Enhance Transmission Performance Research Articles

A hybrid approach to secure and compress data streams in cloud computing environment

Cloud computing has revolutionized the way businesses and individuals manage and utilize computing resources, providing significant benefits such as scalability, flexibility, and cost-effectiveness. However, the increasing use of cloud computing to store and transmit sensitive data has raised concerns about data security. Ensuring confidentiality and data integrity while enabling effective data transmission is a significant challenge. To overcome this issue, the proposed approach integrates encryption and compression methods to enhance transmission performance in the cloud and prevent unauthorized access to confidential information. This approach applies multiple layers of robust encryption algorithms, followed by LZMA, which aims to compress data size while ensuring data security. The proposed approach is well-suited for real-time implementation and delivers high encryption quality and compression capabilities. Various performance metrics evaluate its performance, including space-saving percentage, processing time, and the NIST randomness test. It provides a substantial improvement in space-saving percentage from 58.63% to 81.8%, ensuring efficiency. The security analysis confirms that ciphertexts generated by this approach pass all NIST tests, generating a 99% confidence level regarding the randomness of the ciphertext. The proposed hybrid approach offers an effective solution for addressing the challenges of securing sensitive data while taking advantage of the benefits of cloud computing.

Non-Gaussian approach: Withstanding loss and noise of multi-scattering underwater channel for continuous-variable quantum teleportation

Underwater quantum communication plays a crucial role in ensuring secure data transmission and extensible quantum networks in underwater environments. However, the implementation of such applications encounters challenges due to the light attenuation caused by the complicated natural seawater. This paper focuses on employing a model based on seawater chlorophyll-a concentration to characterize the absorption and scattering of light through quantum channels. We propose a multi-scattering random channel model, which demonstrates characteristics of the excess noise in different propagation directions of communication links. Furthermore, we consider the fidelity of a continuous-variable quantum teleportation through seawater channel. To enhance transmission performance, non-Gaussian operations have been conducted. Numerical simulations show that incorporating non-Gaussian operations enables the protocol to achieve higher fidelity transmission or lower fidelity fading rates over longer transmission distances.

Performance Analysis of NOMA-Based Hybrid Satellite-Terrestrial Relay Networks With CCI

Hybrid satellite-terrestrial relay networks (HSTRNs) which exploit relay cooperative technology in the integrated system of satellites and terrestrial base stations (BSs) are expected to offer enhanced transmission performance benefited from the spatial gain of independent fading paths. To enable multi-user accessing and resource sharing among users, non-orthogonal multiple access (NOMA) technique can be applied in HSTRNs. In this paper, we consider a NOMA-based HSTRN where a satellite transmits signals to a relay base station (RBS) and a destination ground station (DGS), and RBS also serves a cellular user (CU) and DGS simultaneously by leveraging NOMA scheme. We assume that the satellite shares spectrum with a number of cellular small BSs (SBSs), hence SBSs will cause co-channel interference (CCI) to DGS, RBS and CU. We examine the transmission characteristics of the satellite and terrestrial links, and derive the closed-form expressions of the outage probability (OP) and average symbol error rate (ASER) of DGS and CU, respectively. Specially, we consider the effect of perfect and imperfect successive interference cancellation (SIC) on the ASER performance of CU. Then, considering the stochastic characteristics of satellite links and CCI, we analyze the mean energy efficiency (MEE) of the satellite and propose an optimal power allocation scheme which maximizes the MEE of the satellite and achieves system performance optimization. Simulation results demonstrate the effectiveness of the theoretical analysis and the proposed power allocation scheme.

Improving the data rate for long distance visible light communication using h-BN/CdZnSeS@ZnSeS quantum dot composite.

Quantum dots (QDs) are exploited in visible light communication (VLC) due to their unique optical properties. However, it is still a challenge to conquer heating generation and photobleaching under prolonged illumination. In this paper, we proposed to utilize hexagonal boron nitride (h-BN) nanoplates to improve the thermal stability and photo stability of QDs and long-distance VLC data rate. After heating to 373 K and cooling to the initial temperature, photoluminescence (PL) emission intensity recovers to 62% of the original intensity and after 33 hours of illumination, PL emission intensity still maintains 80% of the initial intensity, while that of the bare QDs is only 34% and 53%, respectively. The QDs/h-BN composites perform a maximum achievable data rate of 98 Mbit/s by applying on-off keying (OOK) modulation, while the bare QDs are only 78 Mbps. In the process of extending the transmission distance from 0.3 m to 5 m, the QDs/h-BN composites exhibit superior luminosity corresponding to higher transmission data rates than bare QDs. Particularly, when the transmission distance reaches 5 m, the QDs/h-BN composites still show a clear eye diagram at a transmission rate of 50 Mbps while the eye diagram of bare QDs is indistinguishable at 25 Mbps. During 50 hours of continuous illumination, the QDs/h-BN composites keep a relatively stable bit error rate (BER) at 80 Mbps while that of QDs continuously increase, and the -3 dB bandwidth of QDs/h-BN composites keep around10 MHz while the bare QDs decrease from 12.6 MHz to 8.5 MHz. After illumination, the QDs/h-BN composites still indicate a clear eye diagram at a data rate of 50 Mbps while that of pure QDs is indistinguishable. Our results provide a feasible solution for realizing an enhanced transmission performance of QDs in longer-distance VLC.

