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VoIP over the 3G data channel comes to the iPhone

I discussed last September how AT&T was considering opening up the 3G data channel to third party voice applications like Skype. According to Rethink Wireless, Steve Jobs mentioned in passing at this week’s iPad extravaganza that it is now a done deal.

Rethink mentions iCall and Skype as beneficiaries. Another notable one is Fring. Google Voice is not yet in this category, since it uses the cellular voice channel rather than the data channel, so it is not strictly speaking VoIP; the same applies to Skype for the iPhone.

According to Boaz Zilberman, Chief Architect at Fring, the Fring iPhone client needed no changes to implement VoIP on the 3G data channel. It was simply a matter of reprogramming the Fring servers to not block it. Apple also required a change to Fring’s customer license agreements, requiring the customer to use this feature only if permitted by his service provider. AT&T now allows it, but non-US carriers may have different policies.

Boaz also mentioned some interesting points about VoIP on the 3G data channel compared with EDGE/GPRS and Wi-Fi. He said that Fring only uses the codecs built in to handsets to avoid the battery drain of software codecs. He said that his preferred codec is AMR-NB; he feels the bandwidth constraints and packet loss inherent in wireless communications negate the audio quality benefits of wideband codecs. 3G data calls often sound better than Wi-Fi calls – the increased latency (100 ms additional round-trip according to Boaz) is balanced by reduced packet loss. 20% of Fring’s calls run on GPRS/EDGE, where the latency is even greater than on 3G; total round trip latency on a GPRS VoIP call is 400-500ms according to Boaz.

As for handsets, Boaz says that Symbian phones are best suited for VoIP, the Nokia N97 being the current champion. Windows Mobile has poor audio path support in its APIs. The iPhone’s greatest advantage is its user interface, it’s disadvantages are lack of background execution and lack of camera APIs. Android is fragmented: each Android device requires different programming to implement VoIP.

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Femtocell pricing chutzpah

It’s like buying an airplane ticket then getting charged extra to get on the plane.

The cellular companies want you to buy cellular service then pay extra to get signal coverage. Gizmodo has a coolly reasoned analysis.

AT&T Wireless is doing the standard telco thing here, conflating pricing for different services. It is sweetening the monthly charge option for femtocells by offering unlimited calling. A more honest pricing scheme would be to provide femtocells free to anybody who has coverage problem, and to offer the femtocell/unlimited calling option as a separate product. Come to think of it, this is probably how AT&T really plans for it to work: if a customer calls to cancel service because of poor coverage, I expect AT&T will offer a free femtocell as a retention incentive.

It is ironic that this issue is coming up at the same time as the wireless carriers are up in arms about the FCC’s new network neutrality initiative. Now that smartphones all have Wi-Fi, if the handsets were truly open we could use our home Wi-Fi signal to get data and voice services from alternative providers when we were at home. No need for femtocells. (T-Mobile@Home is a closed-network version of this.)

Presumably something like this is on the roadmap for Google Voice, which is one of the scenarios that causes the MNOs to fight network neutrality tooth and nail.

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VoIP on the cellular data channel

In a recent letter to the FCC, AT&T said that it had no objection to VoIP applications on the iPhone that communicate over the Wi-Fi connection. It furthermore said:

Consistent with this approach, we plan to take a fresh look at possibly authorizing VoIP capabilities on the iPhone for use on AT&T’s 3G network.

So why would anybody want to do VoIP on the cellular data channel, when there is a cellular voice channel already? Wouldn’t voice on the data channel cost more? And since the voice channel is optimized for voice and the data channel isn’t, wouldn’t voice on the data channel sound even worse than cellular voice already does?

Let’s look at the “why bother?” question first. There are actually at least four reasons you might want to do voice on the cellular data channel:

  1. To save money. If your voice plan has some expensive types of call (for example international calls) you may want to use VoIP on the data channel for toll by-pass. The alternative to this is to use the voice channel to call a local access number for an international toll by-pass service (like RebTel.)
  2. To get better sound quality: the cellular voice codecs are very low bandwidth and sound horrible. You can choose which codec to run over the data network and even go wideband. At IT Expo West a couple of weeks ago David Frankel of ZipDX demoed a wideband voice call on his laptop going through a Sprint Wireless Data Card. The audio quality was excellent.
  3. To get additional service features: companies like DiVitas offer roaming between the cellular and Wi-Fi networks that makes your cell phone act as an extension behind your corporate PBX. All these solutions currently use the cellular voice channel when out of Wi-Fi range, but if they were to go to the data channel they could offer wideband codecs and other differentiating features.
  4. For cases where there is no voice channel. In the example of David Frankel’s demo, the wireless data card doesn’t offer a voice channel, so VoIP on the data channel is the only option for a voice connection.

