Multi-user Access Research Articles

Simultaneous underwater beam steering and PAM4 transmission enabled by the acousto-optic effect.

In this paper, an underwater wireless optical communication (UWOC) system that can simultaneously achieve beam steering and pulse amplitude modulation (PAM) enabled by the acousto-optic effect is proposed and experimentally demonstrated. An approach to manipulate the driving signal of an acousto-optic modulator (AOM) is utilized to simultaneously achieve precise laser emission angle control and signal modulation, which enables high-speed link-switching for multi-user access. The system is tested in a 7-m water tank with a water attenuation coefficient of 0.87 dB/m, and a bit error rate (BER) of 2.99 × 10-3 is realized at a maximum data rate of 1.6 Mbps. The theoretical deflection angle of a 450-nm laser is 4.6 mrad, while the actual steering range could reach up to 5.2 mrad with a horizontal displacement of 36.4 mm at the receiver plane under experimental conditions. We further measured the relationship between the diffraction efficiency of the 1st-order diffracted light and the amplitude as well as the central frequency of the driving signal, which is essential for the generation of the driving signal. The system provides an effective solution for link-switching in the Internet of Underwater Things (IoUT) and high-throughput underwater wireless optical networks.

Application of Intelligent Cloud Computing Technology in Optical Communication Network Security of Smart Grid

In order to improve the security of smart grid optical communication network, this paper combines intelligent cloud computing technology to build a security system of optical communication network of power grid. In the aspect of improving communication security performance, multi-user access is realized by non-orthogonal power domain segmentation, and different users use different powers to add and superimpose the same spectrum resources, so as to increase spectrum utilization. At the sending end, this paper improves the safe channel capacity of users by means of pre-coding and artificial noise, and realizes the safe transmission of information. In terms of transmission stability, the cloud computing platform is used as a data processing platform, and multiple nodes are processed synchronously through optical communication state identification, which can more effectively improve the speed of optical communication state identification data. In order to test the performance of the power grid information dispatching model designed in this paper in optimizing power grid configuration and improving power grid load, simulation experiments are carried out. Through the experimental analysis, we can see that the communication method proposed in this paper can accurately identify the intrusion factors, and can effectively improve the security of smart grid optical communication network.

Survey on Multifaceted Impacts: Assessing the Integration of Augmented Reality (AR) and Virtual Reality(VR) in Education for Autistic Children

This project seeks to develop a groundbreaking Augmented Reality (AR) and Virtual Reality (VR) learning platform tailored for autistic children, addressing their unique educational and social challenges. Featuring multi-user access for collaborative learning, the platform incorporates behavioral analysis to customize learning paths based on individual preferences and challenges. Immersive AR/VR environments simulate real-world scenarios, facilitating the practice of everyday life skills and social interactions in a controlled virtual space. Parental involvement is key, with features for progress tracking and guidance, aiming to empower autistic children with a personalized, inclusive, and supportive learning experience that bridges the gap between home and school. The user-friendly interface ensures accessibility, contributing to the educational empowerment of autistic children in an engaging virtual environment.

Towards Multi-user Access Fairness in Reconfigurable Intelligent Surface Assisted Wireless Networks

Reconfigurable intelligent surface (RIS) provides additional physical channels to existing wireless network infrastructure and has attracted intensive research attention to enhance the communication capacity and extend additional user accommodation. Existing RIS researches mainly focus on optimizing the physical-layer channel utilization, and have yet to consider the multi-user fairness of the medium access process when involving the RIS channel. This article shows that RIS can lead to severely unbalanced access opportunities among RIS-assisted users and others from the experimental analysis. Specifically, we demonstrate that due to the capture effect and unbalanced receiving rate of management frames, RIS-assisted users can have unfair competitive priorities to normal users without RIS resources. To overcome such unfair access issues, we propose a novel antiunfair algorithm that allows equal access opportunities for all kinds of users in a RIS-assisted network. Specifically, we optimize the management frames' modulation and coding scheme (MCS) selections to fight against unexpected bias to balance the access opportunities. We have conducted an experimental evaluation with a practical RIS system showing that the proposed antiunfair algorithm can significantly alleviate the fairness problem without compromising the network performance.

