Hi,

I've been experiencing problems with the 3G Internet lately. What's happening:

1. If I connect to 2.5G network (I'm virtually never connected to the plain 2G network) everything works fine. It's slow but works
2. I switch to the 3G/3.5G network by the status menu applet
3. and connect to mobile Internet, then I'm first connected to the 3G network, then to the 3.5G network. I'm in the 3.5G network with a good signal. Everything works fine
4. After a while (< 1 min) I'm switched back to the 3G network. And from then, mobile Internet fails to work. `ping 208.67.222.222` has 100% packet loss although it used to have 100% received a while back. Reconnecting fixes temporarily (points 3 and 4 once again)

What might be the cause and how can it be fixed?

You cannot stay at 3.5G (HSPA). This is controlled directly by the modem so that it's used only when needed (active transmission).

As for the packet loss... Mobile Internet generally sucks, regardless of country, provider and speed. I have days where I'm disconnected many times in a row and then weeks where the connection is maintained non-stop.

Well, it must be just as you say. Today it works perfectly. Might it be something on the N900's side that it doesn't reconnect to 3.5G or would it be rather some problem on the service provider's side?

i have days where only 2g works, others where only 3g works. using dual it sometimes doesn't switch to 3g. it really does depend on network that day.

reinob beat me to 3.5g info.

Additionally, the timeout of 3.5G -> 3G drop is controlled by network provider's side. For example, in Poland, Aero2 BDI provider tries to drop to 3G every two seconds, while T-Mobile does so every nine.

You can force being in 3.5G constantly, by experimenting with ping and ping packet size. In the above example, T-Mobile require smallest possible ping every 8 seconds, while for Aero2 BDI, only 1KB-sized ping every 2 seconds guarantee staying on 3.5G.

The down side for mobile device is that, keeping 3.5G, you would get very (veeery) poor battery life. It taxes device with 300-400 mA current draw during usage. forcing 3.5G maxes sense on modems connected to desktops or, in some cases, laptops, though, as it ensures low pings (3G pings to common server - like, google - can get as high as 900 ms, 3.5G ones depends on provider and situation, but can be as low as 40 ms).

In your problem's example, everything seems to point a finger on provider being responsible for your problems. That is, if signal strength is decent.
****

Arien Stokowiec