Rehabilitation training is believed to be an effectual strategy that canreduce the risk of dysfunction caused by spasticity.However,achieving visualizationrehabilitation training for patients remains clinically challe...Rehabilitation training is believed to be an effectual strategy that canreduce the risk of dysfunction caused by spasticity.However,achieving visualizationrehabilitation training for patients remains clinically challenging.Herein,wepropose visual rehabilitation training system including iontronic meta-fabrics withskin-friendly and large matrix features,as well as high-resolution image modules fordistribution of human muscle tension.Attributed to the dynamic connection and dissociationof the meta-fabric,the fabric exhibits outstanding tactile sensing properties,such as wide tactile sensing range(0~300 kPa)and high-resolution tactile perception(50 Pa or 0.058%).Meanwhile,thanks to the differential capillary effect,the meta-fabric exhibits a“hitting three birds with one stone”property(dryness wearing experience,long working time and cooling sensing).Based on this,the fabrics can be integrated with garmentsand advanced data analysis systems to manufacture a series of large matrix structure(40×40,1600 sensing units)training devices.Significantly,the tunability of piezo-ionic dynamics of the meta-fabric and the programmability of high-resolution imaging modules allowthis visualization training strategy extendable to various common disease monitoring.Therefore,we believe that our study overcomes theconstraint of standard spasticity rehabilitation training devices in terms of visual display and paves the way for future smart healthcare.展开更多
Holographic multiple-input multiple-output(HMIMO)has become an emerging technology for achieving ultra-high frequency spectral efficiency and spatial resolution in future wireless systems.The increasing antenna apertu...Holographic multiple-input multiple-output(HMIMO)has become an emerging technology for achieving ultra-high frequency spectral efficiency and spatial resolution in future wireless systems.The increasing antenna aperture leads to a more significant characterization of the spherical wavefront in near-field communications in HMIMO scenarios.Beam training as a key technique for wireless communication is worth exploring in this near-field scenario.Compared with the widely researched far-field beam training,the increased dimensionality of the search space for near-field beam training poses a challenge to the complexity and accuracy of the proposed algorithm.In this paper,we introduce several typical near-field beam training methods:exhaustive beam training,hierarchical beam training,and multi-beam training that includes equal interval multi-beam training and hash multi-beam training.The performances of these methods are compared through simulation analysis,and their effectiveness is verified on the hardware testbed as well.Additionally,we provide application scenarios,research challenges,and potential future research directions for near-field beam training.展开更多
Communicating on millimeter wave(mmWave)bands is ushering in a new epoch of mobile communication which provides the availability of 10 Gbps high data rate transmission.However,mmWave links are easily prone to short tr...Communicating on millimeter wave(mmWave)bands is ushering in a new epoch of mobile communication which provides the availability of 10 Gbps high data rate transmission.However,mmWave links are easily prone to short transmission range communication because of the serious free space path loss and the blockage by obstacles.To overcome these challenges,highly directional beams are exploited to achieve robust links by hybrid beamforming.Accurately aligning the transmitter and receiver beams,i.e.beam training,is vitally important to high data rate transmission.However,it may cause huge overhead which has negative effects on initial access,handover,and tracking.Besides,the mobility patterns of users are complicated and dynamic,which may cause tracking error and large tracking latency.An efficient beam tracking method has a positive effect on sustaining robust links.This article provides an overview of the beam training and tracking technologies on mmWave bands and reveals the insights for future research in the 6th Generation(6G)mobile network.Especially,some open research problems are proposed to realize fast,accurate,and robust beam training and tracking.We hope that this survey provides guidelines for the researchers in the area of mmWave communications.展开更多
