Multi-wavelength nanowire micro-LEDs for future high speed optical communication

The future of optoelectronics is directed towards small-area light sources,foremost being microLEDs.However,their use has been inhibited so far primarily due to fabrication and integration challenges,which impair efficiency and yield.Recently,bottom-up nanostructures grown using selective area epitaxy have garnered attention as a solution to the aforementioned issues.Prof.Lan Fu et.al.have used this technique to demonstrate uniform p-i-n core-shell InGaAs/InP nanowire array light emitting diodes.The devices are capable of voltage and geometry-controlled multi-wavelength and high-speed operations.Their publication accentuates the wide capabilities of bottom-up nanostructures to resolve the difficulties of nanoscale optoelectronics.

Achieving high-security and massive-capacity optical communications based on orbital angular momentum configured chaotic laser

Secure and high-speed optical communications are of primary focus in information transmission.Although it is widely accepted that chaotic secure communication can provide superior physical layer security,it is challenging to meet the demand for high-speed increasing communication rate.We theoretically propose and experimentally demonstrate a conceptual paradigm for orbital angular momentum(OAM)configured chaotic laser(OAM-CCL)that allows access to high-security and massivecapacity optical communications.Combining 11 OAM modes and an all-optical feedback chaotic laser,we are able to theoretically empower a well-defined optical communication system with a total transmission capacity of 100 Gb∕s and a bit error rate below the forward error correction threshold 3.8×10^(-3).Furthermore,the OAM-CCL-based communication system is robust to 3D misalignment by resorting to appropriate mode spacing and beam waist.Finally,the conceptual paradigm of the OAM-CCL-based communication system is verified.In contrast to existing systems(traditional free-space optical communication or chaotic optical communication),the OAM-CCL-based communication system has threein-one characteristics of high security,massive capacity,and robustness.The findings demonstrate that this will promote the applicable settings of chaotic laser and provide an alternative promising route to guide high-security and massive-capacity optical communications.

Satellite and high altitude platform-based inter-vehicle communications in vast and desolate areas

In order to solve the problem of inter-vehicle communication （IVC） in vast and desolate areas such as the desert and the Gobi, two vehicle network models are proposed. One is based on satellite communication and the other is based on high altitude platform （ HAP ） communication. The system outline and networking modes of the two models are described. In the satellite communication based model, all the vehicles are equipped with vehicle-bone satellite communication on the move terminals and the communication signals between vehicles are forwarded by satellite. In the high altitude platform-based model, the HAPs are equipped with base station facilities to form aerial base stations, and vehicles can communicate with each other via common terrestrial mobile communication devices. Some key parameters such as path loss, link loss and system capacity are also computed. The analysis shows that both the two models can satisfy the requirement of IVC in the descriptive environment.

5G High Mobility Wireless Communications: Challenges and Solutions

The fifth generation(5G) network is expected to support significantly large amount of mobile data traffic and huge number of wireless connections,to achieve better spectrum- and energy-efficiency,as well as quality of service(QoS) in terms of delay,reliability and security.Furthermore,the 5G network shall also incorporate high mobility requirements as an integral part,providing satisfactory service to users travelling at a speed up to 500 km/h.This paper provides a survey of potential high mobility wireless communication(HMWC) techniques for 5G network.After discussing the typical requirements and challenges of HMWC,key techniques to cope with the challenges are reviewed,including transmission techniques under the fast timevarying channels,network architecture with mobility support,and mobility management.Finally,future research directions on 5G high mobility communications are given.

