Analysis and improvement of the J.83 annex B trellis code for cable modems

The SCTE and IEEE802.14 cable modem standards specify a trellis code that is not a simple variant of one of the Ungerboeck or Wei codes that are commonly used as benchmarks in the industry. As far as the authors know there has been no published analysis of the cable modem code and so we commence this paper with an analysis of the code properties that show it is not as powerful as the better known Wei codes. We then show how a simple modification to the code produces up to 1.2 dB performance improvement.