Bounded angle iterative decoding of LDPC codes

A modification to the usual iterative decoding algorithm for LDPC codes, called bounded angle iterative (BA-I) decoding, is introduced. The modified decoder erases codewords detected during iterations that fall outside a maximum decoding angle with respect to the received observation. The new algorithm is applicable in scenarios that demand a very low undetected error rate but require short LDPC codes that are too vulnerable to undetected errors when the usual iterative decoding algorithm is used. BA-I decoding provides a means of reducing the maximum undetected error rate for short LDPC codes significantly, by incorporating a simple extra condition into the iterative decoder structure without redesigning the code. The reduction in undetected error rate comes at a price of increasing the threshold signal-to-noise ratio (SNR) required for achieving a good overall error rate, but this increase in channel threshold can be minimized by allowing the decoderpsilas maximum decoding angle to vary with SNR.