High-speed Data Transmission Research Articles

Evaluation of Conventional and Imaging MIMO OWC Systems Using Linear Array Design

Multiple-input-multiple-output (MIMO) optical wireless communication systems are potential candidates for high-speed data transmission in indoor environments. In this work, we present an experimental evaluation of two different MIMO systems, i.e., conventional-MIMO (c-MIMO) and imaging-MIMO (i-MIMO) in terms of design considerations. Both systems use the same transmitter configuration featuring a one-dimensional (light-emitting diode) LED transmitting array. On the receiver side, the c-MIMO system employs a similar one-dimensional receiving avalanche photodetector (APD)-based array, whereas the i-MIMO system uses a customized imaging camera-based receiver design. To assess the performance of the two systems, the channel matrix and the bit-error rate are calculated based on the experimental data. At distances shorter than 50 m, the proposed c-MIMO system demonstrates a good transmission performance, particularly when the maximum likelihood detection (MLD) technique is applied. Whereas, at long distances ranging from 40 m to 65 m, the proposed i-MIMO system can ensure an error-free transmission due to the efficient spatial separation between the emitted optical beams. Furthermore, the experimental results confirm that our systems have the potential for high data rates over longer distances in indoor environments.

A robust beam tracking scheme for millimeter wave HetNets

Millimeter Wave (mmWave) communication has been widely acknowledged as an attractive solution to address high-speed transmission of massive data in 5G and beyond 5G systems due to the promising spectrum availability. However, mmWave signals are highly susceptible to blockage and may suffer from rapidly changing channels. Thus, directional/beam tracking becomes imperative yet essential for robust mmWave communications. To address this challenge, we propose a robust beam tracking scheme for mmWave Heterogeneous Networks (HetNets) with multi-connectivity. Different from most existing schemes, the proposed beam tracking scheme is effective for outage events. We first discuss the μWave-assisted beam tracking procedure with and without candidate beams, and then analyze the inherent correlation between mmWave link quality and the operating beamwidth and occlusion range to derive the optimal beamwidth. Theoretical and numerical results show that the proposed beam tracking scheme can improve the robustness of mmWave communications while guaranteeing the rate performance.

Trade-offs in the performance of a Free Space Optical communication system employing DCO-OFDM transmission with a PAPR-dependent DC-bias

Free Space Optical (FSO) communication technology has gained popularity because of its high bandwidth, which supports high-speed data transmission. Despite its merits over Radio Frequency technology, the FSO system performance is restricted by the combined impact of beam divergence, beam scintillation, and beam-wander effects triggered by atmospheric turbulence. A Gamma–Gamma probability density function (PDF) channel model is employed to model the irradiance fluctuations due to turbulence. In this paper, we evaluate the performance metrics of a FSO link employing the Direct Current-biased Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM) modulation technique for different turbulent conditions. In our paper, we determine the DC-bias, which is proportional to peak-to-average-power ratio (PAPR) and a preclipping factor of nclip (<1) in order to reduce the transmitted optical power of the DCO-OFDM signal. We evaluate the average bit error rate (BER) and outage probability of the FSO link by considering the impact of system design parameters related to the OFDM signal, laser beam, and atmospheric turbulence on the received signal. Numerical simulation results show that, depending on the chosen values of PAPR and preclipping, an FSO link can experience either a power saving or a power penalty, for meeting the BER requirement. It is further demonstrated that trade-offs in performance at various levels exist between data transmission rate (QAM size), system power efficiency (preclipping), signal-PAPR and link-span to ensure target signal quality (BER and Outage). Under turbulence, the link with a longer span not only incurs a power penalty but also suffers from a reduced operating range by 3–4 dB.

