Ground Based Synthetic Aperture Radar (GB-SAR) is an effective tool for regional deformation detection, it has the ability of continuous monitoring for a certain area day and night regardless of the weather condition. ASTRO (Advanced Scannable Two-dimensional Rail Observation system) is a GB-SAR system constructed by Institute of Electronics Chinese Academy of Sciences (IECAS). In order to make out the deformation detection performance of ASTRO, GB-SAR imaging geometry is presented, the deformation detection model and the analysis of error sources are derived in this paper. The deformation detection error sources are analyzed using precise deformation geometry. Finally, a deformation detection experiment is carried out using ASTRO, and the results demonstrate the ability of deformation detection.

The micro-Doppler (m-D) effect is introduced for the Multi-Input Multi-Output (MIMO) radar techniques in the paper. Taking rotating target for an example, the m-D effect is analyzed and the parameterized expression is deduced in MIMO radar which transmits OFD-LFM (Orthogonal Frequency Division Linear Frequency Modulation) signals. An algorithm for three-dimensional micro-motion feature extraction is proposed, which extends the m-D signature extraction from the micro-motion projection in Line-Of-Sight (LOS) to the three-dimensional micro-motion feature. By taking advantage of the multi-view of MIMO radar, the three-dimensional micro-motion features are obtained by solving nonlinear multivariable equation systems. Simulation results validate the effectiveness and robustness of the algorithm.

Traditional approaches, such as the Displaced Phase Center Antenna (DPCA) and Along Track Interferometer (ATI), fail to mitigate the negative impact on the detection of?a target and the estimation of the parameters due to the defocus problem associated with the target’s azimuth velocity. In addition, these two approaches also fall short in estimating the target’s azimuth velocity. To solve above problems, this paper proposes a multi-channel moving target detection method which combines the time-frequency analysis method of Modified Discrete Chirp-Fourier Transformation (MDCFT) and dechirp technology. Through accurately estimating?a moving target's doppler parameters, the proposed method can realize the focusing of?the moving target. As a result, the accuracy of estimation on the moving target’s radical velocity, azimuth position, as well as azimuth velocity can be significantly improved. In all, the proposed method can overcome the disadvantages of the traditional DPCA and ATI approaches, and the e fectiveness of the proposed method is proved through both theoretic analysis and compute simulation.

With the sparistiy of the target space, a novel migration imaging algorithm for the stepped-frequency GPR based on compressive sensing is proposed in this paper. The new imaging algorithm removes the direct wave in frequency domain in advance, estimates the regulation parameter with cross validation algorithm, and images the subsurface with sparistiy constraint. The simulation and experimental data show that the new imaging algorithm is effective and practical.

Template-based ATR algorithm needs the storage of massive templates of the targets, which cause a heavy burden of system design and algorithm optimization. On the contrary, model-based algorithm can overcome this drawback and become a promising solution of the next generation ATR system. A new algorithm based on CSAR raw echo of the targets is proposed by applying the SBR (Shooting and Bouncing Rays) method onto the 3D CAD model of the targets, then the recognition procedure is completed via online prediction of the hypothetic targets. The predicted SAR image of the target is more accurate and efficient comparing with the traditional scattering center approach. The simulate experiments validate the proposed method and compare it with the traditional methods.

Based on general MUSIC algorithm, an elevation angle and multipath fading coefficient of the target joint estimation algorithm is proposed in VHF multipath environment. In this algorithm, a virtual multipath fading coefficient is derived from the array covariance matrix and search angles, then a subspace is formed by this coefficient and search angles. When this subspace is orthogonal to the noise subspace, DOA angles are achieved. Simultaneously, the corresponding coefficient is multipath fading coefficient. While overcoming multipath effects to elevation angle measurement, this method retains antenna aperture, and does not require a special antenna array configuration. Theoretical analysis and computer simulation results demonstrate the merits of the new algorithm.

