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BER Performance Analysis of OTFS Systems with Power Allocation

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China Communications 2023年第1期20卷 24-35页

作者： Zhenduo Wang Zhipeng Liu Zhiguo Sun Xiaoyan Ning College of Information and Communication Engineering Harbin Engineering UniversityHarbin 150001China

Orthogonal time frequency space(OTFS),as a novel 2-D modulation technique,has been proposed to achieve better BER performances over delayDoppler channels.In this paper,we propose two different power allocation(PA)algorithms in OTFS systems with zero forcing(ZF)or minimum mean square error(MMSE)equalization,where general formulas with PA are derived in advance under the condition of minimum BER(MBER)criterion.On one hand,a suboptimal MBER power allocation method is put forward to achieve better BER performances,and then analytical BER expressions are derived with proposed PA strategy.Considering the case of MMSE equalization,a combined subsymbol allocation(SA)and PA strategy is raised,where some subsymbols may be abandoned due to worse channel conditions,and then it is proven effectively to improve BER performances through theoretical and simulation results.Furthermore,BER performances with proposed joint SA and PA strategy are also investigated in delay-Doppler channels,where an improved message passing(MP)receiver based on equivalent channel matrix with PA is given.

关键词： OTFS PA ZF MMSE BER analysis

Data-Driven Deep Learning for OTFS Detection

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China Communications 2023年第1期20卷 88-101页

作者： Yi Gong Qingyu Li Fanke Meng Xinru Li Zhan Xu School of Information Communication and Engineering Beijing Information Science and Technology UniversityBeijing 100876China School of Economics and Management Xi’an University of Posts and TelecommunicationsXi’an 710100China Tianjin Yinyuan Information Technology CO. LTD.Tianjin 300202China

Recently,orthogonal time frequency space(OTFS)was presented to alleviate severe Doppler effects in high mobility scenarios.Most of the current OTFS detection schemes rely on perfect channel state information(CSI).However,in real-life systems,the parameters of channels will constantly change,which are often difficult to capture and describe.In this paper,we summarize the existing research on OTFS detection based on data-driven deep learning(DL)and propose three new network structures.The presented three networks include a residual network(ResNet),a dense network(DenseNet),and a residual dense network(RDN)for OTFS detection.The detection schemes based on data-driven paradigms do not require a model that is easy to handle mathematically.Meanwhile,compared with the existing fully connected-deep neural network(FC-DNN)and standard convolutional neural network(CNN),these three new networks can alleviate the problems of gradient explosion and gradient disappearance.Through simulation,it is proved that RDN has the best performance among the three proposed schemes due to the combination of shallow and deep features.RDN can solve the issue of performance loss caused by the traditional network not fully utilizing all the hierarchical information.

关键词： data-driven deep learning OTFS detection

Intelligent Blind Source Separation Technology Based on OTFS Modulation for LEO Satellite Communication

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China Communications 2022年第7期19卷 89-99页

作者： Chengjie Li Lidong Zhu Cheng Guo Tao Liu Zhen Zhang The Key Laboratory for Computer Systems of State Ethnic Affairs Commission School of Computer Science and Technology(Southwest Minzu University)Chengdu 610000China National Key Laboratory of Science and Technology on Communications(University of Electronic Science and Technology of China) Chengdu 610000China College of Computer Science(Sichuan University) Chengdu 610000China

In LEO(Low Earth Orbit)satellite communication system,the orbit height of the satellite is low,the transmission delay is short,the path loss is small,and the frequency multiplexing is more effective.However,it is an unavoidable technical problem of the significant Doppler effect caused by the interference between satellite networks and the high-speed movement of the satellite relative to the ground.In order to improve the target detection efficiency and system security of LEO satellite communication system,blind separation technology is an effective method to process the collision signals received by satellites.Because of the signal has good sparsity in Delay-Doppler domain,in order to improve the blind separation performance of LEO satellite communication system,orthogonal Time-Frequency space(OTFS)modulation is used to convert the sampled signal to Delay-Doppler domain.DBSCAN clustering algorithm is used to classify the sparse signal,so as to separate the original mixed signal.Finally,the simulation results show that the method has a good separation effect,and can significantly improve the detection efficiency of system targets and the security of LEO satellite communication system network.