Lemo: A Cache-Enhanced Learned Optimizer for Concurrent Queries

With the expansion of modern database services, multi-user access has become a crucial feature in various practical application scenarios, including enterprise applications and e-commerce platforms. However, if multiple users submit queries within a short time frame, it can result in potential issues such as redundant computation and query concurrency. Unfortunately, most existing multi-query optimization methods, which aim to enhance query processing efficiency, have not adequately addressed these two problems, especially in the setting where multiple queries are being executed concurrently. To this end, we propose a novel method named Lemo for the multi-query optimization problem. Specifically, we propose a novel value network to predict latencies of concurrent queries as the foundation model for query plan generation. Furthermore, we introduce a shared buffer manager component to cache the intermediate results of sub-queries. The shared buffer manager applies a novel replacement policy to maintain the cached buffer with the objective of maximizing the opportunity for the reuse of the cached sub-queries. Based on the shared buffer, our proposed value network can incorporate the cached results into cost estimation to further guide Lemo in generating query plans, thus avoiding redundant computation. Lemo has been integrated into PostgreSQL and experiments conducted on real datasets with PostgreSQL show that it outperforms all the baselines in efficiency.

Методы разработки защищенного программного обеспечения

This article is devoted to the issue of software protection based on the use of modern security methods. One of these methods is the introduction of procedures into the software system that should reduce the level of errors and the risks of vulnerability to the system and software. The key goal of the stage-by-stage implementation of the developed program is gradual detection of previously undetected errors and code defects. During this stage of software development both the customer and the executor may encounter a rather narrow range of errors related to partial data inconsistency when loading them into databases, as well as failures of program procedure execution due to the use of multi-user access. It is at this stage that the final picture of user interaction with the program is crystallized, and the degree of loyalty of the latter to the developed interface is also determined. If the output of the system to the design capacity after a number of modifications and improvements has occurred without any special complications, it means that the preliminary work on the project and the implementation of the previous stages of development were carried out correctly.

An Improved Integrity-Based Hybrid Multi-User Data Access Control for Cloud Heterogeneous Supply Chain Databases

Cloud-based supply chain applications play a vital role in the multi-user data security framework for heterogeneous data types. The majority of the existing security models work effectively on small to medium-sized datasets with a homogenous data structure. In contrast, Supply Chain Management (SCM) systems in the real world utilize heterogeneous databases. The heterogeneous databases include a massive quantity of raw SCM data and a scanned image of a purchase quotation. In addition, as the size of the database grows, it becomes more challenging to provide data security on multi-user SCM databases. Multi-user datatypes are heterogeneous in structure, and it is complex to apply integrity and confidentiality models due to high computational time and resources. Traditional multi-user integrity algorithms are difficult to process heterogeneous datatypes due to computational time and variation in hash bit size. Conventional attribute-based encryption models such as "Key-policy attribute-based encryption" (KP-ABE), "Ciphertext-Policy Attribute-Based Encryption" (CP-ABE) etc., are used to provide strong data confidentiality on large textual data. Providing security for heterogeneous databases in a multi-user SCM system requires a significant computational runtime for these conventional models. An enhanced integrity-based multi-user access control security model is created for heterogeneous databases in the cloud infrastructure to address the problems with heterogeneous SCM databases. A non-linear integrity model is developed to provide strong integrity verification in the multi-user communication process. A multi-user based access control model is implemented by integrating the multi-user hash values in the encoding and decoding process. Practical results proved that the multi-user non-linear integrity-based multi-access control framework has better runtime and hash bit variation compared to the conventional models on large cloud-based SCM databases.

Round-trip multi-band quantum access network

The quantum network makes use of quantum states to transmit data, which will revolutionize classical communication and allow for some breakthrough applications. Quantum key distribution (QKD) is one prominent application of quantum networks, and can protect data transmission through quantum mechanics. In this work, we propose an expandable and cost-effective quantum access network, in which the round-trip structure makes quantum states travel in a circle to carry information, and the multi-band technique is proposed to support multi-user access. Based on the round-trip multi-band quantum access network, we realize multi-user secure key sharing through the continuous-variable QKD (CV-QKD) protocol. Due to the encoding characteristics of CV-QKD, the quadrature components in different frequency bands can be used to transmit key information for different users. The feasibility of this scheme is confirmed by comprehensive noise analysis, and is verified by a proof-of-principle experiment. The results show that each user can achieve excess noise suppression and 600 bit/s level secure key generation under 30 km standard fiber transmission. Such networks have the ability of multi-user access theoretically and could be expanded by plugging in simple modules. Therefore, it paves the way for near-term large-scale quantum secure networks.