Owing to its fixed revisit period, space-borne SAR is suitable for dynamic monitoring the ground information, and change detection is the key processing technology. In this paper Edgeworth approach is used to fit the statistical distribution model of SAR image in different kind of scenes and the Kullback-Leibler divergence is proposed as a measurement of the difference between two SAR images. The idea of integral image is used to improve the calculation efficiency. The difference image is segmented to extract the changed regions, this approach is demonstrated feasible according to the processing test using real satellite SAR image.

The high resolution imaging of near field targets are interesting for security, non-destructive control and biomedical application. In this paper, high resolution near field ISAR imaging is implemented using Ultra Wide Band (UWB) time domain radar system. Simulation and experiment are both conducted. The target is rotated by turntable. The system is built based on the UWB pulse source, UWB antennas, high performance sampling oscillograph, synchronous trigger pulse and proper motion study data acquisition software. Experiment condition and delay errors compensation method are presented to obtain accurate echo information of the target. And Back Projection (BP) combined with background cancel algorithm is discussed considering the clutter interference in time window. High resolution (8 mm) image is obtained, which exactly represents the position, shape and size of target.

Because of large pixel value change between multitemporal UWB SAR images caused by different imaging geometries, the performance of change detection algorithm based on pixel value difference declines quickly. In order to deal with this problem, a new UWB SAR foliage target change detection algorithm based on local statistic distribution is proposed. In the algorithm, the Gram-Charlier expansion theory and rank order filter are combined to estimate local statistic distribution. Then, the K-L divergence is used to measure the change between local statistic distribution of multitemporal UWB SAR image. And the target can be detected because of large K-L divergence value. Finally, the experimental results show that the algorithm can better deal with the pixel value change between multitemporal UWB SAR images with different imaging geometries and an obvious performance improvement on detection can be obtained.

Two-dimensional fusion of multi-radar signals is a new parameterized imaging method. It can remarkably improve image resolution. In the case of wide bandwidth and small angle observation, scattering of target dependents on frequency. Traditional fusion methods are inapplicability to this case. A new fusion method of multi-radar signals based on GTD model is proposed in this paper, and signal fusion is transformed into a signal sparse representation problem. Then regularization method is used to estimate parameters of scattering model. It dispenses with the step of two-dimensional decoupling, and estimates frequency-dependent factors of target scattering accurately by signal sparse representation. The experiments also show the validity of the method.

In some applications, a target needs to be located by a small-sized mobile platform, such as plane or ship. In this paper, the target is located by a small-sized mobile platform assisted by an array in the base station, which could work together under two modes: Multiple-Input Multiple-Output (MIMO) mode and Multiple-Input Single-Output (MISO) mode. The geometric model is established. Also, the Geometrical Dilution Of Precision (GDOP) of the relative coordinating errors of the target are formulated and factors affecting GDOP are analyzed under the two modes respectively. Simulation results show that: under MIMO mode, the GDOP is irrelevant neither to the azimuth of the target nor to the location of the small mobile platform; the location precision under MIMO mode is higher than that under MISO mode when the small mobile platform is far from the target or the number of array elements is large; however, lower when the small mobile platform is close to the target and the number of array elements is small.

In order to identify the circular oil depots from remote sensing images, a developed Hough transform method based on gradient information is proposed to extract circular oil tanks firstly. Then, the depth-first graph search strategy is employed to group the detected circles and eliminate the false alarms according to the spatial distribution of the oil depots. Finally, the target areas of oil depots are localized. The improved Hough transform reduces the time and space consumption by using the gradient direction information and reducing the dimension of parameter space, and improves the efficiency of circles detection. The graph search strategy can exclude the false targets and locate the target areas, which improves identification accuracy. The experimental results indicate that the proposed algorithm can recognize the oil depots targets fast and accurately, which is suitable for optical remote sensing images of different spatial resolutions.

