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Look-up tables for improved signal processing

Posted: 15 Mar 2013 ?? ?Print Version ?Bookmark and Share

Keywords:DCT? discrete cosine transform? signal processing? Fourier transform? prime-length DCT?

A*STAR Institute for Infocomm Research's Pramod Kumar Meher and his co-workers at Central South University in Changsha, China may have the solution needed to improve mathematical algorithms needed for electronic signal processing.

Advanced mathematical algorithms are essential for processing electronic signals within computers and embedded processors. Scientists and engineers are constantly refining and redesigning their algorithms to obtain higher throughput of information on ever smaller devices that consume less power.

The method Meher and his team developed is an efficient way to implement an important step in signal processing, called the discrete cosine transform (DCT). The method could lead to devices that occupy smaller areas, provide higher throughput of information, and consume less power than existing devices.

The DCT is commonly used for the compression of digital video and audio such as MPEG files. Similar to the better-known Fourier transform, the DCT involves expressing a series of data points as a sum of their product with cosine functions.

Several algorithms and software architectures already exist for computing so-called 'power-of-two-length DCTs'. But, those DCTs are not suitable for all applications. The prime-length DCT is an alternative to the power-of-two-length DCT that has the potential to be more efficient for implementation in hardware, Meher noted.

Meher and his co-workers have focused on computing the DCT of different lengths of practical interest using specialized digital circuits that occupy less area on a silicon chip and use less power, but run at adequate speed. They not only derived a more efficient algorithm for DCT, but also derived new architecturebased on the 'distributed arithmetic' approachfor implementing the algorithm in integrated circuit chips.

Meher and co-workers made use of a theorem that inter-relates the transforms with cyclic convolution of two finite duration sequences. By using look-up tables, this convolution, and thereafter the prime-length DCT, could be performed quickly and accurately.

The team also described a new, efficient algorithm for decomposing the DCTin mathematics, this means rewriting the problem in terms of a combination of simpler quantities. In addition to reducing the required size of read-only memory (ROM), the researchers found that overall their algorithm significantly reduced the computation time.

"We found that the proposed design involves significantly less area and it yields higher throughput with less power consumption than the corresponding existing designs," said Meher. "The structure we propose is highly regular, modular and therefore suitable for Very Large Scale Integration realization."





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