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Feature Article
November 2001

Global Conferencing: Bridging IP And PSTN Networks


Today companies are looking to differentiate themselves based on the services they offer -- not necessarily on their products. In some cases, traditional products -- like the transport of calls -- are becoming a commodity business. This fact is true for PSTN providers as well as for newer mobile operators. We all know it is not uncommon to pay five cents a minute for landline transport and pay $30 a month for 3,600 minutes from a mobile operator. Since the race to get new subscribers seems to have peaked, service providers are looking to create value and reduce customer churn by offering enhanced services that keep customers loyal.

One of the services that these vendors are looking at in order to keep minutes in their network is conferencing. It is still a fact that a simple call that brings key players together -- without involving travel -- is still one of the fastest, most efficient ways to make quick, high-quality decisions. For the service provider, if they can drive down cost and drive up usage, the business customer is likely to use more minutes and stay with a specific carrier. That fact, coupled with the ubiquity of the Internet, is causing service providers as well as their business customers to evaluate the way they handle audio conferencing.

As VoIP becomes more common in business communications, everyone is looking at ways in which both the services and the service delivery mechanism are changing. Lots of questions are being asked: Is anyone using VoIP today? If so, is it affecting the actual conference? Will VoIP change the way we conduct conference calls? Will it impact the way conference calls are established? Will it impact quality?

Who Is Using VoIP?
The appeal of free long-distance calls or inexpensive international calls is attractive to consumers. Even though there may be some reduction in voice quality, consumers will accept it if the savings are large enough. Consumers may even use primitive "push-to-talk" sequences that they would never tolerate on a normal call in order to save money on lengthy international calls.

VoIP has also become common in the business environment. The primary appeals in the business environment is the savings associated with managing a single network and the bandwidth provided by the IP connection to the desktop. Savings on long-distance charges are a secondary benefit, since costs have already declined to a few cents per minute. Systems such as IP/PBX and IP/Centrex will provide business-quality audio. However, it will be years before most businesses have an entirely VoIP infrastructure because of depreciation schedules on existing switching equipment, the lack of five-nines reliability within the data network, and the overall quality of voice calls that run on an IP network. Thus, the challenge for carriers is to provide a platform that can seamlessly bridge traditional PSTN calls with VoIP calls as existing businesses slowly migrate from the PSTN to the more economical VoIP one.

End-User Expectations
The end user isn't interested in technology for technology's sake or whether their call is being carried over PSTN, IP, or the Internet. What they care about is:

  • Ease of use -- participating in a conference call must be as easy as picking up their phone and entering an access number.
  • Voice quality -- business users expect "toll quality" voice. They won't accept long delays, echo, or any other interruptions.
  • Availability anytime/anywhere -- the advantage of conference calls is that participants can join the conference from wherever they are. They must be able to join the call using any available device: a landline phone, a cell phone, or a PC.

The Case For Mixed Conferences
The average conference call involves five to six parties, is usually geographically dispersed, spans corporate boundaries, and can involve customers, partners, or
suppliers. Frequently, parties on a conference call are at a location other than their office and it is unlikely that all parties will be on the same network infrastructure. Even as VoIP becomes commonplace in businesses, conference participants will continue to use the PSTN. VoIP calls will originate from users at smaller locations where the economics of single access networks are easily proven or from a remote location where the end-user has only a single access line for both voice and data.

The challenge is to provide a conferencing solution that seamlessly bridges calls from VoIP networks and the PSTN. Bridging several PSTN calls in a single conference is complex. All PSTN calls arrive as circuit switched calls using network signaling protocols such as T1, E1, or ISDN. Bridging VoIP calls together adds complexity. Packet networks inherently have more delay than circuit-switched networks. And industry standards are still evolving with rivaling network protocols -- H.323, SIP, MGCP, etc.

Bridging PSTN and VoIP calls on a single conference requires terminating the end-user call, no matter what network they originated on, then converting all of the audio streams to a common format, and then providing echo cancellation and mixing the audio streams to ensure a high-quality audio experience.

Conferencing systems designed to bridge the VoIP and PSTN worlds will have an internal gateway that performs the proper protocol and voice compression conversions. Legacy conferencing systems may use external gateways, but overall performance will suffer, and system administration will be more complex.

As the quality and availability of Internet voice traffic increases, the question of how VoIP can be exploited for business communication becomes increasingly important. The promise of cost savings and the creation of valuable new services including using IP for voice are driving considerable interest among providers and businesses alike. The interest stems from the realization that IP costs less because it is more efficient to transport voice as packets over an IP network, versus transport on a switched circuit network.

The cost savings from using IP to transport voice calls can be realized in three areas. The first is through lower conference call termination (phone company "800" number) charges. Conference attendees who can use an IP capable end point (whether soft phone, IP phone handset, or most importantly, traditional handsets tied to a traditional PBX behind a gateway) can make voice calls over IP directly to the service providers conference system.

By using a managed IP network to transport the voice traffic from users to the conference service provider, all circuit switched 800-number calls are avoided. Conferencing Service Providers thus avoid the expensive 800-number charges which average about 25 percent of total operating costs. These charges are paid to the PSTN carrier, for every call, at the rate of approximately two cents per minute: Two cents per minute for every user in every conference. By eliminating these toll charges, conference service providers can save a large portion of their operating costs and gain a significant competitive price advantage.

The IP network required is relatively simple. A customer with a traditional PBX, provisions the conferencing 800-number traffic (a PBX setting) to divert to a router via a T1 line. Gateway cards in the router compress and packetized the voice streams. The router then sends the voice packets over the managed IP network to the conference bridge's IP address. A managed IP service (available from many national Internet service providers) is needed in order to ensure a high quality of service (QoS) for the voice traffic.

The second potential savings from voice traffic over IP is realized by any conferencing service provider that has a geographically dispersed operation. Once regional conferencing equipment sites are linked via IP, resources can be shared (or load leveled) at no additional charge from the phone company. Peaks caused by differences in time zones, or business usage can mean the need to purchase and operate less equipment.

The third savings from VoIP is in the bandwidth reduction with IP to support the same amount (ports) of conferencing. The most common standard for VoIP
traffic is to use G.729.A encoding. G.729.A delivers toll-quality voice, with an 8:1 compression. Meaning that PSTN phone traffic, which required 64K, is sent via IP using only 8K bandwidth. For a large customer of conferencing, this can mean a reduction of T1 lines, and associated monthly charges.

Conferencing is an integral tool of business communications. As VoIP is deployed in the corporate environment, conferencing systems must be able to seamlessly bridge VoIP calls with traditional PSTN calls. A well-designed system will make this requirement transparent to end-users and will provide the same service to all users independent of the transport network. These systems will make it easy for businesses to migrate from an all PSTN infrastructure to a mixed PSTN/VoIP environment as networking technologies continue to evolve.

Conferencing has grown in importance because it is the exception to have key people in the same place at the same time -- not the rule. Conferencing solutions are making it easy to get people together. VoIP is bringing new options into the mix and enabling providers to offer cost effective solutions to their business customers without having these customers sacrifice quality.

Ron Elwell is the CEO of Octave Communications, Inc. Octave has helped set new industry standards for ease of use, capabilities, capacity, reliability, size, performance, and cost.

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