Jufeng Dai

Genetic Watermarking Based on DCT Domain Techniques

In order to increase the speed of genetic watermarking and improve the robustness and imperceptibleness of the algorithm, a new embedding and extracting method with genetic algorithm (GA) was proposed. The AC coefficients of image in DCT domain were modified to embed the watermark. The proposed embedding and extracting method was employed to accelerate the genetic watermarking and to avoid the leak of watermark. GA was used to optimize both the fundamentally conflicting requirements: robustness and invisibility. The experimental results show both the good robustness under attacks and the high fidelity. The time needed to perform the program is greatly decreased. About 1/3 time has been saved

Progressive Image Transmission Over Wavelet Packet Based OFDM

In this paper, a new scheme for progressive image transmission over wavelet packet based orthogonal frequency division multiplexing (WP-OFDM) system is proposed. First, the BER performances of WP-OFDM systems with different Daubechies wavelet as orthogonal basis functions in multipath fading channel are investigated. The results show that there are error floors in the BER curves, so an equalization method is applied to eliminate the error floor. Then in the WP-OFDM system with the equalization method, a joint source channel coding (JSCC) method is introduced to give image encoder output bit streams with different perception importance unequal error protection. Simulation results confirm the effectiveness of our proposed image transmission scheme

Numerical simulation of multi-channel WDM transmission system in non-linear optical fiber communication system

Numerical simulations are of great importance in the study and design of the optical wavelength division multiplexing (WDM) system. In this paper, three kinds of nonlinear phenomena in fibers, which are known as self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave-mixing (FWM), are numerically investigated. In the study, the spacing frequency of 200 GHz for the channel is adopted for all the four laser sources. Also, the light wave is externally modulated by a pseudorandom electric signal of 40 GHz. The infinite-differential method is used for the solving of the nonlinear Schrodinger equation (NLSE) and Gaussian white noise is also taken into consideration. It is proved by the simulation results that high optical power of laser sources can incur serious nonlinear interference in fibers. It is also shown that the dispersion compensation effect can be achieved over 100 km span. The simulation results prove that the model is effective in WDM system performance evaluation.

A Scheme for MPEG-2 to H.264 Transcoding

This paper provides a scheme for MFEG-2 to H.264 transcoding. This scheme is composed of two parts: intra prediction and inter prediction. For the intra prediction part, 8 times 8 block DCT-HT transform-domain converse is used, and then intra mode decision is done in HT domain to obtain the optimum mode, so that good intra prediction is acquired. For the inter prediction part, motion vector (MV) got from variable length decoding (VLD) in MPEG-2 stream is reused as prediction motion vector (PMV) of H.264, then motion prediction mode and search region are reset, so that better prediction result is acquired. Experimental results show that this scheme is feasible

Analyzing the characterization of microstrip with multilayer dielectric structure by complex image method

A rapid-convergent algorithm which calculates the spatial complex images of a point charge in multilayer media is presented. Combining the complex image method and moment method, we analyze two kinds of the structure of the microstrip line. The results are identical with the results in the literature.

A Method of H.264-Based Still Stereoscopic Pictures Compression

Still stereoscopic pictures compression is an important part of auto-stereoscopic techniques. H.264 is an advanced video compression standard, absorbing the advantages of the previous standards. In this paper, still stereoscopic pictures compression is studied, and H.264 coding tools adopted to achieve this compression are discussed. The still stereoscopic pictures compression schemes based on H.264, MPEG-2 and JPEG are compared by the experiments. The experimental results show that with the H.264 compression scheme presented by this paper, high compression rate can be achieved, high quality compressed multi stereo pairs can be acquired and the exact binocular disparities between multi stereo pairs are well preserved

A Novel Implementation of the CFS-PML for Arbitrary Media using DSP Techniques

A novel implementation of the complex frequency shifted perfectly matched layer (CFS-PML) is introduced for truncating the finite-difference time-domain (FDTD) domain. The implementation is based on the uniaxial anisotropic perfectly matched layer (UPML) formulations and digital signal processing (DSP) techniques. One of the novelties is that the realization of the UP ML with the CFS scheme employs the high-order difference equation method without the increase of memory requirement. Particularly, a new algorithm to minimize memory requirement is presented. Additionally, the proposed formulations are derived to be fully independent of the material properties of the FDTD computational domain. Two numerical tests have been carried out in three dimensions to validate these formulations. It is shown that the proposed formulations are efficient in attenuating of evanescent waves and reducing late-time reflections

Experimental investigation of stabilizing all-optical clock recovery in 4x10Gbps OTDM system based on the injection mode-locked fiber ring laser

In this paper, a novel scheme of stabilizing all-optical clock recovery is proposed, which uses a mode-locked fiber ring to extract the same frequency clock pulses from the uneven multiplexing 4×10Gbps optical signals. The super-mode suppression ratio reaches 60dB (for signals of 10Gbit/s) and an improvement of 20dB is achieved by adding stabilization devices. Wavelength shift is less than 0.01nm within 2 hours, and this value is about one sixties of that without adding stabilization devices. The results show much better cavity length stability and noise suppression performance.

A improved space-time trellis coded OFDM scheme for frequency selective fading channels

We have studied the space-time trellis code (STTC) design in OFDM systems. By the research, especially by simulation, it is shown that, in multi-flat fading channels, the STTC-OFDM system can potentially provide more coding gain. We also found that the optimal STTC design is important for OFDM when using space-time codes (STC). By following this conclusion, an improved STTC is designed. Computer simulations have demonstrated a significant performance improvement of our proposed STTC-OFDM over the conventional STTC-OFDM. Further research for the STTC-OFDM system in other channels can also be pursued according to this scheme.

New dispersion-decreasing dispersion management

In this paper, we introduce a new dispersion management method of realizing exponentially decreasing dispersion fiber by using only two kinds of segments of fibers with different dispersions connected together. Exponentially decreasing dispersion fiber is used to obtain the optimum soliton transmission situation. Some simulation results show that this method has more advantages than conventional soliton system, and can significantly improve the system performance.