Convolutional codes with state information for unequal error protection

For convolutional codes which commence encoding in the all-zero state and return to the all-zero state after encoding, the bit error rate for the initial and final few bits is lower as compared to the other bits. This is because the initial and final states are known at the receiver. Motivated by this observation, we propose an encoding scheme wherein the encoder transmits its state information at particular fixed positions in the trellis. The decoder uses the received state information for decoding, resulting in the bits around the transmitted states to be better protected. This scheme can be used for applications which require unequal error protection, wherein some bits have higher importance than others.