By Georgina R. Moon
August 10, 2001
This paper discusses the Voice Over Internet Protocol technology (VoIP). It examines how the technology works, the major components of the technology, and the future uses of the technology.
Voice over Internet Protocol (VoIP) is a technology that uses IP based networks to transport voice communication. The technology takes a voice call, splits it into packets, and then reassembles the packets at a final destination. VoIP technology has come into focus for two major reasons: perceived cost benefits and enhanced communication ability. The ability to make telephone calls and send faxes over IP-based data networks with a suitable quality of service (QoS) and superior cost/benefit has everyone talking about VoIP. Equipment developers and manufacturers are seeing a window of opportunity to innovate and compete. They are busy developing new VoIP-enabled equipment in an attempt to break into the market in time. Internet Service Providers see the possibility of competing with the PSTN (Public Switched Telephone Network) for customers. Users are interested in the integration of voice and data applications in addition to the cost savings.
This technology provides businesses and individuals the ability to use the Internet to make international calls at the cost of local calls. Dawson (2002 ), tells us "VoIP is definitely not an experimental technology anymore," notes Ezequiel Villasenor, director for South America at ITXC Inc. The technology has more than proved its worth in the international and, to a lesser extent, in the domestic long-haul markets. TeleGeography Inc., keeper of international telecom statistics, says the share of international phone-to-phone traffic moving over IP in 2001 hit 6 percent last year, representing a jump from 2.43 billion minutes out of a total of 135 billion international minutes in 2000 to 9.6 billion out of 160 billion total minutes in 2001. ITXC's gateways handled close to 20 percent of that VoIP traffic last year, TeleGeography says.
Although Voice over Internet Protocol (VOIP) technologies have yet to gain the widespread acceptance originally predicted, the value proposition offered by many VOIP service and technology providers is leading industry analysts continue to expect a boom in VOIP technology and strong financial stability amongst VOIP providers in the near future. VOIP traffic is projected to account for approximately 75 percent of the world’s voice traffic by 2007, according to Frost & Sullivan. In the past 12 months VOIP service and technology providers have suffered financially, along with other telecom and Internet-related companies, and multiple VOIP companies lost 90 percent of their stock value. However, the poor financial situation forced VOIP providers to re-examine their business models and many companies have experienced stabilized stock prices and have attained a clear path to profitability."
Legacy telephone switch manufacturers have dominated the telephone industry for the last one hundred years. Up until recently telephone switches were extremely expensive, took up exorbitant amounts of space, and required specialized technicians and engineers to operate. VoIP equipment manufacturers have developed replacement products, which are a fraction of the cost, on an order of magnitudes smaller in physical size, and simply more generic to operate, than a legacy telephone switch.
Circuit switched networks have been the means of voice transport for the last century. IP is based on packet switching, which has a fundamentally different mode of delivery. Circuit switching is based on fixed bandwidth, fixed path connections, and reliable delivery. An Internet Protocol telephone is a telephone that transports voice over a network using data packets instead of circuit-switched connection over voice-only networks. For home users, broadband VoIP offers combined data and voice services through a single connection. This means, for example, that several teen-agers in a single household could e-mail or talk to their friends across town all at the same time, eliminating the need for multiple phone lines. Businesses will benefit by reaping cost savings from the convergence of voice and data services.
Conceptually, Internet telephone gateways work like this:
On one side, the gateway connects to the telephone world. It can communicate with any phone in the world. A phone line plugs into the gateway on this end.
On the other side, the gateway connects to the Internet world. It can communicate with any computer in the world. A computer network plugs into the gateway on this end.
The gateway takes the standard telephone signal, digitizes it (if it is not already digital), significantly compresses it, packetizes it for the Internet using Internet Protocol (IP), and routes it to a destination over the Internet.
The gateway reverses the operation for packets coming in from the network and going out the phone.
Both operations (coming from and going to the phone network) take place at the same time, allowing a full-duplex (two-way) conversation.
Gateways are the key to bringing IP telephony into the mainstream. By bridging the traditional circuit-switched telephony world with the Internet, gateways offer the advantages of IP telephony to the most common, cheapest, most mobile, and easiest-to-use terminal in the world: the standard telephone. Gateways also overcome another significant IP telephony problem: addressing. To address a remote user on a multimedia PC, you must know the user’s Internet Protocol(IP) address. To address a remote user with a gateway product, you only need to know the user’s phone number.