Examination of OOK modulation schemes in Li-Fi systems

Light Fidelity (Li-Fi) is an advanced wireless communication method using visible light spectrum and light emitting diodes (LEDs) for high speed data transmission. In this article, a Li-Fi system using LED arrays is investigated for indoor visible light communication and efficiency of non-return-to-zero (NRZ) and return-to-zero (RZ) on-off keying (OOK) modulation schemes are compared with including inter symbol interference (ISI). For NRZ-OOK, 100 Mbps data rate is reached at 60° FOV angle and for RZ-OOK, 500 Mbps data transmission rate is achieved at the same FOV angle because of reduction in ISI.

Deep Learning for Security in Digital Twins of Cooperative Intelligent Transportation Systems

The purpose is to solve the security problems of the Cooperative Intelligent Transportation System (CITS) Digital Twins (DTs) in the Deep Learning (DL) environment. The DL algorithm is improved; the Convolutional Neural Network (CNN) is combined with Support Vector Regression (SVR); the DTs technology is introduced. Eventually, a CITS DTs model is constructed based on CNN-SVR, whose security performance and effect are analyzed through simulation experiments. Compared with other algorithms, the security prediction accuracy of the proposed algorithm reaches 90.43%. Besides, the proposed algorithm outperforms other algorithms regarding Precision, Recall, and F1. The data transmission performances of the proposed algorithm and other algorithms are compared. The proposed algorithm can ensure that emergency messages can be responded to in time, with a delay of less than 1.8s. Meanwhile, it can better adapt to the road environment, maintain high data transmission speed, and provide reasonable path planning for vehicles so that vehicles can reach their destinations faster. The impacts of different factors on the transportation network are analyzed further. Results suggest that under path guidance, as the Market Penetration Rate (MPR), Following Rate (FR), and Congestion Level (CL) increase, the guidance strategy’s effects become more apparent. When MPR ranges between 40% ~ 80% and the congestion is level III, the ATT decreases the fastest, and the improvement effect of the guidance strategy is more apparent. The proposed DL algorithm model can lower the data transmission delay of the system, increase the prediction accuracy, and reasonably changes the paths to suppress the sprawl of traffic congestions, providing an experimental reference for developing and improving urban transportation.

The Next level of Security Scalable Solution Blockchain (SSSB) in Satellite Communication System

Data security is one of the topmost priorities for government organisations and multinational companies. In particular, extremely sensitive data is regularly transferred between different branches of the government and the military. Hacking and interruption of data transmission of such high-level data transfers can pose a huge risk to the security of a country and to its integrity as well. The method that the article proposes has been implemented on a smaller scale for cryptocurrency transactions by the organisation “Blockstream”. This study serves the purpose of exploring a new use case of blockchain technology using satellite communication in order to establish an extremely secure and very high-speed data transmission connection between two parties. In this idea, the required sensitive data that is to be transferred to another party, sends the data through blockchain method of data transfer. This data is sent to the satellite where the satellite behaves as a node of data transmission in this blockchain connection and the private key is also encoded into the satellite software making it impossible in attempting to hack the encryption of the private key. When the satellite receives this data, it verifies the authenticity of the sender and analyses the encryption of the data. Then this data will be transmitted to its designated receiver. Once the data is received, it will be converted from blockchain to the regular data packets and the information can be shared within its local network. In this article, we explore further about the technology that’s being used to implement the connection from about the technology that’s being used to implement the connection from the ground station to the satellite via blockchain in the present day. The results produced by this article will help in attaining uncompromising security and speed of data transmission which will put an end to the tensions faced by higher authorities while sharing highly classified data.

Vocational Education Platform Based on Block Chain and IoT Technology.

Due to the poor effect of the traditional vocational education platform, it is difficult to meet the requirements of the current Internet education platform. To solve this problem, this paper designs a vocational education platform system based on blockchain and Internet of Things (IoT) technology. First, the system access control strategy based on blockchain technology is introduced into the teaching system so as to improve the security of the teaching system. Then, in order to solve the single point of failure and efficient transmission problems of access control in the IoT environment, this paper proposes an access control strategy based on main side chain cooperation. This strategy introduces a side chain to expand the blockchain and improve the data carrying capacity of the blockchain. To meet the requirements of high-speed data transmission, this paper designs an access control model suitable for the main side chain blockchain structure. Experimental results show that compared with other algorithms, the data request speed of the system in this paper is faster, and the storage space is smaller. Therefore, the proposed technology based on blockchain and IoT can meet the use requirements of vocational education platforms.

Mechanical Vibration Test Based on the Wireless Vibration Monitoring System

In order to apply wireless sensor networks to mechanical vibration monitoring, the author proposes a wireless network topology with multiple data collection points for mechanical vibration monitoring. This structure reduces the transmission load of the data collection point, increases the data transmission rate of the network, balances the energy dissipation in the network, and utilizes the general wireless sensor network hardware platform. The network transmission protocol and related auxiliary mechanisms are designed and implemented, and a wireless vibration monitoring test platform is constructed. The transmission performance of the network structure with multiple data collection points is evaluated through the actual test. The experimental results show that by using the wireless sensor network topology with multiple data collection points, it can meet the requirements of continuous transmission of vibration data obtained by 1 kHz sampling. Conclusion. The system performance of the wireless sensor network based on this network structure has been improved under the condition of general hardware, and the network structure of multiple data collection points shows good performance in the process of high-speed data transmission.

Simulation of Multisensor Energy Data Fusion Transformer Acquisition System Based on FPGA

In order to solve the problems of small signal acquisition range and poor acquisition accuracy of the existing multichannel acquisition system, a multisensor energy data fusion transformer acquisition system simulation method based on FPGA is proposed, and key hardware functions are designed and implemented. The system uses FPGA to control the core logic, synchronously collects and controls the energy data of the CCD camera and the laser rangefinder, organizes and uses an external large-capacity SDRAM group for buffering, and uses a dedicated PCI interface chip PLX9656 to achieve high-speed data transmission. Two pieces of sensor energy data and PCI bus energy data are stored in real time using a large-capacity disk array composed of multiple SATA hard disks. The function and performance of the energy data acquisition and storage system were tested. After the actual system test, the experimental results show that the transmission speed of the system through the PCI bus exceeds 200 MB/s, the writing speed of the continuous disk array is 240 MB/s, and the real-time acquisition and recording speed is 100 MB/ss. Conclusion. The system effectively solves the problems of high-speed data acquisition and storage and large capacity data transmission of key sensor nodes.

Augmented space signal detection method for IM/DD optical communication systems

The demand for high-speed data transmission has increased rapidly in data centers, leading to advanced optical communication technology innovation. At high modulation speed, severe linear and nonlinear signal distortions degrade the link performance. In order to increase the transmission capacity, a robust signal detection method based on quadratic discrimination in augmented space (QDAS) is proposed for high-speed intensity modulation and direct detection (IM/DD) optical communication systems. By projecting along the feature vector initially obtained by the objective function following the generalized Rayleigh quotient, signals with different features can be separated in augmented space. Subsequently, decision optimization is achieved through a quadratic discriminant model. Experimental verification is performed based on the 120 Gbps PAM8-modulated vertical-cavity surface-emitting laser (VCSEL) multimode fiber (MMF) optical link (100 m). The results show that, compared with the traditional Volterra nonlinear equalizer (VNLE), the proposed QDAS detection method shows improved and robust bit error ratio (BER) performance with the same complexity.

Two-stage deep learning-based hybrid precoder design for very large scale massive MIMO systems

Wireless networking is approaching a new era, which necessitates new frequency ranges and novel strategies. With recent circuit growth, communications over the Terahertz (THz) band is proving to be a viable option because of the tremendous bandwidth and low cost. On the other hand, THz signals suffer from significant direction loss, necessitating the use of precoding. In this paper, Deep Learning (DL) based precoding techniques for upcoming 6G networks were examined, along with their complexities. Based on the signal-to-noise ratio (SNR) and spectral efficiency (SE), the proposed DL-based precoding scheme is compared to traditional model-based precoding schemes. The proposed DL-based precoding technique is ideal for 6G networks, according to simulation results. Furthermore, the proposed DL-based precoding technique has lower computational complexity, making it suitable for parallel processing and high-speed data transmission.

