrum and idealistic behavior might not ever be achievable. This could happen when you are
situated next to a radio transmission tower or device, a television transmitter or possibly a non−802.11
2.4 GHz repair facility (wireless phones, and so forth).
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