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Improving real-time voice quality in a VoIP-based telephony design

Improving real-time voice quality in a VoIP-based telephony design

The general purpose SoCs used by today’s cordless or IP phones, integrated access devices and wireless unified communications devices, fully support the software DSP (soft-DSP) required for VoIP by integrating a software voice engine within the system software. Voice engines fit within an embedded processor’s system performance capabilities using soft-DSP implementation techniques, and to guarantee telephony- quality voice performance for VoIP, the system software must meet the real-time requirements of the voice engine.

Next-generation soft-DSP products that incorporate both real-time processing and wideband (high definition) voice communication achieve greater end user satisfaction and market potential than current technology. These products set a new high definition standard for voice communication.

Figure 1. The use of a DMA peripheral to collect audio samples into a buffer for servicing by the voice engine is a more efficient approach than CPLD implementation.

This article discusses how to integrate a voice engine for soft-DSP processing in order to exceed telephony quality communication.

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Using Software Voice Engines Instead of External DSPs

Due to the reduction in hardware cost, a softDSP design is ideal for cost-reduced voice products which provide one to four telephony channels. This includes mobile handsets, which are increasingly providing VoIP services through WiFi. The break-even cost is at over four channels, where the tradeoff between SoC processing power available for softDSP can’t compete with a highly efficient external DSP.

The softDSP approach also works for designs with more than eight channels, where heat, board space, and the need for additional power supplies can become an issue for external DSPs. Such designs typically employ multi-core SoCs. A single core of the SoC can be dedicated to running the softDSP, or the MHz-heavy voice components can be distributed across multiple cores.

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iPod Touch vs Nokia N810 vs Sony Mylo, Ready as Anywhere-Mobile-Internet

Three unified communication devices compared:

Three devices currently available in the market. Note that the Sony Mylo featured here is the second generation model, officially announced at the CES.

iPod Touch

iPod Touch

Nokia N810

Nokia N810

Sony Mylo

Sony Mylo

Screen Size 3.5¿ 4.13¿ 3.5¿
Screen Resolution 480×320 800×480 800×480
Operating System Mobile OS X Linux Linux
Multimedia Formats AAC, MP3, H.264 3GP, AVI, WMV, MP4, H263, H.264, MPEG-1, MPEG-4, RV (RealVideo)
MP3, WMA, AAC, AMR, AWB, M4A, MP2, RA (RealAudio), WAV
WMA/WMA DRM, MP3, AAC, ATRAC and MPEG-4
Connectivity Wi-Fi Wi-Fi, Bluetooth Wi-Fi
Storage Internal - 8/16GB 2 GB Internal, expandable using mini SD upto 8GB 1 GB internal
Flash Support No Adobe Flash 9 - desktop version Adobe Flashlite 3
Browser Safari Firefox based Netfront
VoIP support No Skype/Gizmo Skype
Input Interface Virtual QWERTY Virtual QWERTY/Slideout QWERTY Slideout QWERTY
GPS No Yes No
Third party software No Yes No
FM Radio No Yes No
Content Aggregator No RSS RSS with podcast
Integrated speakers No Yes Yes
Integrated camera for video call No VGA webcam 1.3 MP camera
Instant Mesaging No Yes Yes

Highly usable mobile internet devices are now available!

Dual-mode devices are still yet to come, for 2008.

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WiMax and FMC create Unified Communications

WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is based on the IEEE 802.16 standard, which is also called WirelessMAN. The name WiMAX was created by the WiMAX Forum, which was formed in June 2001 to promote conformance and interoperability of the standard. The forum describes WiMAX as “a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL.”

802.16d

The standard is correctly called 802.16-2004 and was developed by the IEEE 802.16 Task Group d. Therefore the project was called 802.16d, but the standard never was. However, since this standard is frequently called 802.16d.

802.16e

802.16e is an amendment to 802.16-2004, and the amendment is properly referred to as 802.16e-2005. 802.16e-2005 is not a standard in its own right — since it is only an amendment, the original document (802.16-2004) has to be read and then the amendments added to it.

Fixed WiMAX

This is a phrase frequently used to refer to systems built using 802.16-2004 (’802.16d’) and the OFDM PHY as the air interface technology.

Fixed WiMAX deployments do not cater for handoff between Base Stations, therefore the service provider cannot offer mobility.

Mobile WiMAX

A phrase frequently used to refer to systems built using 802.16e-2005 and the OFDMA PHY as the air interface technology. “Mobile WiMAX” implementations can be used to deliver both fixed and mobile services.

Uses

The bandwidth and reach of WiMAX make it suitable for the following potential applications:

  • Connecting Wi-Fi hotspots with each other and to other parts of the Internet.
  • Providing a wireless alternative to cable and DSL for last mile broadband access.
  • Providing high-speed data and telecommunications services.
  • Providing a diverse source of Internet connectivity as part of a business continuity plan. A wireless network can be “always connected”.
  • Providing highly mobile connectivity.

With WiMax in a dual-mode cell phone, the WiMax connection acts as an additional voice connection using VoIP.
Hello soft

Using Voice Call Continuity (VCC), calls can be seamlessly transferred between the VoIP network and the cellular network. This allows true mobility of voice communication! Hello soft

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Fixed Mobile Convergence: Wireless, Wireline, and VoIP Convergence 2005-2010

Insight market research report:

The confluence of technological and market forces reshaping the US telecommunications scene today calls into question the future of the fixed line telephone, a fixture in 95 percent of US homes and businesses. In this study, INSIGHT examines fixed-mobile convergence (FMC), and fixed-mobile substitution, the tendency of telecommunications users to add wireless capability to landlines phones or, in the extreme case, drop their landline service entirely in favor of a cellular phone.