Joint optimized multi-user access and UAV deployments based on heterogeneous revenue in IoT network

With the explosion demands of computation in the internet-of-things (IoT) sector, as an emerging technique with considerable computational capability, unmanned aerial vehicle (UAV) assisted mobile edge computing (MEC) has been proposed to reduce the latency and improve the quality-of-experience (QoE) of the user equipments (UEs). However, being existed massive heterogeneous UEs with different time sensitivity, how to offload the tasks of UEs, and where to deploy the positions of UAVs are two critical factors for the MEC system. In this work, we investigate a multi-UAV-assisted MEC system to maximize the sum of UEs’ revenue in the event that natural disasters block communication conditions. A two-hierarchy Stackelberg game framework model is constructed, with the upper-layer UAVs as leaders performing location deployments, while the lower-layer UEs as followers conducting offloading selections. Different from the existing revenue functions, for followers, we adopt three revenue functions in terms of different UEs having distinct responses to time consuming. Furthermore, both the leader-layer and follower-layer subgame are proved to be exact potential games (EPG) with at least one Nash equilibrium (NE), then demonstrating the existence of Stackelberg equilibrium (SE). Additionally, we evaluate the price of anarchy (PoA) of the NE and illustrate that the value of PoA is relatively small, which corroborates that our solution is close to the global optimum. Finally, the simulation results demonstrate that the proposed solution can improve the total revenue of UEs under guaranteeing the convergence.

Deep-learning-based multi-user framework for end-to-end fiber-MMW communications.

Fiber-wireless integration has been widely studied as a key technology to support radio access networks in sixth-generation wireless communication, empowered by artificial intelligence. In this study, we propose and demonstrate a deep-learning-based end-to-end (E2E) multi-user communication framework for a fiber-mmWave (MMW) integrated system, where artificial neural networks (ANN) are trained and optimized as transmitters, ANN-based channel models (ACM), and receivers. By connecting the computation graphs of multiple transmitters and receivers, we jointly optimize the transmission of multiple users in the E2E framework to support multi-user access in one fiber-MMW channel. To ensure that the framework matches the fiber-MMW channel, we employ a two-step transfer learning technique to train the ACM. In a 46.2 Gbit/s 10-km fiber-MMW transmission experiment, compared with the single-carrier QAM, the E2E framework achieves over 3.5 dB receiver sensitivity gain in the single-user case and 1.5 dB gain in the three-user case under the 7% hard-decision forward error correction threshold.

Effect of Coupling Discretization on Coherent-Ising-Machine-Implemented Hopfield Model

The coherent Ising machine (CIM) is being developed for solving combinatorial optimization problems scalably at high speed. The actual equipment of the measurement-feedback type of CIM (MFB-CIM) uses a field-programmable gate array (FPGA) to calculate the local field. Because the product of the coupling strength matrix and the measured amplitude vector of the optical parametric oscillator pulses must be calculated in real-time to achieve feedback, the coupling strength must have a low-bit discrete representation in the FPGA. By reducing the number of bits of coupling strength, the amount of memory needed to store the coupling matrix can be reduced and the calculation speed increased so that the MFB-CIM can implement more spins. Therefore, it is necessary to reduce the number of bits of coupling strength as much as possible while maintaining the performance in solving combinatorial optimization problems. In this paper, to evaluate the effect of discretization of the coupling strength in the MFB-CIM, we quantitatively evaluate the performance of the Hopfield model with discrete coupling when it is implemented in the CIM. The Hopfield model, which is a canonical model of Ising computation in information statistical mechanics, is defined in a coupling manner called the correlation-type interaction, in common with other models such as Sourlas code, a code division multiple access multiuser detector, and L0 regularization-based compressed sensing. We derived the macroscopic equations (MEs) of the Hopfield model with discrete coupling when it is implemented in the CIM by using the non-equilibrium statistical mechanics method we previously proposed. Moreover, we clarified the relationship between the number of bits of the coupling strength and the critical memory capacity for various pump rates.