An algorithm of real-time detecting and correcting cycle slips for Precise Point Positioning (PPP) is presented. Based on dual-frequency pseudorange and carrier-phase observations, the algorithm can be used for static positioning and dynamic navigation under vigorous ionosphere activity. In order to ensure real-time capability and veracity, data processing and signal processing are combined and a method of reasonableness verification is presented to lower the probability of misjudge. A practical application is also presented to prove the applicability of the algorithm in strong ionospheric influence.

This paper presents a fast real-time multi-target detection algorithm based on line target clustering. Adaptive threshold is applied to image segmentation; And then enclosing rectangle prosthetics, line target extraction and clustering merger are utilized for the binary image to implement full-field pixel-level targets detection and conduct ID tag. So undetected problems caused by the traditional detection algorithm can be avoid; Finally, a five points square predictor and cost function are constructed for trajectory matching, by which the problems of multi-target division, cross, temporarily lost due to overlap and so on are effectively resolved. The experiments are carried on SOPC hardware platform and the results show that the proposed algorithm can perform real-time detection accurately for the deep-space objects.

In order to improve side-lobe performance, traditional filter banks have to increase order number. In this paper Generalized Side-Lobe Canceller (GSC) is introduced to cancel strong jamming signals from side-lobes of filter banks, which can place zeros at stop band adaptively. The matrix form of this adaptive algorithm is provided, based on LMS algorithm. The length of the canceller coefficients is confined so the canceller just cancels strong jamming signals, with little influence on pass band signals. This method realizes the function of high-order filter banks through low-order filter banks and especially suited for weak signal detection. The simulation analysis indicates that it reduces computation quantity relative to high-order filter banks but maintains the same performance.

A numerically robust and low-complexity method of signal subspace estimation is proposed in the paper. The transform matrix to tridiagonalize the covariance matrix of observation data is constructed in the forward recursion of multistage Wiener filter (MSWF), and its columns span the signal subspace. Compared with the traditional method of correlation subtractive structure, the forward recursion in the method is implemented with the Householder unitary transform. Therefore, it strengthens significantly the orthogonality of basis vectors in the signal subspace and improves the numerical robustness, especially in the finite-precision implementation. Besides, a method of calculating the transform matrix is proposed to reduce the computational complexity based on the unitary property of the Householder matrix and backward accumulation of matrices. Finally, simulation results demonstrate the numerical robustness and computational efficiency of the proposed method.

A fourth-order cumulant-based DOA estimation method is presented, considering contradictions between direction finding precision and phase ambiguity in using non-uniform linear array to estimate the Direction Of Arrival (DOA). The new algorithm uses baseline ratio to solve ambiguity, and the constrain that the length of the displacement vectors joining the reference sensors must be less than half-wavelength of the signal is not need, thus accuracy of direction finding is effectively improved. According to the tripartite relationship among steering vector, the eigenvalues of the cumulant matrices and the eigenvectors corresponding to the eigenvalues, the phase differences of each baselines and the signals are automatically paired in the algorithm. The performance of the algorithm is effectively demonstrated with simulation.

With the analysis of the ambiguity function for Discrete Frequency Code Waveform (DFCW) signals, the optimized model for DFCW design is established and the Micro swarm Particle Swarm Optimization (MicPSO) algorithm is proposed to design orthogonal discrete frequency-coding waveforms. As an arrangement issue, the DFCW design is optimized by using Grefenstette coding as MicPSO particle code. The simulated results show that, the DFCW’s Auto-correlation Sidelobe Peak (ASP) and Doppler tolerance are mainly determined by the length of coded signal, and the cross correlation properties is greatly improved based on the optimization method described in this paper. Compared with existing methods, the proposed method can save processing time and obtain better optimization results.

