Stopping criterion for decoding Quasi-Cyclic LDPC codes
AssigneesCommissariat A L'energie Atomique Et Aux Energies Alternatives, Politechnica University of Timisoara, Ecole Nationale Superieure De L'Electronique Et Applications (ENSEA), Cy Cergy Paris Université
InventorsValentin Savin, Oana Boncalo, David Declercq
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Abstract
An in-between layer partial syndrome stopping (IBL-PS) criterion for a layered LDPC decoder. The IBL-PS syndrome is obtained by applying the parity checks (Hr,r+1) of a couple of a first layer (r) and a second layer (r+1) on the variables after the first layer has been processed and before the second layer is processed by the decoder, the decoding being stopped if said in-between layer syndrome (sr,r+1) is satisfied for at least a couple of consecutive layers.
Claims16
A method for decoding an LDPC (low density parity check) code, said code being defined over a GF(2b) field, where b≥1, and wherein a parity-check matrix H, said parity-check matrix having a layered structure, each layer comprising one or more consecutive rows of said matrix, each row of H corresponding to a parity check and each column of H corresponding to a variable, each layer of H involving a variable at most once, each layer being represented a bipartite graph Γr comprising parity check nodes and variable nodes, the decoding of the LDPC code being performed iteratively on the layers of H, each layer being processed in turn until a stopping criterion is met, the processing of a layer comprising message passing between the variable nodes and check nodes of Γr to update values of the variables, wherein the stopping criterion comprises the computation of an in-between layer partial syndrome (sr,r+1) for a couple of consecutive layers constituted by a first layer (r) and a second layer (r+1), the in-between layer partial syndrome being computed by applying parity checks (Hr,r+1) of said first layer and said second layer on variables ({circumflex over (x)}r) after said first layer has been processed and before said second layer is processed, the decoding being stopped if the in-between layer partial syndrome is null for at least one couple of consecutive layers.
An LDPC (low density parity check) code decoder, said code being defined over a GF(2b) field, where b≥1 and wherein a parity-check matrix H, said parity-check matrix having a layered structure, each layer comprising one or more consecutive rows of said matrix, each row corresponding to a parity check and each column corresponding to a variable, each layer of H involving a variable at most once, each layer being represented a bipartite graph Γr comprising parity check nodes and variable nodes, the decoder comprising a layer processor, a first memory for storing extrinsic messages of check nodes and a second memory for storing soft estimates of a word to be decoded, said layer processor comprising variable node units and check node units, each variable node unit being associated with a variable node of Γr and each check node unit being associated with a check node of Γr, the variable node units sending variable node messages to the check node units along edges of graph Γr, the variable node units computing said variable node messages from a word estimate read out from the second memory and extrinsic check node messages read out from the first memory, and the check node units updating the word estimate and said extrinsic messages, based on the variable node messages they have received, wherein the LDPC decoder further comprises a control unit, an in-between layer partial syndrome calculation unit calculating a first partial syndrome (sr) by applying parity checks (Hr) of a first layer (r) having been processed by the layer processor on the updated word estimate and a second partial syndrome (sr+1ant) by applying the parity checks (Hr+1) of a second layer (r+1), consecutive to the first layer, to the same word estimate, said control unit stopping the decoder if the in-between layer partial syndrome is null for at least one couple of consecutive layers.
A method for decoding an LDPC code, said code being defined over a GF(2b) field, where b≥1, and wherein a parity-check matrix H, said parity-check matrix having a layered structure, each layer comprising one or more consecutive rows of said matrix, each row of H corresponding to a parity check and each column of H corresponding to a variable, each layer of H involving a variable at most once, each layer being represented a bipartite graph Γr comprising parity check nodes and variable nodes, the decoding of the LDPC (low density parity check) code being performed iteratively on the layers of H, each layer being processed in turn until a stopping criterion is met, the processing of a layer comprising message passing between the variable nodes and check nodes of Γr to update values of the variables, wherein the stopping criterion comprises the computation of an in-between layer partial syndrome (sr,r+1) for consecutive layers constituted by at least a first layer (r) and a second layer (r+1), the in-between layer partial syndrome being computed by applying parity checks (Hr,r+1) of said first layer and said second layer on variables ({circumflex over (x)}r) after said first layer has been processed and before said second layer is processed, the decoding being stopped if the in-between layer partial syndrome is null for at least a plurality of consecutive layers.
Dependencies are inferred from the claim text.