Ap udp receiving delay？？

[john3]

In my system I have 3 boards: STA, AP and a Host.STA and AP are both mt7621 boards with openwrt in it. STA will send UDP a 1200Byts packet to HOST every 13.5 ms. The connection flow is like: STA--(wifi)-> AP--（rj45 cable）-->Host. I tried a lot to find that, at AP wlan1(which is associated with STA), UDP packet receiving sometimes yield large delays, ranges from 30 ms to 2000 ms. As a result the Host cannnot receive packets at about 13.5 (or maybe little more) ms intervals, causing the system malfunctioning.
So what could be wrong ? The STA and AP board has both mt7612e as the mac card, supporting 802.11ac .I checked the wifi speed at my phone with some tools,showing the wifi speed at about 433Mbps .
At the STA and AP I did the tcpdump, and i checked the intervals of the udp packets ,the results are:
(1)STA

(2)AP

Generally the just less than 1Mbs bit rate is enough for my system, but why could the large delay be observed??

[eduperez]

I my very humble opinion, this is a design error.

A wifi connection cannot guarantee a stable latency. You should make your application resilient to those latency spikes, or use other communication methods.

[john3]

Thanks a lot @eduperez. I know that udp is not a stable protocol。 Iam just curious about the large delay at the AP end, with just a wifi STA and a wired host connected with AP, Is It RIGHT/NORMAL to get such large latency spikes? The whole system is just an LAN.

[john3]

I've got it,the delay is caused by packet loss!! If I try to send every pack twice , the latency will go down a lot.Some packs get lost, and then neiboughing packs' interval rises a lot。The topic over。