Based on simplified electromagnetic vector-sensor array, a new Dimension Reduction Quaternion MUSIC (DR-QMUSIC) algorithm is proposed. In this paper, the quaternion algebra is first introduced since the orthogonality of quaternion is suitable for describing the orthogonal structure of electromagnetic vector-sensor very well. Then, the quaternion model of simplified electromagnetic vector-sensor array is established, and the DOA of polarized signals is estimated by employing the DR-QMUSIC algorithm. Inserting the estimated DOA into the traditional V-MUSIC algorithm, the polarization parameters of polarized signals are estimated. Thus, four unknown parameters of polarized signals are obtained. The simulation experiments are given to validate the proposed algorithm.

Practical speech emotions as impatience and happiness are studied especially for evaluation of emotional well-being in real world applications. Induced natural speech emotion data is collected with a computer game, 74 emotion features are extracted, prosody features and voice quality features are analyzed according to dimensional emotion model, evaluation and selection of acoustic features are carried out for practical emotions in this paper, a method of practical speech emotion classification with rejection decision is proposed for real world occasions. The experiment results show, the speech features analyzed in this paper are suitable for classification of practical speech emotions like impatience and happiness, average recognition rate is above 75%, and the method of emotion classification with rejection decision is necessary for the proper recognition decision of ambiguous or unknown emotion samples, especially for the real world challenges.

This paper proposes a novel object detection method, namely the BPSO-SVM-based detection algorithm that combines Binary Particle Swarm Optimization (BPSO) and Support Vector Machine (SVM) techniques to cope with feature selection issue for object detection under complex scenarios. In the proposed algorithm, object detection is regarded as a two-class categorization problem and feature subset is selected using a wrapper model, in which the BPSO searches the whole feature space and a SVM classifier serves as an evaluator for the goodness of the feature subset selected by the BPSO. Using the proposed BPSO-SVM-based feature selection scheme, feature dimensionality is reduced and classification performance of the SVM classifier is greatly enhanced. Experimental results show the increase on detection accuracy of the proposed algorithm for object detection in complex backgrounds with pose, scale, illumination variations and partial occlusions as well as the significant improvement on detection speed.

Time series approximation representation and similarity measurement is one of the fundamental tasks in time series data mining, and the key to similarity matching. In view of shortcomings of various existing PLR (Piecewise Linear Representation) based similarity measure approaches, like series-length dependent issue and potential recognition error under multi-resolution, a radian based time series piecewise linear representation and radian-distance based similarity measurement are presented to cater for the rapid online segmentation and similarity calculation in this paper. The proposed method is really simple but intuitive, it retains major shape features of the series by using segment radian for fine grained division, and effectively improves the accuracy and reliability of the measurement under multi-resolution. This method is segmentation algorithm independent and can be further applied to similarity query, pattern matching, classification and clustering for time series.

Question retrieval plays important role in question and answering systems. The main problem is how to measure the similarity between candidate questions and query question. This paper presents a tree kernel based method, named weighted tree kernel, to calculate the similarity of sentences’ structures and proposes improvements to the original tree kernel algorithm. In order to reduce the effect on tree kernel bringing by syntactic parsing, a composite kernel is proposed based on the weighted tree kernel and two other string kernels, which can capture syntax, part-of-speech and lexical level information of a sentence, to calculate the semantic similarity between question sentences. Experimental results on Yahoo!Answers dataset show that the proposed method outperforms traditional vector space model based methods by 24.02% in question retrieval accuacry.

In order to reduce the staircasing error of Yee’s leap-frog meshing and accurately model three- dimensional curved conducting objects, a new Conformal MultiResolution Time-Domain (CMRTD) method based on Daubechies’ scaling functions is proposed by combining the MultiResolution Time-Domain (MRTD) algorithm with the Conformal Finite-Difference Time-Domain (CFDTD) algorithm. This paper puts forward to decompose the MRTD update equation based on Daubechies’ scaling functions into a linear combination of several conventional Finite-Difference Time-Domain (FDTD) update equations. Then locally conformal technology is applied to the FDTD decomposition equation on the innermost loop. Finally, all decomposition equations are linearly combined into the CMRTD result. Simulation results show that CMRTD can not only preserve MRTD’s advantages of saving of computational resources and high computational efficiency, but also enhance computational precision obviously.

