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Archive for the ‘DiVitas’ Category

VoIP on the cellular data channel

Thursday, September 17th, 2009

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.

Nokia no longer the only VoWi-Fi friendly phone maker

Friday, August 28th, 2009

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.

DiVitas partners with Avaya

Monday, March 9th, 2009

Last week Avaya announced that it has chosen DiVitas as its preferred partner for mobile unified communications (UC). The companies will do joint marketing and cross-training of their sales forces in a reference sale mode. This is huge for DiVitas because it opens Avaya’s distribution channel to it. According to Phil Klotzkin, Avaya’s senior manager for UC, this channel supplies 20% of the business phone systems world-wide.

The DiVitas solution plugs a small but important gap in Avaya’s product line. Avaya already has a mobile unified communications solution, called one-X Mobile.

One-X Mobile extends PBX features to cell phones, notably the ability to give out a single number that rings on both your cell phone and your desk phone; the ability to do PBX-related actions like 4 digit dialing and transfers; visual voicemail; and the ability to move a call in progress between the cell-phone and the desk phone.

The DiVitas product offers a comparable solution set, but goes beyond one-X Mobile with Wi-Fi voice and a range of social networking features including IM and Presence. Because it uses Wi-Fi, the DiVitas solution requires a dual-mode handset. Virtually all new smartphones are dual-mode, but with the exception of Nokia’s Eseries and Nseries, few of them are well suited to voice over Wi-Fi. One-X Mobile uses the cellular voice channel rather than Wi-Fi, so it runs on a wide variety of phones.

For IM related features both DiVitas and Avaya’s desktop Integrated Presence Server use open source Jabber software. The two will be integrated with each other by the end of the year.

DiVitas/Avaya system diagram

For now the DiVitas handset software (client) is not integrated with the one-X Mobile handset software – the customer will choose one or the other for each user. The DiVitas client and the one-X Mobile client will each retain their different look and feel, and the one-X Mobile client will continue to run on single-mode phones and the DiVitas client on dual-mode.

In a recent interview, Klotzkin said that one-X Mobile is sufficient for most customers, but that there are a few for which dual-mode functionality is essential. Partnering with DiVitas enables Avaya to satisfy those customer needs. One such customer is CSX, the freight company. Some of its far-flung operations are in areas with no cellular coverage; Wi-Fi solves this problem. Avaya has been working with CSX on dual-mode solutions since 2004, when Avaya, Motorola and Proxim introduced the very first dual-mode system.

According to Vivek Khuller, CEO of DiVitas, “CSX has been working with Avaya since the earliest days of dual-mode telephony, and they are finally satisfied. It’s an important accomplishment for both our companies.”

Because the DiVitas solution uses smart-phones CSX gets a useful side benefit, namely that it can run proprietary application software on the phones, eliminating the need for its employees to carry a laptop. The other side benefit is that even in areas of cellular coverage the Wi-Fi connection can be used to save on cellular minutes.

So everybody gains. Avaya plugs a troublesome gap in its product line; DiVitas gets an excellent distribution channel; the Avaya channel adds a fully supported best-of-breed solution to its portfolio; and end users get the familiarity of Avaya with the handset technology of Nokia and the DiVitas software that weaves them together into a user-friendly package.

DiVitas Test Drive

Tuesday, October 28th, 2008

Divitas loaned me a Nokia E71 to try out with their mobile unified communications solution hosted by Sawtel. It’s a very nice phone – looks good, feels good in the hand. It’s also the best-sounding cell phone experience I have ever had, and that’s thanks to DiVitas. All cellular service providers use technology that sacrifices sound quality for increased carrying capacity. By squeezing down the bandwidth used by a call they can fit more calls into each cell, and get by with fewer cell towers, saving money. The standard codec around most of the world is GSM, and it’s the reason that cell calls can never sound as good as landline calls.

But DiVitas uses a Wi-Fi connection for your calls, and they have chosen to use the standard land-line codec, G.711. The effect is startling – a little disorienting even; we are so used to the horrible GSM codec that when a cell phone sounds as good as a land-line the subjective illusion is that it sounds much better.

This is one of the reasons that the type of voice over Wi-Fi solution offered by DiVitas is way better than the one offered by the telco industry, called UMA. UMA uses the GSM codec even over Wi-Fi connections.

But DiVitas didn’t stop with the sound quality. DiVitas has done an excellent job in several other technical areas. The fundamental technology of fixed mobile convergence is the ability to hand off a call in progress from the cellular network to the Wi-Fi network and vice versa.