Moving on to the issue of cost, an iPhone unlimited data plan is $30 per month. “Unlimited” is AT&T’s euphemism for “limited to 5GB per month,” but translated to voice that’s a lot of minutes: even with IP packet overhead the bit-rate of compressed HD voice is going to be around 50K bits per second, which works out to about 13,000 minutes in 5GB. So using it for voice is unlikely to increase your bill. On the other hand, many voice plans are already effectively unlimited, what with rollover minutes, friend and family minutes, night and weekend minutes and whatnot, and you can’t get a phone without a voice plan. So for normal (non-international) use voice on the data channel is not going to reduce your bill, but it is unlikely to increase it, either.

Finally we come to the issue of whether voice sounds better on the voice channel or the data channel. The answer is, it depends on several factors, primarily the codec and the network QoS. With VoIP you can radically improve the sound quality of a call by using a wideband codec, but do impairments on the data channel nullify this benefit?

Technically, the answer is yes. The cellular data channel is not engineered for low latency. Variable delays are introduced by network routing decisions and by router queuing decisions. Latencies in the hundreds of milliseconds are not unusual. This will change with the advent of LTE, where the latencies will be of the order of 10 milliseconds. The available bandwidth is also highly variable, in contrast to the fixed bandwidth allocation of the voice channel. It can sometimes drop below what is needed for voice with even an aggressive variable rate codec.

In practice VoIP on the cellular data channel can sometimes sound much better than regular cellular voice. I mentioned above David Frankel’s demo at IT Expo West. I performed a similar experiment this morning with Michael Graves, with similarly good results. I was on a Polycom desk phone, Michael used Eyebeam on a laptop, and the codec was G.722. The latency on this call was appreciable – I estimated it at around 1 second round trip. There was also some packet loss – not bad for me, but it caused a sub-par experience for Michael. Earlier this week at Jeff Pulver’s HD Connect conference in New York, researchers from Qualcomm demoed a handset running on the Verizon network using EVRC-WB, transcoding to G.722 on Polycom and Gigaset phones in their lab in San Diego. The sound quality was excellent, but the latency was very high – I estimated it at around two seconds round trip.

The ITU addresses latency (delay) in Recommendation G.114. Delay is a problem because normal conversation depends on turn taking. Most people insert pauses of up to about 400 ms as they talk. If nobody else speaks during a pause, they continue. This means that if the one-way delay on a phone conversation is greater than 200 ms, the talker doesn’t hear an interruption within the 400 ms break, and starts talking again, causing frustrating collisions.
The ITU E-Model for call quality identifies a threshold at about 170 ms one-way at which latency becomes a problem. The E-Model also tells us that increasing latency amplifies other impairments – notably echo, which can be severe at low latencies without being a problem, but at high latencies even relatively quiet echo can severely disrupt a talker.

Some people may be able to handle long latencies better than others. Michael observed that he can get used to high latency echo after a few minutes of conversation.

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Nokia no longer the only VoWi-Fi friendly phone maker

Until now, Nokia has been top of the heap in the category of VoIP-friendliness. When I spoke with Richard Watson, CTO of DiVitas, last year in the course of my test drive of the DiVitas system, he pointed out that dual-mode phones are not normally VoIP-friendly. At that time the only phone he recommended was the Nokia E71. There are several reasons for this, primarily the treatment of the voice path and the ease of integration of the VoIP software with the built-in phone software user interfaces. Since then, DiVitas has been working closely with Samsung, and now Richard says several Samsung phones are well suited to Voice over Wi-Fi. Let’s hope this shakes the other phone OEMs loose and gets them working on improving Voice over Wi-Fi performance.

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AT&T, Apple and VoIP on the iPhone

The phone OEMs are customer-driven, and I mean that in a bad way. They view service providers rather than consumers as their customers, and therefore have historically tended to be relatively uninterested in ease of use or performance, concentrating on packing in long checklists of features, many of which went unused by baffled consumers. Nokia seemed to have factions that were more user-oriented, but it took the chutzpah of Steve Jobs to really change the game.