关键词： LEO Doppler effect Delay-Doppler domain OTFS DBSCAN clustering algorithm

Transmit Diversity Scheme Design for Rectangular Pulse Shaping Based OTFS

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China Communications 2022年第3期19卷 116-128页

作者： Dong Wang Bule Sun Fanggang Wang Xiran Li Pu Yuan Dajie Jiang State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 00044China vivo Mobile Communication Co. Ltd.Beijing 100016China

This paper investigates the transmission scheme of the orthogonal time frequency space(OTFS)system with multiple antennas.Previous works have studied the multi-antenna transmitter diversity scheme with the ideal pulse shaping in OTFS systems assuming the wireless channels of two consecutive frames duration are invariant.However,the ideal pulse shaping can not be realized in practice and the channel varies rapidly in two consecutive frames in the high-speed mobility scenarios.To this end,we redesign the multi-antenna transmitter diversity scheme to ensure its practicability in the rectangular-pulsebased OTFS systems.At first,the information symbols of each antenna are divided into two half frames along the Doppler domain.Then,the guard symbols are carefully arranged to eliminate the interference between two half frames,and to ensure the equivalent channels of two half frames being identical.By considering the positions of the guard symbols,the transmission codeword is designed and a low complexity linear detection is proposed.Finally,simulation results validate that the bit error rate performance of the proposed scheme has the superiority over the existing works.

关键词： guard symbols multiple antennas OTFS transmit diversity

Joint Multi-Domain Channel Estimation Based on Sparse Bayesian Learning for OTFS System

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China Communications 2023年第1期20卷 14-23页

作者： Yong Liao Xue Li School of Microelectronics and Communication Engineering Chongqing UniversityChongqing 400044China

Since orthogonal time-frequency space(OTFS)can effectively handle the problems caused by Doppler effect in high-mobility environment,it has gradually become a promising candidate for modulation scheme in the next generation of mobile communication.However,the inter-Doppler interference(IDI)problem caused by fractional Doppler poses great challenges to channel estimation.To avoid this problem,this paper proposes a joint time and delayDoppler(DD)domain based on sparse Bayesian learning(SBL)channel estimation algorithm.Firstly,we derive the original channel response(OCR)from the time domain channel impulse response(CIR),which can reflect the channel variation during one OTFS symbol.Compare with the traditional channel model,the OCR can avoid the IDI problem.After that,the dimension of OCR is reduced by using the basis expansion model(BEM)and the relationship between the time and DD domain channel model,so that we have turned the underdetermined problem into an overdetermined problem.Finally,in terms of sparsity of channel in delay domain,SBL algorithm is used to estimate the basis coefficients in the BEM without any priori information of channel.The simulation results show the effectiveness and superiority of the proposed channel estimation algorithm.

关键词： OTFS sparse Bayesian learning basis expansion model channel estimation

OTFS-Based Efficient Handover Authentication Scheme with Privacy-Preserving for High Mobility Scenarios

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China Communications 2023年第1期20卷 36-49页

作者： Dawei Li Di Liu Yu Sun Jianwei Liu School of Cyber Science and Technology Beihang UniversityBeijing 100191China

Handover authentication in high mobility scenarios is characterized by frequent and shortterm parallel execution.Moreover,the penetration loss and Doppler frequency shift caused by high speed also lead to the deterioration of network link quality.Therefore,high mobility scenarios require handover schemes with less handover overhead.However,some existing schemes that meet this requirement cannot provide strong security guarantees,while some schemes that can provide strong security guarantees have large handover overheads.To solve this dilemma,we propose a privacy-preserving handover authentication scheme that can provide strong security guarantees with less computational cost.Based on Orthogonal Time Frequency Space(OTFS)link and Key Encapsulation Mechanism(KEM),we establish the shared key between protocol entities in the initial authentication phase,thereby reducing the overhead in the handover phase.Our proposed scheme can achieve mutual authentication and key agreement among the user equipment,relay node,and authentication server.We demonstrate that our proposed scheme can achieve user anonymity,unlinkability,perfect forward secrecy,and resistance to various attacks through security analysis including the Tamarin.The performance evaluation results show that our scheme has a small computational cost compared with other schemes and can also provide a strong guarantee of security properties.

