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25 August 2006, Volume 27 Issue 8

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Overview

Current development of satellite communications technology

Zhong-min GAN,Geng-xin ZHANG

2006, 27(8):  2-9.  doi:1000-436X(2006)08-0002-08

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A summary and review about some hot points in current satellite communications technology was given. Firstly, the associated concept and developments of broadband satellite communication were introduced, then the main technical issues that need to be solved was proposed, and examples of the typical application were given. Secondly, based on the introduction of current developments about mobile satellite communication, the characteristics and key technology were studied. Finally, the basic concept of space communication network was introduced, the network composition and individual function were given, and some new technology that need to be developed was analized.

Academic paper

Fairness based channel borrowing strategy for multimedia LEO satellite communications

Fei HUANG,Hui XU,Shi-qi WU

2006, 27(8):  10-17.  doi:1000-436X(2006)08-0010-08

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A LEO satellite mobility model and user multimedia traffic model was built firstly, then a novel channel bor-rowing strategy (CBS) was proposed and its performance was evaluated and compared with several existing channel al-location schemes through computer simulation. Simulation results show this scheme can satisfy the QoS requirement of LEO satellite multimedia service very well, at the same time, keeping resource utilization high, finally discussed the fair-ness and system performance under three different channel borrowing strategies.

Delay constraint minimum interruption routing algorithm for mobile satellite network

Tao ZHANG,Zhong-kan LIU,Jun ZHANG

2006, 27(8):  18-24.  doi:1000-436X(2006)08-0018-07

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By the analysis of the characteristics of mobile satellite network, such as a long delay and a topological time-varying, a novel satellite network delay constraint optimal path (SDCOP) algorithm, which could obtain a path to sat-isfy the delay constraint condition as well as the minimization of interruption during the service, was proposed. This algo-rithm exploits the predictive nature of connectivity changes of time-varying topological to decrease the influence in the QoS routing performance caused by the handover. Besides, it has a low computing complexity to adapt to the restricted computing capability of satellite equipments. Correlative simulation indicates that this novel algorithm is superior to other current algo-rithm in respect of computing complexity, service blocking probability and interrupting probability etc.

Design of regional coverage satellite system with common-track constellation

Ting-yong WU,Li-dong ZHU,Shi-qi WU

2006, 27(8):  25-30.  doi:1000-436X(2006)08-0025-06

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A design method for implementing regional coverage satellite communication system with medium earth orbit (MEO) common-track constellation (CTC) was studied. A coded notation which can describe CTC entirely was proposed and some optimal constellation schemes for China were presented. Moreover, the parameters of these constellations were adjusted again according to the time-varying traffic distribution density, which improved the consistency between the coverage performance of constellations and the traffic distribution density. The simulation results show that CTC can provide favorable coverage performance to China area with fewer satellites.

Adaptive fuzzy filter algorithm for LEO communication channel estimation

Yong-ning ZHUO,Li-dong ZHU,Shi-qi WU

2006, 27(8):  31-34.  doi:1000-436X(2006)08-0031-04

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A novel adaptive LMS filter algorithm based on fuzzy rules was proposed. Through building many fuzzy sets over the space of channel gained value and the increment value of channel gain, in addition to the setting of fuzzy rules, an adaptive algorithm incorporated with human experience was set up, which was adaptive to the time_varing character-istics of LEO satellite channel. The results of the simulation validate the algorithm.

Study on satellite adaptive nulling antennas with hybrid genetic algorithm

Jun JIN,Hua-li WANG,Tao DUAN,Yun-zhi LIU

2006, 27(8):  35-40.  doi:1000-436X(2006)08-0035-06

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Combining genetic algorithm with LMS, a hybrid genetic algorithm (GA_LMS) for satellite adaptive nulling antenna beam space was proposed. The hybrid algorithm performance of various parameter selections was studied. At last a simultaneous parameter adaptation scheme was introduced. The scheme could reduce difficulty and improve effi-ciency of parameter selection and can dynamically adjust the parameters for better anti-jamming performance.

