Design and Implementation of An Active Multibeam Antenna System with 64 RF Channels and 256 Antenna Elements for Massive MIMO Application in 5G Wireless Communications

This paper focuses on the design and implementation of an active multibeam antenna system for massive MIMO applications in 5G wireless communications.The highly integrated active multibeam antenna system is designed and implemented at 5.8 GHz with 64 RF Channels and 256 antenna elements.The 64-channel highly integrated active multibeam antenna system provides a verification platform for digital beamforming algorithm and massive MIMO channel estimation for next generation wireless communications.

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.

High-speed railway channel measurements and characterizations: a review

Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.

Broadband Communications for High-Speed Trains via NDN Wireless Mesh Network

With the increasing utilization of High-Speed Trains （HSTs）, the need for a reliable and high-bandwidth Internet access under high-speed mobility scenarios has become more demanding. In static, walking, and low mobility environments, TCP/IP （transmission control protocol/Internet protocol） can work well. However, TCP/IP cannot work well in high-speed scenarios because of reliability and handoff delay problems. This is mainly because the mobile node is required to maintain the connection to the corresponding node when it handovers to another access point node. In this paper, we propose a named data networking wireless mesh network architecture for HST wireless communication （NDN-Mesh-T）, which combines the advantages of Wireless Mesh Networks （WMNs） and NDN architectures. We attempt to solve the reliability and handoff delay problems to enable high bandwidth and low latency in Internet access in HST scenarios. To further improve reliability and bandwidth utilization, we propose a Direction-Aware Forwarding （DAF） strategy to forward Interest packet along the direction of the running train. The simulation results show that the proposed scheme can significantly reduce the packet loss rate by up to 51% compared to TCP/IP network architecture. Moreover, the proposed mechanism can reduce the network load, handoff delay, and data redundancy.

Design of intelligent detecting system based on wireless transmission

An intelligent detecting system based on wireless transmission is designed. Its hardware includes the card reading module, the wireless digital transmission module, the LCD module, the random password keyboard module and a 16×16 lattice word database based on e-Flash MM36SB020. Its software is a communication protocol between the central control computer and the entrance management base station. To resolve the conflicting problems occurred during the data transmission, a method of delaying time at random is proposed.

Crest Factor Reduction for OFDM Using Selective Subcarrier Degradation

This paper describes a crest factor reduction （CFR） method that reduces peaks in the time domain by modifying selected data subcarriers within an OFDM signal. The data subcarriers selected for modification vary with each symbol interval and are limited to those subcarriers whose aata elements are mapped onto the outer boundary of the constellation. In the proposed method, a set of peaks are identified within an OFDM symbol interval. Data subcarriers whose data element has a positive or negative correlation with the set peak are selected. For a subcarrier with an outer element and a significant positive correlation, a bit error （reversal） is intentionally introduced. This moves the data element to the opposite side of the constellation. Outer elements on negatively-correlatea subcarriers are increased in magnitude along the real or imaginary axis. Experimental results show that selecting the correct subcarriers for bit reversals and outward enhancements reduces the peak-to-average power ratio （PAPR） of the OFDM signal to a target value and limits in-band degradation measured by bit error rate （BER） and error vector magnitude （EVM）.

Performance of MIMO Systems Using Space Time Block Codes (STBC)

Digital Communications, in relation to wireless networks, have taken off in recent years due to the expanding need to communicate faster and more efficiently. A popular way to achieve this is by using wireless Multiple Input Multiple Output (MIMO) communication systems. MIMO systems utilize Space Time Block Codes (STBC) as one of the leading ways to obtain higher data rates with limited bandwidth and power. With several STBC methods currently available, this paper analyzes simulations using Orthogonal Space Time Block Codes (OSTBC) in Rayleigh fading channels to evaluate the performance of MIMO systems. The selection to use a Rayleigh fading channel as a model for a non-line-of-sight (nLOS) environment is selected to mimic installations where a large number of signal paths and reflections are expected. All simulations are coded, generated and plotted using MATLAB resulting in graphical data representing the bit-error rate (BER) to signal-to-noise ratio (Eb/N0) or SNR. Each simulation captures how different configurations of key variables including code rate, diversity and antenna count can impact system performance. Four modulation schemes (BPSK, QPSK, 16-QAM and 64-QAM) are included in each simulation. Conclusive evidence based upon these simulations suggests higher diversity gains were achieved with a greater number of antennas. The most significant factor for increasing system performance was using a lower count of transmit antennas with a higher count of receive antennas.

A Secured Message Transmission Protocol for Vehicular Ad Hoc Networks

Vehicular Ad hoc Networks(VANETs)become a very crucial addition in the Intelligent Transportation System(ITS).It is challenging for a VANET system to provide security services and parallelly maintain high throughput by utilizing limited resources.To overcome these challenges,we propose a blockchain-based Secured Cluster-based MAC(SCB-MAC)protocol.The nearby vehicles heading towards the same direction will form a cluster and each of the clusters has its blockchain to store and distribute the safety messages.The message which contains emergency information and requires Strict Delay Requirement(SDR)for transmission are called safety messages(SM).Cluster Members(CMs)sign SMs with their private keys while sending them to the blockchain to confirm authentication,integrity,and confidentiality of the message.A Certificate Authority(CA)is responsible for physical verification,key generation,and privacy preservation of the vehicles.We implemented a test scenario as proof of concept and tested the safety message transmission(SMT)protocol in a real-world platform.Computational and storage overhead analysis shows that the proposed protocol for SMT implements security,authentication,integrity,robustness,non-repudiation,etc.while maintaining the SDR.Messages that are less important compared to the SMs are called non-safety messages(NSM)and vehicles use RTS/CTS mechanism for NSM transmission.Numerical studies show that the proposed NSM transmission method maintains 6 times more throughput,2 times less delay and 125%less Packet Dropping Rate(PDR)than traditional MAC protocols.These results prove that the proposed protocol outperforms the traditional MAC protocols.

Novel Low-Complexity Low-Latency Orthogonal Frequency Division Multiplexing Transmitter

Traditional orthogonal frequency division multiplexing(OFDM) transmitter is implemented by exploiting inverse fast Fourier transform(IFFT), up-sampling, and low pass shaping filter(LPSF) modules, which occupy a large number of hardware resources and severely lower down the operation speed. To address these limitations, we propose a novel OFDM transmitter architecture, by which the aforementioned modules can be discarded and replaced with some simple switches. In the proposed architecture, direct digital synthesis(DDS) method is employed to generate digital sub-carriers and to transform OFDM data from frequency domain to time domain. Through some sophisticated simplifications, the proposed architecture can avoid using multipliers and remarkably save hardware resources. Finally, comparative experiments are carried out on field programmable gate array(FPGA) platform which demonstrates that our DDS-based architecture saves more than half of the hardware resources and doubles the achievable maximum frequency compared with traditional structure.