The reciprocity of Wuhan-Wanning and Wanning-Wuhan ionospheric HF channel is firstly analyzed by using Wuhan Ionospheric Oblique Incidence Sounding System (WIOISS). The WIOISS is a new type ionospheric oblique sounding radar based on the GPS time and frequency synchronization. The group delay and HF channel scattering function between the two ways is compared through the swept-frequency mode and fixed-frequency mode. Accordingly, based on the experiment results the Wuhan-Wanning link and Wanning-Wuhan link have a good reciprocity.

In this article, based on a coupled cavity TWT design software, Orprogr code, the simulation design of a X band coupled cavity TWT is performed for realizing the expected electric characteristics. Under the condition of the above-mentioned design results, a depressed collector is designed with the minimum collector efficiency of 71.5% and the electron beam may relatively evenly spreads on the surface of each sub-area of the depressed collector. Then the influence of laminar flow, electrode shape, voltage drop and electrical field on the distribution of the beam is discussed by analyzing the spreading of electron beam on the surface of each sub-area of the depressed collector.

The sheet beam with a large width-high ratio is nonaxisymmetrical, which is very suitable to the formation of the electron beam in high power microwave and millimeter wave vacuum devices. In this paper, a 2D macroparticle model is proposed for developing a program to study the sheet beam transmission. The transmission of the sheet beam in an uniform magnetic field and Periodic Cusped Magnetic (PCM) field is discussed, and the calculation results are compared with the single particle model and 3D PIC software, which show good agreement with 3D PIC software’s and the computation time is greatly reduced.

With the widespread use of mobile devices, issues like roaming authentication and identification privacy become increasingly prominent. This paper analyses the shortcomings of existing protocols of roaming authentication in term of anonymity and security that these protocols can not guarantee at the same time anonymity of mobile terminals and the filtration of illegal request. Based on elliptic-curve cryptography and proxy signature, a new anonymous protocol that allows a pair of proxy signature keys to be shared among some mobile devices randomly is proposed. Through analysis and verification using AVISPA, it shows that the new protocol realizes anonymity, the filtration of illegal request, mutual authentication and secure distribution of session key. It not only improves the security, but also reduces the computational load, which makes it more suitable for mobile devices with limited power.

By changing sharing and recovering ways of the verification image, a verifiable Visual Cryptography Scheme (VCS) based on iterative algorithm is proposed in this paper. Since the verification image is shared with special algorithms, and the verification process is optimized through iterative algorithm, the proposed scheme not only makes the pixel expansion much smaller, but also improves the checking efficiency greatly. Furthermore, verification images are perfectly recovered by the XOR operation introduced.

 Web service selection based on QoS is still challenging because the multiple QoS registration centers and heterogeneous QoS models make decision-making hard. Based on Multi-Attribute Group Decision-Making (MAGDM) theory, this paper presents a novel Multiple Registration centers and Heterogeneous QoS model’s Web Service Selection Algorithm (MRHQ_WSSA) to solve the above difficulties for the first time. Through evaluating the QoS information of all QoS registration centers, MRHQ_WSSA can obtain the synthetically optimal composition plan. It includes five main steps: normalizing the user’s QoS preference, calculating the group preference, weighting normalized decision-matrix, determining group ideal solution and calculating the relative closeness to the group ideal solution. And a set of experiments demonstrate the benefits and effectiveness of the approach.

Semiring algebra can be used to compute the trustworthiness between nodes, for it is a good description of the trustworthiness calculation rules issues. However, the existing semiring trust model does not define dynamic issues based on time. A semiring trust model based on the adaptive forgetting scheme is proposed to describe the dynamic of trust, and improve the existing semiring trust model, making up for its shortcoming of not defining dynamic issues. Simulation results show that proposed trust model distinguishes effectively between normal nodes and malicious nodes and resists on-off attacks, which improves the security of Ad hoc networks.