High Frequency Communication Network with Diversity: System Structure and Key Enabling Techniques

High frequency sky wave communication suffers from poor performance including poor link quality and low link success rate. To enhance performance, diversity technology is proposed in the high frequency communication network(HFCN) in this paper.First, we present the benefits and the challenges by introducing diversity technology into the existing HFCN. Secondly, to exploit the benefits fully and overcome the challenges, we propose a system structure suitable for deploying diversity technology in HFCN in large scale,based on the cloud radio access network and software defined network. Moreover, we present a general structure for the real-time updating frequency management system that plays a more important role especially when resource consuming(e.g., frequency) diversity technology is deployed. Thirdly, we investigate the key techniques enabling diversity technology deployment. Finally, we point out the future research directions to help the HFCN with diversity work more efficiently and intelligently.

Adaptive Antenna-Activation Based Beamforming for Large-Scale MIMO Communication Systems of High Speed Railway

Large-scale array aided beamforming improves the spectral efficiency(SE) as a benefit of high angular resolution.When dual-beam downlink beamforming is applied to the train moving towards cell edge,the inter-beam ambiguity(IBA) increases as the directional difference between beams becomes smaller.An adaptive antenna activation based beamforming scheme was proposed to mitigate IBA.In the district near the base station(BS),all antenna elements(AEs) were activated to generate two beams.As the distance from the train to the BS increased,only the minimum number of AEs satisfying the resolution criterion would be activated.At the cell edge,one beam was switched off due to intolerable IBA.The proposed scheme can achieve SE gain to the non-adaptive scheme and show more robustness against the direction-of-arrival(DOA) estimation error.

High-Sensitivity Acquisition of Ultrahigh Dynamic Direct Sequence Spread Spectrum Signals in Space Communications

According to the requirements of the high-sensitivity acquisition of Direct Sequence Spread Spectrum(DSSS) signals under ultrahigh dynamic environments in space communications, a three-dimensional joint search of the phase of Pseudo-Noise-code(PN-code),Doppler frequency and its rate-of-change is presented to achieve high sensitivity in sensing high-frequency dynamics. By eliminating the correlation peak loss caused by ultrahigh Doppler frequency and its rate-of-change offset,the proposed method improves the acquisition sensitivity by increasing the non-coherent accumulation time. The validity of the algorithm is proved by theoretical analysis and simulation results. It is shown that signals with a carrier- to-noise ratio as low as 39 dBHz can be captured with high performance when the Doppler frequency is up to ±1 MHz and its rate-of-change is up to ±200 kHz/s.

Guest editorial: special issue on high mobility wireless communications

The high-speed railway and high-way networks are now expanding at a phenomenal speed in Chinaand in many other parts of the world. The related broadband wireless communication over high-speed trains and highway vehicles is a very challenging task due to hostile transmission channel conditions. The demand for such services is growing rapidly, following the proliferation of laptop/tablet computers and smart phones. This motivates the research on wireless communications in the high mobility environments.

Analysis of OFDM Applied to Powerline High Speed Digital Communication

The low voltage powerline is becoming a powerful solution to home network, building automation, and internet access as a result of its wide distribution, easy access and little maintenance. The character of powerline channel is very complicated because it is an open net. This article analysed the character of the powerline channel,introduced the basics of OFDM(Orthogonal Frequency Division Multiplexing), and studied the OFDM applied into powerline high speed digital communication.

Photonics-assisted THz wireless communication enabled by wide-bandwidth packaged backilluminated modified uni-traveling-carrier photodiode

This paper presents a wide-bandwidth back-illuminated modified uni-traveling-carrier photodiode(MUTC-PD)packaged with standard WR-5 rectangular waveguide for high-speed wireless communications.With optimized epitaxy structure and coplanar waveguide electrodes,the fabricated 4-μm-diameter PD exhibits ultra-flat frequency response and high saturation power.Integrated passive circuits including low-loss bias-tee and E-plane probe are designed to package the PD into a compact module with waveguide output.The packaged PD module has demonstrated a flat frequency response with fluctuations within±2.75 d B over a broadband of 140–220 GHz and a high saturated output power of-7.8 d Bm(166μW)at 140 GHz.For wireless communication applications,the packaged PD is used to implement 1-m free space transmission at carrier frequencies of 150.5 and 210.5 GHz,with transmission rates of 75 and 90 Gbps,respectively.