The human brain is highly plastic.Cognitive training is usually used to modify functional connectivity of brain networks.Moreover,the structures of brain networks may determine its dynamic behavior which is related to...The human brain is highly plastic.Cognitive training is usually used to modify functional connectivity of brain networks.Moreover,the structures of brain networks may determine its dynamic behavior which is related to human cognitive abilities.To study the effect of functional connectivity on the brain dynamics,the dynamic model based on functional connections of the brain and the Hindmarsh–Rose model is utilized in this work.The resting-state fMRI data from the experimental group undergoing abacus-based mental calculation(AMC)training and from the control group are used to construct the functional brain networks.The dynamic behavior of brain at the resting and task states for the AMC group and the control group are simulated with the above-mentioned dynamic model.In the resting state,there are the differences of brain activation between the AMC group and the control group,and more brain regions are inspired in the AMC group.A stimulus with sinusoidal signals to brain networks is introduced to simulate the brain dynamics in the task states.The dynamic characteristics are extracted by the excitation rates,the response intensities and the state distributions.The change in the functional connectivity of brain networks with the AMC training would in turn improve the brain response to external stimulus,and make the brain more efficient in processing tasks.展开更多
Tri-Training算法是半监督算法中的一种,其初始分类器性能受有标记样本影响较大,当样本数目不足时,分类器性能相对较弱,会直接影响后续迭代.为此提出IFS-Tri-Training(Tri-Training based on intuitionistic fuzzy sets)算法,引入SOM算...Tri-Training算法是半监督算法中的一种,其初始分类器性能受有标记样本影响较大,当样本数目不足时,分类器性能相对较弱,会直接影响后续迭代.为此提出IFS-Tri-Training(Tri-Training based on intuitionistic fuzzy sets)算法,引入SOM算法构建直觉模糊集,使得分类器在多因素下综合判别无标记样本,提高无标记样本的使用率,从而在迭代中扩展有标记样本集.在多个UCI数据上进行实验,结果数据表明,分类器的性能得到提高,学习无标记样本过程是影响分类器的关键点.展开更多
This paper, with the training of the international talents possessing remarkable English listening and speaking ability,mainly discusses the specific application of the cognitive strategy in different stages of colleg...This paper, with the training of the international talents possessing remarkable English listening and speaking ability,mainly discusses the specific application of the cognitive strategy in different stages of college English listening comprehension.It is expected that the paper can bring some useful enlightenments on the international talents training.展开更多
The project delves into the preliminary findings of a survey of both trainers and students on the practice of using student peer feedback in interpreting practice.It first explains the theoretical foundation which jus...The project delves into the preliminary findings of a survey of both trainers and students on the practice of using student peer feedback in interpreting practice.It first explains the theoretical foundation which justifies the use of peer feedback in interpreting practice,the research methodology and data collection.Then it brings forth specific findings concerning the implementation of peer feedback in the interpreting class followed by discussions of the role and features of student peer feedback as a means to help students ready for the booth.Analysis of the results shows that peer feedback in interpreting practice keeps students on-task,attentive and help them spot their own problems.Trainers and students themselves point to similar features of student peer feedback as focusing on comprehension of the original,word choice and numbers.The preliminary findings of the survey demonstrate the roles and features of student peer feedback in interpreting practice and point to the possible way of enhancing student’s learning curve through more effective peer feedback.展开更多
A survey of language training centers(LTCs)in Dalian,China was conducted,to ascertain the strengths and weaknesses,or the differentiating factors,of such centers.The survey was undertaken to understand the current lan...A survey of language training centers(LTCs)in Dalian,China was conducted,to ascertain the strengths and weaknesses,or the differentiating factors,of such centers.The survey was undertaken to understand the current landscape of after-school institutes in the region,particularly those that offer training in English as a second/foreign language.The information uncovered by the research is considered beneficial not only to entrepreneurs who may wish to be involved in this industry,but also to college English majors who may wish to teach at an LTC.展开更多
This paper mainly deals with the comprehensive knowledge system of learning strategy.Then it tries to probe the steps of strategy training and it's significance to English teaching.
