WiFi high latency

Question

I got some problems with my WiFi setup.

In my setup I use a Macbook Pro and a TP-Link WR1043ND v1 (OpenWRT). WiFi Channel is set to 6 (already tried other channels and 20/40Mhz width)

If I ping my macbook or my router from my macbook, the ping is really high.

64 bytes from 192.168.1.103: seq=18 ttl=64 time=7.691 ms
64 bytes from 192.168.1.103: seq=19 ttl=64 time=142.177 ms
64 bytes from 192.168.1.103: seq=20 ttl=64 time=47.343 ms
64 bytes from 192.168.1.103: seq=21 ttl=64 time=16.513 ms
64 bytes from 192.168.1.103: seq=22 ttl=64 time=2.803 ms
64 bytes from 192.168.1.103: seq=23 ttl=64 time=5.725 ms
64 bytes from 192.168.1.103: seq=24 ttl=64 time=7.585 ms
64 bytes from 192.168.1.103: seq=25 ttl=64 time=25.981 ms
64 bytes from 192.168.1.103: seq=26 ttl=64 time=2.464 ms
64 bytes from 192.168.1.103: seq=27 ttl=64 time=6.762 ms
64 bytes from 192.168.1.103: seq=28 ttl=64 time=8.677 ms
64 bytes from 192.168.1.103: seq=29 ttl=64 time=16.521 ms
64 bytes from 192.168.1.103: seq=30 ttl=64 time=1.204 ms
64 bytes from 192.168.1.103: seq=31 ttl=64 time=1.849 ms
64 bytes from 192.168.1.103: seq=32 ttl=64 time=134.936 ms
64 bytes from 192.168.1.103: seq=33 ttl=64 time=51.255 ms
64 bytes from 192.168.1.103: seq=34 ttl=64 time=17.032 ms
64 bytes from 192.168.1.103: seq=35 ttl=64 time=17.399 ms
64 bytes from 192.168.1.103: seq=36 ttl=64 time=8.177 ms
64 bytes from 192.168.1.103: seq=37 ttl=64 time=5.048 ms
64 bytes from 192.168.1.103: seq=38 ttl=64 time=2.198 ms

I already tried another router (Linksys E2000) but its exactly the same.

Answer 1

Your latency is acceptable for Wi-fi networks. My usual latency in 5GHz network is around 15 with 200ms spikes. It is also a good idea to move wireless router across your location in order to identify the best spot for optimal signal coverage.

Answer 2

This is normal for WiFi, but indeed not acceptable behavior. If you want to get your hands dirty, check out the make-wifi-fast project from bufferbloat.net. Your access point uses the ath9k wifi chipset, which tends to get improvements first.

Some background on their progress can be found at: http://blog.cerowrt.org/

They've made a network measurement tool called "flent". Another way to watch the latency is: Google Fiber's 'blip' tool

Maybe something simple you can try right away is build OpenWRT trunk with these Minstrel-blues patches. It improves Linux's data rate selection by keeping better statistics on rate effectiveness instead of dropping lower and lower. This might improve latency.

Answer 3

As per @schreda comment, it seems like there is a bug with Chromecast. For some reason Chromecast opens an AP with the same channel as the router it's connected to. This is causing interference.

A factory reset of Chromecast solved this problem. I read that sometimes you have to try it several times to reset Chromecast until the bug doesn't occur anymore.