High－Performance Network Communications for CSCW

Computer supported cooperative work as a new multi disciplinary research area, brings a lot of new challenges for the computer technologies. Having analyzed the CSCW applications by using the groupware space time matrix, we conclude that the communicatio

Model and Implementation of Communication Link Management Supporting High Availability

Despite the rapid evolution in all aspects of computer technology, both the computer hardware and software are prone to numerous failure conditions. In this paper, we analyzed the characteristic of a computer system and the methods of constructing a system, proposed a communication link management model supporting high availability for network applications, Which will greatly increase the high availability of network applications. Then we elaborated on heartbeat or service detect, fail-over, service take-over, switchback and error recovery process of the model. In the process of constructing the communication link, we implemented the link management and service take-over with high availability requirement, and discussed the state and the state transition of building the communication link between the hosts, depicted the message transfer and the start of timer. At Last, we applied the designed high availability system to a network billing system, and showed how the system was constructed and implemented, which perfectly satisfied the system requirements. Key words high availability - service take-over - fail-over - communication link management CLC number TP 393 Foundation item: Supported by the National Natural Science Foundation of China (60132030)Biography: Luo Juan (1974-), female, Ph. D candidate, research direction: high speed network and information security.

100G and Beyond: Trends in Ultrahigh-Speed Communications (Part Ⅰ)

Fiber optics underpins the communication infrastruture of today＇s information society. Rapid rogl：ess in advanced modulation formats, high＇gain coding, optical amplification, coherent detection with digital signal processing, and new

FSS Based Circular Polarizer for High-Speed Wireless Communication at 75 GHz

An FSS based circular polarizer for high-speed wireless communication at 75 GHz is presented. It has been designed on a low loss substrate with cross-dipole elements. Both simulation and measured results showed more than 98% circular polarization at 75 GHz. Moreover, 3 dB axial-ratio bandwidth of 6.8 GHz (Simulation) and 7.8 GHz (Measured) has been achieved. The proposed design has many advantages over the recently published research such as simplicity, low-profile, percentage bandwidth, frequency of operation and relative insertion loss.

Analysis of Wide-Bandgap Material OPFET UV Detectors for High Dynamic Range Imaging and Communication Applications

The ultraviolet (UV) photoresponses of Wurtzite GaN, ZnO, and 6H-SiC-based Optical Field Effect Transistor (OPFET) detectors are estimated with an in-depth analysis of the same considering the generalized model and the front-illuminated model for high resolution imaging and UV communication applications. The gate materials considered for the proposed study are gold (Au) and Indium-Tin-Oxide (ITO) for GaN, Au for SiC, and Au and silver dioxide (AgO2) for ZnO. The results indicate significant improvement in the Linear Dynamic Range (LDR) over the previously investigated GaN OPFET (buried-gate, front-illuminated and generalized) models with Au gate. The generalized model has superior dynamic range than the front-illuminated model. In terms of responsivity, all the models including buried-gate OPFET exhibit high and comparable photoresponses. Buried-gate devices on the whole, exhibit faster response than the surface gate models except in the AgO2-ZnO generalized OPFET model wherein the switching time is the lowest. The generalized model enables faster switching than the front-illuminated model. The switching times in all the cases are of the order of nanoseconds to picoseconds. The SiC generalized OPFET model shows the highest 3-dB bandwidths of 11.88 GHz, 36.2 GHz, and 364 GHz, and modest unity-gain cut-off frequencies of 4.62 GHz, 8.71 GHz, and 5.71 GHz at the optical power densities of 0.575 μW/cm2, 0.575 mW/cm2, and 0.575 W/cm2 respectively. These are in overall, the highest detection-cum-amplifi-cation bandwidths among all the investigated devices. The same device exhibits the highest LDR of 73.3 dB. The device performance is superior to most of the other existing detectors along with comparable LDR, thus, emerging as a high performance photodetector for imaging and communication applications. All the detectors show considerably high detectivities owing to the high responsivity values. The results have been analyzed by the photovoltaic and the photoconductive effects, and the series resistance effects and will aid in conducting further research. The results are in line with the experiments and the commercially available software simulations. The devices will greatly contribute towards single photon counting, high resolution imaging, and UV communication applications.

