XCC - wondering about ac-WiFi asymmetric client speed

[M_Nees]

I got this XCC WLAN client report shown:

(XCC 5.36.02 - report truncated - AP310i)

XCC-V5.36.02# show clients apserial XXXXX-XXXXXX00000

Protocol   Radio  SSID       Aut./Priv.    OS         RSS(dBm)  Avg.Rate
                                                                (Mbps)
                                                              Sent/Recvd 

5.0ac|L|S  2      XX-MDE     None/WPA-PSK  Apple iOS  -55       360/6                      
5.0ac|L|S  2      XX-MDE     None/WPA-PSK  Apple iOS  -55       300/6                      
5.0ac|L|S  2      XX-MEDIEN  None/-        Apple iOS  -63       400/6                      
2.4n       1      XX-Mobile  None/WPA-PSK  Apple iOS  -96       0/0                        

XCC-V5.36.02#

i wondering about the asymmetric speed of this apple clients (while RSS is good).

It seems to be a general behaviour of smartphones (means android also). Windows clients seem to have symmetric speeds.

Is  anybody able to explain this behavior ?

Also seeing some rates as a point number e.g. “102.3 Mbps”. Does XCC Controller calculates some averages ? If yes within which timerange ? (maybe during whole session or within a fix amount of time?)

How can i understand the displayed direction in this report - View of Controller/AP or View of client?

Given above example does this apple phone send or receive only with 6 Mbps ?

BR,

Matthias

[Gareth_Mitchell]

Hi Matthias

It sounds like you have got to the bottom of this question now.  As Stephan said, there are a lot of factors in choosing data rates as shown in mcsindex website, guard interval, modulation etc all come into play.  Each device will also use its own algorithm, almost all of which are proprietary and closed source.

Laptops generally have much more capable antennas and larger batteries that allows them to use higher data rates than smartphones.

If you have any more questions please let us know.

Have a good weekend.

-Gareth 

[StephanH]

IEEE 802.11ac-2013 wikipedia article (https://en.wikipedia.org/wiki/IEEE_802.11ac-2013) give me a good overview about the possible data rates - and to my surprise there a lot of possibles rates - also the seen point number rates.

A complete overview of all current MCS depending on the different wifi standards and number of spatial streams can be found here: http://mcsindex.com/

[StephanH]

Hello Matthias,

• confirm every data packet also having a 802.11 data rate (if tcpdump is done on a radio interface) - and this rate changes/adapts 

please note that the speed, Wireshark shows, is not really included or transmitted in the wireless packet.
This and other information that can be seen in the traces belong to the so-called pseudo headers and are read by programs such as Wireshark from the driver! Also the radio tap header is a pseudo header.

[M_Nees]

Here an example of a done wireshark trace within a quite lab environment: