Dynamic Allocation for Watermark Payload in MC-CDMA System under Fading Attack
Abstract
This paper introduces an efficient watermark allocation algorithm for payload improvement in multicarrier code division multiple access (MC-CDMA) system using carrier in-terferometry (CI) spreading codes through simultaneous support of high and low process gain (PG) embedding on priority basis. High priority watermark bits are assigned to all host samples at high chip rate, while low priority bits are gradually increased through alternate use of host sample and odd-even splitting of CI spreading codes. The minimization of cross-correlation among different CI code patterns is exploited for new watermark bit allocation and also improves bit error rate (BER) through cancelation of multiple bit interference (MBI), which results from simultaneous embedding of large additional bits. Simulation results show that dynamic bit allocation maintains acceptable BER at much higher watermark payload through the increase in number of independent host sample decomposition but at low watermark-to-noise ratio (WNR). Simulation results also show that dynamic bit allocation improves peak-to-average distortion (PAD) ratio reduction compared to fixed allocation.