Markey (2001
) explains that "VoIP gateways are where the data packet switched network meets the PSTN.
At the gateway, VoIP data packets are collected, buffered and sent over the
PSTN at a constant rate. Conversely, voice transmissions from the PSTN are
compressed and converted to IP data packets and sent over the data network.
Gateways have at least one network connection and one or more voice ports.
Delay may be introduced in the buffering between the telephony subsystem
and the compression subsystem. Many gateways also perform echo cancellation,
DTMF (dual tone multifrequency) tone detection and regeneration, and fax
detection in the compression subsystem. The IP subsystem, which packetizes
the compressed voice data, also contributes delay in a gateway. To achieve
high-quality IP telephony communications, a gateway must send a full duplex
stream of small data packets in real time to satisfy the time division multiplexed
telephony interface. This asynchronous to synchronous translation is implemented
by adding buffers between the subsy stems. Since most of the voice compression,
conversion and jitter buffering occurs at the VoIP gateway, synchronization
is essential to minimize latency and optimize QoS".
Today’s IP telephony products exceed this latency, so most connections sound like traditional calls routed over a satellite circuit (which are usable, but require some getting used to. Even today, the products are well suited to many applications. Moreover, the latency will continue to improve, driven by three factors:
Improved Gateways. Developers are just beginning to squeeze latency out of the first generations of products.
Deployment over private networks. By deploying gateways on private circuits, organizations and service providers can control the bandwidth utilization and, hence, the latency.
Internet development.
Today’s Internet was not designed with real-time communication in mind. It will
take some time for the world’s routers to be upgraded and for operational
aspects (like how to bill for high quality of services) to be resolved, but the
Internet world is moving fast in that direction.
Overall, industry-experts agree that LAN-based VoIP solutions are often equivalent or better than regular phone service. The actual VoIP quality businesses will experience is affected by a number of factors: WAN bandwidth, voice compression, data traffic levels, and latency (the distance of the call and the number of router hops. Of these factors, the only one that cannot be controlled is latency. In the case of bandwidth, more is always better. The higher the bandwidth, the better the voice quality.
Silence suppression/voice activity detection is an
interesting feature used to maximize bandwidth resources. The silences during a
phone call usually account for 60% of the call time – time not available for
data. The silence suppression feature frees this unused call bandwidth for data
traffic. When used with the comfort noise generation feature, unused bandwidth
is reclaimed while simulating background noise like that heard in voice
networks to reassure users they are still connected at the other end.
Many applications have been identified that can be
implemented by VoIP. The long-run benefits of VoIP include support for
multimedia and multiservice applications; something which today’s telephone
system can’t compete with. Voice messages can be prepared using a telephone and
then delivered to an integrated voice/data mailbox using Internet or intranet
services. Voice annotated documents; multimedia files, etc., can easily become
the standard within office suites in the near future. IP telephony can be used
for real-time facsimile transmission. Fax transmission quality is typically
affected by network delays, machine compatibility, and analog signal. To send
faxes over packet networks, an interface unit must convert the data to packet
form, handle the conversion of signaling and control protocols and ensure
complete delivery of the scanned data in the correct order. Packet loss and
end-to-end delay are even more critical here than in voice applications.
Growth in the VoIP market is expected to be considerable over the next few years. Mier (2001 )states that: “Voice over IP isn't making much of an impact in companies just yet, but deployments are expected to pick up considerably in the next two years, according to the results of an exclusive Miercom/Network World survey of nearly 100 voice-over-IP equipment vendors. To get a sense of where the voice-over-IP market is and where it's headed, Miercom received detailed responses from 96 voice-over-IP equipment vendors including 3Com, Altigen, Avaya, Cisco, Clarent, ECI Telecom, Ericsson, Lucent, Motorola, Nortel, Nuera, Shoreline, Siemens and Sphere.
