AP PHY data rates

[GERALD LECAILLIER]

Hello,

AP 1600 has PHY data rates up to 300 Mbps, and 2600 up to 450 Mbps.

With 1600 AP, if I have a client connected at 300 Mbps on the radio 5 GHz (MCS index 15, 40 Mhz) and another client connected at 130 Mbps on the radio 2.4 GHz at 130 Mbps (MCS index 15, 20 Mhz); how will the AP handle the traffic ?

Will the AP force one of the client to lower data rates, or will it drop some paquets ?

I'm a little bit confuse about the behavior in high density environment,

Thanks a lot,

Regards

[ericgarnel · Accepted solution]

The 20 MHz client will only use the primary channel whereas the 40 MHz client will pass traffic on both primary & secondary channels

All management traffic will be on the primary channel as well.

You state that one client is on 5 GHz while the other is on 2.4 GHz.  They will not be affected by each other over the air, but will share the same DS as the AP directs their traffic towards the wire.  Then both client flows will cross the same ethernet connection as they exit the AP onto the wire.

[GERALD LECAILLIER]

Hello,

Thanks for the explanation.

So if the AP is connected on a Gigabit port, the AP 1600 will forward 450 Mbs on this port.

But if the switch port is a 100 Mbs, it will drop 350 Mbps.

So when the 1600 datasheets tells phy rates up to 300 Mbps, we must read 300 Mbps for 5 Ghz (40 Mhz) + 270 Mbps for 2.4 Ghz (40 Mhz).

Thanks a lot,

Regards

[ericgarnel]

Gerald,

Wi-fi is half duplex medium and data rate does not equal throughput

Here is a good guide on the issue:

http://www.speedguide.net/faq_in_q.php?qid=374

As wi-fi performance is determined by the client, AP and external factors such as interference, wi-fi overhead, distance, loss, etc. figure throughput somewhere @ 50 - 60% of data rate at best. On top of that, there will be tcp/ip overhead too.

It will always drop to the lowest common denominator.  So if the switchport is only 100 mbps, that is your bottleneck for traffic that goes over it.

Use some tools like iperf or jperf to do some client-server testing between laptops to see what the actual throughput is.

If you are using MacBooks, there is a great app in the Mac App Store called WiFiPerf

Eric