Efficient soft value generation for coded bits in a turbo decoder

A decoder circuit configured to, for each of at least one iteration in at least one soft-input soft-output decoding process:

• calculate intermediate probability values associated with each possible transition between a first plurality of candidate decoder states at a first time and a second plurality of candidate decoder states at a second time;
• compute two or more partial combined values from the intermediate probability values, the partial combined values corresponding to possible combinations of two or more systematic bits, two or more parity bits, or at least one systematic bit and at least one parity bit;
• estimate a soft value for each of at least one systematic bit of the received communications data corresponding to the interval between the first and second times, as a first function of the partial combined values;
• and
• estimate a soft value for each of at least one parity bit of the received communications data corresponding to the interval between the first and second times, as a second function of the partial combined values.

A communications receiver configured to receive communications data encoded at a communications transmitter by a turbo encoder comprising two constituent convolutional encoders, the communications receiver comprising a turbo decoding circuit that comprises two convolutional decoder circuits, wherein each of the convolutional decoder circuits is configured to, for each of at least one iteration in at least one soft-input soft-output decoding process:

• calculate intermediate probability values associated with each possible transition between a first plurality of candidate decoder states at a first time and a second plurality of candidate decoder states at a second time;
• compute two or more partial combined values from the intermediate probability values, the partial combined values corresponding to possible combinations of two or more systematic bits, two or more parity bits, or at least one systematic bit and at least one parity bit;
• estimate a soft value for each of at least one systematic bit of the received communications data corresponding to the interval between the first and second times, as a first function of the partial combined values;
• and
• estimate a soft value for each of at least one parity bit of the received communications data corresponding to the interval between the first and second times, as a second function of the partial combined values.