The convergence of data and voice in telecommunications systems is creating
a growing list of new services, equipment, and service providers. Technology
is racing to fulfill the goal of transparent and seamless voice and data
access over a single communication device or channel. This convergence
process is complicated by the diversity of existing voice communication
systems and the extent of deployment of legacy PSTN equipment. Moreover,
merging historically independent data and voice communications systems is
confusing to both end users and service providers. Through this column, I
hope to allay fears surrounding quality and reliability, explore the needs
of the major equipment segments, and help end users and operators make
Much of what you read about today regarding Internet telephony technology
focuses on when everything will work together. I would like to get beyond
the hype and get to the next useful step of implementation. This column will
address specific problems and examine issues related to real-world
situations and networks that are deployed today. This is important because
the issues covered will aim to provide practical information from the
service provider perspective to gain an understanding of convergence and how
to solve some of the key issues that the industry is working to resolve.
Each month, I'll define the problem and provide an explanation of the cause.
I will then explain how a particular problem can be managed from a technical
viewpoint and provide solutions.
For example, network operators who want to offer multiservice access over
their broadband access network, or voice services over their private
network, are concerned with managing calls from the IAD (integrated access
device) to the gateway, back to the PSTN. The main issues here include
connecting back to the PSTN, compatibility, and quality.
IT'S ALL ABOUT CONVERGENCE
A good example of what is going on today with Internet telephony
technology as a seamless communication method can be related to the early
days of e-mail. As the use of computers has evolved, people used desktop PCs
to easily generate information and then used methods such as fax and mail to
enable the communication. Then, technology allowed us to combine
communication information generation and communication (convergence) through
the PC with the use of Ethernet LANs. This required the technology to
integrate the communication and the computer simultaneously. This did not
happen overnight. There were issues with e-mail, just as there are issues
with voice and data convergence in the network. There are complexities to
bringing the pieces together that were separate before.
ISSUES OF CONVERGENCE
Network convergence is not rolling out across the network at the same
pace, much the way e-mail was adopted at different rates. There are
limitations on the applications of convergence because of the adoption rates
and other technical aspects. With the e-mail example, initially there was
not enough bandwidth for sending attachments, or the network was not
dependable enough for this application. The issues of convergence that I
will examine that are the most pertinent today and the most critical for
wide-scale adoption and implementation include QoS (Quality of Service),
access, and interoperability.
Quality of Service
The problems surrounding QoS are the grading and service guarantees of
the networks used. This relates directly to latency and missing/delayed
packets in the network, the main culprits for today's lower-than-desired QoS
levels. The question remains, is a guaranteed quality level possible? And,
what are the different quality issues and how can they impact the voice
system to satisfy the end users? Solutions to these problems are vital in
helping plan large-scale deployments.
Access is related to what business the service provider is in. If a service
provider wants to offer converged voice and data services, a customer base
must be able to be reached and it must be determined how the customer will
access the network. There are new ways to access them such as over a cable
modem, DSL modem, or dial-up, and old ways including the universal PSTN. The
issues are determining what access methods are available to the service
provider, and what access method will work for the service provider and the
Service providers offering separate access services use a gateway or
concentrator to connect to the network. An alternative is if a service
provider uses a connection such as a cable or a DSL. The problem today is
that people have access to either voice networks or data networks, so there
is a need to add a new "converged network." For instance, by
leveraging the PSTN, the end user doesn't access the network directly. The
service provider has a converged network. On the flip side, with Web
click-to-talk services for example, the user is connected to a converged
network. The problem with this application is there may be a limited number
of users able to connect or may not have the appropriate equipment or
resources. When looking at converged networks, there are issues surrounding
converged access from the user to the network (such as bandwidth,
interoperability, and reliability), and issues with convergence on the
network (such as QoS and interoperability). Can you name what the issues
Interoperability is key to enabling convergence from point to point
across the network, making sure all parts of the network work together.
Issues surrounding interoperability are accommodating bandwidth variations,
standardization, and guaranteeing QoS levels between the different parts of
the network. Another interoperability challenge is implementing virtual
circuits (VC) across different protocols. These can include VoIP, VoATM,
VoDSL, VoCable, VoIP PBX, and IP phones.
Whether a provider is using data backbone bandwidth to provide voice
services and tap the voice market, or using broadband data access service to
tap the voice market, there is huge opportunity and many reasons for being
excited about the potential of Internet telephony technology.
An examination of the range of Internet telephony technologies and their
benefits will yield a picture of how, when, and where this technology will
be deployed. We can then extrapolate to estimate the complete evolution of
the converged network. This will take into consideration the growth of
networking bandwidth, quality over quantity, and what the applications are
that are driving convergence.
The next two columns will provide insight into some of the QoS, access,
and interoperability issues facing two real-world applications:
Long-distance wholesaling and multiservice access systems.
Scot Robertson is the director of marketing for Remote Access Products
at Analog Devices, Inc., a leading manufacturer of precision
high-performance integrated circuits used in analog and digital signal
processing applications. Scot can be reached at email@example.com.
to the July 2000 table of contents ]