Using Voice over IP (VoIP) in Mobile Networks

Early in the last decade, service providers viewed VoIP as a threat to their traditional revenue streams. This has turned out to be true and is made possible by VoIP and the Internet, which is not distance-sensitive with respect to the cost of access. It is clear that VoIP will play an even more prominent role in all telecommunications networks moving forward and will completely replace circuit-switched voice.

VoIP has been around since the mid-1990s. The International Telecommunications Union (ITU) standardized the first signaling protocol for VoIP. The protocol, classified as a conferencing standard, is referred to as H.323.

The Internet Engineering Task Force (IETF) entered the scene in the late 1990s with what became a competing protocol called the Session Initiation Protocol (SIP). In 2003 the IETF released an updated version that fixed many issues with the original protocol. Since that time, SIP has become widespread in supporting the signaling functions for most real-time applications today.

There is one other key ingredient for VoIP that involves the packaging of the bits that make up the real-time voice or video communication. The protocol that accomplishes this is called the Real-time Transport Protocol (RTP). The IETF was also responsible for developing this protocol. Apparently it never seemed necessary to develop another competing protocol to RTP, so this has been the sole standard for media transport from the beginning.

To summarize the protocols, we have these two key ingredients that are used for signaling (SIP) and transport (RTP) of real-time communications over IP packet-based networks.

One thing to bear in mind is that these same protocols are used for voice or video traffic over IP networks, which both represent time-sensitive traffic (from end-to-end ). The biggest difference between voice and video IP traffic is the volume of data, or bits. Obviously, video demands a higher throughput than voice (exactly how much, depends on the resolution of the video and the compression method used). A voice or audio channel is necessary in conjunction with a video stream (i.e., silent video conferencing is not something desired by users).

The key difference between voice and video traffic versus transferring ordinary data files is the necessity to deliver a steady stream of traffic because it is time-sensitive. This is best achieved by allowing time-sensitive traffic to have priority, or right-of-way, over other types of non-time-sensitive data traffic. The term that defines this process is typically called Quality of Service (QoS).

There are three different groups of standards that have evolved over time that represent the majority of mobile cellular communications today.

Referencing back to 2nd generation (digital) mobile cellular networks, there were two key standards that became global standards. First, Global System for Mobile communications (GSM) was developed by the European Telecommunications Standards Institute (ETSI). This has become the most widely deployed mobile cellular voice technology in the world. The other 2nd Generation Standard is called Code Division Multiple Access (CDMA). This standard was initially developed by Qualcomm. An industry trade group was formed to provide an eco system for the cdma-One standard.

At the turn of the millennium, 2nd generation mobile standards began their evolution to 3rd generation standards. The move to 3G mobile networks would take a herculean effort on the part of engineers to accomplish the task. Therefore, regional standards bodies throughout the world formed standards partnerships in order to accomplish the task.

ETSI passed the torch to the 3rd Generation Partnership Project (3GPP), which transformed GSM into a new 3G standard called Universal Mobile Telecommunications System (UMTS) that used, what was at that time, a new air interface called Wideband CDMA, or W-CDMA.

The torch-bearer for the 3G standards development involving cdmaOne is the 3rd Generation Partnership Project 2 (3GPP2). Two 3G standards were created out of this partnership. The first became known as 1x Radio Transmission Technology (RTT) and the second was 1x Evolution Data Optimized (EV-DO). 1x stood for the original CDMA channel size of 1.25 MHz (as opposed to the W-CDMA, which was 5 MHz). The former (1xRTT) supported voice and lower-speed data traffic. The later (1xEV-DO) supported only data but at much higher data rates versus 1xRTT.

Recall that at the beginning of this section three groups of standards were mentioned. The third mobile cellular standard comes from the Institute of Electrical and Electronic Engineers (IEEE). The IEEE has created a whole series of standards involving both Local Area Networks (LANs) and Metropolitan Area Networks (MANs). These IEEE standards are formed under a group called the 802 committee, which was formed in February of 1980.

The standard that evolved into a mobile cellular standard is known as 802.16. A group of interested parties that wanted to promote 802.16 standards was formed, called Worldwide Interoperability for Microwave Access (WiMAX). That is why the 802.16 standards are also known as WiMAX. In 2004, the IEEE combined several standards documents that loosely formed the 802.16 framework into one cohesive standard, called 802.16-2004. This standard provided capability for creating a fixed-point microwave access network that provided broadband wireless connections.

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Alexander Graham Bell speaks, and 2013 hears his voice

1 of 2. A wax-covered cardboard disc is seen in this undated Smithsonian National Museum of American History image.