关键词： high mobility condition handover authentication privacy-preserving Tamarin OTFS

Radar Sensing via OTFS Signaling

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中国通信:英文版 2023年第9期20卷 34-45页

作者： Kecheng Zhang Zhongjie Li Weijie Yuan Yunlong Cai Feifei Gao Department of Electronic and Electrical Engineering Southern University of Science and TechnologyShenzhen 518055China College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Department of Automation Tsinghua UniversityBeijing 100084China

By multiplexing information symbols in the delay-Doppler(DD)domain,orthogonal time frequency space(OTFS)is a promising candidate for future wireless communication in high-mobility scenarios.In addition to the superior communication performance,OTFS is also a natural choice for radar sensing since the primary parameters(range and velocity of targets)in radar signal processing can be inferred directly from the delay and Doppler shifts.Though there are several works on OTFS radar sensing,most of them consider the integer parameter estimation only,while the delay and Doppler shifts are usually fractional in the real world.In this paper,we propose a two-step method to estimate the fractional delay and Doppler shifts.We first perform the two-dimensional(2D)correlation between the received and transmitted DD domain symbols to obtain the integer parts of the parameters.Then a difference-based method is implemented to estimate the fractional parts of delay and Doppler indices.Meanwhile,we implement a target detection method based on a generalized likelihood ratio test since the number of potential targets in the sensing scenario is usually unknown.The simulation results show that the proposed method can obtain the delay and Doppler shifts accurately and get the number of sensing targets with a high detection probability.

关键词： OTFS radar sensing delay-Doppler(DD)domain fractional delay and Doppler

Low PAPR Channel Estimation for OTFS with Scattered Superimposed Pilots

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China Communications 2023年第1期20卷 79-87页

作者： Wei Liu Liyi Zou Baoming Bai Teng Sun State Key Labs of Integrated Service Networks Xidian UniversityXi’an 710071China The 54th Research Institute of CETC Shijiazhuang Hebei 050081China

Orthogonal time frequency space(OTFS)modulation has been proven to be superior to traditional orthogonal frequency division multiplexing(OFDM)systems in high-speed communication scenarios.However,the existing channel estimation schemes may results in poor peak to average power ratio(PAPR)performance of OTFS system or low spectrum efficiency.Hence,in this paper,we propose a low PAPR channel estimation scheme with high spectrum efficiency.Specifically,we design a multiple scattered pilot pattern,where multiple low power pilot symbols are superimposed with data symbols in delay-Doppler domain.Furthermore,we propose the placement rules for pilot symbols,which can guarantee the low PAPR.Moreover,the data aided iterative channel estimation was invoked,where joint channel estimation is proposed by exploiting multiple independent received signals instead of only one received signal in the existing scheme,which can mitigate the interference imposed by data symbols for channel estimation.Simulation results shows that the proposed multiple scattered pilot aided channel estimation scheme can significantly reduce the PAPR while keeping the high spectrum efficiency.

关键词： OTFS channel estimation superimposed pilots PAPR interference mitigation

Cubature Kalman Filter Based Millimeter Wave Beam Tracking for OTFS Systems

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China Communications 2023年第7期20卷 233-240页

作者： Xiaohan Qi Jianxiao Xie College of Physics and Electronic Information Engineering Zhejiang Normal UniversityJinhua 321000China

In this paper,a Millimeter wave(mmWave)beam tracking problem is studied in orthogonal time frequency space(OTFS)systems.Considering the nonlinearity of beamforming and the constraints of existing Kalman-filtering based beam tracking schemes,we propose a novel Cubature Kalman Filter(CKF)framework tracking the channel state information(CSI)to manage the challenge of highspeed channel variation in single-user moving scene for OTFS systems.Aiming for low complexity for mobile settings,this paper trains only one beam pair to track a path to maintain the reliable communication link in the analog beamforming architecture.Simulation results show that our proposed method has better tracking performance to improve the accuracy of the estimated beam angle compared with prior work.

关键词： OTFS millimeter wave beam tracking Cubature Kalman Filter