Separation algorithm of paired carrier multiple access based on independent component analysis

Jian WAN,Hua XU,Zhong-liang ZHU

2006, 27(8):  41-44.  doi:1000-436X(2006)08-0041-04

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Based on the introduction of paired carrier multiple access(PCMA) technology, a new algorithm was proposed to separate the satellite PCMA downlink mixed signals with independent component analysis(ICA). The new algorithm utilized maximum negentropy as the separating criterion which could overcome the limitation that the power of two up-link signals could not be different too much. The computer simulations testified the validity of the algorithm.

Topological dynamics analysis of Walker-constellation satellite networks

Chun-dong SHE,Jun-feng WANG,Li-xiang LIU,Ming-tian ZHOU

2006, 27(8):  45-51.  doi:1000-436X(2006)08-0045-07

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The dynamical activates of low earth orbit (LEO) Walker constellation satellite network topologies was quanti-fied. The number and length of network snapshots were formulated concisely. It compensates for the simplified topologi-cal assumptions in many LEO satellite network related investigations. The thorough understanding of this basic feature not only provides for an accurate quantification of network behavior, but also guides future constellation design for satel-lite networks.

Algorithm of passive “Beidou” /INS closed-loop integrated using two level filter

Fa-qin GAO,Zhan-zhong TAN

2006, 27(8):  52-56.  doi:1000-436X(2006)08-0052-05

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One scheme of integrated navigation Kalman filter positioning algorithm was put forward to apply to “Beidou”and INS integrated navigation system. Using the pseudo-range's velocity of changing as observations, on the basis of the high stable clock, a closed loop Kalman filtering model that can revise the attitude error of INS was put out, its biggest optimism was that it could change between the close-loop method and open-loop method steadily. Finally, by computer simulation, it explain that our scheme improve the positioning precision effectively when the satellites in sight are less then two ones, and it also show that our scheme can revise the attitude error of INS effectively and estimate the user's velocity in high precision.

Interferometric signal simulation of spaceborne InSAR system

Zao-yu SUN,Dian-nong LIANG,Xing-qiang LU,Yong-sheng ZHANG

2006, 27(8):  57-61.  doi:1000-436X(2006)08-0057-05

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In order to supply data to the signal processing study of spaceborne InSAR system, the interferometric signal simulation was studied. At first the geometric model, backscattering model and signal model needed by the simulation was analyzed. Using these models the simulation process was given. Then the relationship between facet number and correlation coefficient was analyzed. The analysis shows that by using right facet number the simulated signal can inter-fere and the correlation coefficient can near its theoretic value. Simulated results can validate this method.

Optimization of regional coverage satellite constellations based on ant colony algorithm

Jiao-long WEI,Zhao-hui CEN

2006, 27(8):  62-66.  doi:1000-436X(2006)08-0062-05

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First, an optimization model of constellation parameters aimed at improving coverage performance was built. Second, defining the new strategy of sorting and transferring based on Continuous space, Ant colony algotithm (ACA) was improved, the particular case that multi-objects could not be compatible was also included, and an optimization framework was proposed. Finally, the simulation results demonstrate the effect of ACA, which can improve the efficiency of optimization.

Research on PAPR reduction scheme in QAM-OFDM satellite communication system

Chen ZHANG,Yao-wen FU,Er-yang ZHANG

2006, 27(8):  67-72.  doi:1000-436X(2006)08-0067-06

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Orthogonal frequency division multiplexing (OFDM) has high spectral efficiency and high tolerance to multi-path fading that make it a very attractive technique for satellite communication. But the problem of high peak-to-average power ratio (PAPR) of OFDM signal limits the application in satellite communication systems. In order to satisfy the re-quirements of high speed data rate and high reliability transmission of satellite communication, a novel PAPR reduction scheme for quadrature amplitude modulated (QAM) OFDM signal, namely partial trellis shaping was proposed and the BER performance of QAM-OFDM satellite communication system over AWGN, frequency selective Rician fading channel was analyzed. Simulation results show that the scheme can not only reduce the PAPR effectively, but also im-prove the system BER performance greatly when combing error control coding.

