Paul G. Flikkema. Spread-spectrum techniques for wireless communications. IEEE Signal Processing, 14(3):26--36, May 1997. 17  Home/Search   Document Not in Database   Summary   Related Articles   Check

....simply , where and are realizations of the respective random processes and . In the context of random processes: 1) Since and are independent and (2) where is the cross power spectrum of and . We remark that many current watermarking methods are based on spread spectrum communications [15] [16]. The seminal work on digital image fingerprinting by Cox et al. in [3] popularized the use of direct sequence spread spectrum for watermarking. The model (1) encompasses spread spectrum watermarking, discussed in more detail in [4] and [17] for example. B. Distortion Measure To quantify signal ....

P. G. Flikkema, "Spread-spectrum techniques for wireless communications, " IEEE Signal Processing Mag., vol. 14, pp. 26--36, May 1997.

....and the output are the estimated MPEG4 animation parameters. The method estimates the FAPs with very satisfying accuracy. For details, please refer to [4, 5] 4 Watermarking of MPEG 4 Facial Animation Parameters For embedding of watermark data into the FAPs, we adopt a spread spectrum approach [6] that has been applied similarly to image and video watermarking before [3, 7, 8] The idea is to apply small changes to the FAPs that seem random and are not conspicuous but correlate with a secret pseudo random key. The correlation can be exploited to retrieve the embedded information later on. ....

Paul G. Flikkema. Spread-spectrum techniques for wireless communications. IEEE Signal Processing, 14(3):26-- 36, May 1997.

....major research contributions are highlighted. It needs to be reemphasized that there have been many contributions made by other researchers on this topic in the literature that we are not able to list due to space limits of this section. The IEEE Signal Processing Magazine article by Flikkema [72] provides a signal processing perspective for spread spectrum wireless communication systems. In a companion paper, Laster and Reed [130] give an excellent overview of interference rejection in digital wireless communications. They present the significance of the interference rejection problem in ....

P.G. Flikkema, "Spread-spectrum techniques for wireless communication, " IEEE Signal Processing Mag., vol. 14, no. 3, pp. 26-36, May 1997.

.... Specific techniques for embedding watermarks differ, depending on the type of document (e.g. text, image, or video) However, most current watermarking methods [2,10 13] can be interpreted sometimes very loosely as forms of spread spectrum communications, or simply spread spectrum (SS) [14,15]. Spread spectrum has been studied for years for both military and civilian applications. We present an example of a SS system and then highlight the properties that make SS useful for watermarking. 6 3.1 An Example Spread Spectrum System We now present a discrete time example 1 of a common ....

Flikkema, P. G., Spread-spectrum techniques for wireless communications. IEEE Signal Processing Magazine, 1997, 14, 26--36. 19

....have the following limitations: SS allows detection of a known watermark, but the fundamentally large bandwidth requirement does not facilitate the extraction of a long bit sequence or logo from an audio signal or an image. SS approaches are specifically vulnerable to the near far problem [6]. For watermarking this implies that if the energy of the watermark is reduced due to fading like distortions on the watermark, any residual correlation between the host signal and watermark can result in unreliable detection. Most SS approaches are not adaptive. That is, they neither take into ....

P. G. Flikkema, "Spread-spectrum techniques for wireless communications," IEEE Signal Processing Magazine, vol. 14, pp. 26-36, May 1997.

....is any processing of a watermarked document that may impair the watermark [4, 5] A watermark should also usually be robust, meaning that it cannot be impaired or removed without also making the attacked document useless. Most watermarking methods employ some form of spread spectrum communications [6], whose properties may enable it to meet these requirements. Currently, it is difficult to analyze robustness because it is difficult to model the vast set of possible attacks. Consequently, it is not clear how to design a watermark to enhance its robustness. Some researchers (e.g. 1, 2] have ....

P. G. Flikkema, "Spread-spectrum techniques for wireless communications," IEEE Signal Proc. Magazine, vol. 14, no. 3, pp. 26--36, May 1997.

....[2] use frequency domain perceptual masking models, motivated by the notion that a watermark that is well matched to the frequency content of the original document can be hidden effectively. 2 A Model for Watermarking Most current watermarking methods are forms of spread spectrum communications [4, 5], in which a noise like transmitted message w[n] is subject to additive interference x[n] As a general watermarking model, let us represent the original document and the watermark by the discrete time random processes (DTRPs) x[n] and w[n] respectively. Both processes are ergodic, zero mean, and ....