Pillar-Based Cooperative Perception from Point Clouds for 6G-Enabled Cooperative Autonomous Vehicles

3D object detection is a significant aspect of the perception module in autonomous driving; however, with current technology, data sharing between vehicles and cloud servers for cooperative 3D object detection under the strict latency requirement is limited by the communication bandwidth. The sixth-generation (6G) networks have accelerated the transmission rate of the sensor data significantly with extreme low-latency and high-speed data transmission. However, which sensor data format and when to transmit it are still challenging. To address these issues, this study proposes a cooperative perception framework combined with a pillar-based encoder and Octomap-based compression at edges for connected autonomous vehicles to reduce the amount of missing detection in blind spots and further distances. This approach satisfies the constraints on the accuracy of the task perception and provides drivers or autonomous vehicles with sufficient reaction time by applying fixed encoders to learn a representation of point clouds (LiDAR sensor data). Extensive experiment results show that the proposed approach outperforms the previous cooperative perception schemes running at 30 Hz, and the accuracy of the object bounding box results in further distances (greater than 12 m). Furthermore, this approach achieves a lower total delay for the procession of the fusion data and the transmission of the cooperative perception message. To the best of our knowledge, this study is the first to introduce a pillar-based encoder and Octomap-based compression framework for cooperative perception between vehicles and edges in connected autonomous driving.

Multi-dimensional disturbance secure communication system with dynamic key hiding transmission based on power-domain non-orthogonal multiple access

Data security is becoming more critical in networks as high-speed and large-capacity optical transmission becomes more common. Cryptographic protocols at the MAC layer and higher tiers of the protocol stack are under threat as a result of quantum computer developments. Optical physical layer encryption has great advantages in optical communication security transmission, which can be compatible with a variety of networks, and achieve an efficient and secured ultra-high high-speed data transmission. In this work, we propose a physical layer encryption scheme based on orthogonal frequency division multiplexing power-domain non-orthogonal multiple access (OFDM-PD-NOMA) technique for the dynamic key hiding transmission and multi-dimensional disturbance. The encryption scheme realizes multi-point mutual-coupling key transmission and multi-dimensional disturbance encryption by a 3D discrete chaotic model. The encrypted data and the dynamic key are transmitted together by multichannel signals in PD-NOMA, then, the chaotic signal generated by chaotic generator is used to mask the dynamic key. 3D chaotic sequences generated by the dynamic key are used to encrypt bits, symbols and carriers of the original signal. The initial key, the dynamic key and the chaotic signal realize multi-point mutual-coupling. We conduct a 74.6 Gb/s encrypted quadrature phase shift keying (QPSK)-OFDM-PD-NOMA signal transmission over 2 km 7 core fiber. The key space of encrypted scheme can reach 10462. Finally, experimental results show that the original data can be recovered accurately, and the bit error rate (BER) of the dynamic key is close to zero. The security and reliability of the system have been verified, and this scheme has an important application prospect in the future optical communication system.

High-speed performance evaluation of ultra-flexible polymer waveguides supporting meter-scale optical interconnects.

We demonstrate bandwidth measurement and high-speed data transmission of meter-scale connectorized ultra-flexible multimode waveguide links with a maximum length of 180 cm. The pulses propagating through the waveguides broadened linearly with the increase of the length from 20 cm to 240 cm and the estimated mode delay from the pulse broadening was 0.093 ps/cm. The corresponding waveguide bandwidth decreased inversely with the increase of waveguide length, leading to a bandwidth-length product of 42 GHz·m. Degradation in bandwidth due to the introduction of bending or twisting was small when the samples were bent with a bending radius as small as 1 mm for 3 turns or twisted for 4 full turns, respectively. Error-free transmission of 30 Gb/s non-return-to-zero (NRZ) signal was achieved with a record link length up to 140 cm to the best of our knowledge. Our results show that the demonstrated flexible waveguides have both excellent optical and mechanical properties and are ideal for high-speed optical interconnects application especially those have a strict requirement on flexibility.