Research on positioning precision testing methods in GPS continuously operating reference station system

Wei-ming TANG,Yi-dong LOU,Hui LIU,Ri-gao CHEN,Qiu YANG

2006, 27(8):  73-77.  doi:1000-436X(2006)08-0073-05

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The positioning precision testing methods of CORS were introduced in detail. Based on the testing method of static fixed point and the method of comparing with the post-processing positioning result, land and regular geometrical track kinematic testing method and fixed baseline length relative testing method were put forward. The testing resulted of a CORS system obtained with the former three methods show that the proposed method are valid and fit to the general precision testing of most CORS system.

Technical Report

Rain attenuation distribution characteristic of Ka band satellite communication

Jian KANG,Yu-fei WANG

2006, 27(8):  78-81.  doi:1000-436X(2006)08-0078-04

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Using the ITU-R rain attenuation forecasting model, and based on the rainfall data and the geographic location parameters of main cities in our country,the isograms of rain attenuation distribution for the communication satellite with the orbital location 92° E in Ka band (30/20GHz) was presentd. A further analysis was made on the rain attenuation char-acteristic of the Ka band satellite communication system by integrating with the landform and the climate distribution pattern in our country. The results could be used as the theoretical basis when designing the Ka band satellite communica-tion system.

Study on demodulating multi-channel FDMA/FSK signals on board based on FFT

Ke-gang PAN,Bang-ning ZHANG,Dao-sheng GUO

2006, 27(8):  82-86.  doi:1000-436X(2006)08-0082-05

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An algorithm was proposed to demodulate multi-channel FDMA/FSK signals based on fast Fourier trans-form(FFT). The algorithm was analysed in detail theoretically, and it was proved that the performance is the same as that of FSK with ideal non-coherent detection, and it also presented a method of estimating the frequency offset using FFT. Then the system was simulated, which validates the analysis. The algorithm is easy to be realized and is suitable for processing on board.

Adaptive algorithm to compensate varying group_delay

Zhi-xing YANG,Yong-jun DENG,Chang-yong PAN,Jian SONG

2006, 27(8):  87-92.  doi:1000-436X(2006)08-0087-06

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A simple and effective adaptive algorithm was proposed to compensate varying group delay in data transmission employing baseband signal processing. Based on the structure of an all-digital parallel receiver (APRX), the algorithm util-ized the gradient descent (GD) algorithm to iteratively minimize the cost function of constant modulus algorithm (CMA), and updates the coefficients of group delay compensator. Simulation results show that the group delay can be effectively and adaptively compensated by the proposed algorithm, where the closed eye-diagram is opened successfully.

GPS signal fast acquisition algorithm using differential code and block processing techniques

Lei HUANG,Qi-shan ZHANG,Yan-hong KOU

2006, 27(8):  93-97.  doi:1000-436X(2006)08-0093-05

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A novel GPS signal acquisition algorithm using differential C/A codes and block processing techniques was proposed. It was integrated with the advantages of serial correlation method in the time domain, differential digital matched filter method and block processing techniques in the frequency domain, and realized a good compromise be-tween acquisition time and resources consumption, which not only improved the acquisition speed but also reduced the hardware consumption while maintaining an identical processing gain. The experiment results show the algorithm can work well.

Bit error rate performance analysis of TCM-8PSK system based on band-limited nonlinear satellite channel

Jing LI,Zhen-fang LIU,Ai-hong LI,Rong-jun SHEN

2006, 27(8):  98-103.  doi:1000-436X(2006)08-0098-06

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The performance of error probability for TCM-8PSK over the band-limited nonlinear satellite channel was de-rived firstly. Then, the dynamic simulation tool —— Simulink included in Matlab was used to simulate and verify the derivation result and the optimal working point for QPSK and TCM-8PSK were found under the condition of Saleh nonlinear model. Finally, the equalization algorithm used to improve the effects of nonlinear distortion was presented and at the same time the performance was simulated. The results of derivation and simulation show that it is necessary to study of TCM-8PSK for nonlinear satellite channel.