Facebook in the External Communication of High Schools

The study is based on the i^dea of intersection of two current trends： The increasing importance of social networking services on the one hand, and on the other hand, the increase in the high schools＇ need to be successful on the （school） market. Facebook, the most popular social networking service currently, is gradually transforming its form from the leisure and entertainment media towards the more serious media suitable for many traditional types of messages. At the same time, high schools, in addition to traditional forms of reaching out the public, are trying to find and use new forms of communication media, including social networking services. In this study, the author will focus on the current status of the social networking service----Facebook, used as a communication tool of high schools in Slovakia. The presented data are based on exploratory research followed by discursive analysis.

China Launches Its First High-Throughput Communications Satellite

China launched the SJ-13(ChinaSat-16)satellite at 7:04 p.m.on April12 on a LM-3B carrier rocket from the Xichang Satellite Launch Center.The satellite was developed by the China Academy of Space Technology(CAST)with a design lifetime of 15 years.SJ-13,China’s first high-throughput communications satellite that applies electric propulsion technology,is the first satellite based on the DFH-4S platform and will conduct high speed laser communications tests for the first time in China.

A Brief Discussion on the Application of Task-based Language Teaching to Improve the Teaching Quality of English Communication Classes in Junior High Schools

With the progress and development of society and the continuous advancement of curriculum standard reform,society has higher requirements for students’English skills.The junior high school stage is the best time to cultivate students’communication skills,however,junior high school English classes are currently still based on traditional teaching as the main teaching method,which only focuses on cultivating students’reading and writing skills,thus neglecting the training of listening and speaking skills.Despite its evident benefits,the implementation of the task-based language teaching(TBLT)method in junior high school English communication classes is not without challenges.The current state of these classes reveals a significant gap in the integration of communicative tasks into the teaching process.This gap stems from a variety of factors,including the lack of appropriate resources,insufficient teacher training,and the deeply ingrained reliance on traditional teaching methods.This study will briefly explain the definition and characteristics of the task-based language teaching method,analyze the current situation of junior high school English communication classes,the difficulties of using TBLT in junior high school English classrooms,and the application methods of task-based teaching methods.The teaching method makes up for the shortcomings of English communication classes in junior high schools and improves the quality of teaching.

A two-step quantum secure direct communication protocol with hyperentanglement

We propose a two-step quantum secure direct communication （QSDC） protocol with hyperentanglement in both the spatial-mode and the polarization degrees of freedom of photon pairs which can in principle be produced with a beta barium borate crystal. The secret message can be encoded on the photon pairs with unitary operations in these two degrees of freedom independently. This QSDC protocol has a higher capacity than the original two-step QSDC protocol as each photon pair can carry 4 bits of information. Compared with the QSDC protocol based on hyperdense coding, this QSDC protocol has the immunity to Trojan horse attack strategies with the process for determining the number of the photons in each quantum signal as it is a one-way quantum communication protocol.

New Developments in Maritime Communications： a Comprehensive Survey

This paper summarizes the requirements for modem maritime wireless communication networks in the marine environments including the sea- to-sea and sea-to-shore communication scenarios. The existing maritime wireless communication sys- tems are presented and the development of the state-of-the-art maritime communication systems is surveyed. Furthermore, a hierarchical and integrated maritime network architecture is proposed to satisfy the increasing various classes of services which demand different Quality of Service （QoS）. Finally, the open issues for further development of maritime communications are identified.