Credit: Reuters/Smithsonian Institution Archives/Handout

By Deborah Zabarenko

WASHINGTON | Mon Apr 29, 2013 3:36pm EDT

WASHINGTON (Reuters) - Nine years after he placed the first telephone call, Alexander Graham Bell tried another experiment: he recorded his voice on a wax-covered cardboard disc on April 15, 1885, and gave it an audio signature: "Hear my voice - Alexander Graham Bell."

The flimsy disc was silent for 138 years as part of the Smithsonian Museum's collection of early recorded sound, until digital imaging, computer science, a hand-written transcript and a bit of archival detective work confirmed it as the only known recording of Bell's voice.

Carlene Stephens, curator of the Smithsonian's National Museum of American history, first saw this disc and nearly 400 other audio artifacts donated by Bell when she joined the museum in 1974, but she didn't dare play them then.

"Their experimental nature and fragile condition ... made them unsuitable for playback," Stephens said by email.

"We recognized these materials were significant to the early history of sound recording, but because they were considered unplayable, we stored them away safely and hoped for the day playback technology would catch up with our interest in hearing the content," she wrote.

That day came in 2008, when Stephens learned that scientists at the Lawrence Berkeley National Laboratory in California had retrieved 10 seconds of the French folk song "Au Clair de la Lune" from a 1860 recording of sound waves made as squiggles on soot-covered paper. That was nearly two decades before Thomas Edison's oldest known playable recording, made in 1888.

If the Berkeley scientists could coax sound out of sooty paper, Stephens reckoned, perhaps they could decipher those silent records she had guarded for decades.

She contacted Carl Haber at Berkeley and Peter Alyea, a digital conversion specialist at the Library of Congress. They chose six recordings from the collection, including the one that turned out to be the Bell audio, and made ultra-high-definition three-dimensional images of them.

The Berkeley lab's scanner captures gigapixels of information, and not just width and height but the depth of the grooves, with measurements down to 100 nanometers, or 250 times smaller than the width of a human hair, Haber said by telephone.

DEEP WIGGLES

Depth is important with these old recordings, Haber said, because a lot of the information about how it sounds is stored in the deep parts of the grooves.

"It's not necessarily a groove that wiggles from side to side, it wiggles up and down," he said. "If you just took a regular (two-dimensional) picture of it, you don't get the information you need."

Haber and Berkeley colleague Earl Cornell used an algorithm to turn that image into sound, without touching the delicate disc. The system is known as IRENE/3D, short for Image, Reconstruct, Erase Noise, Etc.

Most of the recording is Bell's Scottish-accented voice saying a series of numbers, and then dollar figures, such as "three dollars and a half," "seven dollars and 29 cents" and finally, "$3,785.56."

This suggests Bell was thinking about a machine for business recording, Stephens said.

"The recording on its own is historically interesting and important," Stephens wrote. "It answers questions about Bell personally - what kind of accent did he have? (he was a Scot who lived in England, Canada and the United States) ... How did he pronounce his middle name? ('Gray-hum' not 'Gram')."

The job of authenticating the disc began with a hand-written transcript of the recording signed by Bell (online here).

In 2011, Patrick Feaster, an Indiana University sound-media historian, inventoried notations on the discs and cylinders in the Smithsonian's collection. Many were scratched on wax and all but illegible, Stephens recalled.

"We then matched up one wax-and-cardboard disc, from April 15, 1885," Stephens wrote. "When we recovered sound from the recording ... the content matched the transcript word for word. It is a recording of Bell speaking."

Similar scanners are used in quality assurance for micromanufactured products such as microchips, optical components and to assure the flatness of touch screens. Dentists use them to take three-dimensional pictures of cavities to aid in making custom fillings.

The Berkeley lab has worked with the Smithsonian and the Library of Congress to learn more about the earliest audio records, some on tinfoil or even paper. And while Haber and his colleagues now know how to authenticate the recordings, they cannot do all the records that may exist.

The Northeast Document Conservation Center in Massachusetts is working with the Berkeley lab on a digital reformatting service for early audio recordings. There could be as many as 46 million of these early recordings in the United States.

The Bell recording was made at a time of creative ferment, Haber said, as Bell, Edison and others invented devices to change the way Americans communicate.

"Those guys were creating the future," Haber said.

(Reporting by Deborah Zabarenko; editing by Marilyn W. Thompson and Jackie Frank)

View the original article here

Alexander Graham Bell speaks, and 2013 hears his voice

1 of 2. A wax-covered cardboard disc is seen in this undated Smithsonian National Museum of American History image.

