A New Transmission Scheme for Additional Bits with Rotated LDPC Coded Signals

In this work, a new coding scheme is proposed for transmitting additional bits along with low-density parity-check (LDPC) coded data at no expense of bandwidth or transmission power. At the transmitter, the LDPC coded bits are first flipped in a random-like way specified by the additional bits and then mapped into a sequence of two-dimensional signals. The modulated sequence is then partitioned into several groups, each of which is rotated by an angle that is also specified by the additional bits, resulting in a sequence of transmitted signals. At the receiver, the additional bits are detected by a serial list decoding algorithm with an early stopping criterion. Then, by removing the effect of the additional bits, the LDPC coded data can be decoded as usual. Simulation results show that, for a rate-1/2 LDPC code of length 8064, up to twenty-four additional bits can be reliably transmitted along with LDPC coded QPSK signaling.