A Wideband Dual-Polarized Ring-Loaded Cross Bowtie Antenna for Wireless Capsule Endoscopes: Design and Link Analysis

This work presents a novel on- body wideband dual-polarized antenna to stabilize and enhance the link performance of wireless capsule endoscopy systems. By introducing a cross-bowtie structure with a planar compact feed method, the antenna achieves a dual-polarized performance with high port-to-port isolation. A loaded ring with additional stubs is also implemented to further enhance the bandwidth and provide a flat in-band performance from 381 to 990 MHz. The proposed antenna is measured with both homogeneous phantom and ex vivo test to validate the impedance matching performance. To validate the effectiveness of the proposed on- body antenna on the communication link, a capsule helical antenna with omnidirectional radiation pattern is designed and measured. Finally, comprehensive link studies are conducted considering the varied capsule orientations and locations, with a peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{21}\vert $ </tex-math></inline-formula> value of–25.5 dB at the 60 mm implant depth and an acceptable link loss due to the capsule position error. The proposed on- body antenna can be regarded as a good candidate for a practical capsule endoscopy system due to its stable and enhanced transmission performance when compared with its counterparts.

FPCB as an Acoustic Matching Layer for 1D Linear Ultrasound Transducer Arrays.

An acoustic matching layer is an essential component of an ultrasound transducer to achieve maximum ultrasound transmission efficiency. Here, we develop a flexible printed circuit board (FPCB) with a composite structure consisting of multiple polyimide and copper layers and demonstrate it as a novel acoustic matching layer. With a flexible substrate and robust ACF bonding, the FPCB not only serves as an acoustic matching layer between piezoelectric elements and the surrounding medium but also as a ground for the electrical connection between the transducer array elements and the folded substrate. A 1D linear ultrasound transducer array with the FPCB matching layer exhibits larger output pressure, wider -3dB bandwidth, and higher ultrasound beam intensity compared to that of an ultrasound transducer array with the alumina/epoxy matching layer, which is one of the most commonly applied composite matching layers. The enhanced transmission performance verifies that the proposed FPCB is an excellent matching layer for 1D linear ultrasound transducer arrays.

Precoded and pre-equalized multi-band FBMC transmission enabled by radio-frequency DACs and the undersampling technique.

In this Letter, we use radio-frequency digital-to-analog converters (DACs) operating in different frequency response modes to generate a high spectral-efficiency multi-band (MB) filter bank multicarrier (FBMC) signal. In the receiver, the undersampling technique is employed to realize down-conversions. No electrical mixers are required. Besides, discrete Fourier transform and orthogonal circulant matrix transform precoding techniques combined with channel-independent digital pre-equalization are enabled to enhance transmission performance. Both numerical simulations and offline experiments are performed. The relevant results show that the MB-FBMC without a cyclic prefix (CP) is robust against inter-symbol interference induced by the band-pass filtering. By using precoding and pre-equalization techniques, the bit error rate can be improved by more than one order of magnitude. In contrast, an additional 12.5% CP overhead is required for the MB orthogonal frequency division multiplexing system to achieve such an improvement.

On the Capacity of Reconfigurable Intelligent Surface Assisted MIMO Symbiotic Communications

Reconfigurable intelligent surfaces (RISs) appear as one of the most promising paradigms for future wireless communications, because of their high adjustability for diverse communication demands and the additional information-carrying capability by reflecting patterns. This paper investigates the capacity of RIS-assisted multiple-input multiple-output (MIMO) symbiotic communications utilizing multiple reflecting patterns, where each reflecting pattern is non-uniformly activated to carry additional information. To enhance transmission performance, the reflecting patterns, reflecting activation probability, and the transmit covariance matrix are jointly designed. Since the exact expression of the system capacity is intractable, the lower and upper bounds on the capacity are derived and used for optimization in this paper. Based on the lower bound on the capacity, a gradient ascent algorithm is developed to find the optimal reflecting patterns, reflecting activation probability, and the transmit covariance matrix. By taking advantage of the concise-form upper bound on the capacity, closed-form solutions of the reflecting activation probability and transmit covariance matrix can be derived after optimizing the reflecting patterns. The superiority of the proposed design is investigated and verified by computer simulations. Some selected numerical results demonstrate that the proposed design can achieve a higher capacity than the benchmark adopting only one reflecting pattern.

