I seem to be a bit confused


What is the difference between tethering and using one's BB as a dial-up modem?

My contract has free on-device internet access but as soon as I'm going to use it as a dial-up modem, then I'm going to get charged. (And it is expensive to do this).

Its the same thing.
We call using your BB as a modem = tethering.

So, is there a way to "stream" the BB's connection to a PC or laptop?

Thats what tethering is.
You use the connection of the blackberry through the dial up modem to your laptop.
Its called thethering because they are thether (connected) together.

Now I'm really confused.
When I connect my BB to my PC and I dial-up (from the PC), the PC is using the BB as a normal modem. The phone dial-up in to my service provider, establish a connection with my PC and I get charges.

Is there no way to use the current connection that the BB has?

As MD said that is what tethering is, using the BB wireless provider's data connection to carry data.

You can't use a Blackberry as a dial up modem in the sense that you MODulate the data on an audio channel which is then DEModulated by a modem on the other end. The voice channels of modern cell phone networks just don't support the audio quality needed for anything but the slowest of modem speeds.

The confusion arises from the fact that tethering uses AT commands to 'dial' a particular number that instructs the phone to establish a PPP connection with the computer and connect the PPP data steam to the wireless carriers TCP gateway. This allows you to use dial up protocols included in most PC operating systems to establish a tethered connection you a phone. You can not for example use the AT commands to establish a call to your ISP's modem bank.

Assuming you have a Blackberry Data Plan, you could accomplish what you want to do by installing Desktop Manager on the laptop and connecting the blackberry using Bluetooth (if supported on both) or a USB cable which should cause your blackberry to use the Service Routing Protocol (also known as Serial Bypass from days when blackberries used serial connections) to connect with the BIS/BES through Desktop Manager.

Thank you for the reply. I understand it a bit better now. I think my service provider set up the system to catch this, and charge for it :(

btw, a cellphone (on GSM) digitize the voice channel, thus your voice get digitized, compressed, broken into packets and streamed. The network it self does a how bunch of stuff with these packets. Then the phone on the other side un-digitize the sorted packets, decompress them and play it to the other person (it is a whole bunch of stuff that happens very fast).

Also, did you know that the cellphone operators injects what is call "comfort noise" in this communication channel. Because of analogue landlines, we got used to the "white noise" on the line. Thus if there is dead silence, we tend to think that the call was dropped...

Very likely. Some providers aren't but you won't get them to tell you that officially because they may decide to do so in the future.

Yes, they're called CODECs and are designed to do speech. A single call could be coded and decoded more than once depending on the hardware on each end. They don't usually perform very well on the kind of signals a modem would use.

Yes, they also introduce local echo so that we don't yell into the phone, most of this is done as close to the endpoint as possible so they don't have to ship white noise and echos around the world.