Performance Analysis of Multiband Impulse Radio UWB Communication System Based on PSWF

To improve the data transmission rate and use spectrum flexibly, a new spectrum allocation method for Multiband Impulse Radio UWB (MB-IR-UWB) is proposed in this paper based on the band-limited and orthogonal characteristics of Prolate Spheroidal Wave Function (PSWF). The system model is built and the bit error rate (BER) formula is deprived by binary time hopping pulse position modulation under additive white Gaussian noise. Moreover, the system performance is analyzed via MATLB simulation. The results indicate that MB-IR-UWB system performance of BER is the same with single-band UWB. However, in the proposed scheme the data can be transmitted in multiple parallel bands, which enjoys much higher transmission rate. In addition, PSWF pulse duration affects the BER performance.

Dispersion characteristics of a slow wave structure with a modified photonic band gap

This paper studies the dispersion characteristics of a modified photonic band-gap slow-wave structure with an open boundary by simulation and experiment.A mode launcher with a wheel radiator and a coupling probe is presented to excite a pure TM 01-like mode.The cold test and simulation results show that the TM 01-like mode is effectively excited and no parasitic modes appear.The dispersion characteristics obtained from the cold test are in good agreement with the calculated results.

Optimization and Realization of G.729 Speech Coding Algorithm

The principles of G.729 algorithm are analyzed. It proposes an optimal approach of adaptive codebook search. Realized on fixed point DSP TMS320VC5410,the searching time of the optimal algorithm is thus significantly decreased,and the result shows that the speech quality is not decreased.

ALGORITHMS AND ARCHITECTURE IMPLEMENTATIONS OF MIMO OFDM BASEBAND RECEIVER BASED ON THE SIMD DSP CORE

This letter presents a programmable single-chip architecture for Multi-Input and Multi-Output (MIMO) OFDM baseband receiver. The architecture comprises a Single Instruction Multiple Data (SIMD) DSP core and three coprocessors that are used for synchronization, FFT and channel decoder. In this MIMO OFDM system, the Zero Correlation Zone (ZCZ) code is used as the synchronization word preamble of packet in the physical layer in order to avoid the interference from other transmitting antennas. Furthermore, a simple channel estimation algorithm is proposed which is appropriate for the SIMD DSP computation.

Key Radar Signal Sorting and Recognition Method Based on Clustering Combined with PRI Transform Algorithm

In this paper,we investigate the problem of key radar signal sorting and recognition in electronic intelligence(ELINT).Our major contribution is the development of a combined approach based on clustering and pulse repetition interval(PRI)transform algorithm,to solve the problem that the traditional methods based on pulse description word(PDW)were not exclusively targeted at tiny particular signals and were less time-efficient.We achieve this in three steps:firstly,PDW presorting is carried out by the DBSCAN(Density-Based Spatial Clustering of Applications with Noise)clustering algorithm,and then PRI estimates of each cluster are obtained by the PRI transform algorithm.Finally,by judging the matching between various PRI estimates and key targets,it is determined whether the current signal contains key target signals or not.Simulation results show that the proposed method should improve the time efficiency of key signal recognition and deal with the complex signal environment with noise interference and overlapping signals.

Interworking MIPv6 and SIP in 3GPP networks

At present,using Mobile IP for complementing the link layer mobility in 3G has been researched widely,although MIP is not be supported explicitly in 3GPP.In this paper,we discuss the necessity of deployment MIPv6 in 3GPP.Furthermore,IMS(IP Multimedia Subsystem)was deployed in 3GPP.IMS uses SIP protocol to manage the multimedia sessions.In order to seamlessly support the real-time multimedia communication in mobility environment,it is important to interwork SIP and MIP.Some problems about interworking SIP and MIP are analysed.Then an optimized solution of interworking between SIP and MIPv6 is presented.The solution provides the effective routing and reduces the handoff delay and traffic burden inside Home Agent.

