Print and Generation Copy Image Watermarking Based on Spread Spectrum Technique

Protection of copyright is a crucial issue in the data transmission and distribution. Considering the fact that there are different types of information available for misuse and manipulation by all the internet users it is necessary to establish the rules for copyright protection of a certain content. In this paper, special attention is given to the technical aspects of copyright protection. We took a digital image and a digital watermark into consideration. The original image has undergone a discrete wavelet transformation. Then, spread spectrum techniques were applied to the watermark. Digital watermark is then embedded into the original image. The aim of the paper is to present the comparison of results obtained using two different spread spectrum techniques in image watermarking.

In general, after a watermarked image is printed, copied several times and scanned, the watermark usually cannot be extracted rightly, as well as distorted by noise. To solve this problem, in this paper, two watermarks were embedded into the image. The first one is a periodic watermark. The second one is the real watermark message. These two watermarks are embedded into the image by modifying the gray value of each pixel. The cover image is not needed when the watermark is detected. Both of these two watermarks are estimated exploiting the properties of HVS (Human Visual System) and extracted through the same key-dependent 2D sequences. Experiments results show that the scheme can resist print, generation copy and scan process.

An enhanced hybrid image watermarking scheme for security of medical and non-medical images based on DWT and 2-D SVD

With the growth of multimedia systems in distributed environments, the research of multimedia security as well as multimedia copyright protection becomes an important issue. As a potential and effective way to solve this problem, digital watermarking becomes a very active research area of signal and information processing. Many watermark algorithms have been proposed to address this issue of ownership identification. Discrete Cosine Transform (DCT) based spread-spectrum watermarking is one of the famous techniques. Another possible domain for watermark embedding is the wavelet domain. One of the many advantages over the Discrete Wavelet Transform (DWT) is that more accurately model aspects of the human visual system (HVS). In this paper a proposed algorithm is defined based on the combination between the benefits provides by using wavelet domain and profits of Code division multiple access (CDMA) spread-spectrum technique. A pseudo-random sequence (key) that related to hidden message is embedded into the significant DWT coefficients of a cover image to produce a watermarked image. Experimental results demonstrate that the proposed algorithm is perceptual invisible and robust against many attacks such as lossy image compression and Additive White Gaussian Noise (AWGN). Keywords: digital watermark, wavelet transform, CDMA technique.

Due to a world wide surge in the intelligent vehicle highway system (IVHS), the field of automatic vehicle identification (AVI) has been rapidly growing. The use of spread spectrum communications has not yet pervaded the AVI market. However, in the already cramped electromagnetic environment, spread spectrum techniques have gained significant popularity in many growing areas of wireless communication. AVI is perfectly suited to benefit. The fundamental advantage of spread spectrum technology in AVI applications is its invulnerability to interference and its ability to operate alongside narrow band communication systems already in place. The second advantage is the ease of licensing for spread spectrum AVI, since it does not require a dedicated frequency spectrum. It is also possible for several spread spectrum AVI systems to operate simultaneously in the vicinity of each other, using different spreading codes. This article concentrates on architecture as well as applied key signal processing techniques for a proposed direct sequence spread spectrum (DSSS) AVI system. A functional block diagram that outlines the major components of the system is presented. The system consists of three major functional parts: interrogator, transponder, and trigger. Free flow of traffic can be maintained only if the interrogator can isolate each vehicle in a common interrogation zone. DSSS allows this through code division multiple access (CDMA). The triggering system is based on the principles of speed enforcement radar. The proposed digital modulation scheme is BPSK. The DSSS modulator applies a Gold pseudo-random (PN) code to spread the spectrum of the binary signal. Despreading is carried out through the use of a PN matched filter. The antenna is assumed to have a 60/spl deg/ half-power radiation field and is placed on an existing overpass approximately 6 meters above the roadway. With 50 mW antenna transmit power, link budget analysis indicates that sufficient bit energy-to-noise power spectral density ratio is available at the receiver to generate an excellent bit error rate without requiring error control coding.

Digital watermarking has been proposed as a method for discouragement of illegal copying and distribution of copyrighted material. Currently proposed algorithms of digital watermarking in the context of the video are robust against unintentional attacks, but many of them do not protect enough against malicious attacks. This paper presents a new video watermarking system with improved robustness, which is based on spread spectrum technique. Finally, we also present results, which verify the enhanced robustness of proposed system against malicious and non-malicious attacks.

There is able to be critical performance impairment because satellite digital broadcasting system such as DVB-S2 is sensitive to heavy rain environment. This feature of the satellite channel does not only make users be able to give inconvenient broadcasting service but they cannot see the service. Spread spectrum technique is the new proposal which can overcome those problems that are generated due to rain attenuation. Applying spread spectrum to DVB-S2 system, we examine how effective the technique is in the broadcast system. Assuming that signal power and channel bandwidth are same in the proposed system and the original system, the reason why spread spectrum technique is effective in heavy rain environment will be demonstrated. And using computer simulation, the performance improvement is shown.

