www.yota.ru was originally created to launch a WiMax-based VoIP service to compete with the cell providers. Not sure if they've launched the VoIP part yet, but clearly it's feasible, otherwise they would not have gotten financing.

PS. Skype = VoIP thinking is the thing which hurts widespread VoIP deployment the most.

Heh, my parents can use skype, but not install it. However, they're also SIP users. A company offered to transfer their old landline number to VoIP. Completely painless, fetch tablephone from company, plug it into broadband router, just worked, at a tenth of the price. Multiple clients allowed, so one could enter the settings on the cellphones, tablets and computers too, and have a fully mobile landline number over voip!

As I dont have a normal landline number myself, I'm waiting for someone to begin taking mobile numbers and putting them on voip or parallelling them with an actual mobile phone, sort of like UMA but without the fail and lack of interoperability..

I get my home ADSL and my 3G data access through the same provider who also do VOIP.

On a recent trip away I put the data only 3G SIM I have into my phone[1] and hooked the N810 to that. I then used VOIP to have long cheap conversations with my mother either on her landline or on her VOIP with the same provider. We used the native Internet Call software rather than Skype or Gizmo.

A half hour call cost me about 8c in data.

THis was only viable where I could get a 3G signal, which meant the coastal bits of Australia and some odd spots like Broken Hill. But in the capital cities it was fine. This does mean that it's not a viable phone replacement unless you do no travel or only to capital cities.

I talk with her on the VOIP when at home, via the N810 and its wireless connection, so doing it via 3G's simple enough.

I'm really hanging out for the N900 with SIM slot! (except that I'd have to port Gene Cash's Calendar myself and I have no idea if I'm up to that. It's the killer app for the N8*0 for me, head and shoulders above the other available PIM offerings. Please someone, rescue it! Gene's vanished off the net....)

Zebee

[1] the phone and normal phone SIM is owned by work, so I don't do long personal calls on it

May i ask where that number came from?

I used my N810 as a VOIP phone last year on a trip in Africa. I was tethered on an EDGE connection and was successfully able to make and receive 5-10 minute calls using the built in SIP and I also used Skype a couple of times. I have also managed to make video calls from N810 to n800 using an EDGE connection before. The latency doesn't seem to matter so much than a pretty strong signal.

Basically if the new tablet can switch between wifi and 3G/EDGE pretty seamlessly it will be a good VOIP phone. The new ATT network here in the US is supposedly upgrading to HSPA+ which can be all IP in its infrastructure and LTE I believe is also designed to be all IP. There is definitely the possibility that the next generation of mobile phones (3 or 4 + years away) will be all IP and perhaps even one flat rate for voice, messaging and data.

I never got more than 2 hours of active usage out of my n800.

Its a case by case question to which the answer depends on a a lot of factors many of which reside in TCP/IP. Here are some common factors.

The provider. On both end. And even inbetween. They could
* Cap or prioritize certain traffic
* Use filtering of ports and/or protocols
* Have bottlenecks (ie. overbooking)

Some other aspects to think of is the quality of the SIP server. Stability and perfomance. But also latency could be related to where the SIP server is located, and whether you use SIP <-> SIP or SIP <-> PSTN. The codecs your SIP server supports for audio (and ehm, video...) and priority you defined in your SIP client used for audio are also worth taking a look at. Some codecs are better than others, at the cost of costing more bandwidth, CPU time, and so forth. Speaking of which. Multitasking works in Maemo, and mobile phones, but if some application is using all CPU time this could influence other applications like VoIP/SIP applications.

More important however is the protocols used. In practice this refers to layer-1 and layer-2. Some networks always have a high latency. Satelite, for example, is especially known for this. This sucks for stuff like VoIP/SIP and gaming. WiMAX and LTE provide QoS by design of protocol standard. HS*PA, EDGE, UMTS (WCDMA) do not (but this can be worked around with unofficual hacks just like that is used on say WiFi and ethernet). At to that you'll have bad upload speed. You cannot use your full upload bandwidth and use VoIP/SIP. For HS*PA and current EDGE, UMTS (WCDMA) this is clearly a problem but even on standard, consumer grade ADSL1 8192/1024 lines this means that when someone starts to upload that 1 MB picture via MSN this influences the RTP (used by SIP) data. Plus, you have to keep in mind overbooking.