一种基于局部密度的高光谱异常检测背景纯化方法（英文）

在高光谱异常检测的基于背景的估计的研究中,背景中存在的异常像元会对背景估计的准确性产生不利影响,通过获得一个不包含异常目标的纯净背景可以有助于提高异常目标检测算法的检测率。因此,本文提出一种基于局部密度的背景纯化方法以去除背景中的异常像元。经典的RX算法(Reed-Xiaoli detector,RXD)在背景统计信息估计时,因初始背景中存在异常像元而产生失真现象。这使RX算法的检测结果具有较高的虚警率。在本文中,将像元的局部密度作为该像元的异常度标签,通过最大类间方差法去除初始背景中潜在的异常像元,最后可以得到更纯净的背景集。利用纯化背景得到更准确的背景统计信息,可以有效降低RX算法的虚警率。首先,通过度量一定半径内的光谱邻域,获得像元的局部密度,半径选取为距离矩阵的平均中位数;然后,基于局部密度设计了两步分割策略:第一步,将原始背景分割为一个包含大部分背景像元的集合及一个混合着背景像元和异常像元的小子集。第二步,利用最大类间方差法处理小子集,获得一个判别阈值,去除局部密度小于该阈值的像元,得到纯净的背景。最后,利用RX检测算法和基于协同表示的检测算法验证所提背景纯化算法的有效性。本文算法对于圣地亚哥海军基地数据和Spec TIR数据,AUC值比LRXD分别提高了0.0246和0.0068,并且相比于其它算法有较高的检测率。实验结果说明,密度背景纯化方法有效抑制了异常点对背景数据的干扰,使背景协方差和均值等参数更准确,降低了虚警率。在计算密度时,需要人为设定半径值。对于两幅高光谱数据,在不同半径选择下DBRAD最大AUC差值为0.0088和0.0012,实验结果表明,人为选择半径值可能会对最后的检测效果造成较大影响。如何自适应选取半径将是下一步研究的重点。

Fabrication of 160-nm T-gate metamorphic AlInAs/GaInAs HEMTs on GaAs substrates by metal organic chemical vapour deposition

The fabrication and performance of 160-nm gate-length metamorphic AlInAs/GaInAs high electron mobility tran-sistors (mHEMTs) grown on GaAs substrate by metal organic chemical vapour deposition (MOCVD) are reported. By using a novel combined optical and e-beam photolithography technology, submicron mHEMTs devices have been achieved. The devices exhibit good DC and RF performance. The maximum current density was 817 mA/mm and the maximum transconductance was 828 mS/mm. The non-alloyed Ohmic contact resistance Rc was as low as 0.02 Ω- mm. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) were 146 GHz and 189 GHz, respectively. This device has the highest fT yet reported for a 160-nm gate-length HEMTs grown by MOCVD. The output conductance is 28.9 mS/mm, which results in a large voltage gain of 28.6. Also, an input capacitance to gate-drain feedback capacitance ratio, Cgs/Cgd, of 4.3 is obtained in the device.

Mobile channel estimation for MU-MIMO systems using KL expansion based extrapolation

In multi-user multiple input multiple output(MU-MIMO) systems,the outdated channel state information at the transmitter caused by channel time variation has been shown to greatly reduce the achievable ergodic sum capacity.A simple yet effective solution to this problem is presented by designing a channel extrapolator relying on Karhunen-Loeve(KL) expansion of timevarying channels.In this scheme,channel estimation is done at the base station(BS) rather than at the user terminal(UT),which thereby dispenses the channel parameters feedback from the UT to the BS.Moreover,the inherent channel correlation and the parsimonious parameterization properties of the KL expansion are respectively exploited to reduce the channel mismatch error and the computational complexity.Simulations show that the presented scheme outperforms conventional schemes in terms of both channel estimation mean square error(MSE) and ergodic capacity.

