SoC Integration Delivers on Promise of
BY MAJID FOODEEI, PRINCIPAL SYSTEM
ENGINEER, CENTILLIUM COMMUNICATIONS, INC.
During the halcyon days of rapid network build-outs and robust
infrastructure budgets, experts and pundits declared that VoIP was a
technology destined to take the market by storm. They said that everything
was in place for VoIP to post huge market share gains. Yet, even before
economic realities set in and companies were forced to face capital
expenditure cutbacks, early deployments of VoIP systems were plagued by high
costs and poor voice quality causing companies to delay deployments.
Today, new deployments of
next-generation VoIP systems are rapidly changing these old quality and cost
perceptions. Designers have overcome these problems through system-on-a-chip
(SoC) integration. Tasks that used to take scores of chips to accomplish are
now done by a single system-on-a-chip (SoC) design. Now, a single SoC
combines multiple specialized DSPs, discrete network processors (NPs), and
software codecs and algorithms into a tightly integrated solution that
delivers on the promise of VoIP ï¿½ reduced equipment and operating costs,
better than toll quality voice, and higher reliability.
Network designs have evolved too. New network models place an emphasis on
combining voice and data onto a single converged network. In an effort to
lower overall costs, service providers are turning to a collapsed Central
Office (CO) model that shifts the functionalities of switching to Customer
Premises Equipment (CPE). This shift results in a simplified CO and is
speeding the deployment of softswitches in networks. These softswitches
enable service providers to deploy new voice services that add value for
their customer base without the considerable expense of rebuilding their
Although legacy circuit-switched telephone networks are not yet being
replaced on a wide-scale basis, service providers are evaluating and finding
ways to capitalize on the advantages VoIP systems. Such equipment, based on
SoC voice processors, deliver cost efficient, high-quality systems that are
easy to test and upgrade to new services.
SoCs MAKE THE DIFFERENCE
To meet todayï¿½s market challenges, industry leaders are embracing efficient
solutions that come from very high-density SoC-based VoIP systems. Advanced
SoC designs process from 100 to 1,000 channels per chip with a full range of
echo cancellation and telephony IP features (hundreds of channels for the
most complex codecs) and a tightly integrated silicon and software bundle.
This reduces part count and system complexity as well as power consumption ï¿½
crucial advancements for systems deployed in harsh environments with
Unlike SoC designs, multi-chip solutions place
higher demands on DSP and NP building blocks. Advanced VoIP SoCs provide
unprecedented capabilities (close to 30-giga-MAC DSP and one-giga-op/sec NP
plus up to three to five times higher capacity than the alternative with
close to three times lower power/channel consumption) on a single integrated
chip with which system-level software is bundled.
The most flexible system-on-a-chip approach
integrates high-performance digital signal processing and network processing
on the same die. This is essential because the complexity of codecs has gone
from less than 10-MIPS a few years ago to more than 40-MIPS for some of
todayï¿½s complex codecs today. The DSP portion of the chip also handles
tandem free operation, transcoding, voice quality enhancement algorithms,
and echo cancellation required in cellular wireless networks.
Networking protocols are also growing from
basic IP and ATM AAL1, AAL2 support, to a whole range of new layers for
features such as MPLS or VLAN or RTCP with extensions for voice quality.
Many of these protocols and voice quality enhancement algorithms run
concurrently, which makes it essential that DSP and network-processing
elements work in harmony. The SoC approach has proven to be the best way to
EVOLUTION OF DSP PROCESSORS
Incorporating the myriad standards driving rich voice quality requires
substantial processing power. Technology has changed vastly from the early
days of VoIP processors. Every year, MIPS processing advances yet DSP
providers have merely adapted their general-purpose products.
DSP performance increases have come through
increased speed and the migration to more advanced process technologies on
which the circuits are built. Additionally codec, network processing, and
voice quality algorithms have been increasing in complexity and have, in
some cases, surpassed the advances in DSPs. The bulk of the cost in early
VoIP systems comes from boards that are populated with the general purpose
DSPs. This approach does not result in systems that can meet todayï¿½s
aggressive cost, density, power, and space constraints.
In the past four years, the model for VoIP SoCs
has evolved, shifting the model toward overall system innovation, not just
increases in core speeds and geometric process advances.
The innovation revolves around the tight
integration of the DSP and network processing functions together with the
firmware. In contrast, the general purpose DSP model and initial SoC model
both rely on a single, front-end NP which can become bottlenecked while
trying to perform deep packet processing and high throughput aggregation
In the advanced SoC approach
within the distributed NP model, deep packet processing is provided in the
components within the SoCs. This provides a more scalable solution in view
of increasingly complex requirements placed on VoIP systems. The general
purpose DSP approach utilizes more components creating complexity. More
complexity results in lowered reliability and reduced capability for service
purpose DSP approach also requires tedious programming and management of the
software and the byzantine task of integrating the software with the other
pieces of the system. The SoC approach provides a complete system with a
large block of software. This integration allows the box vendor to
concentrate on adding their own specific value to the system they are
building, thus accelerating time-to-market.
When designers integrate software components
from DSP and NP vendors, they face the arduous task of efficiently mating
vastly different software approaches into a cohesive system. Even with
bundled software components that work together, maintenance becomes
cumbersome and there is the added cost.
All the benefits of an SoC approach offers tremendous advantages for
equipment and service providers looking to gain an edge on competitors.
First and foremost is reduced system cost. Next is reduced time-to-market
and service providersï¿½ superior ability to meet the challenges of
integrating next-generation services that address wireless, IP, ATM,
interworking, transcoding, and several other important services. More DSP
capability also means higher quality of services (e.g., adding voice
enhancement algorithms, and the like).
Service providers concerned with revenue-bearing services, equipment,
deployment costs, and operating expenses can benefit from all of the
advantages presented by next-generation VoIP systems based on advanced SoC
design. Moreover, systems built on advanced SoC voice processors provide the
easiest and most cost effective migration path while keeping future
operations and upgrade costs to a minimum.
Majid Foodeei is Principal System Engineer at Centillium Communications,
Inc. Centillium designs and markets communications chipset solutions for
central office equipment, digital subscriber line access multiplexer (DSLAM),
digital loop carrier (DLC) line cards, and customer premises equipment for
Digital Subscriber Line (DSL), Voice over Packet (VoP) and premises
networking. For more information, visit
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