Not sure I am following you 100% here, your problem is with the wireless connection to the router, not the ADSL connection to the ISP??
Here is my take on this if I followed your issue correctly.
If at any point you get within about 15% of the total link speed, in either direction, you will start saturating the connection and latency will rise, causing acknowlegements to be delayed, causing a rapid drop in your data rate in both directions or a total break down in the IP connection. After about 2000 ms (2 seconds) of latency IP packets are considered dead and are not likely to be re-transmitted.
You indicate you can cap the data rate and things are fine until you hit a trip point. Not sure what wireless you are using, B or G, but in any event if the wireless signal is not VERY strong, the modulation scheme changes and the actual link speed actually drops. Additionally if you have other users on this wireless link, it cuts into what you are capable of using as it is a share resource.
It appears that you are having problem around 250 kbps or 30 kBps.
Start an extended ping between the machine that is connected wirelessly to the router (wireless client IP address to wireless router IP address) and see what happens to the ping times as you increase the data transfer. If you see a rise in latency, somehow the link is probably saturating.
Other issues that can cause problems are interference, other unknown wireless users and firmware issues with either the wireless router or the wireless client device.
JamesO
Here is my take on this if I followed your issue correctly.
If at any point you get within about 15% of the total link speed, in either direction, you will start saturating the connection and latency will rise, causing acknowlegements to be delayed, causing a rapid drop in your data rate in both directions or a total break down in the IP connection. After about 2000 ms (2 seconds) of latency IP packets are considered dead and are not likely to be re-transmitted.
You indicate you can cap the data rate and things are fine until you hit a trip point. Not sure what wireless you are using, B or G, but in any event if the wireless signal is not VERY strong, the modulation scheme changes and the actual link speed actually drops. Additionally if you have other users on this wireless link, it cuts into what you are capable of using as it is a share resource.
It appears that you are having problem around 250 kbps or 30 kBps.
Start an extended ping between the machine that is connected wirelessly to the router (wireless client IP address to wireless router IP address) and see what happens to the ping times as you increase the data transfer. If you see a rise in latency, somehow the link is probably saturating.
Other issues that can cause problems are interference, other unknown wireless users and firmware issues with either the wireless router or the wireless client device.
JamesO
