Question Which part of a WIFI router's stack causes jitter?

[dr_sacha_k]

Hello!

Thanks in advance for your help.

The diagram linked below plots the differences between times of arrival at the receiving end of a wifi link.

wifi_jitter_screenshot.png

drive.google.com

Most packets seem to take exactly 2ms to arrive, but there are wide variations below and above this standard arrival time.
Would anyone know which part of the system causes these variations, and if there is a way to minimise them?

Thank you!

All the best,
- Sacha

 

[BFG-9000]

I'll suggest you refer to the Make Wifi Fast project. It is working on 802.11ac chips using ath9k, ath10k and Mediatek MT76 drivers, and work is being done on 802.11ax Mediatek chips.

 

[kanewolf]

Hello!

Thanks in advance for your help.

The diagram linked below plots the differences between times of arrival at the receiving end of a wifi link.

wifi_jitter_screenshot.png

drive.google.com

Most packets seem to take exactly 2ms to arrive, but there are wide variations below and above this standard arrival time.
Would anyone know which part of the system causes these variations, and if there is a way to minimise them?

Thank you!

All the best,
- Sacha

Two factors in WIFI, IMO. One, WIFI is shared bandwidth. ALL devices have to share. Even share with competing neighbors WIFI. Two, WIFI is half-duplex. A device can either transmit or receive. If it is transmitting it has to wait to receive. This is just the way WIFI was designed.

 

[bill001g]

In addition to the above unlike almost all other protocols wifi retransmits damaged data. Data most time is damaged by other signals that can be from any number of device that operate on the same radio frequencies.

Retransmitting data takes time.

This can't really be fixed since it is fundamental to design of wifi. In general the only application that this causes a issue for is online games. Most other applications use buffers to hide these variations. In the same you linked the values are so low they will not even cause a issue in a game. Most games you need spikes more than 100ms to see it.