Separated electrodes for the enhancement of high-speed data transmission in vertical-cavity surface-emitting laser arrays.

In this work, a novel design for the electrodes in a near quasi-single-mode (QSM) vertical-cavity surface-emitting laser (VCSEL) array with Zn-diffusion apertures inside is demonstrated to produce an effective improvement in the high-speed data transmission performance. By separating the electrodes in a compact 2×2 coupled VCSEL array into two parts, one for pure dc current injection and the other for large ac signal modulation, a significant enhancement in the high-speed data transmission performance can be observed. Compared with the single electrode reference, which parallels 4 VCSEL units in the array, the demonstrated array with its separated electrode design exhibits greater dampening of electrical-optical (E-O) frequency response and a larger 3-dB E-O bandwidth (19 vs. 15 GHz) under the same amount of total bias current (20 mA). Moreover, this significant improvement in dynamic performance does not come at the cost of any degradation in the static performance in terms of the maximum near QSM optical output power (17 mW @ 20 mA) and the Gaussian-like optical far-field pattern which has a narrow divergence angle (full-width half maximum (FWHM): 10° at 20 mA). The advantages of the separated electrode design lead to a much better quality of 32 Gbit/sec eye-opening as compared to that of the reference device (jitter: 1.5 vs. 2.8 ps) and error-free 32 Gbit/sec transmissions over a 500 m multi-mode fiber has been achieved under a moderate total bias current of 20 mA.

High-speed waveguide Ge/Si avalanche photodiode with a gain-bandwidth product of 615 GHz

High-sensitivity and high-bandwidth receivers are always demanded for high-speed optical link systems. As a key element, an avalanche photodiode (APD) is often regarded as one of the most attractive options for achieving high sensitivity owing to the potential high internal gain. In this paper, a 48-GHz waveguide Ge/Si avalanche photodiode operating at the O-band (1310 nm) is designed with a lateral reach-through structure and fabricated with simplified processes. The fabricated APD shows a high primary responsivity of 0.93 A/W at the unit-gain voltage of−4.7V. It has an avalanche gain of 12.8 and a record gain-bandwidth product of∼615GHzwith an input optical power of−15dBmwhen operating at a bias voltage of−14V. The present Ge/Si APD is used successfully for high-speed data receiving, showing a sensitivity improvement about 7.6 dB for KP4-FEC operation (i.e., BER=2.4×10−4) with 50 Gbps non-return-to-zero (NRZ) data, compared with the case of using the reference PIN PD on the same chip. The sensitivity of the receiver with the present APD for NRZ signals is about−21.3dBm,−17.8dBm, and−12.6dBmfor KP4-FEC operation with different data rates of 50 Gbps, 80 Gbps, and 100 Gbps, while the sensitivity for four-level pulse amplitude modulation signals is about−13.2dBmand−11.3dBmfor KP4-FEC operation with different data rates of 25 and 50 Gbaud. Such high-performance APDs pave the way to achieve high-speed and high-sensitivity data transmissions.

Design of multichannel adaptive filter by constructing multidimensional Wiener-Hopf equation

In the satellite-to-ground high-speed data transmission link, there are signal self-interference problems of symbols in the co-channel, as well as between orthogonal and polarized channels. A multichannel adaptive filter is designed by constructing a multichannel Wiener-Hopf equation, and the influence of five channel nonideal factors is suppressed to improve the BER performance. Experiments show that this method is effective to suppress the signal self-interference, and the BER floor is optimized from 1E-3 to 1E-7.

