Method and apparatus for min star calculations in a map decoder

Details Method and apparatus for min star calculations in a map decoder Method and apparatus for min star calculations in a map decoder

2006-04-04

2006-04-04

Vanderpuye, Kenneth (Department: 2634)

Pulse or digital communications

Receivers

Particular pulse demodulator or detector

C375S262000, C375S265000, C714S786000

Reexamination Certificate

active

07023934

ABSTRACT:
Method and apparatus for Min star calculations in a Map decoder. Min star calculations are performed by a circuit that includes a first circuit that performs an Min(A,B) operation simultaneously with a circuit that calculates a −log(1+e−|A−B|) value. The sign bit of the A−B calculation is used to select whether A or B is a minimum. The A−B calculation is also used to select either −log(1+e−|A−B|) or −log(1+e−|B−A|) as the correct calculation. In order to hasten the selection of either −log(1+e−|A−B|) or −log(1+e−|B−A|) as the correct calculation the apparatus does not wait for the A−B calculation to complete. Any bit of the A−B calculation between the third bit and final (sign bit) can be used for the selection. If an incorrect value is selected a log saturation circuit may correct the value. In addition an offset may be added −log(1+e−|A−B|) or −log(1+e−|B−A|) to assure that the calculation does not become negative, necessitating the use of an additional sign bit thereby increasing circuit complexity and slowing down the calculation. Additionally the log terms are computed based on a partial result of the A−B calculation.

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