The large scale and high speed networks create massive data and have low detection accuracy. To address the problems, the idea “module” is brought from complex network into anomaly detection area. Firstly, the relations between network partition strategy and network detection accuracy are modeled, and a theoretically proof is given that partition strategy which based on network modularity is favorable for anomaly detection. Secondly, the module-based detection is proved that has higher detection rate and efficiency than network-based detection by theoretical analysis and experiments. Finally, by using flow-splitting and parallel processing technologies this approach can improve efficiency obviously.

In this paper, the definition of joint k-error 2-adic complexity is first proposed, as well as joint k-error 2-adic complexity is used to measure the stability of 2-adic complexity of periodic multisequences. Then some enumeration results are derived for two kinds of joint error 2-adic complexity and the lower bounds are presented for their expected values of m-fold multisequences of period N, which 2^N-1=p,p₁p₂, respectively. Furthermore, it is showed that the formula 2^N-1=p^e(e>1), has no solution. The results are important for studying the stability of joint 2-adic complexity of multisequences.

A new distinguishing attack is presented on Shannon algorithm. The distinguish attack is built by using linear approximations of both the non-linear feedback shift register and the non-linear filtration function, and 32 distinguishers are derived which the bias is 2^-28. Therefore, the Shannon algorithm is distinguishable from truly random cipher after observing 2⁵² keystreams words on average.

Impossible differential attack should be launched with the construction of impossible difference. This paper investigates the construction method of impossible differences for (2n,r,t)_GFNSP overall structure. A kind of (4n+1)-round impossible differences and the construct method with computation complexity O(n²r¹⁰) are presented. And this paper provides the structure of (4n+1)-round impossible differences against the DSM strategy which is proposed by Shirai et al..

An Incremental Coded Bi-directional Relaying (ICBR) scheme based on network coding and space-time cooperation is proposed, which utilizes the feedback information from nodes in the system. Cooperation in this way could improve resource efficiency and network throughput. The outage probabilities and the network-coding gain of different bi-directional relaying schemes are developed and analyzed. The numerical results show that compared with the other two schemes, ICBR scheme brings three-order diversity gain in fast fading channels and higher coding gain in slow fading channels. Furthermore, the theoretical results are verified with the simulation results.

Channel capacities and sensing parameters for Secondary Users (SUs) based on Opportunistic Spectrum Access (OSA) technique are studied in this paper. First, characteristics of the Signal-to-Interference-and-Noise Ratio (SINR) of SUs are discussed, from which the expressions about the average SINR are derived under interference and non-interference cases. Then, the influences of SINR on the channel capacity under OSA mode are discussed. After that, the data frame length and the detection frequency are designed from the cross layer design  and stochastic characteristics of fading channels points of view. It can be seen from the analysis that the channel occupancy mode of the Primary Users (PUs) has influence on the SINR of SUs. It also has been proved that the scheme which joins the characteristics on the physical layer with occupancy mode of PUs, can reduce the collision probability between SUs and PUs. Meanwhile, it can improve the frequency efficiency of the system on the condition of meeting the required throughput of SUs.

Making use of the advantage of classical Low Density Parity Check (LDPC) codes based on Balance Incomplete Block Designs (BIBD), a novel construction of quantum LDPC codes is proposed in this paper. The constructed check matrix satisfies the requirement of self-dual quantum code with sparse ‘1’ element and has only one 4 girth in every two rows. The simulation results show that the quantum LDPC codes constructed by this method, such as GF(6t+1), GF(12t+1) have longer code length, more sparse check matrix and good performance than that of other method based on BIBDs.

Trivium has successfully been chosen as one of the final ciphers by eSTREAM. It has a simple and elegant structure. Although Trivium has attached a lot of interest, it remains unbroken. By finding more linear approximations, a linear cryptanalysis of 2-round Trivium is made by utilizing multiple approximations and a more efficient distinguishing attack is proposed. Compared with current single linear cryptanalysis, this method allows for a reduction in the amount of data required for a successful attack. That is to say, if n linear approximations can be found, this method can supply the success rate with 1/n of the data amount required by a simple linear cryptanalysis. This study shows that there are still some defects in the design of stream cipher Trivium, further safety analysis are needed before its going into the implementation.

