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Parameter estimation of DSSS signals in non-cooperative communication system 认领 引用 被引量：3
1
作者 Zhang Xiaoming Zhang Zhongzhao 《Journal of Systems Engineering and Electronics》 SCIE EI 2007年第1期14-21,共8页
A new adaptive estimator for direct sequence spread spectrum （DSSS） signals using fourth-order cumulant based adaptive method is considered. The general higher-order statistics may not be easily applied in signal pr... A new adaptive estimator for direct sequence spread spectrum （DSSS） signals using fourth-order cumulant based adaptive method is considered. The general higher-order statistics may not be easily applied in signal processing with too complex computation. Based on the fourth-order cumulant with 1-D slices and adaptive filters, an efficient algorithm is proposed to solve the problem and is extended for nonstationary stochastic processes. In order to achieve the accurate parameter estimation of direct sequence spread spectrum （DSSS） signals, the fast step uses the modified fourth-order cumulant to reduce the computing complexity. While the second step employs an adaptive recursive system to estimate the power spectrum in the frequency domain. In the case of intercepted signals without large enough data samples, the estimator provides good performance in parameter estimation and white Gaussian noise suppression. Computer simulations are included to corroborate the theoretical development with different signal-to-noise ratio conditions and recursive coefficients. 展开更多
关键词 Four order cumulant Parameter estimation Adaptive estimator DSSS signal
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Deterministic simulation of UWB indoor propagation channel 认领 引用 被引量：2
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作者 Wang Yang Zhang Naitong +1 位作者 Zhang Qinyu Zhang Zhongzhao 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第3期447-452,共6页
A site-specific model of UWB pulse propagation in indoor environment is addressed. The simulation utilizes the principles of geometrical optics （GO） for direct and reflected paths＇ tracing and the time domain techn... A site-specific model of UWB pulse propagation in indoor environment is addressed. The simulation utilizes the principles of geometrical optics （GO） for direct and reflected paths＇ tracing and the time domain technique for describing the transient electromagnetic field reflected from wall, floor, ceiling, and objects. The polarization of the received waveform is determined by taking into account the radiation pattern of the transmitting and receiving antennas, as well as the polarization changes owing to every reflection. The model provides more intrinsical interpretations for UWB pulse propagation in realistic indoor environment. 展开更多
关键词 UWB time domain indoor propagation channel diffraction.
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Utility function based fair data scheduling algorithm for OFDM wireless network 认领 引用 被引量：3
3
作者 Guo Kunqi Sun Lixin Jia Shilou 《Journal of Systems Engineering and Electronics》 SCIE EI 2007年第4期731-738,共8页
A system model is formulated as the maximization of a total utility function to achieve fair downlink data scheduling in multiuser orthogonal frequency division multiplexing （OFDM） wireless networks. A dynamic subca... A system model is formulated as the maximization of a total utility function to achieve fair downlink data scheduling in multiuser orthogonal frequency division multiplexing （OFDM） wireless networks. A dynamic subcarrier allocation algorithm （DSAA） is proposed, to optimize the system model. The subcarrier allocation decision is made by the proposed DSAA according to the maximum value of total utility function with respect to the queue mean waiting time. Simulation results demonstrate that compared to the conventional algorithms, the proposed algorithm has better delay performance and can provide fairness under different loads by using different utility functions. 展开更多
关键词 OFDM scheduling algorithm utility function.
