Node processors for use in parity check decoders

A device for performing node processing operations as part of a message passing decoding process, the device comprising:

• an accumulator module for processing, in sequence, input messages corresponding to a plurality of nodes, one set of input messages being received per node, the number of messages in a set of messages corresponding to a node being equal to a degree, D, of said node, where D is a non-zero positive integer, the accumulator module including:
• a summing circuit for generating a total node sum as a function of the value of each received message in a set of messages corresponding to a node, one total node sum being generated for each received set of messages;
• a storage device for storing the generated total node sum;
• a controllable delay unit for storing said input messages processed by said summing circuit to generate each total sum by a period of time proportional to the degree of the node to which the input messages correspond;
• and
• a message generation module for generating output messages corresponding to a node from the total sum corresponding to the node and the delayed messages corresponding to said node, the message generation module generating one output message for each input message corresponding to a node.

A node processor for use in a message passing decoding system, the node processor including:

• an accumulator module for generating a total message sum from a set of received messages corresponding to a node;
• a message delay line including a variable delay element for storing the messages in each set of received messages for a period of time directly proportional to the degree of a node to which the stored message corresponds;
• and
• a subtractor module coupled to said accumulator module and to said message delay line, the subtractor module subtracting each delayed message corresponding to a node from the total message sum generated by the accumulator module from the set of received messages corresponding to the same node as the delayed messages being subtracted.

A method of performing node processing operations in a message passing decoder, the method comprising the steps of:

• sequentially receiving messages to be processed, each message corresponding to a node, messages corresponding to the same node being part of a set of messages, sets of messages corresponding to a plurality of different nodes being received over a period of time;
• generating from each set of received messages corresponding to a node, a total message sum corresponding to the same node as the set of messages used to generate the total sum;
• delaying each individual received message for a period of time directly proportional to the degree of the node to which the individual received message corresponds;
• and
• subtracting each delayed message, from the total message sum corresponding to the same node as the delayed message, to thereby generate an output message.