Gigabyte AP GN-A16B sharing working

[buckinghamrd]

Hi all
Finally got my 2 AP's talking to share my ADSL connection (before you get excited I didn't say it was across a boundary). One question which I can find no info on - under WDS if you scan for an AP it gives a signal indicator. My figure varies between 1 and 100. Mostly it is closer to 1 than 100. Now the connection isn't fast but easly faster than 0.5Meg needed. So logic would dictate to me that closer to 1 is better but that doesn't seem to make sense. Its too much hassel to bring them closer to check which value is better as they are all set up - anybody know which is a stronger signal 1 or 100?

 

[podo]

buckinghamrd,

We have the same thing, the value here seems to hover around 27. As far as I can tell, this is an aggregate value calculated on the averages of signal strength and signal quality. The higher the value, the better the connection should be. Don't confuse better with faster though, there are many factors that might influence the speed of your connection, generally, WDS will cause a 50% drop in total throughput from the outset, because of the way the APs forward the radio packets between them, but anything from distance to objects in between, to bottlenecks on your ethernet and even on the PCs could cause additional slow down.

I've found that I can improve the signal quality and speed very slightly, and eliminate packet loss completely, by tuning some of the internal settings of the AP.

If you have the 1.192 firmware (I'm sure you do, if you have WDS), check in the "Wireless" / "Advanced Settings" menu. Two settings there you want to pay particular attention to are "Fragment Threshold" and "RTS Threshold". When properly tuned, these settings will influence the way your APs behave. When fragmentation threshold is set more or less correctly, your AP will break up very large packets, which would otherwise cause the frequency band to be engaged for longer than usual intervals, causing a bottleneck for other transmitting devices and the other AP. If RTS threshold is set correctly, it will cause the APs to perform "clear to send" negotiations for larger packets. This means that before sending a large packet, the AP will check that the frequency band is open, then send a "clear to send" request. At this point, all other APs and wireless devices will give the AP a short interval in which to transmit the larger packet, without interference.

The RTS setting is especially important as it helps to eliminate collisions, where two devices attempt to transmit on the frequency band at the same time. Normally, in such cases, both sides would just re-transmit the packet after a delay, but that is not very desirable for high performance networks. It might also lead to some packet loss in extreme cases. RTS becomes even more important in a WDS set-up, since you might easily have what are known as "invisible" nodes. The weak wireless transmissions from wireless devices might be visible to one of your APs, but are probably not visible to the other AP. Now, let's say one AP begins to send a packet to the next AP, and at the same time, a wireless card sends a signal to the second AP, because it could not see the first AP transmitting, and did not know that it should wait for its turn. The second AP would receive two transmissions at the same time, and both sides would need to re-transmit because of the interference. With RTS settings in place, this situation should not occur.

Note that for any of this to be really effective, you need to set the same settings for your wireless cards aswell. Most cards will not have fragmentation, in such cases, you may ignore it and set it up only on the APs. That will already help a little bit. All cards should have RTS, and you would be wise to enable it for larger packets as it should improve your network performance, even if only slightly.

There is some debate as to the correct value for these settings, but I have found that the following settings work quite well. Try setting these up and let me know.

My settings:

Fragment Threshold: 1476
RTS Threshold: 512

Hope this helps a bit.

Willie Viljoen
Web Developer

Adaptive Web Development

 

[buckinghamrd]

Thanks podo - I'll give them a try. I must admit after finally getting them to work I may let it just chill for a while (position made a huge difference to performance - even moving one AP 30 cm lower in position made the difference to it working or not). My problem was a combination of distance +- 70m and very leafy vegitation. I was also very relieved when they were still a happily talking during a downpour. Less in terms of transmission (I read the post about rain and wireless) but in terms of my fibreglass boxes I used been watertight . Thanks again for all the advice from the forum.