Indeed, most of the image energy is concentrated in DC coefficients, thus, encrypting them affects considerably the image content.
It has been shown that H will be a block-banded matrix with significant block coefficients concentrated in a banded structure, with width D along the diagonal [6, 8, 19].
In the case of time-varying Rayleigh fading channels[25], it has been shown that H will be a banded matrix with significant coefficients concentrated in a banded structure, with width D along the diagonal.
Admitting that the informative part of a signal is concentrated in few wavelet coefficients having high absolute value, while the noise part is distributed in wavelet coefficients having low absolute value.
In this case, the estimated coefficients are concentrated close to the actual values of c1,1 and c2,1.
The practical function of wavelet transform is the signal decorrelation, and all the information of the signal are concentrated into the wavelet coefficients with large amplitude.
Since most of the image information is concentrated in a few coefficients, the high-frequencies subbands are processed with hard- or soft-thresholding operations.
It leverages the banded sparse structure of the single-user LTV MIMO system matrix, where the significant channel coefficients are concentrated in a banded structure along the diagonal [6, 8, 19] as shown in Figure 1 (right).
The DCT follows, therefore, the energy of the Radon projection concentrated in the first coefficients of the resulting RDCT representation, which can be eventually used as the host signal where to embed the watermark.
Hence, considering the quantization noise caused by shifted compression, for any (m i, n i ) whose coefficients are concentrated in the range of - 3 × σ m i, n i SJR, 3 × σ m i, n i SJR, i.e., ∫ f = - 3 × σ m i, n i SJR 3 × σ m i, n i SJR h m i, n i SD f ≥ 80%%, the mode is discarded and replaced with the mode with the next largest discriminative value outside the candidate set. 4.