This is very challenging, and it is an area where DiVitas claims to lead. So the first thing I did after turning on the phone was to make a call to check it out. I didn’t need to look at the on-screen indicator to know that the call was running over my office Wi-Fi network. The sound quality (did I mention this before?) was superb. So I walked out of range of the WLAN and sure enough the call handed over to the cellular network without dropping. There was a brief interlude of music and the call continued. Going back into the WLAN coverage area the handoff was completely seamless, perceptible only by the improvement in call quality as it moved from the cellular to the WLAN network.

Superior sound quality and seamless handover, while impressive to an engineer who knows what’s entailed, are not really sexy to regular users – it’s just a phone behaving like you would expect. DiVitas takes it to the next level by overcoming another technical challenge, delivering a polished, well thought-through, feature rich and well integrated user interface on the phone.

Actually, the DiVitas software client for the handset overcomes two challenges. The technical challenge of integration with the phone’s native software environment, and the design challenges of usability and usefulness. User interfaces are a matter of personal taste; the best are those that don’t get in the way of doing what you want. I disappointed the people at DiVitas by discarding their carefully written instructions and forging ahead by trial and error. Considering the potential consequences of this behavior I got away lightly. Everything worked the way I expected it to, and there were some nice touches, including Skype-like presence icons by the names in the directory.
While we’re on the topic of the directory, one thing that jumps out is the four digit phone numbers.

This is an indicator of yet another set of technical challenges that DiVitas has overcome to deliver their solution, namely integration with the corporate PBX, and presentation of the PBX features through the cell-phone user interface. DiVitas users will actually get a superior experience of the PBX through their cell phone compared to their desk phone. This is because the DiVitas software has a computer industry heritage rather than a telco heritage; it takes advantage of the nice big color screen with features like the presence icons and voice mail presented in an on-screen list like on the iPhone.

So the big news here is that a product has finally caught up with the hype around enterprise Mobile Unified Communications. All my criticisms (DiVitas got an earful) are nitpicking. For me the system worked as advertised, and that’s saying a lot.

Femtocell versus Wi-Fi

Thursday, July 17th, 2008

Rethink Research has published an interesting article relating the new Wi-Fi voice certification to the outlook for femtocells.

The idea of the article is that voice over Wi-Fi for cell phones is competing with femtocells, and that femtocells may win out. The article distinguishes between business voice and consumer voice, saying that service providers see femtocells as “an important stalking horse for greater control of corporate customers. ” This gives a hint of why femtocells may be unattractive to businesses: many of them would rather not yield this control.

Consumer voice service is controlled by service providers. They have three options in this space: do nothing, deploy femtocells or deploy Wi-Fi. Do nothing is the obvious best choice, since neither of the other options carries a revenue upside. But poor coverage in a home discourages usage and risks cancellations of subscriptions. So in areas of poor coverage something like femtocells or UMA (voice over Wi-Fi) is attractive to service providers. For both technologies the service provider subsidizes the wireless router, but femtocells will remain more expensive than Wi-Fi routers because of their lower sales volumes, so Wi-Fi is more attractive on this count. But UMA requires phones with Wi-Fi, while femtocells will work with any phone in the service provider’s line-up, including legacy ones. So the customers’ experience of femtocells is better – they can choose or keep the phone they want and still get improved coverage at home. This benefit of femtocells clearly outweighs the marginal price advantage of Wi-Fi routers. Femtocells may help subscriber retention in another way: a Wi-Fi router is not tied to any particular cellular service provider, while a femtocell only works with the carrier that supplied it.

The situation in businesses is different. They generally prefer to control their own voice systems, which is why they have PBXs. But a substantial number of business calls are now made on cell phones, even on company premises. These calls don’t go through the PBX, so they are not least-cost-routed and they are not logged or managed by the IT department. Femtocells don’t fix these problems, but Voice over Wi-Fi does. Not service provider Voice over Wi-Fi, like UMA, but SIP-based Voice over Wi-Fi from companies like DiVitas and Agito. What about phone choice though? Won’t corporate customers be stuck with a limited choice of handsets? The answer is yes, only a limited number of phones have Wi-Fi: less than 10% of those sold in 2008. But in the category of enterprise smart phones, like the Nokia Eseries and Blackberries, the attach rate of Wi-Fi will soon be close to 100%.

So femtocells are a good way for service providers to remedy churn caused by poor residential coverage for consumers, but Wi-Fi may be the better option for businesses that want to regain control over their voice traffic.