FEATURE: VoIP Quality of Service: Just Getting Started

VoIP Quality of Service: Just Getting Started
Texas Instruments' Fred Zimmerman says that with VoIP quality now matching or exceeding PSTN levels, it's time for the industry to move to the next level.

Echo, packet loss, jitter and other VoIP quality of service (QoS) concerns have taken center stage in the growing VoIP marketplace, and rightfully so. Now though, service providers, equipment manufacturers, technology suppliers and other participants are delving deeper, plumbing the motivations of VoIP's ultimate arbiter, the consumer.

Of course, good quality voice is the basis for VoIP's success. Without addressing and placing VoIP's voice quality at least on par with the voice service available on the public switched telephone network (PSTN), there would be no viable VoIP marketplace. Without solid voice quality, the VoIP conversation ends, both literally and figuratively.

Many of these voice quality hurdles have been crossed thanks to a great deal of industry-wide work on standards development, as well as new hardware and software innovations both in the infrastructure and on the client end. For example, the creative application of digital signal processing technology has solved many of the echo, delay, jitter and packet loss issues in today's VoIP networks. In fact, a case can be made that, with such innovations as wideband codecs, the quality of voice on VoIP networks today can exceed that of the PSTN.

The next phase of VoIP market development will depend on a wider view of QoS, one that examines QoS as a consumer gestalt involving the entire fabric of perceptions, preferences and emotional and rational responses that consumers have in relation to VoIP. More and more, application support and system-wide features and functionality will play a crucial role in the overall QoS of packet telephony services. This shift from an inward focus on technology to an outward focus on consumers will drive the next era of growth.


Telephony has conditioned a set of responses in subscribers. Potential VoIP users expect that when a wire, any wire, is plugged into an RJ11 jack, any jack, the desired service is provided.

So, for example, the brand of the residential gateway device one uses shouldn't have a bearing on how a certain brand of PC or an Apple Macintosh functions on a VoIP network. Or, a subscriber shouldn't fret whether the fax machine in the corner will work with a particular service provider's VoIP switching systems. Situations involving everyday interoperability issues can sour a potential subscriber's entire attitude toward VoIP. Some of the most common situations involve the following:

Fax Machines: Fax machines are still a mainstay in many, if not most, small and home-based businesses. The fax machine is easy to use, requires little technical expertise and can quickly transmit or receive critical business documents. And even though digital signatures are becoming more prevalent, fax machines still remain the primary means of quickly transmitting legal documents requiring a signature. If a business is contemplating a migration to VoIP to reduce its voice communications costs, the office's VoIP gateway must be able to accommodate the protocols and other requirements that are unique to fax machines.

Low-speed modems: Despite the rapid rise in broadband access, some residential applications still feature low-speed modems. For example, a TiVo box activates a low-speed modem at night to download the next day's programming guide. If a residential VoIP gateway device has difficulty handling these types of low-speed modem applications, the perception of VoIP QoS on the part of the consumers in the home will certainly be adversely affected.

Touch Tone Functionality: A number of applications like credit card readers, answering machines, voice mail systems and others rely on the analog dual-tone multi-frequency (DTMF) signals of the traditional telephony network. VoIP service providers must take into account how they will accommodate these legacy applications in their digital, packet-based communications networks. Because touch tone signals vary throughout the world, DTMF support can be challenging to a VoIP manufacturer. However, accurately transmitting and interpreting these tones is imperative for a viable VoIP service.

The Upside to VoIP QoS

In a sense, VoIP technologies and services have been playing catch-up when it comes to QoS. That's always the case when a legacy technology has set the standard that a newer technology must achieve. Fortunately for the marketplace, the game of catch-up is coming to an end. Already, some VoIP services are surpassing analog telephony services in terms of enhanced features and perceived quality of voice communications. Soon features and enhancements that can only come from digital technology will be developed and rolled out to the marketplace, differentiating VoIP as a feature-rich, robust service that's superior to services limited to the traditional analog switched network. At the same time, application-specific and system-wide factors will be vital in smoothing out the QoS landscape between packet telephony and traditional telephony services. When this phase begins, VoIP will truly be a technology whose time has come.

Fred Zimmerman is Texas Instruments' executive director of VoIP CPE solutions.