Intelligent Reflecting Surface Aided Network under Interference toward 6G Applications

6G networks are capable of providing high-speed data transmission but suffer from interference in different application scenarios because of high-level spectrum utilization, massive connectivity, and the complex wireless environment. Intelligent reflecting surface (IRS) is a promising technology for dynamic configuration of the wireless propagation environment, providing new approaches to cope with the interference problem. In this article, we investigate the progress and potential of the IRS-aided network for the 6G system affected by interference. We first identify the IRS deployment and the resistance effort on interference suppression in different 6G scenarios. Then we present the typical IRS-aided network with interference, investigate the advantages of IRS, and summarize the representative recent novel works researching various schemes against interference. In particular, we discuss the IRS design against network interference by cooperating with different vital technologies, including beamforming, semi-passive IRS, non-orthogonal multiple access, artificial intelligence, and simultaneously wireless information and power transfer. Furthermore, we present a foresight vision of the upcoming requirements and trends for possible future research topics.

Nearly 70 Gbit/s NRZ-OOK encoding of a dual-mode 850 nm VCSEL with a highly In-doped and small Zn-diffused emission area

By pre-emphasized encoding of a dual-mode 850 nm vertical-cavity surface-emitting laser (VCSEL), the nearly 70 Gbit/s on–off keying (OOK) transmission performance is performed for the ultrafast data link. This VCSEL is designed with a new structural configuration, including 6 μm oxidized aperture and 4 μm Zn-diffused emission aperture, which exhibits dual-mode lasing with a threshold current of 0.75 mA, a nonsaturated power of 2.2 mW at 8 mA, and a differential quantum efficiency of 0.38 under a lensed OM4 multimode fiber (MMF) coupling scheme. In particular, the high indium (In) dopant density in the quantum well increases its differential gain coefficient to upshift the relaxation oscillation frequency, which effectively broadens the modulation bandwidth to high-speed data transmission. For the back-to-back transmission, the VCSEL coupled with a lensed OM4-MMF (1 m) for short-reach link reveals an NRZ-OOK transmission at 66 and 69 Gbit/s with a corresponding bit-error ratio (BER) of 5.9 × 10 − 10 and 10 − 5 for error-free decoding after forward-error correction. When employing graded-index single-mode fiber (GI-SMF) with 100 m length as the transmission segment, the VCSEL linked to the GI-SMF connected with a lensed OM4-MMF (1 m) collimator can provide the pre-emphasized NRZ-OOK transmission at 51 Gbit/s with a BER of 4.5 × 10 − 10 and SNR of 14.1 dB.

Microresonator frequency comb based high-speed transmission of intensity modulated direct detection data.

Globally, the long-haul transmission of ultra-high bandwidth data is enabled through coherent communications. Driven by the rapid pace of growth in interconnectivity over the last decade, long-haul data transmission has reached capacities on the order of tens to hundreds of terabits per second, over fiber reaches which may span thousands of kilometers. Data center communications operate in regimes featuring shorter reaches and higher cost sensitivity. While integrated microresonator frequency combs are poised to revolutionize light sources used for high-speed data transmission over fiber, recent progress has focused largely on coherent detection schemes. Furthermore, though state-of-the-art intensity modulators are advancing in speed, it has not been demonstrated in the literature if microresonator-based comb lines can accommodate higher intensity modulated direction data (IMDD) line rates in tandem with these advancements. In this manuscript, we demonstrate the use of microresonator frequency combs pumped with a single laser for the transmission of high-speed IMDD data. We demonstrate error-free transmission of 30 Gbs-1 per comb non-return-to-zero data over fiber lengths of 6 km, as well as bit error rates under the forward error correction limit for propagation through 20 km of optical fiber. 60 Gbs-1 and 42 Gbs-1 pulse modulation amplitude 4 (PAM4) data modulated on each frequency comb line is further quantified to have a bit error rate under the forward error correction limit for fiber reaches of up to 6 km and 20 km respectively. The results showcase CMOS-compatible microresonator frequency comb modulated using IMDD formats as a promising technology for high-speed transmission in the data center transceiver industry.