Low latency-constrained high rate coding: LDPC codes vs. convolutional codes

This paper complements and generalizes the results in [1], [2] while taking new formulas from [3] into account. We compare convolutional and LDPC codes of different rates with respect to their structural delay. This property is intrinsic to the encoding and decoding process and gives a fundamental limit to the achievable latency for end-to-end communication, even when infinite processing speed is assumed. We show that in the case of very low delay convolutional codes perform better than LDPC codes and even break fundamental existence bounds for block codes for some rates. Furthermore, non-punctured convolutional codes can benefit from their shorter constraint length and reduce the delay further.