[Wireless config] Option distance not work when startup

Installing and Using OpenWrt Network and Wireless Configuration
1

I have some problem when config distance in wireless device, can anyone have me fix it?

  • I'm using Lima 8 devices, config in ap-client wds mode? Two Lima fix using mcs0, bandwidth 20, setup in range 20m and test wireless through put using iperf:
    • When option distance set < 20000. it's work oke, throught put same with the theory.
    • When config ~ 20000, sometime throughput is smaller than theory throughtput. In case smaller, I using 'wifi reload' in ap side then throughtput become same with theory.
    • When config > 20000 ( my test setup is 40000), throughtput always < theory throughtput but when call " wifi reload" in ap side, throughtput increase ~ 1Mbps.
      I know that distance option affect throughtput because it changes timing in wireless driver , but i dont know why my distance option in wireless config not work when device reboot, it seen to be apply when reload wifi. How can i fix it? i want throughtput when device start is the best.
2

From what I recall the distance tooltip/docs say it's only good for distances >1000 metres. i.e. 1km?

3

But i dont know why throughtput increase when using "wifi reload". Is it a bug in driver?

4

20m is much less than 1000m. I'd say it's not a valid test?

It doesn't look like it's something you should be pursuing for such a short range.

Do you plan on creating a long distance link?

If you're planning on doing a long distance link you'll probably need to change your test setup. If you can't get the units that far apart for testing purposes you're probably doing to need another method of introducing a propagation delay. A dumb solution is an attenuator and like a km or two of coax. But that will take out multipath and a bunch of other stuff =P

I've seen multipath and other emulators for long distance 3g links but IDK how one would do it cheaply. Best is probably just create a good OOB management setup and put the other AP very far away

I don't know enough about frame times for 802.11 and what the distance optimisations do. But to put these terms and relate them to the speed of light and the 802.11 guard intervals and frame times.

One should probably have a look at a wifi frame time calculator and then have a look at what these distance optimisations do?

Note c is speed of light:

c/1000m ~ 300kHz.

c/20m ~ 15MHz

If you look at the guard intervals for 802.11:

400ns, 800ns, 1.6 us, 3.2us. You're looking

~2.5MHz through to ~277kHz.

Regarding frame times. I think you're in the order of hundreds of microseconds through to milliseconds.

5

When I set a value here under 100, it's ignored.