Anti-Jamming RIS Communications Using DQN-Based Algorithm

Wireless sensor networks (WSNs) are widely applied in battlefield surveillance, where the data collection (e.g. target tracking or contention zone observation) employed by local sensor nodes needs to send to military bases for tactical decisions. Since data transmissions are susceptible to malicious attacks, jammers of adversaries can successfully block their victim’s communications by transmitting interfering signals to legitimate transmissions. Nowadays, owing to the ability to reconfigure the wireless propagation medium, reconfigurable intelligent surface (RIS) is regarded as an effective tool to enhance transmission performance, especially in the jamming context. This paper considers the anti-jamming communication tactical scenario of a solar-powered RIS network, in which the RIS is used to improve the uplink transmission performance between a wireless device (WD) and a base station (BS). We investigate the long-term anti-jamming communications of the WD powered by a solar energy harvester. Our objective is to jointly assign the optimal amount of transmission energy and the RIS phase shifts to maximize the data rate of the system in the long run. To this end, we formulate an anti-jamming communication optimization problem as a Markov decision process (MDP) framework and then design a deep Q network (DQN)-based algorithm to generate an optimal policy. As a result, the optimal resource allocation is achieved through trial-and-error interactions with environment by observing the predefined rewards and the network state transition. The Python simulation results conducted by averaging 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> time slots show that the proposed algorithm is not only able to learn from environment, but also yields better performance than baseline schemes under network changes. Moreover, the performance of RIS communication schemes is verified to be superior to that of without-RIS communication schemes in the jamming context.

Subtraction dual‐wavelength for enhanced transmission performance of free‐space optical communication over turbulence effect

Performance of a free-space optical communication system is influenced by atmospheric turbulence which degrades signal transmission quality. A gamma–gamma channel model is employed to characterise this turbulence under weak-to-strong conditions. The proposed dual diffuser modulation using subtraction dual-wavelength concept is combined with a phase screen diffuser to improve signal transmission. Its performances are compared with conventional intensity modulation-direct detection on off keying and partial coherent beam on off keying techniques. In comparison, results show that the dual diffuser modulation demonstrates superior performances in both received power and bit rate transmission under different turbulence conditions.

Probabilistic shaping based constellation encryption for physical layer security in OFDM RoF system.

The physical layer security of radio-over-fiber (RoF) system is a very important problem for future communication. In this paper, a novel probabilistic shaping (PS) based constellation encryption scheme is proposed in which two bit-level encryption operations are firstly performed according to chaotic sequences and hash values. The chaotic sequences are generated by hyperchaotic system and hash values are obtained by SHA-512. Then PS is applied to enhance transmission performance. After PS-16-quadrature amplitude modulation (QAM), constellation encryption is implemented aiming at maintaining overall shaping distribution unchanged and improving security. An encrypted PS-16-QAM orthogonal frequency division multiplexing (OFDM) signal is successfully transmitted over 50 km standard single-mode fiber (SSMF) and 5 m wireless channel in our experiment. The results demonstrate that the key space of 10121 is achieved to defend malicious attacks. Moreover, the proposed PS-based encryption scheme can obtain approximately 2.4 dB gain at a BER of 10-3 compared with traditional OFDM signal. Thus, the proposed scheme has a good application prospect in the future OFDM-RoF system due to the dominant BER and security performance.

Enhanced transmission performance based on ultrathin broadband circular hole array metasurface

A high transmittance broadband metasurface with Si and STO layers is verified in 100–130 THz. This metasurface achieves a transmission peak (Amplitude 78.1%, Resonance frequency 112.2 THz) with a complete Si layer, or a broad transmission band (Average transmittance 82.3%, bandwidth 5.1 THz) with a Si layer defined by a circular hole array. The influence of structural parameters (period P and diameter D) on this transmission band is measured. In the first set of measurements, the average transmittance and bandwidth of this metasurface remain unchanged with P increasing. In the second set of measurements, however, the average transmittance is increased from 82.3% to 92.7%, and bandwidth is enhanced from 5.1 THz to 7.2 THz with D increasing. Finally, the sensitivity of the metasurface to temperature is measured. When temperature increases from 300 K to 360 K, average transmittance increases from 82.3% to 95.4%, and bandwidth enhances from 5.1 THz to 10.3 THz. When temperature reduces, the average transmittance and bandwidth decrease. This metasurface exploits the potential of temperature sensing.