Lateral distance measurement system for AVCS (advanced vehicle control systems) has been developed in the various countries. This paper describes a lateral distance measurement system using spread spectrum (SS) technique. Our method does not require significant infrastructure investment because it is based on the reflected signal from the guardrails currently installed on many roads. The range resolution of SS radar is generally equal to the length of one chip because it is based on the correlation using chip synchronization. We propose a short range measurement system utilizing the slope of the correlation function of m-sequence as an application of SS technique and indicate the results of the experiment.

This article presents two-dimensional (2-D) scattering centres' parameter estimation based on linear uniform multi-input multi-output (MIMO) radars. Unlike single-input single-output (SISO) radars, MIMO radars transmit multiple detection signals at the same time. We assume that each antenna of a MIMO radar transmits signals with a set of different spread spectrum codes so as to distinguish the echoes from all antennas. Then, with spread spectrum and de-spread spectrum techniques, each antenna of a MIMO radar could distinguish its own stepped-up frequency echoes transmitted by itself. In this article, we take m sequences as spread spectrum codes and assume that the ratio between the MIMO radars array aperture and the target distance is much less than 1, then we use 2-D fast Fourier transform (FFT) and matrix extended matrix pencil (MEMP) methods to extract 2-D scattering centres' parameters after MIMO radar have received de-spread echoes. Simulations illustrate that both SISO radars and linear uniform MIMO radars using the spread spectrum technique can get similar estimation results, and the MEMP method can afford super-resolution estimation results, whereas the 2-D FFT method is more useful when the number of MIMO radar array elements are no more than the number of scattering centres.

Troposcatter radio links may be a low cost alternative for long distance communications, or when the transmitter and the receiver are separated by difficult terrain that prevent from line-of-sight communications. These links permit one to preserve satellite resources in the case of civil applications, so as to overcome geographical barriers (oceans, mountains, desert, etc.). They also can easily and rapidly be installed for emergency situations in both civil and military cases. They represent a good solution in the case of single transhorizon hops of length limited to several hundreds of kilometers. The problem is that the transmission is based on the presence of multipath, whose dispersion is very varying on long periods. Wide-band transmission schemes can be then employed, like OFDM or spread spectrum techniques. The limitations of OFDM in presence of non-linearities of the amplifiers has often led one to prefer spread spectrum techniques in the case of troposcatter links: direct sequence (DS) or frequency hopping (FH). All the more so as other characteristics of spread spectrum are exploited for performance and also discretion purposes, as we are concerned with military tactical transmissions. The implementation of hybrid DS/FH spread spectrum receivers, which realize a maximal ratio combination of the paths (RAKE) is presented. After a description of the channel, we then describe the communication systems involved, and finally estimate the bit error rate.

Random codekey selection using codebook without pre-shared keys for anti-jamming in WBAN

Inter-vehicle communication is an essential part of any intelligent transportation system (ITS). It allows vehicles to share surrounding road traffic information to support safe driving and road traffic management. Current systems use spread spectrum (SS) techniques: direct sequence (DS) or frequency hopping (FH). This paper proposes an implementation of a hybrid system in which DSSS and FHSS techniques are combined to provide performance and scalability improvements over a system that uses either of the SS techniques. Also this paper presents a theoretical analysis showing the improvement in the overall system capacity of the proposed system and the results of the computer simulations conducted. The results show that given an equal bandwidth, the hybrid system out performed the DS or FH systems. It showed superior bit error rate (BER) performance and scalability.

In this paper, we propose to embed the watermark information in the log-2-spatio domain by means of spread spectrum technique. In log-2-spatio domain, the variance of the information is reduced significantly. This improves the efficiency and robustness of spread spectrum technique. Low intensity and mid-band regions are selected to embed the information in order to guarantee an invisible watermark as well as the robustness to JPEG compression. Simulation results show that the embedded information still survives up to the JPEG compression ratio of 14.7.

In this paper a multiplexing technique based on Walsh functions (sequency multiplexing) is described for the mobile spread spectrum multiple-access (SSMA) communication system. At the base station, the bit streams forwarded to each of 2K users are partitioned into two branches. In each branch it is first multiplexed by the corresponding Walsh function identifying a user and then it is spread by a PN sequence identifying one of two orthogonal components of the carrier of the branches. This multiplexing method makes all spread spectrum channels orthogonal and perfectly separated in the ideal case (provided perfect synchronization is achieved) at the same path, so it decreases the multiple access interferences. It is shown that sequency multiplexing combined with the spread spectrum technique is a suitable method for use on the down link of CDMA mobile communication system.

Indoor wireless infrared transmission is severely impaired by noise and interference produced by artificial ambient light. The interference produced by fluorescent lamps driven by electronic ballasts causes very large power penalties. In this paper spread spectrum techniques are proposed to combat the penalties caused by artificial light interference. Analytical, simulation and experimental results of bit error rate versus signal-to-noise ratio are presented for a 1 Mb/s spread spectrum wireless infrared system. The results show that spread spectrum techniques reduce the degradation due to artificial light interference.