Very low variable-rate convolutional codes for unequal error protection in DS-CDMA systems

Convolutional codes based on Hadamard sequences can achieve both orthogonality and variable rate. In contrast with other convolutional coding techniques, these codes incur no processing gain penalty in direct-sequence code-division multiple-access (DS-CDMA) systems. We describe a class of such codes called "telescopic protection codes". These codes enable variable-rate error protection in the manner of rate-compatible punctured-convolutional (RCPC) codes, but preserve the Hadamard orthogonality properties necessary to maintain processing gain that RCPC codes lack.