NOVEL RADAR SIGNAL SORTING METHOD BASED ON GEOMETRIC COVERING

With the increase of complexity of electromagnetic environment and continuous appearance of advanced system radars,signals received by radar reconnaissance receivers become even more intensive and complex.Therefore,traditional radar sorting methods based on neural network algorithms and support vector machine(SVM) cannot process them effectively.Aiming at solving this problem,a novel radar signal sorting method based on the cloud model theory and the geometric covering algorithm is proposed.By applying the geometric covering algorithm to divide input signals into different covering domains based on their distribution characteristics,the method can overcome a typical problem that it is easy for traditional sorting algorithms to fall into the local extrema due to the use of complex nonlinear equation to describe input signals.The method uses the cloud model to describe the membership degree between signals to be sorted and their covering domains,thus it avoids the disadvantage that traditional sorting methods based on hard clustering cannot deinterleave the signal samples with overlapped parameters. Experimental results show that the presented method can effectively sort advanced system radar signals with overlapped parameters in complex electromagnetic environment.

Performance Analysis of Optimal Demodulation for APK Without Constellation Knowledge

In this paper,a novel demodulation algorithm without constellation knowledge ( CK) for Amplitude-Phase Keying ( APK) signals is introduced,which is based on the minimum probability of symbol error ( MPSE) criterion,optimal in performance and suitable for non-cooperative communication. For reducing the complexity,an on-line algorithm is derived. Using preceding algorithms,asymptotic performance of the proposed algorithm is proved theoretically. Numerical simulations are also provided to validate the analytical results. Our study of asymptotic performance shows that the performance of demodulation for any APK signals without CK is identical with the APK optimal receiver with CK when the number of available data symbols goes to infinity.

Detecting hydrosonic signal using a polarization technique

Some optical fiber hydrophones, such as PGC Mach-Zehnder Interferometer, have a birefringence of single mode optical fibers which induce signal fading. Especially, if two optical beams from the optical arms are orthogonal, the interferomic signal can’t be detected at all. Here a new method is introduced. This is to translate the detected phase difference into a linearly polarized angle, then detect it, so that polarization inducing signal fading will be avoided. In theory, this problem is solved. Furthermore, the effect on measurement results from optical source fluctuation becomes little when using the polarization technique.

APPLICATION OF TURBO CODES IN HIGH-SPEED REAL-TIME CHANNEL

The time delay of Turbo codes due to its iterative decoding is the main bottleneck of its application in real-time channel. However, the time delay can be greatly shortened through the adoption of parallel decod-ing algorithm, dividing the received bits into several sub-blocks and processing in parallel. This letter mainly discusses the applicability of turbo codes in high-speed real-time channel through the study of a parallel turbo decoding algorithm based on 3GPP-proposed turbo encoder and interleaver in various channel. Simulation re-sult shows that, by choosing an appropriate sub-block length, the time delay can be obviously shortened with-out degrading the performance and increasing hardware complexity, and furthermore indicates the applicability of Turbo codes in high-speed real-time channel.

Research on Carrier Synchronization of QPSK Based on Simulink

As an important part of the communication system, synchronization technology is a communication system to run the correct protection, has been a hot topic in communication systems research. Four-phase phase shift keying (QPSK) circuit structure is relatively simple, and has a good band utilization, in the modern communication has a wide range of applications. Corresponding research on carrier synchronization for QPSK coherent demodulation is carried out. By comparing several carrier recovery loops, The quaternary loose tail loop is selected as carrier recovery loop. First of all, the core part of the digital phase-locked loop analysis and implementation, and finally through the tool Simulink to complete the realization of the system.