The article examines the world experience of e-learning as well as distance education technologies within the education process organization on higher and post-higher education programs.There have been listed the resu...The article examines the world experience of e-learning as well as distance education technologies within the education process organization on higher and post-higher education programs.There have been listed the results of the most popular e-learning platforms analysis.Furthermore,there have been looked through the core legislative background of the development of the mentioned technologies in Russia and worldwide among the universities,specialized in seafarers training.There have been also drawn up the points of the Admiral Makarov State University of Maritime and Inland Shipping(Admiral Makarov SUMIS)design of the distance education system LMS"FARWATER"in compliance with the International Convention on Standards of Training,Certification and Watchkeeping for Seafarers(STCW Convention).The practical application of distance education system to the advanced professional training has been discussed in the article.展开更多
Based on the experience and lessons of modern apprenticeship in the UK,this paper analyzes the problems existing in the process of the training of business English majors in higher vocational colleges in China,and put...Based on the experience and lessons of modern apprenticeship in the UK,this paper analyzes the problems existing in the process of the training of business English majors in higher vocational colleges in China,and puts forward the“three identities in four phases”personnel training model which is suitable for the business English majors in higher vocational colleges in China.It provides a reference for the development of business English majors in relevant higher vocational colleges.展开更多
This paper studies English training for student volunteers at large scale sports events with a comprehensive investigation of the undergraduate student volunteers from Capital University of Physical Education who have...This paper studies English training for student volunteers at large scale sports events with a comprehensive investigation of the undergraduate student volunteers from Capital University of Physical Education who have taken part in large scale sports events.By examining the current volunteer training situation,the author finds that there is a sever lack of professional and systematical English training for student volunteers at large scale sports events.The study shows focusing on sports events knowledge and requirements of the volunteers’specific job is crucial to the service level of the volunteers.The study concludes that the problem can be solved by developing new course books,innovating new flexible training methods,and offering more comprehensive training content.The recommended training methods include intensive group training,computer aided teaching,task training and on-the-spot training to make them fit their work soon.展开更多
The aim of foreign language teaching in the contemporary is to develop foreign language talents who own intercultural competence.Thus,it is necessary to improve teachers’cultural quality and intercultural awareness.T...The aim of foreign language teaching in the contemporary is to develop foreign language talents who own intercultural competence.Thus,it is necessary to improve teachers’cultural quality and intercultural awareness.The paper explores some relevant training courses on culture and intercultural awareness,and discusses the deficiency of these courses.展开更多
Overseas three-month intra-university training program is rear in Yunnan,China.Using adult learning and social con-structivism as theoretical basis,the author,introduces the background of the program and the course de...Overseas three-month intra-university training program is rear in Yunnan,China.Using adult learning and social con-structivism as theoretical basis,the author,introduces the background of the program and the course design,highlighting the inten-tion for the program and similar programs.展开更多
The participants of an overseas three-month program in this paper were divided into 3 levels according to their English language competences,and classroom observation,and interview were conducted during the learning p...The participants of an overseas three-month program in this paper were divided into 3 levels according to their English language competences,and classroom observation,and interview were conducted during the learning process.Results show the English language competences,interpretation,learners’education and research background and motivation are determining factors affecting classroom behavioral performance and learning effectiveness.展开更多
The vocational education and training(VET)system helps people from culturally and linguistically diverse(CALD)back-grounds to integrate and settle into society.However,successful completion of VET is closely related t...The vocational education and training(VET)system helps people from culturally and linguistically diverse(CALD)back-grounds to integrate and settle into society.However,successful completion of VET is closely related to CALD learners’language skills.This literature review aims at identifying the main methods of language skills improvement for VET learners from CALD backgrounds.Five language support/training methods based on different theoretical models are also introduced in this literature re-view,including the model outlines and target groups.展开更多
Virtual reality(VR) training technology in the mining industry is a new field of research and utilization.The successful application of VR training system is critical to mine safety and production. Through the statist...Virtual reality(VR) training technology in the mining industry is a new field of research and utilization.The successful application of VR training system is critical to mine safety and production. Through the statistics of the current research and applications of VR training systems in mining industry, all the input/output devices are classified. Based on the classifications of the input/output devices that are used in the VR system, the current VR training systems for the mining industry could be divided into three types: screen-based general type, projector-based customized type, and head-mounted display(HMD)-based intuitive type. By employing a VR headset, a smartphone and a leap motion device, an HMDbased intuitive type VR training system prototype for drilling in underground mines has been developed.Ten trainees tried both the HMD-based intuitive system and the screen-based general control system to compare the experiences and training effects. The results show that the HMD-based system can give a much better user experience and is easy to use. Three of the five components of a VR training system,namely, the user, the tasks, and software and database should be given more attention in future research.With more available technologies of input and output devices, VR engines, and system software, the VR training system will eventually yield much better training results, and will play a more important role in as a training tool for mine safety.展开更多