According to Kelly (2001 ), “Allied Business Intelligence (ABI) projects the VoIP-equipment market will grow from $3.7 billion posted in 2000 to $12.3 billion in 2006. ABI also expects the enterprise segment to quadruple in the same time period to $4.6 billion. "In just a few years, service providers and enterprises across the globe have recognized the cost savings found in toll arbitrage and the opportunity for the future development of enhanced services that cannot be offered by the public switched telephone network," states an ABI report. Other observers indicate, however, that VoIP growth among enterprises might take somewhat longer. "We view the migration to packet telephony as a 20-year process, in which we are now at about year three," says John Marcus, Probe Research vice president of global IP business services. "This year, we expect VoIP to account for less than 1% of total voice traffic, rising to about 14% in 2006.”
Recent developments show voice communication moving in new
directions. The online butler best known for searching is also part of an
e-business package used by corporate Web sites to assist customers. Ask Jeeves
has added a voice component. It communicates with customers via VoIP when sales
or support issues escalate and human contact makes more sense. Sega Enterprises
is bringing free, Internet-based voice communication into its video game platform.
People will be able to play and talk with each other at the same time and can
actually talk to anybody in the world from their game console.
Researchers are adapting voice over Internet protocol
technology to establish communication between Earth and spacecraft, satellites,
and perhaps someday, other planets. Using modified commercial approaches,
scientists will design space-based and mobile Internet standards that provide
access to science mission data and interactive communication with inhabited and
uninhabited spacecraft. These technologies also will become the connection with
to a future Mars-based communication infrastructure.
Berry (2000 ) tells us that "Research is being down in a space communications concept laboratory know as the in-space Internet node testbed. The facility simulates a terrestrial network using the Internet to connect to space-based IP nodes for data, voice, and video communications. One application involves transmitting VoIP with the ground-side voice module attached to the NASA Glenn Center’s private branch exchange. NASA then runs VoIP to the space-side of the network using the same satellite used for data, voice and data are transmitted simultaneously. An Advanced Communications Technology Satellite (ACTS) T1 link is currently used in this laboratory environment. The terrestrial side of the network uses a 100BaseT for communications. A 900-megahertz cordless telephone and a laptop that uses a 100BaseT network are attached to a router. This equipment will be placed in a spacecraft, allowing VoIP technology to take a new step. Although VoIP testing is not fully implemented in space, the ACTS technology used in testing is live, with the data network operating through space."
Today, more and more companies are seeing the value of transporting voice
over IP networks to reduce telephone and facsimile costs and to set the stage
for advanced multimedia applications. Providing high quality telephony over
IP networks is one of the key steps in the convergence of voice, video, and
data communications services. Voice over IP has now been proven feasible
and the race is on to adopt standards, design terminals and gateways, and
to begin the roll-out of services on a global scale. The technical difficulties
of transporting voice and the complexities of building commercial products
are many of the challenges companies are facing today. The power of being
able to use the Internet to call overseas to persons who do not have computers
is what makes VoIP the communication system of the millennium. In addition,
the person making the call does not need to be near his or her computer.
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Berry, Sharon, “Infant Voice Over Internet Protocol Takes Grown-up Steps Into Space,” Signal Magazine [magazine online], February 2000 19 paragraphs. Available from
http://www.us.net/signal/Arclhive/Feb00/infant-feb.htm
Mier, Edwin, “The enterprise VoIP update,” Network World,
[magazine online], August, 27, 2001 Available from http://www2.nwfusion.com/research/2001/0827featside.html
Kelly, Sean, “VoIP enterprise growth: not so fast. (Allied Business Intelligence's voice-over-IP report)(Industry Trend or Event)(Statistical Data Included),” Communications News, [magazine online], July, 2001 7 paragraphs. Available from http://www.findarticles.com/cf_0/m0CMN/7_38/76769685/p1/article.jhtml?term=VoIP+articles
Dawson, Fred, "VoIP Evolution Service Providers Become More Comfortable with Packet Technology," Packet Telecom [newsletter online] March, 2002 27 paragraphs. Available from http://www.phoneplusinternational.com/articles/231packet.html
Markey, Jennifer, "Synchronization: The Key to Mass Market VoIP," Telecommunications [magazine online], February, 2001 20 paragraphs. Available from
http://www.findarticles.com/cf_0/m0TLC/2_35/70711368/p1/article.jhtml?term=VoIP