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US 6,662,337 B1Granted
Digital transmission system and method
AssigneeAgere Systems Inc.
InventorStephan ten Brink
Life of this patent
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Abstract
A transmission system is disclosed in which a multilevel modulated signal is transmitted. The soft output information of a channel decoder is fed back and utilized by a soft demapping device in order to improve the decoding result by further iterative decoding steps. The receiver includes a demapper for generating a demapped signal, bit deinterleaver for generating a demapped and deinterleaved signal and a decoder for generating soft reliability values representative of the decoded signal. These soft reliability values are then bit interleaved and fed back to the demapper, as a priori knowledge, for use in further iterations of the decoding process. Two mappings are mixed adaptively dependent on the channel conditions and the number of iterations to be used.
Claims26
A digital transmission system, comprising:
- a coder for coding an input signal with an error checking or error correcting code, an interleaver for interleaving the bits of the coded signal, a mapper for mapping the interleaved coded signal into a multilevel signal, and a transmitter for sending the multilevel signal over a noisy channel in a transmission medium;
- a receiver for receiving the multilevel signal distorted by noise (noisy multilevel signal), a demapper having a first input for receiving the noisy multilevel signal and operative to provide a soft demapped signal at an output a deinterleaver, for deinterleaving the demapped signal, a decoder to decode the deinterleaved demapped signal to provide a soft decoded signal, an interleaver to interleave the decoded signal, the demapper having a second input for receiving the interleaved decoded signal and being operative to recalculate the demapped signal iteratively using the noisy signal and the soft decoded signal,
- characterized bye:
- a mapping store for storing two different mappings having different mutual information;
- means for deriving an indication of the channel conditions;
- means for selecting t e mappings in a mixing ratio dependent on the derived indication of channel conditions, the mapper and demapper being operatively responsive to the selected mapping.
3 more elements
A digital transmission system, comprising:
- a coder for coding an input signal with an error checking or error correcting code, an interleaver for interleaving the bits of the coded signal, a mapper for mapping the interleaved coded signal into a multilevel signal, and a transmitter for sending the multilevel signal over a noisy channel in a transmission medium;
- a receiver for receiving the multilevel signal distorted by noise (noisy multilevel signal), a demapper having a first input for receiving the noisy multilevel signal and operative to provide a soft demapped signal at an output, a deinterleaver, for deinterleaving the demapped signal, a decoder to decode the deinterleaved demapped signal to provide a soft decoded signal, an interleaver to interleave the decoded signal, the demapper having a second input for receiving the interleaved decoded signal and being operative to recalculate the demapped signal iteratively using the noisy signal and the soft decoded signal,
- characterized by:
- a mapping store for storing two different mappings having different mutual information;
- means for determining the number of iterations to be carried out from a plurality of possible numbers of iteration;
- and
- means for selecting the mappings in a mixing ratio dependent on the number of iterations as determined, the mapper and demapper being operatively responsive to the selected mapping.
4 more elements
A digital transmission system, comprising:
- a coder for coding an input signal with an error checking or error correcting code, an interleaver for interleaving the bits of the coded signal,
- a mapper for mapping the interleaved coded signal into a multilevel signal, and a transmitter for sending the multilevel signal over a noisy channel in a transmission medium;
- a receiver for receiving the multilevel signal distorted by noise (noisy multilevel signal), a demapper having a first input for receiving the noisy multilevel signal and operative to provide a soft demapped signal at an output, a deinterleaver, for deinterleaving the demapped signal, a decoder to decode the deinterleaved demapped signal to provide a soft decoded signal, an interleaver to interleave the decoded signal, the demapper having a second input for receiving the interleaved decoded signal and being operative to recalculate the demapped signal iteratively using the noisy signal and the soft decoded signal,
- characterized by:
- a mapping store for storing two different mappings having different mutual information;
- means for deriving an indication of the channel conditions;
- means for determining the number of iterations to be carried out from a plurality of possible numbers of iterations;
- and
- means for selecting the mappings in a mixing ratio dependent on the derived indication of channel conditions and on the number of iterations as determined, the mapper and demapper being operatively responsive to the selected mapping.
6 more elements
A method of transmitting a digital signal, comprising:
- coding an input signal with an error checking or error correcting code, interleaving the bits of the coded signal, mapping the interleaved coded signal into a multilevel signal, sending the multilevel signal over a noisy channel in a transmission medium;
- receiving the multilevel signal distorted by noise (noisy multilevel signal), demapping the noisy multilevel signal to provide a soft demapped signal, deinterleaving the demapped signal, decoding the deinterleaved demapped signal to provide a soft decoded signal, interleaving the decoded signal, recalculating the demapped signal iteratively using the noisy signal and the soft decoded signal,
- characterized by:
- storing two different mappings having different mutual information;
- deriving an indication of the channel conditions;
- and
- selecting the mappings in a mixing ratio dependent on the derived indication of channel conditions, the mapping and demapping being operatively responsive to the selected mapping and demapping.
4 more elements
A method of transmitting a digital signal, comprising:
- coding an input signal with an error checking or error correcting code, interleaving the bits of the coded signal, mapping the interleaved coded signal into a multilevel signal, sending the multilevel signal over a noisy channel in a transmission medium,
- receiving the multilevel signal distorted by noise (noisy multilevel signal), demapping the noisy multilevel signal to provide a soft demapped signal at an output, deinterleaving the demapped signal, decoding the deinterleaved demapped signal to provide a soft decoded signal, interleaving the decoded signal, recalculating the demapped signal iteratively using the noisy signal and the soft decoded signal,
- characterized by:
- storing two different mappings having different mutual information;
- determining the number of iterations to be carried out from a plurality of possible numbers of iteration;
- and
- selecting the mappings in a mixing ratio dependent on the number of iterations as determined, the mapping and demapping being operatively responsive to the selected mapping.
4 more elements
A method of transmitting a digital signal, comprising:
- coding an input signal with an error checking or error correcting code, interleaving the bits of the coded signal, mapping the interleaved coded signal into a multilevel signal, sending the multilevel signal over a noisy channel in a transmission medium;
- receiving the multilevel signal distorted by noise (noisy multilevel signal), demapping the noisy multilevel signal to provide a soft demapped signal, deinterleaving the demapped signal, decoding the deinterleaved demapped signal to provide a soft decoded signal, interleaving the decoded signal, recalculating the demapped signal iteratively using the noisy signal and the soft decoded signal,
- characterized by:
- storing two different mappings having different mutual information;
- deriving an indication of the channel conditions;
- determining the number of iterations to be carried out from a plurality of possible numbers of iterations;
- and
- selecting the mappings in a mixing ratio dependent on the derived indication of channel conditions and on the number of iterations as determined, the mapping and demapping being operatively responsive to the selected mapping.
5 more elements
A method of transmitting a digital signal, as claimed in 21, in which the soft demapped and soft decoded signals are likelihood ratios.
A method of transmitting a digital signal, as claimed in 21, in which the soft demapped and soft decoded signals are log-likelihood ratios.
Dependencies are inferred from the claim text.