Reconfigurable intelligent surface(RIS)is more likely to develop into extremely large-scale RIS(XL-RIS)to efficiently boost the system capacity for future 6 G communications.Beam training is an effective way to acquir...Reconfigurable intelligent surface(RIS)is more likely to develop into extremely large-scale RIS(XL-RIS)to efficiently boost the system capacity for future 6 G communications.Beam training is an effective way to acquire channel state information(CSI)for XL-RIS.Existing beam training schemes rely on the far-field codebook.However,due to the large aperture of XL-RIS,the scatters are more likely to be in the near-field region of XL-RIS.The far-field codebook mismatches the near-field channel model.Thus,the existing far-field beam training scheme will cause severe performance loss in the XL-RIS assisted nearfield communications.To solve this problem,we propose the efficient near-field beam training schemes by designing the near-field codebook to match the nearfield channel model.Specifically,we firstly design the near-field codebook by considering the near-field cascaded array steering vector of XL-RIS.Then,the optimal codeword for XL-RIS is obtained by the exhausted training procedure.To reduce the beam training overhead,we further design a hierarchical nearfield codebook and propose the corresponding hierarchical near-field beam training scheme,where different levels of sub-codebooks are searched in turn with reduced codebook size.Simulation results show the proposed near-field beam training schemes outperform the existing far-field beam training scheme.展开更多
基金supported by the National Key Research and Development Program(2022YFB3805800)National Natural Science Foundation of China(52473307,22208178,62301290)+9 种基金Taishan Scholar Program of Shandong Province in China(tsqn202211116)Shandong Provincial Universities Youth Innovation Technology Plan Team(2023KJ223)Natural Science Foundation of Shandong Province of China(ZR2023YQ037,ZR2020QE074,ZR2023QE043,ZR2022QE174)Shandong Province Science and Technology Small and Medium sized Enterprise Innovation Ability Enhancement Project(2023TSGC0344,2023TSGC1006)Natural Science Foundation of Qingdao(23-2-1-249-zyyd-jch,24-4-4-zrjj-56-jch)Anhui Province Postdoctoral Researcher Research Activity Funding Project(2023B706)Qingdao Key Technology Research and Industrialization Demonstration Projects(23-1-7-zdfn-2-hz)Qingdao Shinan District Science and Technology Plan Project(2022-3-005-DZ)Suqian Key Research and Development Plan(H202310)Jinan City-School Integration Development Strategy Project for the Year 2023 under Grant(JNSX2023088).
文摘Rehabilitation training is believed to be an effectual strategy that canreduce the risk of dysfunction caused by spasticity.However,achieving visualizationrehabilitation training for patients remains clinically challenging.Herein,wepropose visual rehabilitation training system including iontronic meta-fabrics withskin-friendly and large matrix features,as well as high-resolution image modules fordistribution of human muscle tension.Attributed to the dynamic connection and dissociationof the meta-fabric,the fabric exhibits outstanding tactile sensing properties,such as wide tactile sensing range(0~300 kPa)and high-resolution tactile perception(50 Pa or 0.058%).Meanwhile,thanks to the differential capillary effect,the meta-fabric exhibits a“hitting three birds with one stone”property(dryness wearing experience,long working time and cooling sensing).Based on this,the fabrics can be integrated with garmentsand advanced data analysis systems to manufacture a series of large matrix structure(40×40,1600 sensing units)training devices.Significantly,the tunability of piezo-ionic dynamics of the meta-fabric and the programmability of high-resolution imaging modules allowthis visualization training strategy extendable to various common disease monitoring.Therefore,we believe that our study overcomes theconstraint of standard spasticity rehabilitation training devices in terms of visual display and paves the way for future smart healthcare.
文摘Holographic multiple-input multiple-output(HMIMO)has become an emerging technology for achieving ultra-high frequency spectral efficiency and spatial resolution in future wireless systems.The increasing antenna aperture leads to a more significant characterization of the spherical wavefront in near-field communications in HMIMO scenarios.Beam training as a key technique for wireless communication is worth exploring in this near-field scenario.Compared with the widely researched far-field beam training,the increased dimensionality of the search space for near-field beam training poses a challenge to the complexity and accuracy of the proposed algorithm.In this paper,we introduce several typical near-field beam training methods:exhaustive beam training,hierarchical beam training,and multi-beam training that includes equal interval multi-beam training and hash multi-beam training.The performances of these methods are compared through simulation analysis,and their effectiveness is verified on the hardware testbed as well.Additionally,we provide application scenarios,research challenges,and potential future research directions for near-field beam training.
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grant 92267202in part by the Municipal Government of Quzhou under Grant 2023D027+2 种基金in part by the National Natural Science Foundation of China(NSFC)under Grant 62321001in part by the National Key Research and Development Program of China under Grant 2020YFA0711303in part by the Beijing Natural Science Foundation under Grant Z220004.
