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technology editorial

By Laurie B. Falconer

The business market for supporting telephone systems worldwide is worth more than US $600 billion today, and is growing at about four percent per year. This market holds tremendous potential in two areas in particular: traditional telephony services in developing countries, and data transmission worldwide. As a result of this market situation, many large carriers today are investing tremendously in data networks. However, at the same time, even in markets like the United States and parts of Asia, carriers are struggling to support the growth in the need for voice lines in addition to those already established.

As a result, carriers are investigating how they might be able to utilize data networks to augment, and in some cases replace, current voice networks. This is considered by many in the industry to be a daunting task, due to the conflicting network characteristics of traditional voice networks and data networks. The following chart exemplifies this phenomenon.

Overcoming any technical obstacles for utilizing data networks for voice services is a must for these carriers, however. The benefits for carriers who achieve this goal are simple, but highly important.

The first major benefit for a carrier utilizing a data network for voice services is that the carrier only has one network to maintain. The data network is actually a much more efficient means for transporting voice traffic, mainly because through compression technology, the carrier can support many more customers and therefore, calls, at the same time. With the combination of having just one network to maintain along with the increased efficiency of transmitting voice over the data network, the carrier saves money.

The second major benefit provides the carrier with the opportunity to increase revenues. The carrier can now offer multiple lines to each customer over the existing line already in place to the home or business, and the carrier can charge for the service without the additional cost of installing additional physical phone lines.

In addition, the carrier can now support voice, data, possibly video, and fax services all over the same line, therefore making the most of the already installed telephone line.

For the telephone customer, he or she can buy services from the carrier such as high-speed data and multiple phone lines for far less money than this type of service would have cost years ago. In fact, with all things considered, the combined voice and data services are relatively inexpensive.

The bottom line is that the carriers are evolving their networks to support this type of scenario. The new evolved networks feature high traffic volume growth, high revenue generation, efficient bandwidth utilization, and high quality of service.

This sounds like a lot to achieve. But with technical advancements in the past two years, there are solutions for carriers now that never existed before. The technology that has been developed to support the evolved network is known in the industry as Voice over Packet (VoP).

The way the technology works is fairly straightforward and can be broken down into four basic steps:

Step 1: Compress the voice traffic according to the quality and cost-savings specifications of the carrier. This compression takes place within a piece of equipment called the Integrated Access Device (IAD).

Step 2: Take the compressed Voice and convert it into a data packet such as Synchronous Transfer Model (ATM) or Internet Protocal (IP) packets. This is also handled by the IAD equipment.

Step 3: Transmit the voice packets along the phone lines in a higher section of the frequency spectrum than traditional voice traffic. A part of the IAD also functions as a modem that sends the traffic across the line.

Step 4: Receive the packets at the telephone company's office into a piece of equipment known as a gateway. The gateway also has a chip in it that uncompresses and converts the packets back to basic telephone traffic and sends it out across the traditional telephone network.

There are many variations of these steps, and of course, the steps are more complex than they appear to be here. For example, the compression can be done at a variety of rates. The level of compression the carrier utilizes, as mentioned above, can vary depending on the level of service guarantee made to the customer, or the level of cost savings the carrier wishes to achieve.

In addition, the carrier may wish to mimic the telephony features that the customer gets with traditional telephone service, such as voice mail, call waiting, call forwarding, and call screening. These are functions that the equipment may include, and which are very important, particularly for the support of business customers.

Also, the IAD and Gateway must also include the flexibility for the carrier to provide service at the same toll quality customers get with traditional telephone networks. Early developments of the VoP technology included issues such as delay and echo. In the early VoP trials, customers were encountering delay and significant levels of echo could be heard on the line. This impacts the quality of the service the customer gets, and therefore impacts the carriers' ability to get and retain customers.

Another challenge for carriers in converting to the utilization of a data network for voice is the integration of multiple types of data networks and how to transmit voice traffic throughout all the network types. There are basically three types of data networks, including Frame Relay, Asynchronous Transfer Mode (ATM) and Internet Protocol (IP). With today's advanced technology, the VOP system can handle the conversion of voice packets so they can travel between any of these types of data networks.

With the latest generation of chip development, these issues have been dealt with and can be, for the most part, a thing of the past. What impacts this is how the carrier chooses to trade off efficiency with quality. The following chart shows the trade-off:

In this diagram, there are several keys points shown. First, if efficiency of the network is to increase, compression will go up. If compression goes up, quality can go down. Second, with the addition of Voice Activity Detection (VAD), Silence Suppression (SS), and Comfort Noise Generation (CNG), small problems may arise with VAD front end clipping for example. Delay may be introduced if packet optimization is increased. And finally, the integration of multiple networks can increase packet overheads.

Despite the trade-offs, the benefits to the carriers are clear. Not only can the carrier save costs significantly, but also the carrier can increase revenues by augmenting its current voice network. The industry is moving towards the utilization of data networks for voice, and it is not as daunting as it at first seemed. While carriers today may not yet find it easy, it is definitely on the fast track to becoming easy.