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Communications of the ACM

ACM TechNews

The Blind Codemaker

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Smartphone coding

Credit: Christine Daniloff

Researchers at the Massachusetts Institute of Technology (MIT), Tel Aviv University, and Google have developed a coding scheme that guarantees the fastest possible delivery of data over fluctuating wireless connections without requiring prior knowledge of noise levels.

The system works by creating one long codeword for each message, and then breaking that codeword up into smaller but still effective codewords. "The transmission strategy is that we send the first part of the codeword [and] if it doesn’t succeed, we send the second part, and so on," says MIT professor Gregory Wornell.

When the first part, which was too noisy to decode, is combined with the second and any subsequent parts, the system creates a new encoding message for a higher level of noise. Once the receiver has received enough symbols to decode the underlying message, it signals the sender to stop.

The researchers demonstrated mathematically that at that point the length of the received codeword is the shortest possible length given the channel's noise properties. They created the master codeword by splitting the message into several fragments of equal length. Each of the fragments is then encoded with existing error-correcting codes.

From MIT News 
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