CompactPCI media processing board wears more than one hat

High-grade secure voice and data gateway

One of the largest Private Finance Initiative (PFI) contractors, providing defense and security systems worldwide, was developing a voice and data gateway solution with secure interoperability features. As a leading systems integrator, they are acknowledged experts in the areas of information systems and networks, secure end-to-end communications solutions, and battlespace management systems.

The clientís traditional suppliers were having difficulty meeting the stringent demands placed upon them. While requirements for operating system support, military standard voice codecs, and data communications modem functionality were understood and to a large extent available, a crucial factor concerned the channel density that the small form factor gateway required.

Voice compression and transcoding are DSP-intensive tasks and warrant a degree of flexibility not often found in a COTS product line. The solution had to achieve a guaranteed channel count performance, regardless of the combination of codecs in use. Or to put it another way, the client required sufficient DSP processing power to support 120 channels of all supported codecs in any configuration.

A network connectivity perspective

The client designed the planned gateway from a network connectivity perspective, requiring 120 channels of secure, high-grade voice and data in a small form factor. The gateway was intended to allow the use of many existing compliant devices to achieve end-to-end encrypted speech and data services and interconnects to existing secure speech networks. Two models were to be produced for so called red and black network enclaves.

The client needed an enabling technology solution that would allow it to offer the first such compliant gateway devices in the United Kingdom.

The procurement specification listed support for both commercial and military standard voice codecs. Additional requirements included a V.32 data communications modem and Q.931-based ISDN signaling protocols, Q.SIG and EuroISDN (a.k.a. ETS300). Time frames already committed to meant that Aculab was asked to develop the necessary capabilities in a just a few short months.

Rigorous demands for data rates, latency (delay), Mean Opinion Score (MOS) quality assessments, and throughput performance were stipulated as was the need for the resultant software and APIs to run on the QNX operating system.

The client insisted on a single card CompactPCI form factor solution in order to be able to convert speech or modem data from ISDN to RTP/UDP/IP packet data in the small form factor package they set out to manufacture. Network interfaces and termination were to be standard E1/T1 presented via RJ-45 connectors on RoHS- and standards-compliant hardware.

Aculabís Prosody X cPCI platform, shown in Figure 1, includes IP-to-TDM gateway functionality as a standard option. It has the necessary capabilities and importantly, the inherent flexibility in design, to be able to cope with the clientís requirements.

Figure 1 (click graphic to zoom by 3.5x)

Aculab developed and tested software, firmware, and APIs to run on the QNX operating system and participated in client testing of the resultant software packages.

Apart from porting its regular media processing resources to QNX, Aculab also ported a multichannel, multithread, real-time implementation of the 600/1200/2400 bps enhanced Mixed Excitation Linear Prediction (MELPe) vocoder to its Prosody X DSPs. The U.S. and NATO standard MELPe vocoder (MIL-STD-3005, STANAG 4591) provides complete, state-of-the art, low-rate voice communications.

Aculab designed the MELPe, G.711, and G.729d codecs to be software selectable on a per-call basis and to support 120 channels in any configuration as demanded. In addition, the conventional media processing resources of the Prosody X cPCI card, including recording and playback of G.711 A-law voice data on any channel at any time, were employed.

The payload size and format of the RTP/UDP/IP packets generated by the Prosody X card met the constraints requested by the client in order to minimize the end-to-end delay of the system. Crucially, in order to ensure this was achievable, the jitter buffer is adaptive within ìnî frames and is software selectable. On the ISDN side, Aculabís standard signaling protocol portfolio supplied the detailed support for Q.SIG and EuroISDN, specifically overlap receiving.

A conferencing solution based on the newest voice compression technology

Improved telephony conference voice quality leads to a better user experience and, as a result, to increased service usage.^[1] Many businesses are looking to reduce their travel expenditure and the costs associated with the time lost as a result of business travel, while maintaining or even improving productivity. In the era of ever-growing road traffic congestion and the continuous difficulties related to air travel, the increased use of telephony conferencing services is seen by many as a sensible substitution for the face-to-face way of doing business.

