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Recent developments in VoIP chipsets and architecture

1st April 2013


Internet-protocol (IP) aphone-on-a-chip' handsets are expected to be shipped to the North American market later this year. Here, Nick Flaherty investigates the evolving technologies behind Voice-over-IP and other asssociated broadband services

The idea of using the internet for free long distance and international phone calls has long been one of the dreams of the industry, and the rollout of broadband services based on low-cost chips looks as if it will bring this closer.

One of the key technologies behind the dream is running voice calls over the Internet Protocols of the World Wide Web in voice over IP, or VoIP. But the reality is that the broadband and IP technologies are being used in a different way to offer low-cost calls to the home and office, and many of them are also being called VoIP.

Even so, it is still not as easy as plugging in the modem, getting a microphone for the PC and talking away to Outer Mongolia or, more likely, California, for next to nothing. The Internet has been designed to handle data in a very rugged way, ensuring that all the packets get to their destination by whatever route is available. Unfortunately for voice, this means the quality of the resulting conversation leaves a lot to be desired, and so people are finding other ways of using the Internet infrastructure to handle voice calls.

""We see voice over IP as being part of a broader landscape of voice services in the broadband arena,"" said Duncan Greatwood, vice president of marketing for Virata. Part of that is the rise of the internet phone. But this requires both developments in the infrastructure, with high performance chips powering voice gateways added to phone exchanges, and also low-cost chips to make the internet phones practical for the consumer market.

Virata, which spun out of the AT&T labs in Cambridge in the UK as ATM Ltd, develops chips for all these systems, and so has no particular axe to grind. It has seen the USA with its more developed internet infrastructure as the prime mover so far. ""The bulk of our business is in the US,"" said Greatwood, ""but we are expecting and seeing growth increasing in Europe and Asia and if we look forward over the next few months it is possible that the business will be growing faster in Europe and Asia than the US.""

He see three kinds of voice running over the internet, from integrating voice directly into the public data network to the full IP network via existing networking technologies such as the well established Asynchronous Transfer Mode (ATM) and Digital Subscriber Loop (DSL).

""Voice over ATM is far and away the bulk of voice over the internet today,“ he said. "This uses the BLES [Broadband Loop Emulation Services] specification from the DSL Forum. The vast majority of voice over DSL from companies such as Coppercom and Jetstream is using BLES.""

Chip maker Texas Instruments has teamed up with General Bandwidth to demonstrate voice over DSL (VoDSL) solutions supporting BLES at the DSL Forum booth at the recent Consumer Electronics Show in Las Vegas.

The BLES standard is the first open standard to promote interoperability for VoDSL by providing a standards-based mechanism that enables VoDSL equipment to support multiple voice channels over a single loop, thereby eliminating the need for additional loops. With VoDSL, a wide range of voice services will be offered for both consumers and businesses, including bundled voice and data services, multiple virtual lines and highly managed lines.

"Industry-wide support of this standard will accelerate VoDSL deployment because OEMs can now build voice-enabled equipment that is globally interoperable,“ said Dennis Gatens, product management director at Telogy Networks, a Texas Instruments company.

The demonstration features TI's 6E/4000R VoDSL customer premises equipment evaluation system with the Telogy Software with BLES support and TI's TMS320C54x programmable DSPs. This is linked up to General Bandwidth's G6 VoBroadband gateway.

In addition to BLES, the system supports pulse code modulation (PCM)/adaptive differential pulse code modulation (ADPCM) and low bit rate (LBR) voice CODEC technology. LBR CODECs provide an 8:1 reduction in the bandwidth required for each voice channel.

Quality of service

"Voice over IP is a very attractive concept but it has some barriers to adoption which are bigger than the BLES approach. IP services are not on the whole very well equipped for quality of service mechanisms today, while most of the BLES specification is about the control software from the IWF and the central office for the quality of service,"" said Greatwood at Virata.

Coming up is the multi-protocol label switching (MPLS), and this is one of the possible means for guaranteeing IP quality of service in the core network, he says, but this is a complicated protocol. Then there is another protocol called DiffServe which is another IP QoS signalling mechanism that is simpler than MPLS but does not scale very well.

"So what we see is a box that understands both, with MPLS in the core and Diffserve to the home,“ he said. "The problem with the quality-of-service issue is that you have to have the quality everywhere you want to go so there is a critical mass problem until you have MPLS in every router in the internet. With BLES you can have the QoS everywhere already. IP may ultimately be even bigger than BLES but it does have these barriers, and despite the tremendous growth in the internet, the IP network is not as ubiquitous as the phone network.“

Virata itself is neutral, and will sell chips for both approaches. "We think that BLES is valid and VoIP is valid and we have customers doing both,“ said Greatwood. "We have customers building VoIP equipment using a similar topology to the ATM approach, but these are using the RTP real-time protocol rather than the traditional TCP/IP as a substitute for the AAL2 cells.“

Alongside its own Helium and Beryllium chips for ADSL, Virata has taken the Texas Instruments C54x digital signal processors and added its own software for Voice over DSL (VoDSL) to create a chip it calls Magnesium. But the advantage is that Magnesium can be combined with Virata's Helium chip and third-party analogue front end (AFE) and line driver, or with the Beryllium chip and Neon AFE in chipsets called Azurite, for a VoDSL gateway or Internet Access Device (IAD).