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Multi-constraint quality of service routing algorithm for dynamic topology networks 认领 引用 被引量：4
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作者 Wang Ping Chen Bingcai +1 位作者 Gu Xuemai Liu Gongliang 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第1期58-64,共7页
An adaptive multi-QoS routing algorithm called AMQRA is proposed for dynamic topology networks, such as satellite networks and Ad-hoc networks. The AMQRA is a distributed and mobile-agents-based routing algorithm, whi... An adaptive multi-QoS routing algorithm called AMQRA is proposed for dynamic topology networks, such as satellite networks and Ad-hoc networks. The AMQRA is a distributed and mobile-agents-based routing algorithm, which combines ant quantity system （AQS） with ant colony optimization （ACO） that is used in AntNet routing algorithm. In dynamic topology networks, the AMQRA achieves timely optimization for concave metric QoS constraint and fast convergence. The proposed routing algorithm is simulated in Iridium satellite constellation on OPNET. The results show that AMQRA not only outperforms the AntNet in convergence rate in dynamic topology networks but also can optimize concave metric QoS constraint and reasonably allot bandwidth to the load to avoid networks congestion. 展开更多
关键词 routing QoS dynamic topology networks
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Resource allocation for multiuser STBC-BF MIMO-OFDM downlink with imperfect channel information 认领 引用 被引量：1
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作者 Zhang Chengwen Liao Minghong +1 位作者 Zhang Zhongzhao Meng Weixiao 《Journal of Systems Engineering and Electronics》 SCIE EI 2009年第4期687-693,共7页
To improve the performance of a multiuser MIMO-OFDM system with imperfect channel status information, a downlink adaptive resource allocation algorithm which combines space-time block coding and beam forming （STBC-BF... To improve the performance of a multiuser MIMO-OFDM system with imperfect channel status information, a downlink adaptive resource allocation algorithm which combines space-time block coding and beam forming （STBC-BF） is proposed. The algorithm allocates the subcarriers with a shared manner. A zero forcing processing with joint Rx-Tx is used to suppress the co-channel interference （CCI） and to construct uncorrelated channels for STBC. An adaptive power allocation for the STBC equivalent channels can increase signal to interference and noise ratio at the receiver. Simulation results show that under the condition of an imperfect CSI, the proposed algorithm improves the system performance and reduces the number of BS transmit antennas required. 展开更多
关键词 resource allocation MIMO-OFDM multiuser STBC-BF CCI suppression
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Heuristic based data scheduling algorithm for OFDMA wireless network 认领 引用
6
作者 Guo Kunqi Sun Lixin +1 位作者 Jia Shilou Yu Xiaoyang 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第1期46-51,共6页
A system model based on joint layer mechanism is formulated for optimal data scheduling over fixed point-to-point links in OFDMA ad-hoc wireless networks. A distributed scheduling algorithm （DSA） for system model op... A system model based on joint layer mechanism is formulated for optimal data scheduling over fixed point-to-point links in OFDMA ad-hoc wireless networks. A distributed scheduling algorithm （DSA） for system model optimization is proposed that combines the randomly chosen subcarrier according to the channel condition of local subcarriers with link power control to limit interference caused by the reuse of subcarrier among links. For the global fairness improvement of algorithms, a global power control scheduling algorithm （GPCSA） based on the proposed DSA is presented and dynamically allocates global power according to difference between average carrier-noise-ratio of selected local links and system link protection ratio. Simulation results demonstrate that the proposed algorithms achieve better efficiency and fairness compared with other existing algorithms. 展开更多
关键词 orthogonal frequency division multiplexing access （OFDMA） scheduling algorithm ad-hoc
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Resource allocation with CCI suppression for multiuser MIMO-OFDM downlink in correlated channels 认领 引用 被引量：1
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作者 Zhang Chengwen Zhang Zhongzhao Ma Yongkui 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第2期213-219,共7页
To minimize the overall transmit power while maintaining a constant data rate and target BER,a downlink adaptive resource allocation algorithm with jointing the exclusive manner and the shared manner is proposed for m... To minimize the overall transmit power while maintaining a constant data rate and target BER,a downlink adaptive resource allocation algorithm with jointing the exclusive manner and the shared manner is proposed for multiuser MIMO-OFDM system in correlated channels.The algorithm allocates all the subcarriers to different users according to their spatial correlations.The users with high spatial correlation are allocated in the same group and the exclusive manner is applied.The shared manner with an improved null broadening method,which improves the performance of co-channel interference(CCI)suppression and decreases the number of transmit antennas required,is applied between the different group users.As the user's direction of departure(DOD)changes very slowly,a looking up table method is used to reduce the computational complexity.The simulation results show that despite the angle spread of DOD,when compared with the exclusive manner,the proposed algorithm improves the spectral efficiency,and when compared with the TDMA-ZF(zero forcing)shared manner,the proposed algorithm decreases the total transmit power by at least 1 dB. 展开更多
关键词 resource allocation MIMO-OFDM multiuser CCI suppression zero forcing null broadening.
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Research on handover algorithm to reduce the blocking probability in LEO satellite network 认领 引用 被引量：1
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作者 Chen Bingcai Zhang Naitong +1 位作者 Nie Boxun Zhou Tingxian 《Journal of Systems Engineering and Electronics》 2006年第1期30-36,共7页
Based on the characteristics of guaranteed handover （GH） algorithm, the finite capacity in one system makes the blocking probability （PB） of GH algorithm increase rapidly in the case of high traffic losd. So, when... Based on the characteristics of guaranteed handover （GH） algorithm, the finite capacity in one system makes the blocking probability （PB） of GH algorithm increase rapidly in the case of high traffic losd. So, when large amounts of multimedia services are transmitted via a single low earth orbit （LEO） satellite system, the PB of it is much higher. In order to solve the problem, a novel handover scheme defined by multi-tier optimal layer selection is proposed. The scheme sufficiently takes into account the characteristics of double-tier satellite network, which is constituted by LEO satellites combined with medium earth orbit （MEO） satellites, and the multimedia transmitted by such network, so it can augment this systematic capacity and effectively reduces the traffic loed in the LEO which performs GH algorithm. The detailed processes are also presented. The simulation and numerical results show that the approach integrated with GH algorithm achieves a significant improvement in the PB and practicality, as compared to the single LEO layer network. 展开更多
关键词 satellite handover double-tier satellite network LEO MEO GH algorithm multi-tier optimal layer selection.