Novel key management and authentication scheme for ad hoc space networks

De-ming YANG,De-jun MU,Zhong XU

2006, 27(8):  104-107.  doi:1000-436X(2006)08-0104-04

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To be implemented using a flexible distributed architecture consisting of a constellation of dynamically de-ployed or configured satellites that were networked together into an integrated information system, the satellites could form an ad hoc self-organizational network, which posed unique challenges to security for the network. A novel and flexible security architecture was proposed, which aimed to provide public key infrastructure and authentication scheme. Based on the absolute distributed certificate authority almost any standard public-key-based authentication protocol could be adopted directly. In cases where the space nodes involved were extremely limited in computational resources, a light-weight authentication scheme that provided integrity and confidentiality based on cryptographic hash functions and symmetric key cryptography was proposed.

Research on a fuzzy adaptive state estimator for INS/GPS integrated navigation system

Xin-long WANG

2006, 27(8):  108-112.  doi:1000-436X(2006)08-0108-05

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A fuzzy adaptive state estimator was proposed and the configuration was given, and how to use it to estimate navigation parameters and to replace the extended Kalman filtering were studied. The fuzzy adaptive state estimator was to use the Kalman filtering to configurate a fuzzy reasoning process, and to train fuzzy reasoning through neural networks, and it automatically adjusted parameters of a fuzzy system by input and output samples. Consequently, the optimum navigation parameters of the INS/GPS integrated could be estimated. The simulation results show if it to use the fuzzy logic adaptive state estimator to initial alignment of the navigation system, then the alignment time is reduced consid-erably.

Short essay

Research on secure routing algorithm in satellite networks

Zhe LI,Jun LIU

2006, 27(8):  113-118.  doi:1000-436X(2006)08-0113-06

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The key technologies in satellite networks security were researched. A security routing algorithm was proposed. By static configuration combining together with dynamic adjustment, the algorithm realized dynamic routing. Based on the credence model, the security mechanism was added. When it found there was malicious behavior in the network, it would react actively. It effectively guaranteed the security of satellite networks and protectd the network from kinds of attacks.

Adaptive routing strategy in multi layer satellite communication networks

Hui LI,Xue-mai GU

2006, 27(8):  119-128.  doi:1000-436X(2006)08-0119-10

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The characteristics of multi-coverage of multilayer satellite networks make sure of good validity and reliability of the space-based networks. Walker delta type constellation guarantees permanent inter satellite links between satellites in the same layer and provides nonpermanent inter orbit links, both of which make an autonomic satellite backbone. Un-der statistic model of traffic flow from global perspective, multilayer satellite networks consider path delay and ISL link weight adopt adaptive routing strategy and bear more reliability. Compare with single layer satellite networks, multilayer satellite networks distribute traffic more evenly and have smaller percent of lost packet, network normalized link load and total path weight of special path, which do favor to decreasing percent of blocking probability of network and the special path.

Research on design of permanent inter-satellite-links in satellite networks

Zhen-yong WANG,Ping WANG,Xue-mai GU,Qing GUO

2006, 27(8):  129-133.  doi:1000-436X(2006)08-0129-05

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Based on constellation designation, conditions of permanent inter-satellite-links were analyzed in order to solve problems of continual handoff caused by relative movements of satellites in different orbits in satellite networks. A scheme to design constellations with permanent inter-satellite-links was proposed, and conditions to maintain in-ter-satellite-links were analyzed. By simulations, results are shown and examples are introduced for verification.

