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Spread spectrum (SS) modulation is used widely to design robust digital watermarking schemes but in most cases due importance is not given on capacity and data imperceptibility aspects. In this paper, properties of spreading code are studied and a robust SS watermarking scheme is designed accordingly to embed multiple messages in different directions after signal decomposition. It has been observed that biorthogonal wavelet decomposition offers higher embedding capacity due to better directional selectivity compared to classical dyadic wavelet transform. Successive interference cancelation (SIC) is applied to improve robustness performance significantly compared to matched filter detection.