Credit: Reuters/Smithsonian Institution Archives/Handout

By Deborah Zabarenko

WASHINGTON | Mon Apr 29, 2013 3:36pm EDT

WASHINGTON (Reuters) - Nine years after he placed the first telephone call, Alexander Graham Bell tried another experiment: he recorded his voice on a wax-covered cardboard disc on April 15, 1885, and gave it an audio signature: "Hear my voice - Alexander Graham Bell."

The flimsy disc was silent for 138 years as part of the Smithsonian Museum's collection of early recorded sound, until digital imaging, computer science, a hand-written transcript and a bit of archival detective work confirmed it as the only known recording of Bell's voice.

Carlene Stephens, curator of the Smithsonian's National Museum of American history, first saw this disc and nearly 400 other audio artifacts donated by Bell when she joined the museum in 1974, but she didn't dare play them then.

"Their experimental nature and fragile condition ... made them unsuitable for playback," Stephens said by email.

"We recognized these materials were significant to the early history of sound recording, but because they were considered unplayable, we stored them away safely and hoped for the day playback technology would catch up with our interest in hearing the content," she wrote.

That day came in 2008, when Stephens learned that scientists at the Lawrence Berkeley National Laboratory in California had retrieved 10 seconds of the French folk song "Au Clair de la Lune" from a 1860 recording of sound waves made as squiggles on soot-covered paper. That was nearly two decades before Thomas Edison's oldest known playable recording, made in 1888.

If the Berkeley scientists could coax sound out of sooty paper, Stephens reckoned, perhaps they could decipher those silent records she had guarded for decades.

She contacted Carl Haber at Berkeley and Peter Alyea, a digital conversion specialist at the Library of Congress. They chose six recordings from the collection, including the one that turned out to be the Bell audio, and made ultra-high-definition three-dimensional images of them.

The Berkeley lab's scanner captures gigapixels of information, and not just width and height but the depth of the grooves, with measurements down to 100 nanometers, or 250 times smaller than the width of a human hair, Haber said by telephone.

DEEP WIGGLES

Depth is important with these old recordings, Haber said, because a lot of the information about how it sounds is stored in the deep parts of the grooves.

"It's not necessarily a groove that wiggles from side to side, it wiggles up and down," he said. "If you just took a regular (two-dimensional) picture of it, you don't get the information you need."

Haber and Berkeley colleague Earl Cornell used an algorithm to turn that image into sound, without touching the delicate disc. The system is known as IRENE/3D, short for Image, Reconstruct, Erase Noise, Etc.

Most of the recording is Bell's Scottish-accented voice saying a series of numbers, and then dollar figures, such as "three dollars and a half," "seven dollars and 29 cents" and finally, "$3,785.56."

This suggests Bell was thinking about a machine for business recording, Stephens said.

"The recording on its own is historically interesting and important," Stephens wrote. "It answers questions about Bell personally - what kind of accent did he have? (he was a Scot who lived in England, Canada and the United States) ... How did he pronounce his middle name? ('Gray-hum' not 'Gram')."

The job of authenticating the disc began with a hand-written transcript of the recording signed by Bell (online here).

In 2011, Patrick Feaster, an Indiana University sound-media historian, inventoried notations on the discs and cylinders in the Smithsonian's collection. Many were scratched on wax and all but illegible, Stephens recalled.

"We then matched up one wax-and-cardboard disc, from April 15, 1885," Stephens wrote. "When we recovered sound from the recording ... the content matched the transcript word for word. It is a recording of Bell speaking."

Similar scanners are used in quality assurance for micromanufactured products such as microchips, optical components and to assure the flatness of touch screens. Dentists use them to take three-dimensional pictures of cavities to aid in making custom fillings.

The Berkeley lab has worked with the Smithsonian and the Library of Congress to learn more about the earliest audio records, some on tinfoil or even paper. And while Haber and his colleagues now know how to authenticate the recordings, they cannot do all the records that may exist.

The Northeast Document Conservation Center in Massachusetts is working with the Berkeley lab on a digital reformatting service for early audio recordings. There could be as many as 46 million of these early recordings in the United States.

The Bell recording was made at a time of creative ferment, Haber said, as Bell, Edison and others invented devices to change the way Americans communicate.

"Those guys were creating the future," Haber said.

(Reporting by Deborah Zabarenko; editing by Marilyn W. Thompson and Jackie Frank)

View the original article here