Originally Posted by Jerome

You don't understand. If the cell is only serving you, your figures are correct. In real usage, and more so if everybody tries to use voip, umts (or hsdpa, which really is umts with a better modem) degrades. You won't get that upload.

What is so difficult to understand? Radio is simple: you have one medium and it has a maximum capacity. Whatever tricks you use, when the capacity is exhausted, that's it.

You don't have that problem with wires, because it is not a shared medium. When some users bog down their connection running p2p clients like mad or having skype relaying the traffic of half the planet, it is not a problem for the rest of the users. You have a problem with data over air, because when one user abuses the cell, everybody's connection goes dripping. And building additional cells costs money.

Originally Posted by Jerome

You don't understand.

If the cell is only serving you, your figures are correct. In real usage, and more so if everybody tries to use voip, umts (or hsdpa, which really is umts with a better modem) degrades. You won't get that upload.

What is so difficult to understand? Radio is simple: you have one medium and it has a maximum capacity. Whatever tricks you use, when the capacity is exhausted, that's it.

I am not comparing codecs, I am explaining the fundamental problem telcos have with sip over air.

The system is not financially tenable in the second case, especially if these users chose wasteful codecs (out of ignorance usually).

You don't have that problem with wires, because it is not a shared medium.

A problem we have doing the RNP (Radio Network Planning) for 3G networks, is that the cell capacity per user decreases with the number of users (they share a fixed bandwidth), but also the cell size become smaller as the number of users in the cell grows. In some cases we saw some zones lossing the signal (becoming black zones) when the number of users in a cell increases significantly.

I only know that I stopped using my 3G modem some 8 months ago

Then you don't get what you're paying for, and you can sue the 3G provider for that. If they advertise with 384 kbit upload, and you don't get 1/6 of that, its serious trouble.

Originally Posted by Jerome

But for this you cannot sue: the contracts always say "up to 384 Kbits/s". Maybe you should read the legalize of typical data contracts: they offer you web access at speeds around DSL. Everything else is a gray zone. You can sue if you don't get any service (like TA-t3) or even clearly unacceptable quality (e.g. very slow). You can't if you don't get top service all the time, or if some applications either unusual or explicitly prohibited (voip) do not work. That is the basic reality in plain English.

I mean: it is quite interesting to discuss technicalities, but as far as the tablet is concerned, it all ends up the same: a tablet with voip over hsdpa is not a phone replacement. Either because the provider will block it (as they write in their contracts already) or because it will not work in practice when the cell gets busy (because lag increases to unacceptable levels).

Now we do not know how the cell part will be in the next tablet, but there are two choices:
-either it will be usable as a phone (not over data, but directly as a phone) and we basically have an iPhone competitor
-or it will be data only and we have an equivalent to current offers for the eeepc with an usb 3G modem bundle.

Neither one of these offers is very appealing to me at present, but there is certainly a market for them. But it is not a revolutionary concept as the first tablet was.

Originally Posted by Texrat

On the subject of data plans, Verizon adds month-to-month: http://biz.yahoo.com/prnews/080922/ny34211.html?.v=1