US 7,237,181 B2 · Methods and apparatus for reducing error floors in message passing decoders

Abstract

An iterative message passing decoder, e.g., an LDPC decoder, operating in conjunction with a soft input-soft output signal processing unit, e.g., an ISI detector, has an error floor performance region influenced by the decoder's sub-optimal message passing nature. Error floor reduction is achieved by a simple message re-initialization mechanism. Decoder edge states, e.g., constraint to variable node messages in decoder memory, are reinitialized, e.g., for an iteration, during the decoding after soft values provided by signal processing unit have improved. During the message re-initialization and for some subsequent amount of iterative decoder processing, extrinsic information fed back from the decoder to the signal processing unit and/or soft values delivered to the decoder from the signal processing unit, in an outer communications loop, is temporarily frozen, e.g., using a switch and a buffer. Then, the outer communications loop is restored as the decoding continues, achieving improved decoding performance.

Claims40

Dependent claims

An apparatus used for performing decoding operations, said apparatus comprising:

a soft input-soft output signal processing unit for processing input values to be decoded, said soft input-soft output signal processing unit including a feedback information input for receiving feedback information and a soft information value output for outputting information values generated by said soft input-soft output signal processing unit;
an iterative decoder for performing message passing decoder operations using an internal message passing decoder loop, said iterative decoder having a soft information value input and a feedback information output, said soft information value input being coupled to said soft information value output of said soft input-soft output signal processing unit, said feedback information output being coupled to said feedback information input of said soft input-soft output signal processing unit;
means for interrupting, prior to completion of decoding a set of input data values supplied to said soft input-soft output signal processing unit, communication in an outer communication loop including said soft input-soft output signal processing unit and said iterative decoder, said means for interrupting stopping the communication of at least one of i) feedback information from said iterative decoder to said soft input-soft output decoder and ii) information values from said soft input-soft output signal processing unit to said iterative decoder;
and
means for re-initializing at least one of the messages used in said message passing iterative decoder while decoding said set of input data values.

2 more elements

An apparatus used for performing decoding operations, said apparatus comprising:

a soft input-soft output signal processing unit for processing input values to be decoded, said soft input-soft output signal processing unit including a feedback information input for receiving feedback information and a soft information value output for outputting information values generated by said soft input-soft output signal processing unit;
an iterative decoder for performing message passing decoder operations using an internal message passing decoder loop, said iterative decoder having a soft information value input and a feedback information output, said soft information value input being coupled to said soft information value output of said soft input-soft output signal processing unit, said feedback information output being coupled to said feedback information input of said soft input-soft output signal processing unit;
means for interrupting, prior to completion of decoding a set of input data values supplied to said soft input-soft output signal processing unit, communication in an outer communication loop including said soft input-soft output signal processing unit and said iterative decoder, said means for interrupting stopping the communication of at least one of i) feedback information from said iterative decoder to said soft input-soft output decoder and ii) information values from said soft input-soft output signal processing unit to said iterative decoder;
means for re-initializing at least one of the messages used in said message passing iterative decoder while decoding said set of input data values;
and
wherein said means for interrupting includes a switch positioned between the feedback information output of said iterative decoder and the feedback information input of said soft input-soft output signal processing unit.

3 more elements

An apparatus used for performing decoding operations, said apparatus comprising:

a soft input-soft output signal processing unit for processing input values to be decoded, said soft input-soft output signal processing unit including a feedback information input for receiving feedback information and a soft information value output for outputting information values generated by said soft input-soft output signal processing unit;
an iterative decoder for performing message passing decoder operations using an internal message passing decoder loop, said iterative decoder having a soft information value input and a feedback information output, said soft information value input being coupled to said soft information value output of said soft input-soft output signal processing unit, said feedback information output being coupled to said feedback information input of said soft input-soft output signal processing unit;
means for interrupting, prior to completion of decoding a set of input data values supplied to said soft input-soft output signal processing unit, communication in an outer communication loop including said soft input-soft output signal processing unit and said iterative decoder, said means for interrupting stopping the communication of at least one of i) feedback information from said iterative decoder to said soft input-soft output decoder and ii) information values from said soft input-soft output signal processing unit to said iterative decoder;
means for re-initializing at least one of the messages used in said message passing iterative decoder while decoding said set of input data values;
and
wherein said means for interrupting includes a switch positioned between the soft information value output of the signal processing unit and the soft information value input of said iterative decoder.

3 more elements

A method for decoding data input to be decoded, said method comprising:

operating a soft input-soft output signal processing unit to receive feedback information from an iterative decoder and input data to be decoded and to generate information values from said input data as a function of feedback information received from the iterative decoder;
operating an iterative decoder to perform message passing decoder operations using an inner message passing decoder loop, said step of operating an iterative decoder including operating the inner message passing decoder loop to receive information values and to generate there from feedback information used by said soft input-soft output signal processing unit;
interrupting, communication in an outer communication loop including said soft input-soft output signal processing unit and said iterative decoder, said interrupting including stopping the communication of at least one of i) feedback information from said iterative decoder to said soft input-soft output decoder and ii) information values from said soft input-soft output signal processing unit to said iterative decoder;
re-initializing at least one message communicated in said inner message passing decoder loop which are used by said message passing iterative decoder prior to successful decoding of said set of input data values;
and
continuing said decoding of said set of input data values using said re-initialized messages.

3 more elements

A method of decoding input data to be decoded using an iterative message passing decoder, the method comprising the steps of:

generating a set of soft values from said input data to be decoded;
supplying the generated soft values to said iterative message passing decoder;
operating the message passing decoder to perform a plurality of message passing decoder operations to decode said soft values supplied to said iterative message passing decoder, said plurality of message passing decoder operations including the generation of messages used by the decoder to decode said soft values and the generation of extrinsic information which can be used to improve the generation of soft values from said input data;
generating an updated set of soft values from said input data and said extrinsic information;
supplying the updated set of soft values generated from said input data to said message passing decoder;
re-initializing at least one message generated by said performed message passing decoder operations;
and
operating the message passing decoder to perform a plurality of additional message passing decoder operations to decode said additional soft values supplied to said iterative message passing decoder and said re-initialized messages, said plurality of message passing decoder operations including the generation of additional extrinsic information.

5 more elements

Dependencies are inferred from the claim text.

Methods and apparatus for reducing error floors in message passing decoders

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Methods and apparatus for reducing error floors in message passing decoders

Life of this patent

Abstract

Claims40