Towards Near-Field Communications for 6G:Challenges and Opportunities

Extremely large-scale multiple-input multiple-output(XL-MIMO)and terahertz(THz)communications are pivotal candidate technologies for supporting the development of 6G mobile networks.However,these techniques invalidate the common assumptions of far-field plane waves and introduce many new properties.To accurately understand the performance of these new techniques,spherical wave modeling of near-field communications needs to be applied for future research.Hence,the investigation of near-field communication holds significant importance for the advancement of 6G,which brings many new and open research challenges in contrast to conventional far-field communication.In this paper,we first formulate a general model of the near-field channel and discuss the influence of spatial nonstationary properties on the near-field channel modeling.Subsequently,we discuss the challenges encountered in the near field in terms of beam training,localization,and transmission scheme design,respectively.Finally,we point out some promising research directions for near-field communications.

MmWave extra-large-scale MIMO based active user detection and channel estimation for high-speed railway communications

The current High-Speed Railway(HSR)communications increasingly fail to satisfy the massive access services of numerous user equipment brought by the increasing number of people traveling by HSRs.To this end,this paper investigates millimeter-Wave(mmWave)extra-large scale(XL)-MIMO-based massive Internet-of-Things(loT)access in near-field HSR communications,and proposes a block simultaneous orthogonal matching pursuit(B-SOMP)-based Active User Detection(AUD)and Channel Estimation(CE)scheme by exploiting the spatial block sparsity of the XLMIMO-based massive access channels.Specifically,we first model the uplink mmWave XL-MIMO channels,which exhibit the near-field propagation characteristics of electromagnetic signals and the spatial non-stationarity of mmWave XL-MIMO arrays.By exploiting the spatial block sparsity and common frequency-domain sparsity pattern of massive access channels,the joint AUD and CE problem can be then formulated as a Multiple Measurement Vectors Compressive Sensing(MIMV-CS)problem.Based on the designed sensing matrix,a B-SOMP algorithm is proposed to achieve joint AUD and CE.Finally,simulation results show that the proposed solution can obtain a better AUD and CE performance than the conventional CS-based scheme for massive IoT access in near-field HSR communications.

Focusing Ability Enhancement in Broadside Direction of Array:From UCA to UCCA

To meet the ever-increasing demand for the data rates of wireless communications,extremely large-scale antenna array(ELAA)has emerged as one of the candidate technologies for future 6G communications.The significantly increased number of antennas in ELAA gives rise to near-field communications,necessitating tailored beamforming techniques within the near-field regions to accommodate the spherical-wave propagation characteristics.Among various array geometries of ELAA,uniform circular array(UCA)has gained much attention for its distinct capability of maintaining uniform beam pattern across different azimuth angles.However,existing analysis of near-field UCA beamforming indicates that the near-field region severely declines in the broadside of UCA,where the system fails to benefit from near-field communications.To tackle this problem,the near-field beamforming technique of uniform concentric circular arrays(UCCAs)is investigated in this paper,which has the potential to enlarge the near-field region in the broadside direction.First,the analysis of beamforming gain in the 3D space with UCA and UCCA is provided.Then,the distinct beamforming characteristics that set UCCA apart from UCA are delineated,revealing the superiority of UCCA in extending the near-field region in broadside at the cost of slightly reduced near-field region in the coplane.Simulation results are provided to verify the effectiveness of the theoretical analysis of beamforming gain with UCCA and the enhanced focusing ability of UCCA in the broadside direction.

Security Threats to Business Information Systems Using NFC Read/Write Mode

Radio Frequency IDentification(RFID)and related technologies such as Near Field Communication(NFC)are becoming essential in industrial contexts thanks to their ability to perform contactless data exchange,either device-to-device or tag-to-device.One of the three main operation modes of NFC,called read/write mode,makes use of the latter type of interaction.It is extensively used in business information systems that make use of NFC tags to provide the end-user with augmented information in one of several available NFC data exchange formats,such as plain text,simple URLs or enriched URLs.Using a wide variety of physical form factors,NFC-compatible tags(wireless transponders)are currently available in many locations with applications going from smart posters,contactless tokens,tap-and-go payments or transport ticketing to automated device configuration,patient identification at hospitals or inventory management within supply chains.Most of these applications handle sensitive processes or data.This paper proposes a complete security threat model for the read/write operation mode of NFC used in Next Generation Industrial IoT(Nx-IIoT)contexts.This model,based on a wellknown methodology,STRIDE,allows developers and users to identify NFC applications vulnerabilities or weaknesses,analyze potential threats,propose risk management strategies,and design mitigation mechanisms to mention only some significant examples.

An Initial Approach for a NFC M-Ticketing Urban Transport System

Public transport plays an important role in the daily lives of hundreds of millions of people. The limited national and local finances starve the public transport networks of funding, although greater usage would imply important environmental and financial benefits. The recent advances in mobile technologies and services could be harnessed to increase the attractiveness and efficiency of various public transport systems. Increasingly flexible electronic ticketing, smart cards and real-time information feeds via smartphones are making transportation networks faster, cheaper and more efficient for both the passengers and operators. In this paper, we present our approach in designing and implementing an M-ticketing system for urban transport based on NFC technology. We make initial design decisions based on a study of two similar systems Oyster and U-Go. We make use of Microsoft technologies for the prototype implementation and we propose a test suite to validate the system. We conclude on presenting the experience gained from this project and propose a set of further developments in order for the prototype to become more realistic.