New MAC protocol for broadband multimedia satellite networks

Jian-you LIU,Qing GUO,Gong-liang LIU

2006, 27(8):  134-138.  doi:1000-436X(2006)08-0134-05

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A new MF-TDMA based MAC protocol, called CRRAP (combined reservation and random access protocol), was proposed for broadband multimedia satellite networks. It adopted combined random and piggy-backed reservation, combined demand assignment and free assignment. Simulation results show that CRRAP can reduce end-to-end delay in high system load situation, which contribute to throughput performance. In addition, it achieves high bandwidth utiliza-tion.

Networking model and traffic analysis for integrating ad hoc and LEO satellite terminals

Xiao-yan WANG,Hao WANG,Yan DONG,Zai-lu HUANG

2006, 27(8):  139-143.  doi:1000-436X(2006)08-0139-05

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The compromise between the utilization rate of valuable satellite channels and the blocking probability of new call was hardly to achieve. Enlightened by the advantages of ad hoc networking, a new scheme was proposed which al-lowed the terminals to work in alternative mode according the instructions from the satellite's signaling channel, meaned to communicate with other terminals in ad hoc mode when they were in a distance shorter than the maximum ad hoc communication distance and when the system was in busy state or in normal satellite communication mode when the system was idle. So the overflow traffic in nearer distance might get serviced with ad hoc mode and the system's parame-ters was improved. Simulation results show that the proposed scheme has decreased the realistic call blocking probability and increased the valid channel utility rate of the system.

Academic communication

Research on integrated navigation system by rubidium clock

Ting-jun LI,Xue-yuan LIN,Wen-hong DONG,Jun-hai QIU

2006, 27(8):  144-147.  doi:1000-436X(2006)08-0144-04

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On the basis of introducing the limitations of the double-star positioning system, the precision rubidium clock was put forward to be the internal clock of the RDSS receiver. If the receiver could measure the pseudo-ranges from the user to the satellites, with the help of barometer, the RDSS could be integrated with the strap-down inertial navigation system based on pseudo-range. The simulation result shows that the output navigation parameters of the integrated sys-tem have the characteristic of low error, which offers one new way to develop our country's RDSS.

Study on the application of IGSO into mobile satellite communication

Geng-xin ZHANG,Su-dan LI,Zhong-min GAN

2006, 27(8):  148-154.  doi:1000-436X(2006)08-0148-07

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The related coverage performance, Doppler shift and service-supporting capability of the IGSO constellation was studied for the given area. The results show that, the constellation, which consists of two or three IGSO satellites, can achieve good coverage characteristics (the percent of time of one and more satellites coverage and average elevation an-gle) to the Chinese and nearby area with small Doppler shift. The link budget shows that, adopting IGSO can effectively solve the low elevation angle problem faced by GEO satellite, and similar performance, which can only be implemented by a very big GEO satellite, can be achieved by two or three relatively small IGSO satellites. So the solution of adopting IGSO to provide mobile satellite communication system is technically feasible.

Design and simulation of the control circuit for a CMOS imaging sensor with high resolution and dual shutter mode

Chi ZHANG,Shi-jie YU,Zheng YOU

2006, 27(8):  155-159.  doi:1000-436X(2006)08-0155-05

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A CMOS imaging sensor with high resolution and dual shutter mode for space information acquisition was presented. The theoretical operation principles and characters of rolling shutter and synchronous shutter for the CMOS imaging sensor were analyzed and compared. Design of the control circuit for two shutter modes were proved correct and effective, by analyzing the results from timing simulation and experimental verification. It is concluded that the design of the control circuit is suitable for imaging system on nano-satellite.

Cloud removal from satellite imagery based on SUSAN algorithm

Li LU,Yong-tao WANG,Jin-wen TIAN,Jian LIU

2006, 27(8):  160-164.  doi:1000-436X(2006)08-0160-05

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A new image fusion scheme that could automate remove the cloud covers in the main image was proposed based on SUSAN algorithm. First, the corners were found both in the main image and the reference image based on SUSAN algorithm, and then the matched corners were found using probabilistic relaxation algorithm to register the ref-erence image to the main image. Finally, a cloud-removed image was obtained by fusion. The performance of the pro-posed scheme is demonstrated experimentally.