The industry stays ahead of IPTV quality challenges as it knits together a quilt of standards and measurement algorithms.

Service providers now rolling out IPTV services probably would not agree with the notion that they are making it up as they go along, since that would be an insult to the strategists and technicians who have put hours upon years into the ongoing transformation of telcos into video providers. Yet when you consider how the industry is approaching quality of service for IPTV, it's difficult to come away with any other impression, at least at first glance.

It's not that service providers are haphazardly launching IPTV offerings with poor or untested quality. Test and network management vendors say they are being called in very early in the IPTV projects by carriers that don't want to miss a golden opportunity.

"They know this is something where they have to get it right the first time," said Luis Hernandez, marketing manager at Agilent. "Voice is declining, and video is one of the key ways to come up with the revenue they need to replace that."

However, video remains unconquered territory for most carriers, and there are a wide variety of algorithms being used globally by service providers and their vendor partners to measure and determine video quality for IPTV services. Mean opinion score (MOS) is a quality metric adopted from the voice telephony world that combines surveyed user perceptions about quality with other forms of analysis, also is being used to help quantify video quality. Media delivery index (MDI) is another common algorithm used for measuring video quality. Still another metric is peak signal to noise ratio, which, as the terminology suggests, take into account the power of a video signal relative to the strength of prevailing noise and interference. Other algorithms in use include proprietary approaches from different vendors.

"There are a lot of different types of measurements that we use. Some are in pretty common usage, and there are others, including our own proprietary approaches from SwissQual," said Jeff Schmitz, vice president of product management at Spirent Communications, which acquired SwissQual, a developer of several QoS algorithms, last year.

The issue of quality of service itself is also broken up into multiple factors. There's the concept of transport reliability -- how efficiently video traffic is carried over the network. Quality of the compression of a piece of video must also be considered. There's even issues unrelated to the image itself, such as channel zap rate. How quickly channels can be changed is an important factor in the quality of the user experience.

"A channel zapping time of 100 to 200 milliseconds is considered by viewers to be instantaneous," said Joe Haver, wireline program manager at Agilent. "Acceptable channel zapping delay is generally considered to be around one second total, end-to-end."

All of these factors contribute to an environment in which multiple approaches to standards reign because the telecom industry currently doesn't have a single standard for how to determine quality of service for an IPTV system, and currently draws from a multitude of potential standards. These potential standards eventually may boil down to a single standard recommendation from the International Telecommunications Union, which itself is one of many different industry groups, including most notably the Alliance for Telecommunications Industry Solutions and the Video Quality Experts Group, that are contributing comments and documentation to the overall standards effort.

With so many cooks and potential recipes involved, some might fear that the market could be adversely affected. However, Spirent's Schmitz said the situation hasn't stopped any service providers from deploying IPTV, and that different deployment projects may use different collections of algorithms, depending on the service provider and vendors involved.

But, that situation can't last forever, with IPTV services becoming more broadly availability, systems loading up with video traffic, and competing carriers looking for evidence of who offers the better service. Martin Creaner, chief technology officer of the TeleManagement Forum, said the TMF is try to help during this important service transformation by fostering the guidelines that can be used in the development of service level agreements (SLAs) for IPTV services. SLAs require carriers to meet minimum quality-of-service guarantees.

"One way of looking at video, of course, is that it's just packets," Creaner said. "But, the reality is that it is different from other traffic with its own sensitivities and latency, and while some people in the world have known about that for a long time, we in telecom didn't know too much about it." For instance, while voice telephony is more tolerant of jitter than of latency, the opposite is true of video.

Laurent Phillipart, IPTV engineer at Alcatel and team leader of the TMF's SLA management team, described the handbook as more of an application note that is an addendum to the TMF's existing SLA guide.

"With video, you have to go deep into the packets if you want to know what's going on. The metrics aren't standardized, and that's what you need for SLAs," Phillipart said. "We are working on establishing a single kind of MOS, but I think the industry is still a bit far from this."

