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Guaranteeing Wireless Communication Reliability via an Extended Hybrid Carrier System

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China Communications 2023年第7期20卷 192-202页

作者： Ge Song Xiaojie Fang xuejun sha School of Electronics and Information Engineering Harbin Institute of TechnologyHarbin 150001China Engineering Research Center for Dedicated Communication System Ministry of EducationHarbin 150080China

In this paper,we propose an extended hybrid carrier system based on the weighted fractional Fourier transform to ensure the reliability of wireless *** proposed scheme improves the dispersion and compensation capabilities of the hybrid carrier system for channel fading through the design of the signal power distribution,which has greatly reduced the probability of high-power distortion of the signal and improved the bit error rate performance as a *** analysis has shown the superiority of the extended hybrid carrier *** a lower cost of computational complexity increment,the proposed scheme obtains a performance improvement without occupying additional time-frequency physical *** with the existing hybrid carrier scheme,numerical simulation results have shown that the proposed extended hybrid carrier scheme has better anti-fading performance under the doubly-selective channel and improves the reliability of the wireless communication system effectively.

关键词： extended hybrid carrier weighted frac-tional Fourier transform bit error rate doubly-selective channel

Guaranteeing Wireless Communication Secrecy via a WFRFT-Based Cooperative System

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China Communications 2015年第9期12卷 76-82页

作者： Fang Xiaojie sha xuejun Mei Lin Communication Research Center Harbin Institute of Technology

In this paper, a weighted fractional Fourier transform(WFRFT) based cooperative overlay system, aiming to guarantee physical layer(PHY) security, is proposed. The paper elaborates how WFRFT and physical layer properties of the wireless medium are collaborated to guarantee the secrecy of wireless transmissions. In the proposed system, WFRFT is first preform on the secret data, such that the transmitted signal is distorted and can only be neutralized by inverse-WFRFT with the same parameter. And then two streams of the transformed sequences that bearing different messages are cooperatively and simultaneously transmitted to two legitimate receivers via a beamforming-liked method, respectively. In general, both the rapid spatial decorrelation property and the inherent security features of WFRFT are leveraged, such that only the eavesdropper's is degraded, and hence, the wireless communication secrecy is reliably guaranteed. Numerical simulations are conducted to evaluate the performance of the proposed system in terms of the average bit error rate and the secrecy capacity.

关键词： weighted fractional Fourier trans-form(WFRFT) physical layer(PHY) security secrecy capacity

A Novel Receiving Method for Baseband DSSS Signal based on Phase Domain Processing

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China Communications 2010年第1期7卷 57-64页

作者： sha xuejun Zhan Zongchao Tang Xun Harbin Inst Technol Sch Elect & Informat Engn Harbin 150001 Heilongjiang Pr Peoples R China

In this paper, the phase characteristic disturbance model for baseband direct sequence spread spectrum (DSSS) signal in additive white Gaussian noise (AWGN) environment is established, and the probability density function (PDF) of phase characteristic disturbance is obtained. Then a novel receiver model for baseband DSSS signal based on maximum likelihood (ML) criterion is proposed. The simulation results show that, comparing with correlation scheme, the performance of the proposed method for baseband DSSS signal is 1dB worse in AWGN environment. However, if there is narrow interference in the AWGN environment, the proposed method will show better performance up to 2.5dB, and it has good adaptive resistance to narrowband interference located in different frequency points. This method could be used as an alterative communication scheme for military circumstance when existing strong narrowband interference of various frequencies.

关键词： phase domain processing phase characteristic disturbance ML criterion anti-narrow-band interference

MP-WFRFT and Constellation Scrambling Based Physical Layer Security System

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China Communications 2016年第2期13卷 138-145页

作者： FANG Xiaojie sha xuejun LI Yue Communication Research Center Harbin Institute of Technology

In this paper, a multiple parameters weighted fractional Fourier transform(MPWFRFT) and constellation scrambling(CS) method based physical layer(PHY) security system is proposed. The proposed scheme is executed by two steps. In the first step, MPWFRFT, implemented as the constellation beguiling(CB) method, is applied to change the signal's identity. In the second step the additional pseudo random phase information, regarded as the encryption key, is attached to the original signal to enhance the security. Typically, the pseudo random phase information can be removed effectively by the legitimate receiver. In contrast to the cryptography based encryption algorithms and the conventional PHY secrecy techniques, the main contribution of the proposed scheme is concentrated on the variation in signal's characteristics. Simulation results show that the proposed scheme can prevent the exchanging signal from eavesdroppers' classifi cation or inception. Moreover, the proposed scheme can guarantee the BER performance at a tolerate increasing in computational complexity for the legitimate receivers.

