WiMAX puts service quality on display

Juan Pablo Alfaro believes in the benefits of WiMAX. He isn't just sitting around waiting for them to mature. The general director of MetroVia/Unitel in Guatemala watched four different cellular companies busily build out their separate networks in Guatemala City, each of them setting up their own 60-meter antennas at every potential cell site location in the city, all just to sell what was basically the same service.

The company saw an opportunity to become a broadband wireless service provider using a wholesale model that would encourage competition in the market for services like voice over IP (VoIP). “Our vision was to build a single WiMAX network for all to share,” he said. “It did not make any economic sense to build an independent network for every operator. Instead, we envisioned building a single network for all ISPs that could benefit from the fact of sharing Capex with multiple operators.”

MetroVia has two ISPs on their network offering Internet access today, and one of which will be offering a VoIP product over the network.

Alfaro said his company has been working closely with vendor NextNet Wireless to ensure its capability to offer a quality VoIP service. “The issue of VoIP and QOS in our network is a major concern,” he said “For registered ISPs with VoIP products registered in our network, we are able to offer QOS and allot specific resources for their VoIP calls.”

That is accomplished with the help of a NextNet system capable of distinguishing and defining different layers of service.“Voice over a broadband wireless system is still something that the industry is relatively new at,” said Chuck Riggle, vice president of business development for NextNet. “In a competitive market situation, the quality of service has to be like what you would get from a landline telco.”

Alfaro said MetroVia is very focused on bandwidth management, measurement and traffic shaping in its network and in cooperation with its ISP customers. “Each ISP uses bandwidth differently, and we have, basically agreed to work together to traffic shape all protocols needed for applications beyond surfing and e-mail,” Alfaro said.

For MetroVia, going with a wireline technology was not necessarily an alternative. “Getting wiring permits in our cities is almost impossible,” Alfaro said. “Also, the economics of deploying a plug-and-play application over a wired application are much better. Thanks to our wireless network, we have been able to provide services in all the different zones — metropolitan areas as determined by our municipality — of the city from day one. This would have been impossible with any other wired application.”

The reasons that Alfaro gives for going wireless are exactly the reasons most people in the WiMAX community believe that quality VoIP can be a killer app in a developing country. Far and wide, in Latin America, Asia and Eastern Europe, there are many service providers that have rapidly begun offering VoIP over broadband wireless connections. In some markets, there are simply no alternatives, while in other markets, there is intense competition. Quality is key in both environments.

“You can do VoIP over any kind of connection, but can you do real ‘IP telephony’ with all the quality features over that connection?” asked Paul Sergeant, senior marketing manager for alternative access for Motorola. “There is a difference.”

The WiMAX Forum created service quality types that are relatively similar to existing quality types for wireline packet service quality types, such as best effort, available bit rate, variable bit rate and constant bit rate. “The Applications Working Group in the WiMAX Forum came up with different application configurations and defined how much latency or jitter is acceptable for different services,” NextNet's Riggle said.

For WiMAX, the corresponding service quality types include best effort, non-real-time polling service, real-time polling service and unsolicited grant service. QOS was not part of the very first wave of WiMAX Forum certification testing late last year and early this year, but several vendors have been adhering to these quality expectations for a while.

“QOS wasn't part of [first-wave] certification testing,” said Elvis Tucker, director of solutions and alliances for Aperto Networks. “QOS is not mandated in the standard either. While those service types are defined, how the service flows are actually managed is not. That's where vendors need to be careful. In a network with different kinds of applications and expectations for performance, you want to have a way of managing that nailed-up connection on an end-to-end basis.”

The top-level service type in WiMAX — unsolicited grant service — is the one that targets high-quality voice communications, as it is designed to support real-time data streams that have predictable packet sizes. Meanwhile, the real-time polling service type is designed for bursty traffic containing variable packet sizes — that corresponds directly to the nature of most video applications.

Even if whole real-time polling service seems right for some video applications, Aperto's Tucker notes that users who are increasingly getting used to the idea of being able to watch TV on their mobile phones ultimately may not tolerate shaky or distorted video.

“In some ways, video is even a more sensitive application than voice,” Tucker said. “It requires a lot of bandwidth and can't really tolerate much latency.”

NextNet's Riggle added, “I'm not sure that WiMAX will be a direct replacement for something like cable TV but maybe for streaming applications or specialized video applications.”

Tucker, whose company also has deployed VoIP networks for many carriers worldwide, estimates that at least 50% have some form of voice applications going over their networks. “We have one that is even running Vonage's service over its network,” he said. “Voice is the second-largest application we see after Internet access, and I would say that video is in the 20% to 30% range.”

In many cases, VoIP is being deployed as part of a multi-service mix for specific customers in specific types of markets. Last month, VSNL in India and CSM in Indonesia each deployed Aperto's recently WiMAX Forum-certified system for multiple services, including voice and video.

Applications requiring some promise of quality have taken off well ahead of WiMAX Forum-certified products becoming a mass-market phenomenon. As for the evolution of WIMAX, MetroVia's Alfaro is eagerly anticipating the benefits of standards, product certification and interoperability, but he knows that the broadband wireless success story is already being told.

“The great elusive WIMAX,” he said. “What is it? I think WIMAX as the standard we all imagine as the perfect mobile, high-bandwidth application, with limitless possibilities of access and undenied restrictions of usage, is not here today,” he said. “There are plenty of issues that need to be settled before WIMAX gives us all the benefits we expect from it. Having said this, I believe WIMAX is the way of the future simply because of the ease and practicality of having a portable Internet access application that allows us to service clients efficiently without truck rolls or waiting times.”

But, he added, “In Guatemala, we say, ‘he who strikes first, strikes twice.’ WiMAX will be integrated into our network as it becomes an interoperable standard.”

Although service providers like MetroVia and VNSL are getting a jump on the competition, it's important to note that the worldwide market for VoIP and video over IP is still relatively young, with much more room to grow and mature. “You see numbers like 1 million new VoIP users being added every quarter,” Tucker said. “When you see that kind of growth, you realize that WiMAX will only continue to benefit from that.”

WIMAX SERVICE CLASSES

Service Type	Real Time?	Application Type	Bandwidth
Interactive gaming	Yes	Interactive gaming	50 - 85 kb/s
VoIP, video conference	Yes	VoIP	4 - 64 kb/s
		Video Phone	32 - 284 kb/s
Streaming media	No	Music/speech	5 - 128 kb/s
		Video clips	20 - 384 kps
		Movies streaming	> 2 Mb/s
Information technology	No	Instant messaging	< 250 byte messages
		Web browsing	> 500 kb/s
		E-mail (with attachments)	> 500 kb/s
Media content download (store and forward)	No	Bulk data, movie download	> 1 Mb/s
		Peer-to-peer	> 500 kb/s
Source: WiMAX Forum and Westech Communications white paper