A recent FCC inquiry has provoked a fascinating letter from AT&T on the background of the iPhone and AT&T’s relationship with Apple, including Voice over IP on the iPhone. On the topic of VoIP, the letter says that AT&T bound Apple to not create a VoIP capability for the iPhone, but Apple did not commit to prevent third parties from doing so. AT&T says that it never had any objection to iPhone VoIP applications that run over Wi-Fi, and that it is currently reconsidering its opposition to VoIP applications that run over the 3G data connection. Since the argument that AT&T presents in the letter in favor of restrictions on VoIP is weak, such a reconsideration seems in order.

The argument goes as follows: the explosion of the mobile Internet led by the iPhone was catalyzed by cheap iPhones. iPhones are cheap because of massive subsidies. The subsidies are paid for by the voice services. Therefore, AT&T is justified in protecting its voice service revenues because the subsidies they allow had such a great result: the flourishing of the mobile Internet. The reason this argument is weak is that voice service revenues are not the only way to recoup subsidies. AT&T has discovered that it can charge for the mobile Internet directly, and recoup its subsidies that way. It will not sell a subsidized iPhone without an unlimited data plan, and it increased the price of that mandatory plan by 50% last year. Even with this price increase iPhone sales continued to burgeon. In other words, AT&T may be able to recoup lost voice revenues by charging more for its data services.

This is exactly what the “dumb pipes” crowd has been advocating for over a decade now: connectivity providers should charge a realistic price for connectivity, and not try to subsidize it with unrealistic charges for other services.

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HD Communications Project

As part of the preparation for the fall HD Communications Summit, Jeff Pulver has put up a video clip promoting HD Voice for phone calls. It goes over the familiar arguments:

  • Sound quality on phone calls hasn’t improved since 1937. Since most calls are now made on cell phones, it has actually deteriorated considerably.
  • The move to VoIP has made it technically feasible to make phone calls with CD quality sound or better, yet instead VoIP calls are usually engineered to sound worse than circuit-switched calls (except in the case of Skype.)
  • Improved sound quality on phone calls yields undisputed productivity benefits, particularly when the calls involve multiple accents.
  • Voice has become a commodity service, with minimal margins for service providers, yet HD Voice offers an opportunity for differentiation and potentially improved margins.

The HD Communications Summit is part of the HD Connect Project. The HD Connect Project aims to provide a coordination point for the various companies that have an interest in propagating HD Voice. These companies include equipment and component manufacturers, software developers and service providers.

Among the initiatives of the HD Connect Project is a logo program, like the Wi-Fi Alliance logo program. The logo requirements are currently technically lax, providing an indicator of good intentions rather than certain interoperability. Here’s a draft of the new logo:

HD Connect Draft Logo

Another ingredient of the HD Connect project is the HDConnectNow.org website, billed as “the news and information place for The HD Connect Project.”

It is great that Jeff is stepping up to push HD Voice like this. With the major exception of Skype almost no phone calls are made with wideband codecs (HD Voice). Over the past few years the foundation has been laid for this to change. Several good wideband codecs are now available royalty free, and all the major business phone manufacturers sell mostly (or solely) wideband-capable phones. Residential phones aren’t there yet, but this will change rapidly: the latest DECT standards are wideband, Gigasets are already wideband-capable, and Uniden is enthusiastic about wideband, too. As the installed base of wideband-capable phones grows, wideband calling can begin to happen.

Since most dialing is still done with old-style (E.164) phone numbers, wideband calls will become common within companies before there is much uptake between companies. That will come as VoIP trunking displaces circuit-switched, and as ENUM databases are deployed and used.

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Skype for iPhone

Well, that last post on the likely deficiencies of VoIP on iPhones may turn out to have been overly pessimistic. It looks as though Hell is beginning to freeze over. Skype is now running on iPhones over the Wi-Fi connection, and for a new release it’s running relatively well. AT&T deserves props for letting it happen – unlike T-Mobile, which isn’t letting it happen and therefore deserves whatever the opposite of props is.

6 hours after it was released Skype became the highest-volume download on Apple’s AppStore. In keeping with Skype’s reputation for ease of use, it downloads and installs with no problems, though as one expects with first revisions it has some bugs.

My brief experience with it has included several crashes – twice when I hung up a call and once when a calendar alarm went off in the middle of a call. Another interesting quirk is that when I called a friend on a PC Skype client from my iPhone, I heard him answer twice, about 3 seconds apart. Presumably a revision will be out soon to fix these problems.