So the TMF's SLA Management Team put a study group to work on the subject of video quality measurements for SLAs, and after working on IPTV SLAs for about the last year, the group decided to write a guide to establishing IPTV SLAs. "The purpose of the handbook is really to help people get through all of the potential standards and make sense of them," Creaner said, adding that the IPTV SLA handbook does more than help carriers understand the difference between MOS and MDI.

"So you can use MOS mathematically, but where do you measure and monitor your service for jitter and delay?" Creaner said. "You want to measure the video at the headend before the coding occurs, then measure after transport, then before the home gateway, and then again after it exits the set-top box."

The TMF's IPTV SLA handbook is free to all members. Phillipart said the IPTV SLA application note is available now and that his team will collect comments on their work over a span of a few months before publishing an official version of the note.

Johanne Meyer, vice president of OSS and network management products at Alcatel, and vice chairman of the board for the TMF's supplier committee, said vendors have been eager to contribute to an effort establishing common ground for IPTV service quality -- and not just in the interests of promoting their own products and solutions.

"The quality metrics themselves aren't where the competitive differentiation is for these vendors," she said. "Some say they have more than others, but I think all the suppliers have been more than happy to work together to generate the right metrics to use across the industry, and even harmonize metrics."

Meyer said that, true to its tradition, the TMF ultimately won't be imposing a quality measurement or SLA standard on anyone, only acting in a liaison role to the ITU and other groups that are seeking recommendations and input from its members. Also, vendors like Alcatel that are playing the role of primary vendor for many IPTV deployments will continue to work with many different test vendors and quality measurement algorithms because they need to work from a broad base of experience to give carriers the right advice about testing their new services, Phillipart said.

"The Tier 1 service providers that are doing IPTV are always wanting our advice on what tools to use for video testing," he said. "In Alcatel's labs [its Plano, Texas, location, among others], we have been working with a lot of test vendors, and we take the carriers through the process of how you test, what you are looking for an how to identify problems."

But while quality of an IPTV service goes beyond the quality of just the image itself, Alcatel's Meyer issued a similar reminder that quality of user experience for IPTV isn't just a matter of testing the finished product. Carriers are deploying all types of network elements -- some of which, like TV set-top boxes, they don't have much experience with. They need to think in terms of the entire end-to-end network chain that supports IPTV delivery, making sure systems are interoperable and that content is properly handled.

"If you think about quality of experience, it's more than just the metrics," Meyer said. "All of the equipment in the chain matters, and we have to have an understanding of how all those pieces work and, when there's a fail somewhere, how it will affect the end-to-end service."

The TMF's Creaner said some carriers that have already launched IPTV services have done a good job integrating IPTV into their existing network and service delivery processes -- but some haven't. "It's a mixed bag, really," he said. Acknowledging that service providers are often under tremendous competitive pressure to launch new services quickly, he said some are willing to soft-launch IPTV to gain a competitive edge, and then master quality of service while dealing with what they presume will be a light initial customer load.

The potential risk is obvious. "If you feel like you'll get 500 customers, and you get 5000 instead, then you've got yourself locked in to a legacy system and you've got that tiger by the tail," Creaner said. "Unfortunately, that kind of thing still happens all the time." He advised carriers to "take the extra three months or so" that it takes to prepare a quality services, rather than bowing to the competitive pressure.

IPTV quality of service remains the common industry goal, but also an elusive, multi-faceted issue. In a new service world where quality of user experience matters most, even well-prepared service providers may have to adjust their perceptions and practices as they launch IPTV and customers begin to provide input. Creaner said the telecom industry already is being asked to throw its traditional logic out the window to focus on delivering "expected quality to all customers, and not exactly the best quality, which used to be the idea." That quality expectation is heavily informed by the experience users have had with traditional TV service and cable TV, but as IPTV brings new capabilities and applications to the broadband home, that expectation itself will continue to be a work in progress.

That sort of fluctuation doesn't fit well with the hard-wired logic of SLA guarantees, but carriers will need to adapt as many customers could be willing to pay a premium for a service with guaranteed levels of quality. But, the ongoing Net neutrality issue also could affect how this service environment evolves.

"Will Net neutrality happen?" Creaner said. "If it doesn't happen, then SLAs become God, don't they?"