关键词： weighted fractional Fourier transform(WFRFT) physical layer (PHY) security secrecycapacity

BER analysis of STBC hybrid carrier system based on WFRFT with frequency domain equalization

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Science China(Information Sciences) 2018年第8期61卷 147-159页

作者： Zhenduo WANG Lin MEI xuejun sha Naitong ZHANG Communication Research Center Harbin Institute of Technology Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory

The inherent characteristic of hybrid carrier(HC) scheme based on the weighted-type fractional Fourier transform(WFRFT) is revealed. The proposed linear combination of single carrier(SC) and multicarrier’s(MC) characteristics is helpful to balance the conflicting requirements and achieve the comparative analysis of SC/MC. As an example, analytical SER/BER expressions of HC system with zero forcing(ZF)and minimum mean square error(MMSE) equalization are derived. In addition, the derived BER expressions are extended to multi-input systems. A unified framework of space time block code(STBC) HC scheme is proposed with two WFRFT modules at the transmitter or receiver, where STBC-SC and STBC-MC systems are the special cases of the novel structure.

关键词： single carrier multi-carrier weighted-type fractional Fourier transform hybrid carrier zero forcing minimum mean square error space time block code

Low complexity hybrid power distribution combined with subcarrier allocation algorithm for OFDMA

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Journal of Systems Engineering and Electronics 2011年第6期22卷 879-884页

作者： Weilin Jiang Zhongzhao Zhang xuejun sha Linan Sun School of Electronics and Information Engineering Harbin Institute of Technology Harbin 150080 R R. China

To improve the total throughput of the uplink orthogonal frequency division multiple access system,a low complexity hybrid power distribution（HPD） combined with subcarrier allocation scheme is *** the fairness mechanism for the subcarrier,the inter-cell interference is first analyzed to calculate the capacity of the *** user selects the subcarrier with the largest channel *** on the above subcarrier allocation scheme,a new kind of HPD scheme is proposed,which adopts the waterfilling-power-distributed scheme and the equal-power-distributed scheme in the cell-boundary and the cellcenter,*** results show that compared with the waterfilling-power-distributed scheme in the whole cell,the proposed HPD scheme decreases the system complexity significantly,meanwhile its capacity is 2% higher than that of the equal-powerdistributed scheme over the same subcarrier allocation.

关键词： orthogonal frequency division multiple access(OFDMA) inter-cell interference(ICI) hybrid power distribution(HPD) subcarrier allocation.

Low complexity bit loading algorithm for OFDM system

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Journal of Systems Engineering and Electronics 2006年第1期17卷 71-74页

作者： Yang Yu sha xuejun Zhang Zhonghua National Key Laboratory of Tunable Laser Technology Harbin Inst. of Technology Harbin 150001 P. R. China Communication Research Center Harbin Inst. of Technology Harbin 150001 P. R. China

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.

关键词： OFDM bit loading shannon formula QoS

8-Weighted-Type Fractional Fourier Transform Based Three-Branch Transmission Method

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China Communications 2018年第9期15卷 147-159页

作者： Jing Li xuejun sha Xiaojie Fang Lin Mei Communication Research Center Harbin Institute of Technology

To improve the bit error rate(BER) performance of multiple input multiple output(MIMO) systems with low complexity, a three-branch transmission scheme employing 8-weighted-type fractional Fourier transform(8-WFRFT) module is proposed. In the proposed scheme, the original signal is first decomposed into eight sub-signals and then merged into three component signals by the same carrier pattern. The three signals have mathematical constraint relations among themselves that can counteract the channel fading. They are simultaneously transmitted via three independent antennas after delay regulating. At the receiver, an inverse 8-WFRFT module is employed to obtain the estimated original signal by processing the received signal. Then, the bit error rate(BER) performance, transmitting power, transmission rate, power spectrum and computational complexity of the proposed scheme are analysed in detail. Numerical results show that the proposed scheme has a superior performance compared to STBC based three-antenna transmission scheme, in terms of BER performance.

关键词： 8-weighted-type fractional Fourier transform (8-WFRFT) bit error rate (BER) low complexity multiple input multiple output (MIMO)

Digital computation of the weighted-type fractional Fourier transform

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Science China(Information Sciences) 2013年第7期56卷 85-96页

作者： MEI Lin ZHANG QinYu sha xuejun ZHANG NaiTong Shenzhen Graduate School Harbin Institute of Technology Communication Research Center Harbin Institute of Technology

The paper reveals the time-frequency symmetric property of the weighted-type fractional Fourier transform (WFRFT) by investigating the original definition of the WFRFT, and proposes a discrete algorithm of the WFRFT based on the weighted discrete Fourier transform (WDFT) algorithm with constraint conditions of the definition of the WFRFT and time-domain sampling. When the WDFT is considered in digital computation of the WFRFT, the Fourier transform in the definition of the WFRFT should be defined in frequency (Hz) but not angular frequency (rad/s). The sampling period Δt and sampling duration T should satisfy Δt = T/N = 1/N(1/2) when N-point DFT is utilized. Since Hermite-Gaussian functions are the best known eigenfunctions of the fractional Fourier transform (FRFT), digital computation based on eigendecomposition is also carried out as the additional verification and validation for the WFRFT calculation.

关键词： fractional Fourier transform (FRFT) weighted-type fractional Fourier transform (WFRFT) chirp- type fractional Fourier transform (CFRFT) discrete fractional Fourier transform discrete Fourier transform (DFT)