A flexible ECG patch compatible with NFC RF communication

With the advent of the internet of things,flexible wearable devices are gaining significant research interest,as they are unobtrusive,comfortable to wear and can support continuous observation of physiological signals,helping to monitor wellness or diagnose diseases.Amorphous Indium Gallium Zinc Oxide(a-IGZO)Thin Film Transistors(TFTs)fabricated on flexible substrates are an attractive option to build such bio-signal monitoring systems due to their flexibility,conformability to the human body,and low cost.This paper presents a flexible electrocardiogram(ECG)patch implemented on foil with self-aligned IGZO TFTs,which is capable to acquire the ECG signals,amplify them and convert them to a sequence of bits.The analogue frontend has a measured input-referred noise of 8μV_(rms) in the 1-100 Hz band.The system achieves experimentally 67.4 dB CMRR,58.9 dB PSRR,and 16.5 MΩinput impedance at 50 Hz while using 1 kHz chopping.The signal from the electrodes is transformed to a 105.9-kb/s Manchester-encoded serial bit stream which could be sent wirelessly to a smart phone via Near Field Communication(NFC)for further elaboration.Power consumption is 15.4 mW for the digital and 280μW for the analogue part.This contribution shows the fundamental steps to demonstrate intelligent plasters for biomedical applications based on flexible electronics providing an NFC-compatible digital output bit stream.

An efficient technique to retrieve information from a damaged near-field communication tag

Purpose-The purpose of this paper is to discuss a technique of restoring data from a broken/damaged near-field communication(NFC)tag whose coil is damaged and seems unrecoverable.Design/methodology/approach-This paper discusses a method to restore data from damaged NFC tags by designing a coil that matches the technical specification of NFC for restoring information.In this paper,an NFC tag with a broken antenna coil and its operational NFC chip is used for restoring data by making an external loop antenna for the same chip.Findings-If the NFC tag is damaged,the information stored on the tag can be lost and can cause serious inconvenience.This research provides an excellent mechanism for retrieving all the information accurately from a damaged NFC tag provided the NFC chip is not damaged.Research limitations/implications-One of the major limitations of this research is that the NFC chip remains intact without any damages.Data can only be recoverable if just the antenna of the NFC tag is damaged;any damage to the NFC chip would make it impossible for the data to be recoverable.Practical implications-The research is carried out with limited resources in an academic institute and hence cannot be compared to antenna designs of the industry.Furthermore,industry vendors are using aluminum to design the coil;however,in this study a copper coil is used for coil design since it is far less expensive than aluminum coil.Originality/value-NFC is a rather new short-range wireless technology and not much work is done in this field as far as antenna study is concerned.This study brings a technique to design a coil antenna for a damaged NFC tag to retrieve all the information without losing even a single bit of sensitive information.

软磁材料开发应用新热点

从NFC(近场通信技术)、无线充电技术、逆变器技术、SMC(复合软磁材料)技术、脉冲功率技术等几个技术领域介绍了软磁材料最新开发应用热点,针对不同技术领域对软磁材料及产品的技术要求,展望中国软磁材料及产品开发应用方向。

一种CLF芯片与SIM卡芯片连接的方法

在NFC技术中,CLF芯片与SIM卡的连接是一个重要问题,本文提出了一种具有自主知识产权的CLF与SIM卡的通信方法,采用新的调制解调方式,使得S2信号在S1信号高低电平时都能传输,实现单线连接NFC与SIM卡,以及它们之间的全双工通信。通过对该方法进行电路级的设计和仿真,验证了该方法的正确性和稳定性。

一种基于手机令牌和NFC技术的身份认证系统

针对目前Web站点的身份认证安全问题,提出了一种基于手机令牌和近距离无线通信(NFC,near field communication)技术的身份认证方法,并在Android平台上实现了该系统.该系统利用手机使用手机令牌实现了USBKey的主要功能,当用户访问站点进行注册时,将获得惟一的手机令牌并存于带有加解密功能的手机中.在下次访问站点进行身份认证时,用户可通过手机直接在Web站点进行身份认证,也可通过NFC技术将手机令牌传于PC机,使得用户可在PC机上利用手机进行身份认证.该系统将手机作为类USBKey设备,在增强Web站点身份认证安全的同时,省去了为用户颁发USBKey的流程和成本,具有较强的实用价值.

Multifunctional Semiconducting Fibers for Visual Detection of Sarin Gas

There is a growing need for protective instruments that can be used in extreme environments,including those encountered during exoplanet exploration,anti-terrorism activities,and in chemical plants.These instruments should have the ability to detect external threats visually and monitor internal physiological signals in real time for maximum safety.To address this need,multifunctional semiconducting fibers with visual detection ranging from yellow to red and near-field communication(NFC)capabilities have been developed for use in personal protective clothing.A composite conductive yarn with semiconducting fluorescent probe molecules is embroidered on the clothing,forming an NFC coil that allows for the visual monitoring of atmospheric safety through color changes.The fluorescence detection system was able to selectively detect diethyl chlorophosphate(DCP),a substitute for the toxic gas sarin,with a detection limit of 6.08 ppb,which is lower than the life-threatening concentration of sarin gas.Furthermore,an intelligent protective suit with the abovementioned dual functions was fabricated with good mechanical cycle stability and repeatability.Real-time physiological signals such as the temperature and humidity of the wearer could be read through the NFC conveniently.Such intelligent protective suits can quickly provide an early warning to the identified low-dose DCP and evaluate the health of wearer according to the changes in physiological signals.This study offers a smart,low-cost strategy for designing intelligent protective devices for extreme environments.