Cheng En

An Improved Spatial Error Concealment Algorithm Based on H.264

The losses of packets are inevitable when the video is transported over error-prone networks. Error concealment methods can reduce the quality degradation of the received video by masking the effects of such errors. This paper presents a novel spatial error concealment algorithm based on the directional entropy in the available neighboring Macro Blocks (MBs), which can adaptively switch between weighted pixel average (WPA) adopted in H.264 and an improved directional interpolation algorithm to recover the lost MBs. In this work, the proposed algorithm was evaluated on H.264 reference software JM8.6. The illustrative examples demonstrate that the proposed method can achieve better Peak to Signal-to-Noise Ratio (PSNR) performance and visual quality, compared with WPA and the conventional directional interpolation algorithm respectively.

Analysis and Implementation of NTFS File System Based on Computer Forensics

NTFS, which restores and manages the important data, is a common file system in Windows Operating System,. Tapping and analyzing the useful data of the NTFS file system has become an important means of current computer forensic. Through detailed analysis and research on the storage principles of the NTFS file system, the object-oriented method is put forward to design NTFS file parsing system. This system parses the binary data stored in disk, achieving the total analysis of both the normal files and the deleted files. Then, all the data retrieved can be restored into the form of a friendly user interface which can provide a reliable data source for the computer forensics.

The research of the cooperative OFDM system

The main idea to the OFDM is to divide the channel into many orthogonal sub channels in the frequency, which use parallel transmission sub-carriers to modulate. So that, the signal bandwidth is less than the channel coherence bandwidth, which can effectively eliminate ISI. Cooperative diversity is widely used in wireless communication. By taking the advantage of cooperative communication, we try to combine Cooperative diversity with OFDM. In this paper, key technologies of OFDM system, two types of cooperative protocols to realize cooperative diversity in OFDM systems, and two kinds of combining methods, are proposed. Simulations on two types of cooperative protocols to realize cooperative diversity, on two kinds of combining methods are performed. In addition, we simulated the performance of the cooperative diversity OFDM system with relay nodes located in different locations.

Application of stochastic resonance technology in underwater acoustic weak signal detection

The high frequency Chirp signal in underwater acoustic communication usually submerged in various noise produced by ocean waves, ships, etc. In this paper, based on the principle of stochastic resonance for weak signal detection, the extraction and energy enhancement of high frequency weak signal are achieved by using bistable stochastic resonance system. The genetic algorithm is additionally used to adaptively select the system parameters. Finally, the principle is verified to be correct and feasible with spectrum chart and FRFT through simulation and experiments which provides a new analysis method and design guidance for the enhancement and detection of underwater acoustic weak signal.

Multiuser underwater acoustic communication based on multicarrier-multiple chirp rate shift keying

Multiuser underwater acoustic communication is one of the enabling technologies for the autonomous oceans sampling network (AOSN). Based on explicit relationship between fractional Fourier transform properties of chirp signal and its parameters, we proposed a new modulation and demodulation scheme named multicarrier-multiple chirp rate shift keying (MC-MCrSK). The scheme can support four users communication via underwater acoustic channel with 10 KHz bandwidth. Receiver can increase robustness by virtual time reversal mirror technology (VTRM). The validity of the simulation comparison is verified in experiment. 425 bps data rate per user of the proposed communication scheme is realized in 10 KHz bandwidth.

Notice of Retraction A research of signal combining technologies in cooperative diversity of OFDM communication system

Cooperative diversity is widely used in wireless communication. Because of its own unique advantages, we try to combine Cooperative diversity with OFDM. Key technologies of OFDM, three methods of channel estimation, two types of cooperation, and two combining methods in OFDM system are presented in this paper. Simulations of OFDM cooperative diversity system with two combining methods are performed. The performances of OFDM cooperative diversity system under three methods of channel estimation are simulated and analyzed respectively.

Study on chaotic sequence and RS sequence for underwater communication

Underwater acoustic communication channels are generally characterized as seriously time-space-frequency variant channels with strong multi-path interference, limited bandwidth, severe environment noise and Doppler effect. In underwater acoustic hop frequency communication system, every users information is modulated by a special code on the transmitter, the information will be demodulated by the same code at the receiver. The code mentioned here is pseudo-random sequence, the spectrum of the signal will be expanded. Performance of pseudo-random sequence is directly related to system performance, therefore, pseudo-random sequence is a key point of implementing a hop-frequency communication system. This paper is based on the analysis of acoustic communication channel, some common sequences are evaluated, and simulation is made to compare the performance of chaotic sequence and RS sequence.

Gabor Wigner Transform based on fractional fourier transform for low signal to noise ratio signal detection

To settle the time-frequency analysis problem of multi-component Linear Frequency Modulation(LFM)signals in the presence of low signal to noise ratio, a method called Gabor Wigner Transform(GWT) based on Fractional Fourier Transform(FRFT) is proposed. GWT is a composition of Gabor Transform(GT) and Wigner-Ville Distribution(WVD), hence GWT takes the advantages of both transforms, high resolution of WVD and cross-terms free of GT, but the time-frequency concentration of GWT is lower than that of WVD, the introduction of FRFT is to further improve the time-frequency concentration. LFM signals present a good energy clustering just in the optimal order of FRFT domain, while the white noise will not appear energy clustering in any FRFT domain, so the method has good anti-noise. In the condition of white Gaussian noise, a series of simulations have proved the method not only eliminate the interference of cross terms, but also improve the time-frequency concentration.

Waterworks Flocculants System Based on Machine Vision and Fuzzy Control

Flocculants is one of the most important step in water treatment process, the realization of automatic dosing flocculants is remarkable characteristics in the development of waterworks in recent years. This paper puts forward a kind of low cost automatic waterworks flocculants dosing control system based on machine vision and fuzzy control. The system first collected water samples image by camera, and obtained water quality parameters through the image preprocessing, segmentation and recognition classification, then get flocculants dosage according to the parameter mapping, and finally through the fuzzy PID control and the communication between PC and PLC to realize the flocculants dosing. This system mainly has developed with the combination of software and hardware two parts, which can realize the image processing analysis and the completion of PC, PLC and electrical communication as well as realize the flocculant dosing control automatically.

Embedded system for sea buoy location and tracking

Underwater acoustic communication technology is an effective mean of development and study of the sea. It is widely used in marine environment three-dimensional monitoring, underwater multimedia communication, underwater mobile carrier navigation and positioning, marine resources detection, remote control of submarine topography mapping and offshore oil industry, data acquisition, etc. The sea buoy is an important part of underwater acoustic communication system. It is of great significance to track and locate it. This paper describes the application of the monitoring service of GPRS / GPS module at sea buoy. It can achieve real-time location of underwater acoustic communication devices and route tracking to avoid the loss of the device, as well as assist to retrieve the lost device.