A well-established supplier of reservation-less conferencing services across several key vertical markets, including financial services, healthcare, legal, and higher education, needed to enhance its service with a wideband voice conferencing feature. Based on the newest voice compression technology – the transmission of double the bandwidth of the audio spectrum – this solution produces noticeably superior voice quality compared to traditional analog, digital, and IP telephony.

As a leader in the ìfreeî conferencing market segment, processing tens of millions of call minutes each month, the company wanted to design a new-generation platform capable of delivering a very-large-scale wideband conferencing service and sought a strategic relationship with an enabling technology supplier, Aculab.

Essential criteria for vendor selection included:

• Broader functionality integration possibilities than were possible with the third-party media server alternative
• Simplified deployment
• Higher scalability
• Improved load balancing
• Better fault tolerance
• Higher redundancy
• Greater service reliability

A new conferencing algorithm to operate on a set of Aculabís media processing platforms would enable a wideband matrix conferencing facility with an unlimited number of participants in a single voice conference.

In addition, the requirements included the ability to seamlessly mix voice streams originating from both wideband and narrowband endpoints. Moreover, the wideband variant had to support a full set of essential conferencing features, including:

• The selective mixing of the loudest or active speakers
• Independent volume and gain control for each participant
• Active speaker detection
• Active speaker notification via the Contributing Source Real-Time Control (CSRC) protocol field of the Real-Time Transport Protocol (RTP) media stream
• Dual Tone Multi-Frequency (DTMF) events suppression

The requirements also included an additional set of generic media processing functions, such as: compressed voice recording and playback; transcoding among a set of low-bit rate codecs (G.723.1, G.729, iLBC); support for the encrypted version of the RTP stream (SecureRTP); DTMF detection and generation; DTMF tones relay and user indications via the IETF RFC 2833; and the ability to provide integration with a third-party speech engine (Automatic Speech Recognition [ASR], Text To Speech [TTS]) utilizing the standard Media Resource Control Protocol (MRCP) interface.

An additional major requirement included integration of a new wideband speech codec, Internet Speech Audio Codec (iSAC), initially developed by a third party. While Aculab had a wealth of experience in integration of numerous VoIP and mobile voice codecs, the work on optimizing iSAC performance required a special expertise and deep knowledge of the DSP technology. Integration efforts required reengineering of the packet processing sequencer because the work involved a wideband codec with a variable and adjustable bit rate.

Options in place to enable high density

When the client presented these requirements, Prosody X cPCI, designed as a media processing platform for IP applications, with high density narrowband conferencing functionality as a standard option, had recently been introduced. The client, a long term partner, was well-positioned to fine-tune its feature development.

Prosody X cPCI had options in place to enable high density, feature-rich narrowband conferencing with more than 1000 channels per media processing board and 18000 conferencing parties per single CompactPCI chassis. This was also the case with the media processing functionality used to provide the service. Aculab made a commitment to develop extended functionality requirements for the wideband voice conferencing platform.

Following initial delivery, Aculab was actively involved in supporting the client to develop and integrate its service platform application with Aculabís software and APIs. The final solution is providing the client with industry-leading conferencing capabilities. A scalable, redundant, high density solution, with more than 225 wideband iSAC encoded streams mixed per single board and more than 4000 per CompactPCI chassis, ensures the clientís ability to provide a top-grade conferencing service with minimal operational cost.

References

[1] Communicating naturally — the opportunities of wideband coding, BT Technology Journal, Springer Netherlands, Volume 24, Number 2 / April, 2006, pages 159-166.

Herman Abel is a Product Manager at Aculab and is responsible for development of the Prosody portfolio, new product initiatives, definition of the next-generation product strategy, market analysis, and support of the global sales force. Herman has extensive multidiciplinary knowledge and experience in broadband telecom, wireless communications, consumer electronics, and information technology. Prior to joining Aculab, he obtained an MBA degree at Grenoble Ecole de Management, France.

Ian Colville is a Product Manager at Aculab. He has broad industry knowledge gained during a number of years employed in a variety of management roles by a major telecommunications manufacturer. Ianís industry experience spans marketing, sales, customer service, and project management.