Harvest-and-Opportunistically-Relay: Analyses on Transmission Outage and Covertness

To enhance transmission performance, privacy level, and energy manipulating efficiency of wireless networks, this article initiates a novel simultaneous wireless information and power transfer (SWIPT) full-duplex (FD) relaying protocol, named harvest-and-opportunistically-relay (HOR). Due to the FD characteristics, the dynamic fluctuation of relay’s residual energy is difficult to quantify and track. To solve this problem, the Markov Chain (MC) theory is invoked. Furthermore, to improve the privacy level of the proposed HOR relaying system, covert transmission performance analysis is performed, where closed-form expressions of the optimal detection threshold and minimum detection error probability are derived. Last but not least, with the aid of stationary distribution of the MC, closed-form expression of transmission outage probability is calculated, based on which transmission outage performance is analyzed. Numerical results have validated the correctness of analyses on transmission outage and covertness. The impacts of key system parameters on the performance of transmission outage and covertness are given and discussed. Based on mathematical analysis and numerical results, we showcase that the proposed HOR model can not only reliably enhance the transmission performance via smartly managing residual energy but also efficiently improve the privacy level of the legitimate transmission party via dynamically adjusting the optimal detection threshold.

Introducing coherent MIMO sensing, a fading-resilient, polarization-independent approach to ϕ-OTDR.

Nowadays, long distance optical fibre transmission systems use polarization diversity multiplexed signals to enhance transmission performance. Distributed acoustic sensors (DAS) use the same propagation medium, i.e., single mode optical fibre, and aim at comparable targets such as covering the highest distance with the best signal quality. In the case of sensors, a noiseless transmission enables us to monitor a large quantity of mechanical events along the fibre. This paper aims at extending the perspectives of DAS systems with regard to technology breakthroughs introduced in long haul transmission systems over the past decade. We recently developed a sensor interrogation method based on coherent phase-sensitive optical time domain reflectometry (ϕ-OTDR), with dual polarization multiplexing at the transmitter and polarization diversity at the receiver. We name this technique coherent-MIMO sensing. A study is performed from a dual-polarization numerical model to compare several sensor interrogation techniques, including coherent-MIMO. We demonstrate that dual-polarization probing of a fibre sensor makes it insensitive to polarization effects, decreases the risks of false alarms and thus strongly enhances its sensitivity. The simulations results are validated with an experiment, and finally quantitative data are given on the performance increase enabled by coherent-MIMO sensing.

Enhanced Transmission Performance of a Dipole Antenna Based on a Ceramic Diamond-Structure PBG Substrate with a Defect Cavity

The radiation performance of a dipole antenna on a diamond-structured photonic crystal (PC) substrate with point defects fabricated using three-dimensional (3D) printing technology has been investigated. Meanwhile, according to the reflection properties of the PCs, corresponding dipole antennas were fabricated and packaged with standard coaxial lines. The experimental results showed a strong radiation frequency of the dipole antenna at about 13 GHz, in basic agreement with the strongest reflection frequency of the PCs with point defects. The experimental results also show that the maximum gain of the major lobe in the dipole antenna was close to −67 dB, while the angular range of the major lobe was 5–55°. The maximum gain of the major lobe increased to −60 dB in the composite antenna, representing an improvement of 7 dB compared with the dipole antenna, while the width range of the major lobe was 240–270°. These results show that the use of such substrates based on diamond-structure PCs with point defects could significantly improve the gain and directivity of the antenna, providing a basis for engineering applications.

