Hi,
what throughput can I expect between the two RB751U-2hnD in the following setup?
ap bridge – wds slave
wireless clients on both sides but they normally don’t generate much traffic. These two boxes make seamless wifi between the two buildings in my country house.
I tried running mikrotik bandwidth test. The best I could achieve was 15Mbps with UDP. With TCP I reached 1,5Mbps max. CPU is under 30% in both cases.
Also, I’ve got wireless setup with 20/40 Mhz channel but I’ve never seen two mikrotiks negotiate 40Mhz. The best was as on the screenshot below, but 20Mhz on one side falls back to nothing quite frequently.
I know Tx/Rx between the two Mikrotiks is not the best, but if I turn off wds slave then I still able to conect with my laptop to the distant side (ap bridge) and get wireless speeds MUCH higher than through wds slave.
Another example, I try to upload via ftp from my laptop to my smartphone. And I never get more that 0,5KB/s if both clients are connected to wds slave. However, if I turn off wds and let both connect via very poor signal to the distant ap bridge then I can reach more than 1MB/s.
I tried switching to 20Mhz channels but it didn’t help.
The signal’s weakness between the WDS slave and AP is a big factor.
Wireless is all about time sharing. If you have a weak member of a WLAN, then it really bogs the whole thing down because whenever the weak link gets its turn, it takes comparatively forever to do even the simplest thing that would take much less time for a high-modulation link to accomplish. Compounding things is the fact that a wireless repeater spends half of its time talking to the stations registered to it, and the other half talking to the upstream AP. In this case, the “upstream” half of its time is probably taking much more than half of the time…
So in other words, even in best case scenarios, you can only get 1/2 the performance out of a WDS slave, and it can get much worse than that.
Imagine a traffic light that has sports cars on one of the roads, and tractors on the other road. If the light lets 20 vehicles through at a time, it’s going to take a lot longer for the 20 tractors to roll through the intersection when it’s their turn. So the cars have to wait much longer for the light to turn green on their side…
If it’s at all possible, you should try to get some form of hard-wired connection between the locations. I wouldn’t recommend powerline (it’s always been flaky whenever I’ve come across it), but there are boxes you can buy that can use the in-house telephone wiring (you don’t have a land line phone anymore, right?) or the television coax cable (These devices use a tech called MOCA) and extend your ethernet links that way. If anything, try moving the WDS slave into a spot that gets better reception from the AP, even if it’s further from the area you’re trying to extend into, and see if that helps.
Thank you, ZeroByte, for the exhaustive explanation. It all sounds familiar to me but I couldn’t beleive speed degradation may be so drastic. Now, I see this looks normal and not a software glitch.
In the meanwhile I tried switching wds slave to wds station and connect my laptop to wds station with wire. And that gave considerable improvement! Which proves your logic does work here.
What I’m planning todo in my case is to setup separate P2P wireless link between the two buildings. Couldn’t find anything neat from Mikrotik though and so looking into a pair of LigoWave LigoDLB Propeller 2