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Low complexity bit loading algorithm for OFDM system 认领 引用 被引量：1
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作者 Yang Yu Sha Xuejun Zhang Zhonghua 《Journal of Systems Engineering and Electronics》 2006年第1期71-74,共4页
A new approach to loading for orthogonal frequency division multiplexing （OFDM） system is proposed, this bit-loading algorithm assigns bits to different subchannels in order to minimize the transmit energy. In the a... A new approach to loading for orthogonal frequency division multiplexing （OFDM） system is proposed, this bit-loading algorithm assigns bits to different subchannels in order to minimize the transmit energy. In the algorithm, first most bit are allocated to each subchannels according to channel condition, Shannon formula and QoS require of the user, then the residual bit are allocated to the subchannels bit by bit. In this way the algorithm is efficient while calculation is less complex. This is the first time to load bits with the scale following Shannon formula and the algorithm is of O （4 N） complexity. 展开更多
关键词 OFDM bit loading Shannon formula QoS
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Investigating path loss characteristics of UWB signals in vacancy indoor environment based on time-domain technique 认领 引用 被引量：3
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作者 Wang Yang Zhang Naitong 《Journal of Systems Engineering and Electronics》 2006年第2期296-302,共7页
The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced ... The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced to compute reflection coefficient in a very short time interval. A 5 rays path loss calculation method, which is satisfactory accurate, is developed. 5 typical environments are involved to analyze and generalize the common path loss characteristics in vacancy indoor environment. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponent as distance between transmitter and receiver increasing. 展开更多
关键词 UWB path Loss time-domain multipath indoor environment.
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Simplified calculation of UWB signal transmitting through a finitely conducting slab 认领 引用
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作者 Wang Yang Zhang Naitong Zhang Qinyu Zhang Zhongzhao 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第6期1070-1075,共6页
A simplified closed-form analytic solution for UWB impulse signal transmitting through a finitely conducting slab is proposed. The approach first requires evaluating the impulse response of the slab and then convolvin... A simplified closed-form analytic solution for UWB impulse signal transmitting through a finitely conducting slab is proposed. The approach first requires evaluating the impulse response of the slab and then convolving it with the specified incident field waveform. To obtain the impulsive transmitting field, either for vertical or horizontal polarization, approximations to the refraction coefficients and propagation loss are made, which can be proved to be accurate enough, comparing with their frequency domain solutions. Thereby, it permits simplified closed-form expressions in the time domain for both terms. The resulting transient response for the transmitting impulse field is then given by convolution of the time domMn refraction coefficients and time domain propagation loss. A numerical example of an incident monocyele transmitting through a slab using this technique, is presented, to illustrate the effective use of the method. 展开更多
关键词 ultra-wide band time domain indoor propagation channel multipath.
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Novel evaluation method of TCP performance over satellite links 认领 引用
12
作者 Wang Lina Gu Xuemai 《Journal of Systems Engineering and Electronics》 2006年第2期462-466,F0003,共5页
A novel and efficient method to evaluate the transmission control protocol （TCP） performance over satellite links is presented. A TCP module is divided into three functional blocks, namely data processing, congestio... A novel and efficient method to evaluate the transmission control protocol （TCP） performance over satellite links is presented. A TCP module is divided into three functional blocks, namely data processing, congestion control and error control The re-established TCP module is easy to update TCP congestion control strategy or error control strategy. With the proposed analysis approach, the interactions between different congestion control and error control mechanisms, as well as the performanee of various combination protocols in satellite environments have been investigated. Simulation results obtained through a series of experiments have shown that SNACK-based error control strategy can perform well with any other congestion control strategy. The best performanee can be achieved by TCP NewReno congestion control strategy and SNACK-based error control strategy. 展开更多
关键词 geostationary satellites transmission control protocol congestion control error control.