End-to-End Delay Minimization-Based Joint Rule Caching and Flow Forwarding Algorithm for SDN

Software-defined networking (SDN) technology is expected to offer higher flexibility and programmability and enhanced transmission performance by decoupling control plane from data plane and enabling centralized network management. In SDN, switches may cache a certain number of flow forwarding rules, so that user flows can be forwarded accordingly. In this article, stressing the limited caching space of switches and the heterogeneous transmission performance of switches and links, we jointly design rule caching and flow forwarding strategy for multiple user flows in SDN. To emphasize the importance of the end-to-end delay caused by the transmission and processing of user flows in both the data plane and control plane, we formulate the joint optimization problem as an end-to-end delay minimization problem. As the original optimization problem is a non-deterministic polynomial hard (NP-hard) problem, which cannot be solved directly, we propose a heuristic algorithm which successively solves three subproblems, i.e., flow forwarding subproblem, rule caching and candidate path selection subproblem, and resource sharing subproblem. By applying the K-shortest path algorithm, a priority-based rule caching algorithm, and Lagrangian dual method, respectively, the three subproblems are solved and the joint rule caching and flow forwarding strategy is obtained. Simulation experiments are conducted to examine the effectiveness of the proposed algorithm, and the results indicate that our proposed algorithm is capable of improving system performance by about 20% compared with the previous solutions.

Social-aware data dissemination in opportunistic mobile social networks

Opportunistic Mobile Social Networks (OMSNs), formed by mobile users with social relationships and characteristics, enhance spontaneous communication among users that opportunistically encounter each other. Such networks can be exploited to improve the performance of data forwarding. Discovering optimal relay nodes is one of the important issues for efficient data propagation in OMSNs. Although traditional centrality definitions to identify the nodes features in network, they cannot identify effectively the influential nodes for data dissemination in OMSNs. Existing protocols take advantage of spatial contact frequency and social characteristics to enhance transmission performance. However, existing protocols have not fully exploited the benefits of the relations and the effects between geographical information, social features and user interests. In this paper, we first evaluate these three characteristics of users and design a routing protocol called Geo-Social-Interest (GSI) protocol to select optimal relay nodes. We compare the performance of GSI using real INFOCOM06 data sets. The experiment results demonstrate that GSI overperforms the other protocols with highest data delivery ratio and low communication overhead.

Weighted interframe averaging-based channel estimation for orthogonal frequency division multiplexing passive optical network

Weighted interframe averaging (WIFA)-based channel estimation (CE) is presented for orthogonal frequency division multiplexing passive optical network (OFDM-PON), in which the CE results of the adjacent frames are directly averaged to increase the estimation accuracy. The effectiveness of WIFA combined with conventional least square, intrasymbol frequency-domain averaging, and minimum mean square error, respectively, is demonstrated through 26.7-km standard single-mode fiber transmission. The experimental results show that the WIFA method with low complexity can significantly enhance transmission performance of OFDM-PON.

Asynchronous Transfer Mode (ATM) Technology and Applications

The purpose of this paper is to summarize the Asynchronous Transfer Mode (ATM) technology and determine where it is in its evolutionary development. Technologies that fragment data into small pieces typically have very poor performance because there is no mechanism to detect and retransmit lost cells when a piece of the data is lost in transit. The only way to recover the damaged cell is to retransmit the entire large packet again. An alternative to inefficiently retransmitting the entire packet is to only retransmit the individual cells that are lost or damaged. The ATM technology incorporates the ability to retransmit only the cells in each packet that were not received properly. It also enhances transmission performance by reducing flow control activity required at each network link. Surveying recent products serves as an effective barometer for determining how the ATM technology is evolving. State-of-the-market ATM products indicate that an ATM design solution provides unmatched speed, fault-tolerance, and scalability through multiple, meshed inter-switch connections that support load-sharing across networks. At its current point in evolutionary technological development, ATM is a key enabling communications technology that will introduce new applications to users and network providers, as well as provide higher bandwidth capacity to networks. Because of its high-bandwidth capacity and cell-oriented architecture, ATM is the dominant infrastructure for delivering virtually all types of communications, including data, voice, image, and multimedia, into the buildings and desktops of users around the world. By carefully considering critical performance issues, and accommodating existing legacy systems during ATM implementations, the telecommunications industry has insured that ATM will not only be the design solution of the future, but that it can provide cost effective applications today as well.

Weighted Inter-frame Averaging-Based Channel Estimation for CO-OFDM System

We propose an efficient channel estimation method for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) based on weighted inter-frame averaging (WIFA), in which the channel estimation results of the adjacent frames are averaged to increase the estimation accuracy. The principle of the proposed WIFA method is theoretically analyzed, and the benefit is demonstrated by a polarization-division-multiplexed CO-OFDM transmission experiment. The channel magnitude and phase differences among adjacent frames are investigated. The effectiveness of WIFA method, combined with conventional least square method, time-domain averaging method, and intra-symbol frequency-domain averaging method, respectively, is demonstrated through 240-km standard single-mode fiber transmission with different launched power values. The experimental results show that the WIFA method can significantly enhance transmission performance.