Showing papers by "Johannes B. Huber published in 2003"
TL;DR: This work investigates the well known steganographic tool Jsteg as well as a newer approach proposed by Eggers et al., which relies on histogram-preserving data mapping, which shows weaknesses leading to a certain detectability.
Abstract: Universal blind steganalysis attempts to detect steganographic data without knowledge about the applied steganographic system. Farid proposed such a detection algorithm based on higher-order statistics for separating original images from stego images. His method shows an astonishing performance on current steganographic schemes. Starting from the statistical approach in Farid's algorithm, we investigate the well known steganographic tool Jsteg as well as a newer approach proposed by Eggers et al., which relies on histogram-preserving data mapping. Both schemes show weaknesses leading to a certain detectability. Further analysis shows which statistic characteristics make both schemes vulnerable. Based on these results, the histogram preserving approach is enhanced such that it achieves perfect security with respect to Farid's algorithm.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
42 citations
11 May 2003
TL;DR: The combination of continuous phase modulation (CPM) with direct-sequence code-division multiple access (DS-CDMA) for multiuser transmission over the additive white Gaussian noise channel achieves high performance with very moderate complexity.
Abstract: The combination of continuous phase modulation (CPM) with direct-sequence code-division multiple access (DS-CDMA) for multiuser transmission over the additive white Gaussian noise channel is discussed. Concentrating on the important special case of generalized minimum-shift keying, particularly simple receiver structures are obtained. To emphasize on low complexity, noncoherent reception is proposed and appropriate transmitter and receiver designs are provided. The application of reduced-state noncoherent sequence detection and noncoherent filter adaptation ensures high power efficiency and robustness against channel phase variations. Simulation results confirm that the chosen approach of CPM for DS-CDMA achieves high performance with very moderate complexity.
19 citations
TL;DR: Digital transmission over dispersive channels which suffer from intersymbol interference (ISI) and/or over multiple-input/ multiple-output (MIMO) channels which exhibit multi-user interference is reviewed and the calculated optimum filters for these applications are presented.
18 citations
04 Aug 2003
TL;DR: This work shows how to obtain the information processing characteristic (IPC) introduced by Huettinger et al. for concatenated coding schemes and gives an achievability bound, i.e. it is possible to determine a performance that can surely be achieved if sufficiently many iterations are performed and a large interleaver is used.
Abstract: Asymptotical analysis of concatenated codes with EXIT charts (ten Brink, S., 1999) or the AMCA (Huettinger, S. and Huber, J., 2002) has proven to be a powerful tool for the design of power-efficient communication systems. However, the result of the asymptotical analysis is usually a binary decision, whether convergence of iterative decoding is possible at the chosen signal-to-noise ratio, or not. We show how to obtain the information processing characteristic (IPC) introduced by Huettinger et al. for concatenated coding schemes (see Proc. 39th Allerton Conf. on Commun., Control and Computing, 2001). If asymptotical analysis is performed under the assumption of infinite interleaving and infinitely many iterations, this IPC is a lower bound. Furthermore, it is also possible to estimate the performance of realistic coding schemes by restricting the number of iterations. Finally, the IPC can be used to estimate the resulting bit error ratio for the concatenated coding scheme. As an upper and a lower bound on the bit error ratio for a given IPC exist, we are able to lower bound the performance of any concatenated coding scheme and give an achievability bound, i.e. it is possible to determine a performance that can surely be achieved if sufficiently many iterations are performed and a large interleaver is used.
14 citations
04 Aug 2003
TL;DR: Two parameters based on bitwise pairwise error probabilities for the cases with and without a-priori knowledge are proposed as new measures for a labeling of signal points suited to iterative decoding-demapping and it is demonstrated that the two parameters are closely related to the transfer characteristic of the demapper and accordingly lead to the same design guideline as a TC analysis.
Abstract: A bit-interleaved concatenated coding scheme consisting of an outer convolutional code and an inner space-time modulation together with an iterative decoding-demapping method is analyzed. As a result, two parameters based on bitwise pairwise error probabilities (b-PEP) for the cases with and without a-priori knowledge are proposed as new measures for a labeling of signal points suited to iterative decoding-demapping. In particular, we demonstrate that the two parameters are closely related to the transfer characteristic (TC) of the demapper and accordingly lead to the same design guideline as a TC analysis. By optimizing these two analytical parameters for an orthogonal space-time block code (oSTBC) employing 16QAM constituent symbols w.r.t. an outer simple 4-states rate 1/2 convolutional code, a highly power efficient concatenated scheme with rate of 2 bits per channel use is proposed, which offers an excellent trade off between power efficiency and complexity.
