Search

For the low accuracy of the spectrum sensing of the single node, this paper discusses several popular cooperative spectrum sensing technology. It also proposes a clustering double threshold cooperative spectrum sensing algorithm does two threshold detection based on the double threshold cooperative spectrum sensing algorithm. This algorithm applies or data fusion rule to realize the combination of the data among clusters on the basis of the improvement of the double threshold detection technology. The simulation results show that this algorithm can effectively reduce false alarm rate and undetected rate, and it can improve the overall detection performance.

For the least connections algorithm currently used cannot solve the problem of inaccurately reflecting the load capacity of servers caused by the situation that the difference of resources consumed by different requests is very big, this paper designs a new algorithm named UCM algorithm. It means use the unused rate of the CPU and Memory as the actor to calculate the weight of the server, and introduces a new parameter named load redundant parameter to judge the ability to deal with new requests. By simulation, it simulates a circumstance that many requests are sent synchronously. The least-connections algorithm and UCM algorithm are used in the system. The result indicates that using the UCM algorithm has a shorter response time, and it means saving the time that the system deals with the service requests.

Along with correspond by letter the development of the profession, the wireless signal blast-off the station is gradually small scaled to turn and easily operate. It results in the illegal member made use of it to carry out to break the law the crime activity, influencing the people to usually produce the living work. The want for is related to examine and position the equipment in fight break the law shoot stand break the law the activity of the criminal offence. The huge inconvenience of the traditional wireless monitor equipment physical volume in take. Positioned the calculate way through the RSSI and GPS the Base station to design the fixed position the hardware host of the instrument and the kit software of the smart terminal. Should position the instrument assurance fixed position accuracy to guarantee the equipment physical volume in the meantime of small scaled turn and then hold to turn. The examination and the fixed position function that carries out to stand to the illegal blast-off, only to the experiment and the analysis that the illegal GSM shot station to carry on examination and position.

Human detection is a key problem in computer vision, with several applications that have the potential to positively impact quality of life. In recent years, the number of approaches to detect human in video sequences has grown steadily. This paper proposed a novel approach to improve the capability of human detection. After investigating the image texture analysis methods, we adopt the new good texture descriptor, Local Binary Pattern histogram Fourier (LBPHF). Then we combine the LBPHF with the Histograms of Oriented Gradients (HOG) as feature sets, and use linear SVM to train our classifier. In the experiment on the INRIA personal dataset which is well known relatively good human detection's dataset, it is shown that our detector combining with the LBPHF significantly outperforms the other methods. Moreover, the time cost is much less and the dimension is reduced.

This paper focuses on ARP attacks in switched networks, from ARP protocol perspective, analyses the principle of ARP attacks and the exceptional interrupt occurs they cause when the terminal users access the servers. To quickly and effectively detect ARP spoofing, this paper proposes a WinP cap based detection system of ARP spoofing. Using Win Pcap driver development monitoring software, implements ARP packets capture and analysis in a switched network inspection system. This method does not require a network host to do anything in response, comparing to the other methods, it can reduce the impact of network communication during inspection, and can detect the ARP Spoofing quickly and effectively in switched network.

The requirements of common network communication for the reliability of network transmission are low. It can not meet the requirements of real time and high reliability in the industrial control network traffic. For needs of high reliability in industrial control network communications, this paper analyzes the VxWorks operating system and the structure of the network layer network card drivers. By studying network protocols and its interface functions, this design realized NIC redundancy approach in the driver. According to the Intel 82557 network chip, a dual NIC redundant configuration and some specific code is completed. With initializing in the driver, the two NICs are configured as the same MAC address. Using the same IP address, the NIC link status monitoring is completed, and according to the link state, the backup NIC is switched without being detected by the network protocol layer. This design can guarantee the reliability of the network communication to the greatest extent, and then improve the quality of network communication, finally ensure the real-time transmission in the industrial control networks.

The amount of data during OPC Client and OPC Server communications is an important parameter to design an equipment, a network and a system, but it has never been given in the theoretical calculations or tests. In this paper amount of data is tested, and the result of the test is analyzed by designing and making six groups of experiments, then recording, analyzing and operating the data. In the end, empirical formula is obtained for the first time in the OPC Client and OPC Server Communications. The empirical formula shows that relationship between the amount of data per second and the number of the data item is almost linear, and relationship between rate and the number of the data item is similar to the above-mentioned relations. Based on above-mentioned conclusions, the test will explain how much data every OPC Client or OPC Server can load.

In the application of some embedded systems such as the ship-borne routers, ATM machines and so on, many low-power embedded CPU needs connection with PCI-104 bus. However, these low-power embedded CPUs don't have the bus interface of PCI-104 (PCI). In order to solve this problem, this paper designs FPGA-based PCI-104 bus interfaces of the low-power embedded CPU. Through the analysis of PCI-104 bus protocol and the corresponding interface signal sequence, the method of Top_Down is applied to the modeling of the seven functional modules of PCI-104 bus interface such as the configuration register module, base address check module, state machine module, etc. Besides, in consideration that these CPUs can also be taken as the coprocessors, the master and target device interfaces of PCI-104 bus are programmed with the utilization of Verilog language, and the finite-state machine of the master device and the target device is structured in detail. Through the Modelsim simulation verification, it has been proved that the interface can meet the timing requirements of the PCI-104 bus specification, so as to connect these low-power embedded CPUs with PCI-104 bus expansion board. It also can realize to upgrade CPU on the PCI-104 bus board.

Cooperative diversity has attracted great attention in recent years. In such a system, even single-antenna terminals can achieve spatial diversity with the help of other terminals. In this paper, we focus on the outage performance of cooperative diversity. The outage probabilities of several mean cooperative protocols are analyzed and compared. Theory analysis and simulation results show that the outage performances of these protocols vary with the channel conditions, and we may choose the appropriate cooperative protocol according to the channel conditions.

The anti-noise performance of direct sequence spread spectrum (DSSS) communication system is analyzed in this paper. The new result given in the paper shows that anti-noise performance of DSSS system is different from classic result. The attenuation to input narrowband noise in DSSS system is the function of the relative position between the narrowband noise and carrier frequency of DSSS system, and it is discontinuous. The attenuation to input broadband noise is about 0.46dB better than in classic result. The results can be utilized in design and application of spread spectrum system.

A novel wavelet-based vector quantization (WVQ) is presented for SAR image compression at low bit rates. Through analysis of the decomposed wavelet coefficients' statistic property, establish directional vectors based on spatial orientation tree (SOT) structure and apply LBG algorithm to train codebook and vector quantization of wavelet coefficients. For a typical SAR image, the reconstructed images coded by WVQ achieve gains 0.1dB to 1.0dB on average in PSNR and preserve superior perceptual quality compared with the coding results of set partitioning in hierarchical trees (SPIHT) algorithm at low bit rates.

A constrained resource allocation scheme is proposed in this paper to achieve optimized dynamic data scheduling in next generation wireless networks (NGWN). By modeling the problem as the solution to the maximization of the total utility function, we derive the optimization resource allocation model by instantaneously estimating the integrated information on channel condition and queue length of each user node as well as the set of subcarriers available. On the problem of maximizing the total utility function with respect to the average waiting time of each user queue over time window, we present an algorithm with low computation complexity for dynamic subcarrier allocation. Simulation results and mathematical analyses demonstrate that compared with the conventional approach, this scheme achieves higher efficiency due to making the most use of diversity of time, frequency and multiuser and can provide different required level of fairness by appropriately devising the utility function.