文摘Communicating on millimeter wave(mmWave)bands is ushering in a new epoch of mobile communication which provides the availability of 10 Gbps high data rate transmission.However,mmWave links are easily prone to short transmission range communication because of the serious free space path loss and the blockage by obstacles.To overcome these challenges,highly directional beams are exploited to achieve robust links by hybrid beamforming.Accurately aligning the transmitter and receiver beams,i.e.beam training,is vitally important to high data rate transmission.However,it may cause huge overhead which has negative effects on initial access,handover,and tracking.Besides,the mobility patterns of users are complicated and dynamic,which may cause tracking error and large tracking latency.An efficient beam tracking method has a positive effect on sustaining robust links.This article provides an overview of the beam training and tracking technologies on mmWave bands and reveals the insights for future research in the 6th Generation(6G)mobile network.Especially,some open research problems are proposed to realize fast,accurate,and robust beam training and tracking.We hope that this survey provides guidelines for the researchers in the area of mmWave communications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62276229 and 32071096).
文摘The human brain is highly plastic.Cognitive training is usually used to modify functional connectivity of brain networks.Moreover,the structures of brain networks may determine its dynamic behavior which is related to human cognitive abilities.To study the effect of functional connectivity on the brain dynamics,the dynamic model based on functional connections of the brain and the Hindmarsh–Rose model is utilized in this work.The resting-state fMRI data from the experimental group undergoing abacus-based mental calculation(AMC)training and from the control group are used to construct the functional brain networks.The dynamic behavior of brain at the resting and task states for the AMC group and the control group are simulated with the above-mentioned dynamic model.In the resting state,there are the differences of brain activation between the AMC group and the control group,and more brain regions are inspired in the AMC group.A stimulus with sinusoidal signals to brain networks is introduced to simulate the brain dynamics in the task states.The dynamic characteristics are extracted by the excitation rates,the response intensities and the state distributions.The change in the functional connectivity of brain networks with the AMC training would in turn improve the brain response to external stimulus,and make the brain more efficient in processing tasks.
文摘Tri-Training算法是半监督算法中的一种,其初始分类器性能受有标记样本影响较大,当样本数目不足时,分类器性能相对较弱,会直接影响后续迭代.为此提出IFS-Tri-Training(Tri-Training based on intuitionistic fuzzy sets)算法,引入SOM算法构建直觉模糊集,使得分类器在多因素下综合判别无标记样本,提高无标记样本的使用率,从而在迭代中扩展有标记样本集.在多个UCI数据上进行实验,结果数据表明,分类器的性能得到提高,学习无标记样本过程是影响分类器的关键点.
文摘This paper, with the training of the international talents possessing remarkable English listening and speaking ability,mainly discusses the specific application of the cognitive strategy in different stages of college English listening comprehension.It is expected that the paper can bring some useful enlightenments on the international talents training.
文摘The project delves into the preliminary findings of a survey of both trainers and students on the practice of using student peer feedback in interpreting practice.It first explains the theoretical foundation which justifies the use of peer feedback in interpreting practice,the research methodology and data collection.Then it brings forth specific findings concerning the implementation of peer feedback in the interpreting class followed by discussions of the role and features of student peer feedback as a means to help students ready for the booth.Analysis of the results shows that peer feedback in interpreting practice keeps students on-task,attentive and help them spot their own problems.Trainers and students themselves point to similar features of student peer feedback as focusing on comprehension of the original,word choice and numbers.The preliminary findings of the survey demonstrate the roles and features of student peer feedback in interpreting practice and point to the possible way of enhancing student’s learning curve through more effective peer feedback.
文摘A survey of language training centers(LTCs)in Dalian,China was conducted,to ascertain the strengths and weaknesses,or the differentiating factors,of such centers.The survey was undertaken to understand the current landscape of after-school institutes in the region,particularly those that offer training in English as a second/foreign language.The information uncovered by the research is considered beneficial not only to entrepreneurs who may wish to be involved in this industry,but also to college English majors who may wish to teach at an LTC.
文摘This paper mainly deals with the comprehensive knowledge system of learning strategy.Then it tries to probe the steps of strategy training and it's significance to English teaching.
文摘The article examines the world experience of e-learning as well as distance education technologies within the education process organization on higher and post-higher education programs.There have been listed the results of the most popular e-learning platforms analysis.Furthermore,there have been looked through the core legislative background of the development of the mentioned technologies in Russia and worldwide among the universities,specialized in seafarers training.There have been also drawn up the points of the Admiral Makarov State University of Maritime and Inland Shipping(Admiral Makarov SUMIS)design of the distance education system LMS"FARWATER"in compliance with the International Convention on Standards of Training,Certification and Watchkeeping for Seafarers(STCW Convention).The practical application of distance education system to the advanced professional training has been discussed in the article.