13 citations
15 Sep 2003
TL;DR: The transmission scheme employing modulo reduction mod-/spl Lambda/ precoding is an attractive strategy when transmitting over AWGN channels, which suffer from additive noise, and an additional interference term, which is already known at the transmitter side.
Abstract: This paper discusses the use of modulo arithmetics in the precoding scheme for N-dimensional data symbols. The transmission scheme employing modulo reduction mod-/spl Lambda/ precoding is an attractive strategy when transmitting over AWGN channels, which suffer from additive noise, and an additional interference term, which is already known at the transmitter side. The capacity of channels and the use of optimum lattice quantizers for minimum error entropy approach applying numerical optimization are also studied.
12 citations
14 Dec 2003
TL;DR: Digital transmission over dispersive channels which suffer from intersymbol interference and multiuser interference is reviewed and the optimality of DFE with respect to channel capacity is shown.
Abstract: Digital transmission over dispersive channels which suffer from intersymbol interference and multiuser interference is reviewed. In particular, the digital signal processing required at the receiver for performing combined spatial/temporal decision-feedback equalization is studied and the aims of processing the received signal are discussed. The calculation of the optimum filters by solving a factorization problem and an practical algorithm for its solution are reviewed. Finally, the optimality of DFE with respect to channel capacity is shown.
8 citations
TL;DR: In this paper, a scalar Costa watermarking scheme based on scalar quantizers has been proposed for one-dimensional embedding in the modulo channel with AWGN attack.
Abstract: Blind spread-spectrum watermarking schemes with correlation based detection algorithms suffer significantly from host signal interference. Improvements are possible when considering the host signal as side-information to the watermark encoder. Costa showed that, in a specific case, host signal interference can be avoided completely. The scalar Costa scheme, which operates on structured codebooks based on scalar quantizers, performs relatively close to the ideal Costa scheme in terms of maximum rate of reliable communication (capacity) over a channel with AWGN attack. The concept of amplitude limited channels in conjunction with repetition of the signal constellation is also known in the communications community by the name modulo channel, which has been studied into great detail. Starting from the modulo channel, which implies a constraint on the amplitude in the receiver, we model the watermarking scenario based on scalar quantizers. The capacity of this model is presented and compared to the theoretical results for SCS watermarking in the case of AWGN attacks. A final analysis of SCS in terms of optimality, based on the results with the modulo channel, shows that even binary SCS is near optimum for one-dimensional (symbol-by-symbol) embedding in terms of capacity
for an i.i.d. Gaussian host signal and an appropriate AWGN attack.
1 citations
TL;DR: A novel criterion, that is ‘capacity rule’ plus ‘mapping rule‘, for the design of the optimum MLC scheme for radio systems over Rayleigh fading channels is proposed and a few of key issues related to design an optimum M LC system are investigated.
Abstract: For the narrow band Wireless Code Division Multiple Access (WCDMA) system, there are some channel coding schemes proposed and applied like Turbo code and convolutional codes. But for the 4G Code Division Multiple Access (CDMA) wideband systems, we have to use new channel coding schemes with high bandwidth efficiency. In this case, multilevel coding (MLC) scheme is easy to map to Multiple Quardrature Amplitude Modulation (MQAM) modulation strategy to be used for 4G, and MLC+MQAM will be a potential channel coding scheme for the error correcting of next generation of mobile systems.
A novel criterion, that is ‘capacity rule’ plus ‘mapping rule’, for the design of the optimum MLC scheme for radio systems over Rayleigh fading channels is proposed in this paper. Based on this theory, a few of key issues related to design an optimum MLC system are investigated. These include a novel optimum design criterion proposed, different mapping strategies, different decoding methods of MLC/MSD and MLC/Parallel Decoding on Levels (PDL) and their performance comparison over Additive White Gaussian Noise (AWGN) and Rayleigh fading channels respectively. Copyright © 2003 John Wiley & Sons, Ltd.