P. G. Flikkema, "Spread-spectrum techniques for wireless communications," IEEE Signal Proc. Magazine, vol. 14, pp. 26--36, May 1997.

....use multiplicative noise [9, 27, 67, 74, 78, 83] or use non Gaussian noise [36, 38, 39, 79, 206] 32, 106] can create or enhance the sensations of touch and balance. SR designs might lead to better schemes to filter or multiplex the faint signals found in spread spectrum communication systems [71, 227]. These systems transmit and detect faint signals in noisy backgrounds across wide bands of frequencies. SR designs might also exploit the signalbased crosstalk noise found in cellular systems [142, 229] Ethernet packet flows [143] or Internet congestion [113] The study of SR has emerged ....

P. G. Flikkema, "Spread-Spectrum Techniques for Wireless Communication," Signal Processing Magazine, vol. 14, no. 3, pp. 26--36, 1997.

....addition over DeltaFAP for all frames from I( 1) up to the current frame. The described method estimates the FAPs with very satisfying accuracy [15] 4 Watermarking of MPEG 4 Facial Animation Parameters For embedding of watermark data into the FAPs, we adopt a spread spectrum approach [23] that has been applied similarly to image and video watermarking before [5,8,9] The idea is to apply small changes to the FAPs that seem random and are not conspicuous but correlate with a secret pseudo random key. The correlation can be exploited to retrieve the embedded information later on. ....

Paul G. Flikkema. Spread-spectrum techniques for wireless communications. IEEE Signal Processing, 14(3):26--36, May 1997.

....given in section 4 confirming the performance and applicability of the presented schemes. Conclusions are given in section 5. 2 Spread Spectrum Watermarking of Uncompressed Video Spread spectrum communication schemes transmit a narrow band signal via a wide band channel by frequency spreading [19]. For watermarking, ideas from spread spectrum communications are highly applicable: a narrow band signal (the watermark) has to be transmitted via a wide band channel with interference (the image or video signal) Specifically, the idea of direct sequence spread spectrum communication can be ....

....by embedding one bit of information into cr pixels of the video signal. The spread sequence b i is amplified with a locally adjustable amplitude factor ff i 0 and is then modulated by a binary pseudo noise sequence p i ; p i 2 f Gamma1; 1g; i 2 N (3) which serves for frequency spreading [19]. The modulated signal, i.e. the spread spectrum watermark w i = ff i Delta b i Delta p i ; i 2 N (4) is added to the line scanned digital video signal v i yielding the watermarked video signal v i = v i ff i Delta b i Delta p i ; i 2 N (5) which must be re arranged into a matrix for ....

Paul G. Flikkema. Spread-spectrum techniques for wireless communications. IEEE Signal Processing, 14(3):26--36, May 1997.

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Paul G. Flikkema. Spread-spectrum techniques for wireless communications. IEEE Signal Processing, 14(3):26--36, May 1997. 17

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P. G. Flikkema, "Spread-spectrum techniques for wireless communications, " IEEE Signal Processing Mag., vol. 14, pp. 26--36, May 1997.

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P. G. Flikkema, "Spread-spectrum techniques for wireless communication, " Signal Processing Mag., vol. 14, no. 3, pp. 26--36, 1997.

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P. G. Flikkema, "Spread-spectrum techniques for wireless communication, " IEEE Signal Process. Mag., vol. 14, pp. 26--36, May 1997.

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P. G. Flikkema, #Spread-spectrum techniques for wireless communications," IEEE Sig. Proc. Magazine 14, pp. 26#36, May 1997.

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P. G. Flikkema, #Spread-spectrum techniques for wireless communications," IEEE Signal Processing 14, pp. 26# 36, May 1997.

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P. G. Flikkema, "Spread-spectrum techniques for wireless communications," IEEE Sig. Proc. Magazine 14, pp. 26--36, May 1997.

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P. G. Flikkema, "Spread-spectrum techniques for wireless communications," IEEE Signal Processing 14, pp. 26-- 36, May 1997.

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