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Link reliability based hybrid routing for tactical mobile ad hoc network 认领 引用 被引量：3
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作者 Xie Xiaochuan Wei Gang +2 位作者 Wu Keping Wang Gang Jia Shilou 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第2期259-267,共9页
Tactical mobile ad hoc network （MANET） is a collection of mobile nodes forming a temporary network, without the aid of pre-established network infrastructure. The routing protocol has a crucial impact on the network... Tactical mobile ad hoc network （MANET） is a collection of mobile nodes forming a temporary network, without the aid of pre-established network infrastructure. The routing protocol has a crucial impact on the network performance in battlefields. Link reliability based hybrid routing （LRHR） is proposed, which is a novel hybrid routing protocol, for tactical MANET. Contrary to the traditional single path routing strategy, multiple paths are established between a pair of source-destination nodes. In the hybrid routing strategy, the rate of topological change provides a natural mechanism for switching dynamically between table-driven and on-demand routing. The simulation results indicate that the performances of the protocol in packet delivery ratio, routing overhead, and average end-to-end delay are better than the conventional routing protocol. 展开更多
关键词 tactical mobile ad hoc networks hybrid routing link reliability edge weight.
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Adaptive compensating method for Doppler frequency shift using LMS and phase estimation 认领 引用 被引量：7
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作者 Jing Qingfeng Guo Qing 《Journal of Systems Engineering and Electronics》 SCIE EI 2009年第5期913-919,共7页
The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the ph... The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the phase offsets due to frequency shift are linear. Based on this premise, the compensation processes are： firstly, the phase offsets between the baseband neighbor-symbols after clock recovery is unbiasedly estimated among the reference symbols; then, the receiving signals symbols are adjusted by the phase estimation value; finally, the phase offsets after adjusting are compensated by the least mean squares （LMS） algorithm. In order to express the compensation processes and ability clearly, the quadrature phase shift keying （QPSK） modulation signals are regarded as examples for Matlab simulation. BER simulations are carried out using the Monte-Carlo method. The learning curves are obtained to study the algorithm＇s convergence ability. The constellation figures are also simulated to observe the compensation results directly. 展开更多
关键词 Doppler frequency shift least mean square minimum phase shift keying unbiased estimation Matlab simulation.
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Target searching based on modified implicit ROI encoding scheme 认领 引用
15
作者 Bai Xu Zhang Zhongzhao 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第5期888-892,共5页
An EBCOT-based method is proposed to reduce the priority of background coefficients in the ROI code block without compromising algorithm complexity. The region of interest is encoded to a higher quality level than bac... An EBCOT-based method is proposed to reduce the priority of background coefficients in the ROI code block without compromising algorithm complexity. The region of interest is encoded to a higher quality level than background, and the target searching time in video-guided penetrating missile can be shortened. Three kinds of coding schemes based on EBCOT are discussed. Experimental results demonstrate that the proposed method shows higher compression efficiency, lower complexity, and good reconstructed ROI image quality in the lower channel capacity. 展开更多
关键词 video-guided penetrating bomb implicit ROI EBCOT.
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Deconvolution techniques for characterizing indoor UWB wireless channel 认领 引用
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作者 Wang Yang Zhang Naitong Zhang Qinyu Zhang Zhongzhao 《Journal of Systems Engineering and Electronics》 SCIE EI 2008年第4期688-693,共6页
A deconvolution algorithm is proposed to account for the distortions of impulse shape introduced by propagation process. By finding the best correlation of the received waveform with the multiple templates, the number... A deconvolution algorithm is proposed to account for the distortions of impulse shape introduced by propagation process. By finding the best correlation of the received waveform with the multiple templates, the number of multipath components is reduced as the result of eliminating the ＂phantom paths＂, and the captured energy increases. Moreover, it needs only a single reference measurement in real measurement environment （do not need the anechoic chamber）, which by far simplifies the templates acquiring procedure. 展开更多
关键词 ultra-wide band channel model CLEAN algorithm CIR deconvolution.
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Efficient enhancing scheme for TCP performance over satellite-based internet 认领 引用
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作者 Wang Lina Gu Xuemai 《Journal of Systems Engineering and Electronics》 SCIE EI 2007年第1期177-182,共6页
Satellite link characteristics drastically degrade transport control protocol （TCP） performance. An efficient performance enhancing scheme is proposed. The improvement of TCP performance over satellite-based Interue... Satellite link characteristics drastically degrade transport control protocol （TCP） performance. An efficient performance enhancing scheme is proposed. The improvement of TCP performance over satellite-based Interuet is accomplished by protocol transition gateways at each end of a satellite link. The protocol which runs over a satellite link executes the receiver-driven flow control and acknowledgements- and timeouts-based error control strategies. The validity of this TCP performance enhancing scheme is verified by a series of simulation experiments. Results show that the proposed scheme can efficiently enhance the TCP performance over satellite-based Internet and ensure that the available bandwidth resources of the satellite link are fully utilized. 展开更多
关键词 Geostationary satellites Protocol transition gateway Transport control protocol
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