Cambridge Consultants: Turbo code optimization service speeds time to market for advanced wireless systems

provides fast-track to adoption of one of wireless industry's hottest technologies
can give rapid insight into best implementation strategies for WiMAX, DVB, UWB etc

May 23, 2005 -- Cambridge Consultants has developed a powerful software program that demystifies and accelerates the selection of turbo codes for wireless communication systems. Called TurboDesigner, the unique tool addresses the real-world issues that electronic design teams implementing wireless basestations and terminals face when looking to adopt a turbo code based forward error correction (FEC) strategy - allowing the rapid simulation of application-specific coding/decoding. Available as an element of Cambridge Consultants' design services, the software can rapidly reveal the optimum FEC strategy - potentially eliminating weeks of complex design and evaluation using conventional methods such as Monte Carlo simulation.

The new MATLAB-based software can greatly speed and simplify the adoption of turbo codes - which have the potential to generate step-function improvements in wireless system performance with minimal impact on product bill of material costs.

"Our experience has taught us that the right turbo coding implementation can double the coverage or data rate of a wireless system, or halve the amount of transmission power required", says Monty Barlow, DSP Group Leader with Cambridge Consultants. "The technology is extremely desirable - but the problem comes with real-world implementations of decoders – especially those designed for high data rate applications like WiMAX. There are a large number of factors a designer needs to tweak, each with its own subtle effect on performance and cost. This software produces accurate and quick measurement of Turbo code performance".

The TurboDesigner package offers a large selection of Turbo encoding and decoding options, with a simple user interface that allows configuration of parameters to understand their effects, including MAP (Maximum A Posteriori) algorithm choice, mathematical precision, windowing length, iterations, block length, and channel type. Highly efficient C-compiled libraries then provide speedy simulations of results.

Once a choice of code has been made, the package will also synthesize realistic test vectors for HDL simulations, and analyse the outputs from the simulations - providing project teams with a high integrity basis for subsequent decisions on hardware implementations in ASICs, FPGAs, etc.

Developed to support its wireless system design consultancy, TurboDesigner is freely available to clients as an element of the advice or development services offered by Cambridge Consultants.

"Shrinking silicon costs are now enabling wider exploitation of the relatively new technology of Turbo codes", adds Monty Barlow. "For us, the first major focus has been for WiMAX development work - where no suitable off-the-shelf cores exist and we need to design our own hardware - but we also expect Turbo codes to be a significant enabler for other emerging wireless systems such as digital broadcasting, and even UWB".

A datasheet on TurboDesigner is available here

What are turbo codes?

Turbo codes are a relatively new class of error correction codes that are improving the quality of data transfer over limited bandwidth and error-prone links - such as wireless systems that must deal with interference and real-world environmental problems like reflections. The technology comes closest to facilitating the theoretical 'Shannon' limit of maximum information transfer rate over a noisy channel (Bell Labs' Claude Shannon published seminal work on the problem in the late 1940s).

The turbo coding principle was first proposed in 1993 by Professors Claude Berrou and Alain Glavieux. Although their claims that the codes could double throughput for a given transmission power were greeted with scepticism, they turned out to be true. Turbo coding uses powerful interleavers that reduce susceptibility to random and impulsive noise. By working on ‘soft’ bits from the radio receiver, Turbo codes extract as much information as possible from noisy signals.

Turbo codes require two encoders and two decoders per link. These circuit blocks are connected in parallel and work synergistically. They use an iterative process to reduce the amount of data processing required, but still require more computational power than conventional error correction coding systems such as Viterbi, Reed Solomon CC, and BCH. The technology was first applied in satellite and space applications, but as DSP power has increased, they have started to become viable in mainstream wireless applications - beginning with the new generation of 3G phones.

About Cambridge Consultants:

Cambridge Consultants has for over 40 years enabled its clients to turn business opportunities into commercial successes, whether launching first-to-market products, entering new markets or expanding existing markets through the introduction of new technologies. With a team of over 200 engineers, scientists and consultants in offices in Cambridge (UK) and Boston (USA), it is able to offer solutions across a diverse range of industries including healthcare, industrial and consumer products, automotive, transport, energy and wireless communications.