Telecommunications service and usage patterns have been shifting for some time as an increasing percentage of residential and business users switch voice calls to mobile networks: the number of fixed lines has been dropping at nearly a three percent rate for the past several years, even as adoption of mobile phones increases. Nearly 65 percent of Americans, or 195 million people, are expected to be mobile phone subscribers by the close of 2005.

The underlying dynamic of the shift in call volume from fixed to mobile is well documented. As users become more used to the convenience of cellular, long distance and local usage is shifting from wireline to cellular. The average wireline residential toll minutes of use (MOUs) have been dropping at a compounded rate of 15 percent since 2000, while wireless interstate MOUs per user grew at a compounded rate of nearly 40 percent during the same period. According to one FCC study, on the wireless side, the percentage of interstate residential minutes has increased from 16 percent to 26 percent of all wireless minutes. These changes in calling patterns are being reflected in ILEC line losses—a trend likely to continue.

Given such a dynamic, are Americans going to entirely abandon their fixed line phone for cellular calling? Can cellular carriers, using voice over the Internet protocol (VoIP) and leveraging wireless LAN technology, displace PBX manufacturers in the enterprise market?

The need for unified communications in our highly connected lifestyle drives Fixed-Mobile convergence towards the anywhere/anytime communication abilities.  VoIP continues to emerge as a new feature as wireless technologies such as WiFi and WiMax gain broader connectivity.

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Mobile Voice over Internet (VoIP)

Mobile VoIP is an important feature as device manufacturers exploit more powerful processors and less costly memory to meet user needs for ever-more ‘power in their pocket’. Smartphones from mid-2006 are capable of sending and receiving email, browsing the web (albeit at low rates) and in some cases allowing a user to watch TV. Dual-Mode phones (WiFi or WiMax) will increase data rates (faster downloads) in 2008.

With mobile phones incorporating data features, Voice over IP (using Voice over WiFi or Voice over WiMax) becomes an available option.

Voice over Wi-Fi offers potentially free service but is only available within the coverage area of a Wi-Fi Access Point. High speed services from mobile operators using EVDO rev A or HSDPA may have better audio quality and capabilities for metropolitan-wide coverage including fast handoffs among mobile base stations, yet it will cost more than the typical Wi-Fi-based VoIP service. The emerging solution is Voice over WiMax (see: WiMax Standards for Mobile Communications) which has much larger range than Wi-Fi and allows Voice with high quality of service.

VoIP Mobile industry is estimated to grow to 12 Billion Dollars by 2010 in Europe.

One implementation of Fixed mobile convergence enables seamless roaming between WIFI and GSM or CDMA networks. Standards and alliances have been developed and technologies have been demonstrated as early as December 2005. This allows VoIP calls to seamlessly transfer to/from the cellular network, ideally without the user being aware of the handoff.

D2 Technologies’ newly enhanced vPort embedded software with Voice Call Continuity (VCC) and NewStep Networks’ award-winning mobility applications to deliver a completely integrated approach for accelerated FMC deployments in today’s most popular multi-mode mobile environments, including WiFi, WiMAX and GSM. — “VoIP Software Adds Fixed Mobile Convergence Capabilities for Dual-mode Mobile Phones

Dual-Mode PhoneStandard VoIP Systems

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WiMax Standards for Mobile Communications

Mobile WiMAX based upon 802.16e-2005 has been accepted as IP-OFDMA for inclusion as the sixth wireless link system under IMT-2000. This can hasten acceptance by regulatory authorities and operators for use in cellular spectrum. WiMAX II, 802.16m will be proposed for IMT-Advanced 4G.

WiMax

The goal for the long term evolution of both WiMAX and LTE is to achieve 100 Mbit/s mobile and 1 Gbit/s fixed-nomadic bandwidth as set by ITU for 4G NGMN (Next Generation Mobile Network) systems through the adaptive use of MIMO-AAS and smart, granular network topologies. 3GPP LTE and WiMAX-m are concentrating much effort on MIMO-AAS, mobile multi-hop relay networking and related developments needed to deliver 10X and higher Co-Channel reuse multiples.

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Mobile-to-Mobile Convergence vs Fixed-Mobile Convergence

Mobile to mobile convergence (MMC) is a term to describe a technology used in modern computing and telephony. The term is an offshoot of fixed mobile convergence (FMC) and uses dual mode (cellular network and WiFi) phones with a special software client and an application server to connect voice calls and business applications via a VoWLAN and/or through a cellular service.

Mobile to mobile convergence differs from conventional FMC in that the technology uses the WLAN to route calls via the internet as a primary function, and uses the wireless carrier network if the WLAN is not present as a secondary function. It is significant since it is viewed as a means to compete with carrier companies since the calls are routed around the cellular network. This is viewed as a more efficient use of networking technology than standard FMC solutions that are available as well, since most of the latter use the carrier network as the primary means of communication and do not leverage the lower cost and controls of internet protocol-based networks that are generally installed at most modern businesses. In theory, it also provides the capability of providing a greater voice coverage area than either carrier or WLAN technology alone since some areas do not have cellular service coverage and others do not have WiFi.

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Mobile Service Provisions and the Fixed-Mobile Convergence Alliance

Six companies, British Telecom, NTT, Rogers Wireless, Brasil Telecom, Korea Telecom and Swisscom have formed the Fixed-Mobile Convergence Alliance (which as of January 2007 has 26 members) with the purpose to encourage the seamless integration of mobile and fixed-line telephone services.

The “mobile service provisions” aspect refers not only to the ability of subscribers to be able to purchase mobile phone like services as is often seen in co-marketing efforts between providers of land-line services. Rather it is one major ambition of wireless - the ability to have access to all of the above including voice, internet, and content/video while on the go and requiring no tethering to the network via cables.

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