Watermark BER and Channel Capacity Analysis for QPSK-Based RF Watermarking by Constellation Dithering in AWGN Channel

Radio frequency (RF) watermarking is the technology that embeds the hidden information in the normal communication signals without extra bandwidth, which could be used to identify authentication or transmit secret information. Constellation dithering (CD) is one of the RF watermarking schemes and usually used for quadrature phase shift keying signals. In this letter, the two available CD watermarking schemes are analyzed by unified theoretical model and then a new CD scheme is proposed based on the model. All the three schemes are investigated to provide the bit-error-rate formulas for the carrier symbols and watermark bits, and the watermark channel capacities have been presented for the three schemes. The numerical analysis shows that the proposed scheme has the largest watermark channel capacity in the same inaudibility constraint.