The Azurite solution will ship for US$37, compared to a component bill of over $50 for other approaches, says David Moorhouse, director of product development at Virata. This will appeal to both existing DSL modem customers using Helium and new ones looking for a low cost IAD solution

One of companies driving the technology is Taiwanese PC maker Acer, which is using Azurite for Integrated Access Devices (IADs) that deliver high-speed voice and data access over a single twisted-copper-pair to the home.

""We believe the DSL and broadband wireless markets have the potential to ramp at an even faster rate than the PC market did ­ and we intend to be a world leader in that space as well,"" said Simon Lin, CEO of Acer InfoSystems Group. ""We chose Virata's Azurite chipset with its comprehensive voice and data networking software package because it delivers the most powerful processing capability and highest level of integration.“

Asia is a key market for these kinds of devices, says Virata. ""This deal represents a major win for Virata because it not only expands our tier-one customer base, but also highlights the high demand for DSL services in Asia,"" said Tom Foster, vice president of Asia sales for Virata. "Telecommunications providers throughout much of Asia are deploying DSL lines at a rapid rate and companies such as Acer are meeting customer demands for affordable, high-performance DSL solutions by quickly bringing new products to market. This rapid deployment has resulted in Virata being selected by more than 45 Asian equipment manufacturers.""

Agere Systems, formerly the Lucent Technologies Microelectronics Group, also teamed up with Korean chip and equipment maker Samsung Electronics for VOIP systems. Samsung will use Agere's $30 DSP-based Internet Phone-On-A-Chip in its internet telephones.

""Agere offers the industry's most innovative and complete internet telephone semiconductor solution,"" said Hak Joong Choi, senior project manager of business development of the Internet Telephony Group within Samsung Electronics. ""The amount of system-level integration of Agere's solution enables us to lower our electronics costs, and offer more competitively priced Internet telephones at an accelerated pace.""

The first chip in Agere's chipset integrates 13 electronic functions onto a single chip. The DSP integrates a telephone handset analogue-to-digital converter (codec), a speakerphone codec, a speaker amplifier, and a microphone amplifier all in one. The second chip is an ARM 940T processor core for the voice over Internet Protocol (IP) signalling and network management.

Samsung has finished its prototype of an Internet Protocol phone and the company is now moving its research and development effort toward production stage. The company plans to ship this new product using the Phone-On-A-Chip later this year, primarily to the North American market.

Set-top box gateways

But there is a much larger change coming with the new generation of digital satellite and cable set-top boxes with broadband, 'always on' connections. This then has an open line to the Internet and can act as a communications gateway, providing a link between the IP side and the standard cordless or ordinary telephones.

TI has used the Jade processor core developed by MIPS Technologies for what it claims is the first complete able modem chipset to include Voice over IP (VoIP). This is a direct challenge to companies such as Virata, but the chip is also a real contender for turning the cable modem, whether linked to a PC or in a set-top box, into a home communications gateway.

In the triple core TNET C4320, the 125MHz MIPS processor is coupled with two 133MHz C54x DSP core (the same core in the chip that Virata uses for its Azurite chipset alongside an ARM processor) with 320K words of memory.

"Voice is the first akiller' application for cable and, as the technology continues to evolve, only TI has the flexibility, scalability and programmability to quickly and easily change it and continue to deliver the solutions that make digital services over cable a reality,“ said Anton Hierhager, market manager for cable broadband communications in Europe for TI.

The chip has a glueless interface to the TNET C4042 as well as an 8-port USB interface, so that the cable modem can act as a USB extension hub on the PC. It also has a PCI interface for internal PC applications, as well as two 10/100 Ethernet MAC blocks to link to 802.11 wireless LANs, as well as two UARTs intended to link to Bluetooth wireless networks.

The software that is integrated with the chip can handle up to 24 lines of G.711 voice or 8 lines of higher quality G.728 voice in gateways for multiple dwellings which TI is also targeting.

"Voice over IP is voice digitally encoded transmitted in an IP stream and it is as simple as that,"" said Andrew Wallace, worldwide marketing director for settop box maker Pace Micro Technology. "Obviously it's got to be converted using a standard codec, and we are very much into standards, otherwise people can't talk to each other.“

Earlier this year, Pace bought US company Vegastream which is providing IP gateways such as the IWF to regional telcoms operators in the US, and is looking to move this capability into the set-top box so that traditional, low cost, digital cordless phones can be used as IP telephones without having to wait for dedicated units that are going to be more expensive for several years.

This also avoids potential problem with IP networks. With the existing internet infrastructure, every terminal on the network has an IP address, and if every phone in every house also has to have an IP address, that is going to overload the 32bit numbering system. There is a next generation of IP, IP version six or IPv6, being developed with 128bit numbers, but the Pace approach means it is only the set top box that has the IP address, not the phones.

Pace also sees the opportunities for voice over IP away from the traditional PC-based idea. With the set-top box as the gateway, other devices such as handheld computers can link to the internet as well using the same IP address.

""If you want to do voice over the internet by logging onto an internet service provider, I still think it will be a tiny part of the overall voice business,"" said Wallace.





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