RELATIONAL DATABASE WORK OPTIMIZATION OF THE TRANSPORT INFORMATION SYSTEM

Informatization of society poses new challenges and requirements for information systems in transport, which are responsible for data processing and storage. A significant number of performance problems in developed applications are related to databases, because often poor database performance directly affects the application's slowdown. For the normal functioning of the processes of diagnostics of rolling stock and automation systems, decision-making, and the formation of reports in the transport industry, the task of optimizing the management of databases and ensuring their productivity under the condition of simultaneous multi-user access arises. The article discusses the stages of query execution and approaches to increasing the efficiency of the query optimizer. The main factors that depend on the performance of queries in information systems based on relational databases are analyzed. Optimization criteria can include such performance estimates as time required to generate a report, query execution time, speed of finding data in non-indexed fields, maximum number of simultaneous accesses to data in multi-user mode, speed of indexing, as well as update, delete and add operations.

Beyond Nonorthogonal Multiple Access: New Role of Constructive Interference

In this letter, we introduce a novel framework of constructive non-orthogonal multiple access (NOMA) transmission, which provides the merit of interference utilization and breaks through the constructive interference (CI)’s limitation on multiuser (MU) access capability. With dedicated synthetic successive coding and hybrid MU access designs, a novel constructive NOMA (CNOMA) precoder is proposed, which is particularly suitable for the scenario where users have heterogeneous throughput requirements. Explicitly, it makes the composite interference always beneficial to the users having high throughput requirement, while accommodating another sets of users under their subscribed reception-quality requirement. Finally, a number of fundamental properties of the CNOMA design is revealed, such as the tradeoff between utilization of MU interference and improvement of MU access capability. Simulation demonstrates that the proposed CNOMA precoder significantly outperforms the classic CI and minimum-mean-square-error precoders in throughput performance, and meanwhile obtains high access capability close to classic NOMA designs.

Hybrid multi-user access scheme for a visible light communication system.

A hybrid multi-user access scheme based on orthogonal frequency-division multiple access and non-orthogonal multiple access (OFDMA-NOMA) is proposed for visible light communication (VLC) systems with a bandwidth-constrained channel. In the scheme, a novel user resource allocation method is used, to the best of our knowledge, to reduce the unfairness among different users caused by the high-frequency fading characteristic of VLC systems. Furthermore, the particle swarm optimization (PSO) is introduced to satisfy the transmitting power requirements of each user and to improve system performance. Simulation results show that, under the same VLC system conditions, the OFDMA-NOMA scheme with PSO has significant improvements in terms of user capacity and transmission rates compared to the purely NOMA scheme and the OFDMA scheme.

Symbiotic backscatter communications for 6G: principles, approaches, and applications

In recent years, due to the mutualistic sharing of spectrum and energy, symbiotic backscatter communications have attracted considerable attention and provided a potential solution to the spectrum and energy issues in 6G. In symbiotic backscatter communications, the secondary system uses the spectrum and radio frequency signal of the primary system for passive backscatter transmission. Meanwhile, the secondary transmission provides additional multipath to the primary system, which is expected to improve the performance of the primary system. First, the basic concepts and technical principles of symbiotic backscatter communications are introduced. Second, an overview of symbiotic backscatter communications is provided from the aspects of information theory, receiver design, resource allocation, and multiuser access. Third, the applications of the reconfigurable intelligent surface (RIS) in symbiotic backscatter communications are described, and the benefits brought by the introduction of RIS for symbiotic backscatter communications are analyzed and summarized. Finally, the 6G architecture and the application prospects of integrating the symbiotic backscatter communication are illustrated, and the challenges of the symbiotic backscatter communications are discussed.