Other quirky behaviour is a by-product of the iPhone architecture rather than bugs, and will have to be fixed with changes to the way the iPhone works. The biggest issue of this kind is that it is relatively hard to receive calls, since the Skype application has to be running in the foreground to receive a call. This is because the iPhone architecture preserves battery life by not allowing programs to run in the background.

Similar system design characteristics mean that when a cellular call comes in a Skype call in progress is instantly bumped off rather than offering the usual call waiting options. I couldn’t get my Bluetooth headset to work with Skype, so either it can’t be done, or the method to do it doesn’t reach Skype’s exemplary ease of use standards.

Now for the good news. It’s free. It’s free to call from anywhere in the world to anywhere in the world. And the sound quality is very good for a cell phone, even though the codec is only G.729. I expect future revisions to add SILK wideband audio support to deliver sound quality better than anything ever heard on a cell phone before. The chat works beautifully, and it is synchronized with the chat window on your PC, so everything typed by either party appears on both your iPhone and PC screen, with less than a second of lag.

After a half-hour Skype to Skype conversation on the iPhone I looked at my AT&T bill. No voice minutes and no data minutes had been charged, so there appear to be no gotchas in that department. A friend used an iPod Touch to make Skype Wi-Fi calls from an airport hot-spot in Germany – he reports the call quality was fine.

The New York Times review is here

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AT&T to deploy Voice over Wi-Fi on iPhones

Don’t get too excited by Apple’s announcement of a Voice over IP service on the iPhone 3.0. It strains credulity that AT&T would open up the iPhone to work on third party VoIP networks, so presumably the iPhone’s VoIP service will be locked down to AT&T.

AT&T has a large network of Wi-Fi hotspots where iPhone users can get free Wi-Fi service. The iPhone VoIP announcement indicates that AT&T may be rolling out voice over Wi-Fi service for the iPhone. It will probably be SIP, rather than UMA, the technology that T-Mobile uses for this type of service. It is likely to be based on some flavor of IMS, especially since AT&T has recently been rumored to be spinning up its IMS efforts for its U-verse service, which happens to include VoIP. AT&T is talking about a June launch.

An advantage of the SIP flavor of Voice over Wi-Fi is that unlike UMA it can theoretically negotiate any codec, allowing HD Voice conversations between subscribers when they are both on Wi-Fi; wouldn’t that be great? The reference to the “Voice over IP service” in the announcement is too cryptic to determine what’s involved. It may not even include seamless roaming of a call between the cellular and Wi-Fi networks (VCC).

AT&T has several Wi-Fi smartphones in addition to the iPhone. They are mostly based on Windows Mobile, so they can probably be enabled for this service with a software download. The same goes for Blackberries. Actually, RIM may be ahead of the game, since it already has FMC products in the field with T-Mobile, albeit on UMA rather than SIP, while Windows Mobile phones are generally ill-suited to VoIP.

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Skype on Nokia phones. Video telephony for the masses?

At the end of 2008 there were 415 million broadband subscribers world-wide, and Skype claimed 405 million subscribers after a 47% year-on-year growth. So Skype must be topping out, right?

Perhaps not. At the end of 2008 there were 4 billion mobile phone users. Ten times as many as fixed broadband, and four times as many as PCs. Skype just announced that Nokia will be putting Skype on some of its high end phones. If the idea spreads Skype will still have plenty of room to grow.

But there is bigger news hidden here. Video telephony has been just around the corner for about 50 years. This announcement may soon make it commonplace.

I have written before about Skype sound quality, but Skype’s video capabilities also kick the competition. My children make regular intercontinental Skype video calls to their grandmother, and both the sound and video quality are generally excellent now that I have discarded my Linksys router and got an Apple Airport Extreme. If the numbers don’t convince you that Skype video calling is perfectly mainstream, perhaps Oprah will.

The phone mentioned by Nokia as the first to have Skype built in is the N97. Almost all of Nokia’s high end smart phones (the Eseries and Nseries) have Wi-Fi, and many (including the N97) have a “secondary camera” on the same side as the screen for use in video calling. Video calling is supported by the SIP soft-phone software that Nokia puts in almost all these phones, but SIP VoIP is nowhere compared to Skype. So the news that Nokia will be loading Skype onto some of these phones is tantalizing. The existing base of Skype users on PCs will bestow a massive network effect on Skype video calls from Nokia handsets.

The Wi-Fi aspect will help users to get around the carriers’ resistance, which in any case may be waning if the Skype interview linked above is correct.