A Non-Maximally Decimated Dynamic Reconfigurable Channelized Structure Based on Modulated Filter Bank

A structure of dynamic reconfigurable channelized filter bank is proposed in order to solve the problem that the uniform channelized receiver cannot receive the cross-channel and wideband signal. The dynamic reconfigurable channelized filter bank is divided into two parts-the analysis filter bank and the synthesis filter bank. The function of the analysis filter bank is to divide the received signal into several sub-signals according to the channel division. Then the sub-signals of each channel need to be detected and discriminated. At last, we use the sub-signals to reconstruct the original received signal by the synthesis filter bank. The analysis filter and the synthesis filter bank of the dynamic reconfigurable channelized filter bank are all efficient polyphase structures, so it can save more hardware resources and has extensive applicability. The structure is simulated by MATLAB and the simulation results verify the correctness of this structure.

Extracting Knowledge from On-Line Forums for Non-Obstructive Psychological Counseling Q&A System

Psychological counseling Q&A system is enjoying a remarkable and increasing popularity in recent years. Knowledge base is the important component for such kind of systems, but it is difficult and time-consuming to construct the knowledge base manually. Fortunately, there emerges large number of Q&A pairs in many psychological counseling websites, which can provide good source enriching the knowledge base. This paper presents the method of knowledge extraction from psychological consulting Q&A pairs of on-line psychological counseling websites, which include keywords, semantic extension and word sequence. P-XML, which is the knowledge template based on XML, is also designed to store the knowledge. The extracted knowledge has been successfully used in our non-obstructive psychologycal counseling system, called P.A.L., and the experimental results also demonstrated the feasibility and effectiveness of our approach.

Improving the Ability of Predictive Thinking

Improving the ability of predictive thinking is conducive in seeking the future and mastering initiative.In order to improve the ability of predictive thinking,it is necessary to strengthen the spirit of active exploration to give full play to people's subjective initiative.Scientific methodology is the basis for improving this ability.It is necessary to learn and apply dialectical materialist methodology and to master advanced methods in specific subject areas.A deep and broad knowledge system is the fundamental for the development of predictive thinking,hence a deep professional knowledge system and a broad multifield knowledge reserve must be formed.The development of science and technology provides traction in discovering new forecasting directions,more advanced tools for forecasting research,and philosophical epistemological guidance for forecasting.Therefore,there is a need to pay great attention to the development of science and technology.

Real-Time Underwater Image Enhancement Using Adaptive Full-Scale Retinex

Current Retinex-based image enhancement methods with fixed scale filters cannot adapt to situations involving various depths of field and illuminations.In this paper,a simple but effective method based on adaptive full-scale Retinex(AFSR)is proposed to clarify underwater images or videos.First,we design an adaptive full-scale filter that is guided by the optical transmission rate to estimate illumination components.Then,to reduce the computational complexity,we develop a quantitative mapping method instead of non-linear log functions for directly calculating the reflection component.The proposed method is capable of real-time processing of underwater videos using temporal coherence and Fourier transformations.Compared with eight state-of-the-art clarification methods,our method yields comparable or better results for image contrast enhancement,color-cast correction and clarity.

Integrating deep learning to achieve phase compensation for free-space orbital-angular-momentum-encoded quantum key distribution under atmospheric turbulence

A high-dimensional quantum key distribution(QKD), which adopts degrees of freedom of the orbital angular momentum(OAM) states, is beneficial to realize secure and high-speed QKD. However, the helical phase of a vortex beam that carries OAM is sensitive to the atmospheric turbulence and easily distorted. In this paper, an adaptive compensation method using deep learning technology is developed to improve the performance of OAM-encoded QKD schemes. A convolutional neural network model is first trained to learn the mapping relationship of intensity profiles of inputs and the turbulent phase, and such mapping is used as feedback to control a spatial light modulator to generate a phase screen to correct the distorted vortex beam. Then an OAM-encoded QKD scheme with the capability of real-time phase correction is designed, in which the compensation module only needs to extract the intensity distributions of the Gaussian probe beam and thus ensures that the information encoded on OAM states would not be eavesdropped. The results show that our method can efficiently improve the mode purity of the encoded OAM states and extend the secure distance for the involved QKD protocols in the free-space channel, which is not limited to any specific QKD protocol.