Now, there are all kind of tricks to mitigate the damage. A VPC could in one way or another work around restrictions placed by your ISP. You could prioritize ACKs which allows you to better utilize your bandwidth during usage. This limits the damage a bit. You could lower the MTU. You could use traffic shaping to give yourself a guaranteed speed for SIP/VoIP (RTP, actually). However, latency increases when your upload is full and packets are in queue (for example during uploading or photo to MSN, P2P stuff, and so on).

More advanced measures exist as well. You could use TOS field in TCP/IP to specifWiMAX and LTE provide QoS low-latency, and if your provider is good they honour this flag, or better yet allow you -the customer- to apply QoS between you and the first gateway (e.g. DSLAM in case of DSL). Or, maybe your provider has implemented AutoQoS or similar for this purpose. But most won't have do this...

So the answer is: in individual cases it will not by default work well out of box unless it is well thought out like e.g. rolled out by technicians on a corporate network. World-wide the situation needs work; in invidual cases it will work from shitty (jitter, or no connection at all) to very good quality with even high quality audio/video codecs used. Some ISPs are also telcos and don't give a rat about the problem because it competes with their own market. I think around the time of all-IP WWAN like WiMAX and LTE this problem is more or less managed correct world-wide, with some ISPs providing this seemingly while some more liberal ISPs provide a good out of box experience allowing the customer to fine grain and some conservative ISPs blocking or otherwise hammering usage of certain protocols [such as] VoIP/SIP. Net neutrality if also heavily related to the legal ability of this, and perhaps we see laws allowing or forbidding certain practices outlined above.

This happens to me, but _only_ if I use that wi-fi router I have which doesn't support power saving mode. With any normal quality access point I used to be able to keep my N800 on wi-fi and active use the whole day, with all battery bars full.

It would stay on wi-fi 3 days if I just left it sitting there (with gmail notifier, internal email program update, RSS, and maybe Skype running). My battery is now 2.5 years old so it doesn't last that long anymore, but as mentioned above the 2-hour problem _only_ occured with wi-fi AP with no power saving support.

EDIT:
Over to the voip subject:
1) Unless you're close to the cell masts you can't expect to have 3G or 3.5G working. Be happy if even gprs works..
2) Even where 3G works I have found it's got terrible variation in quality, there's often periods of bad packet loss which totally kills latency and that's critical for voip and some other services.
So, in short, I think it'll be a while before voip can replace everything..

Well, maybe that is the case where you are from. Here, there are 3 networks each providing 95- 99% UMTS coverage, usually even HSDPA. Even in buildings you usually have packet data here. With roaming. International roaming remains expensive for now.

Packet loss is deadly indeed. If you use RTP over UDP it would not kill latency btw. That'd be the case with RTP over TCP. In the former case the other side just misses some part of the conversation with (huge) jitter whereas in the latter case there would be (huge) lag. But happens with GSM too. E.g. in tunnels, or lifts in buildings.

I have been using voip(sip through various providers) at our offices since 2005 with pretty much complete reliability. Mind you, I have QOS configured pretty aggressively for VOIP and we have plenty of bandwidth.

I would never think about going back to 'regular' lines. We have moved our office twice and didn't even have to call the local telco for anything, what a treat. Not to mention I can do routing and so much more than I could with a 'regular' call.

But for mobile use, like others have said, VOIP only over a cellular provider data network can be iffy. I have used my n810 tethered to a sprint phone in US and made voip calls, but if you have a sprint phone, might as well just use the phone

I long for the day when mobile data is just that, data, and is packet switched and we can run whatever we want over it. A dumb mobile pipe.