The amount of information and the bit error rate caused by eavesdropper are analyzed while the BB84 quantum key distribution protocol is attacked with intercept/resend attack using different measurement bases. The bit error rate threshold that legitimate user used to determine intercept/resend eavesdropping attack is under 15%, and a new standard is provided for secure quantum communications and the detection of eavesdropper.

Since the bitrate of the whole block is determined by its maximum prediction error and much redundancy exists in the scalar coset coding based compression method for hyperspectral images，a lossless compression method based on classification and coset coding is proposed in this paper to further reduce the bitrate. The current block is classified using the corresponding prediction errors in the previous band to make the pixels with similar inter-band correlations cluster together. Then each class of pixels is then coset coded respectively. The experimental results show that the classification can reduce the bitrate efficiently. Compared to coset coding based method without classification, the lossless compression bitrate of the proposed method is reduced by about 0.4 bpp.

The aichitecture for the Beyond 3rd Generation or 4th Generation wireless nerworks aims at integrating various heterogeneous wireless access networks over an IP backbone. To provide seamless mobility, one of the design issues is the vertical handoff support. In this paper, a SINR (Signal to Interference plus Noise Ratio) and AHP (Analytic Hierarchy Process) based SAW (Simple Additive Weighting) (SASAW) vertical handoff algorithm is proposed, which uses the combined effects of SINR with SINR value from one network being converted to equivalent SINR value to the target network for getting the same data rate, user required bandwidth, user traffic cost and available bandwidth of the participating access networks to construct the attribute matrix and make handoff decisions for multi-attribute QoS consideration according to the features of the traffic. For performance evaluation, four traffic classed defined by 3GPP are considered. The weight relations of decision elements are determined by eigenvalue method of AHP to construct the comparison decision matrix, and then check its Consistency. The weight vector is then produced using the eigenvalue method according to the decision matrix. Finally, SAW algorithm is used to make decision according to the attribute matrix and weight vector. The performance of throughput, dropping probability, user traffic cost and the number of vertical handoff between different vertical handoff decision algorithms are compared. The results show that the proposed scheme can achieve excellent performance according to the characteristics of the traffic by considering the relations of multiple attributions synthetically.

Frame aggregation is one of the efficient methods to improve wireless channel utility of MAC (Media Access Control) and spectral efficiency. Aiming at multi-services, this paper adopts two-level buffer mechanism and polls each queue for aggregation according to aggregation weight factor. The aggregation weight factor of each queue is dynamically adjusted based on the packet overtime urgent factor defined to meet with the delay requirement of each QoS type of service. This paper introduces queue theory into the performance analysis of frame aggregation scheme. A mathematical analysis model is set up. Additionally, the relationship of main performance parameters and system load is quantificationally analyzed. Compared with the performance of the two-level aggregation scheme defined in IEEE 802.11n standard, the proposed scheme indicates the performance of the new frame aggregation scheme is more efficient than the two-level aggregation scheme defined in 802.11n standard.

Navigation message is an important component of satellite signal. Its design will not only influence the system’s performances including timeliness, integrality, flexibility, reliability, extendibility, etc., but also user’s use-cost. The design of various navigation messages is analyzed and compared, especially in aspects of data content, coding performance, layout structure and broadcast style of modernization Global Navigation Satellite System (GNSS). It is indicated that the improvements in the design of navigation message will bring improvement of system performance and make the user easy to use. The navigation message design scheme of China COMPASS system is put forward by consulting the message design schemes of modernization GNSS, which are: multi-coding scheme basing error correcting code, checking code and interleaving code; message layout structure of frame and data block together; intercrossed broadcasting style between or among satellites and frequencies.