文摘Based on the experience and lessons of modern apprenticeship in the UK,this paper analyzes the problems existing in the process of the training of business English majors in higher vocational colleges in China,and puts forward the“three identities in four phases”personnel training model which is suitable for the business English majors in higher vocational colleges in China.It provides a reference for the development of business English majors in relevant higher vocational colleges.
文摘This paper studies English training for student volunteers at large scale sports events with a comprehensive investigation of the undergraduate student volunteers from Capital University of Physical Education who have taken part in large scale sports events.By examining the current volunteer training situation,the author finds that there is a sever lack of professional and systematical English training for student volunteers at large scale sports events.The study shows focusing on sports events knowledge and requirements of the volunteers’specific job is crucial to the service level of the volunteers.The study concludes that the problem can be solved by developing new course books,innovating new flexible training methods,and offering more comprehensive training content.The recommended training methods include intensive group training,computer aided teaching,task training and on-the-spot training to make them fit their work soon.
文摘The aim of foreign language teaching in the contemporary is to develop foreign language talents who own intercultural competence.Thus,it is necessary to improve teachers’cultural quality and intercultural awareness.The paper explores some relevant training courses on culture and intercultural awareness,and discusses the deficiency of these courses.
文摘Overseas three-month intra-university training program is rear in Yunnan,China.Using adult learning and social con-structivism as theoretical basis,the author,introduces the background of the program and the course design,highlighting the inten-tion for the program and similar programs.
文摘The participants of an overseas three-month program in this paper were divided into 3 levels according to their English language competences,and classroom observation,and interview were conducted during the learning process.Results show the English language competences,interpretation,learners’education and research background and motivation are determining factors affecting classroom behavioral performance and learning effectiveness.
文摘The vocational education and training(VET)system helps people from culturally and linguistically diverse(CALD)back-grounds to integrate and settle into society.However,successful completion of VET is closely related to CALD learners’language skills.This literature review aims at identifying the main methods of language skills improvement for VET learners from CALD backgrounds.Five language support/training methods based on different theoretical models are also introduced in this literature re-view,including the model outlines and target groups.
基金funded by the ‘‘twelfth five” National Key Technology Research and Development Program of the Ministry of Science and Technology of China (Grant No. 2015BAK10B00)
文摘Virtual reality(VR) training technology in the mining industry is a new field of research and utilization.The successful application of VR training system is critical to mine safety and production. Through the statistics of the current research and applications of VR training systems in mining industry, all the input/output devices are classified. Based on the classifications of the input/output devices that are used in the VR system, the current VR training systems for the mining industry could be divided into three types: screen-based general type, projector-based customized type, and head-mounted display(HMD)-based intuitive type. By employing a VR headset, a smartphone and a leap motion device, an HMDbased intuitive type VR training system prototype for drilling in underground mines has been developed.Ten trainees tried both the HMD-based intuitive system and the screen-based general control system to compare the experiences and training effects. The results show that the HMD-based system can give a much better user experience and is easy to use. Three of the five components of a VR training system,namely, the user, the tasks, and software and database should be given more attention in future research.With more available technologies of input and output devices, VR engines, and system software, the VR training system will eventually yield much better training results, and will play a more important role in as a training tool for mine safety.
基金supported in part by the National Key Research and Development Program of China(Grant No.2020YFB1807205)in part by the National Natural Science Foundation of China(Grant No.62031019)in part by the European Commission through the H2020-MSCA-ITN META WIRELESS Research Project under Grant 956256。
文摘Reconfigurable intelligent surface(RIS)is more likely to develop into extremely large-scale RIS(XL-RIS)to efficiently boost the system capacity for future 6 G communications.Beam training is an effective way to acquire channel state information(CSI)for XL-RIS.Existing beam training schemes rely on the far-field codebook.However,due to the large aperture of XL-RIS,the scatters are more likely to be in the near-field region of XL-RIS.The far-field codebook mismatches the near-field channel model.Thus,the existing far-field beam training scheme will cause severe performance loss in the XL-RIS assisted nearfield communications.To solve this problem,we propose the efficient near-field beam training schemes by designing the near-field codebook to match the nearfield channel model.Specifically,we firstly design the near-field codebook by considering the near-field cascaded array steering vector of XL-RIS.Then,the optimal codeword for XL-RIS is obtained by the exhausted training procedure.To reduce the beam training overhead,we further design a hierarchical nearfield codebook and propose the corresponding hierarchical near-field beam training scheme,where different levels of sub-codebooks are searched in turn with reduced codebook size.Simulation results show the proposed near-field beam training schemes outperform the existing far-field beam training scheme.
