AP Density vs Transmit Power

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When does density become a problem?
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Christopher Twombley

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Posted 4 years ago

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Raymond Hendrix

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at Ripe65 we installed 17 AP's in the plenary room because there we're 500 ppl with 3 avg 3 devices per person. i'd say with 50ppl per AP density is an issue.
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Jonas Dekkers

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Also depends on which access point you are using
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John Fabry

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You need to study the number of connected devices that are actively moving data. Some client apps will move significantly more data than others.  Just because the device is associated does not mean it is taking bandwidth. Also, keep in mind the number of advertised SSIDs is very important, my practice is no more than 3.  You can have more but you need to not advertise them. Advertising takes up a lot of cycles on the APs. With 17 APs you need to decide which ones will advertise 2.4Ghz, cut down the power on those that are using 2.4 so you can minimize co-channel interference. Similarly, on the 5Ghz radios either you can set the power or allow the system to auto adjust channel and power for proper spacing.  Remember the Aerohive APs only adjust 6DB at a time. So if you start at 19DB the system will only drop to 13DB on a radio. It almost makes sense to start at a lower power and work your way back up.  Everything is about eliminating co-channel interference. Sorry for the long answer, but it should be another two or three pages.
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Marcel

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Actually I did some testing lately on this, since HiveOS 6.1r6a the AP can go down max 9dBm, the bottom limit is 5dBm, so even if you set the max transmit power to 10dBm in the radio profile, it will not get any lower than 5dBm /M
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Raymond Hendrix

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only a handfull used 2.4 and on the lowest power settings stuck below the chairs ;)
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Anders Nilsson

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RF Utilization is a key number to keep an eye on.  Over 30% starts becoming an issue and over 50% you have problems. Over 70% and it's more or less game over and you need a better design.
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Crowdie, Champ

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I have found that density becomes an issue when:

  • The wireless network throughput is adversely affected by transmit retries.
  • Stations are being adversely affected by co-channel and adjacent channel contention.
  • The access point transmit power is forced down well below the station's transmit power.
I have done some dense deployments and the use of external semi-directional antennas is a must.  Do a channel use design and match the antennas to that design.
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David Coleman, Official Rep

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There are numerous issues when it comes to density and capacity planning. One of my favorite Aerohive white papers is about High-Density Design.   Aerohive's best resource regarding this topic is this 100-page document.