Analysis and assessment software for multi-user collaborative cognitive radio networks

<span>Computer simulations are without a doubt a useful methodology that allows to explore research queries and develop prototypes at lower costs and timeframes than those required in hardware processes. The simulation tools used in cognitive radio networks (CRN) are undergoing an active process. Currently, there is no stable simulator that enables to characterize every element of the cognitive cycle and the available tools are a framework for discrete-event software. This work presents the spectral mobility simulator in CRN called “App MultiColl-DCRN”, developed with MATLAB’s app designer. In contrast with other frameworks, the simulator uses real spectral occupancy data and simultaneously analyzes features regarding spectral mobility, decision-making, multi-user access, collaborative scenarios and decentralized architectures. Performance metrics include bandwidth, throughput level, number of failed handoffs, number of total handoffs, number of handoffs with interference, number of anticipated handoffs and number of perfect handoffs. The assessment of the simulator involves three scenarios: the first and second scenarios present a collaborative structure using the multi-criteria optimization and compromise solution (VIKOR) decision-making model and the naïve Bayes prediction technique respectively. The third scenario presents a multi-user structure and uses simple additive weighting (SAW) as a decision-making technique. The present development represents a contribution in the cognitive radio network field since there is currently no software with the same features.</span>

Multi-Access Channel Based on Quantum Detection in Wireless Optical Communication.

In this paper, we propose a novel multi-user access in wireless optical communication based on the quantum detection of the coherent state. In this case, the coherent states are used as the signal carrier and a technique of quantum detection is applied to distinguish between signals from different users. To accomplish this task, two main quantum measurement methods are introduced; one is minimum error discrimination (MED), and the other is unambiguous state discrimination (USD). The theoretical derivation implies that the two methods can both distinguish between the signals from different users efficiently when the average photon number is large enough. Typically, the numerical result shows that in the two-user case, the channel capacity will approach the theoretical maximum limit when the average photon number is greater than 2.5 for MED and 5 for USD in the absence of noise. The MED gains more channel capacity than the USD at the same average photon number. However, the USD wins the error-correction scene with its free-error capability. Furthermore, the detection error probability and channel capacity for the USD with the thermal noise are examined. The result shows that increasing the signal average photon number can continue the USD’s advantage of error-free detection even if in the presence of thermal noise. In addition, compared with non-orthogonal multiple access (NOMA), the bit error rate (BER) against signal-to-noise rate (SNR) performance of USD has been improved.

Robust and adaptable quantum key distribution network without trusted nodes

Quantum key distribution (QKD) networks are promising to serve large numbers of users with information-theoretic secure communication. In QKD networks, the detection-safe protocol, termed measurement-device-independent (MDI) QKD, can naturally enhance realistic security by supporting untrusted measurement nodes. However, the environmental disturbances to quantum states degrade the performance of multi-user communication. Here we propose an MDI-QKD networking scheme with robustness against environmental disturbance and adaptability to multi-user access, where more than two users can generate keys simultaneously regardless of aligning reference frames and compensating channel disturbance on polarization. To achieve this, we introduce the reference-frame-independent protocol as well as a polarization-compensation-free method, design a multi-user measurement unit, and combine it with original two-user units. The scheme is experimentally demonstrated for the improvement of network robustness and adaptability in multi-user scenarios, and the time and device costs of disturbance compensation can be saved from O ( N ) to O ( 1 ) for an N-user network.

Exploring Carrier Sense Multiple Access with Collision Avoidance Techniques for Resource Sharing in Broadband Power Line Communications

A resource sharing in power line communications (PLC) for the home network is restricted by the channel assignment techniques which decide who has the right to gain access to send data. The channel assignment techniques include contention-free and contention-based. The former requires high synchronization due to the deterministic round-trip time. Besides, contention-based utilizes CSMA/CA techniques that allow stations in a network to compete for channel access and are suitable for decentralized network topology. However, a trade-off exists between the number of stations required to gain access versus system efficiency. Whilst some research has been carried out on CSMA/CA resource sharing techniques that allow only one user to transmit, there is very little work done on multiuser access to optimize system efficiency and reduce collisions in a network. The purpose of the current study was to review the CSMA/CA techniques for resource sharing to improve system efficiency in power line communications. In carrying out this study, a systematic literature review methodology to evaluate different related works and determine the most suitable approach to allow multiuser channel access was used. The study further demonstrated the impact multichannel access has on system efficiency. In addition, the study provides recommendations for future research.
 Keywords: CSMA/CA; Medium access control; OFDMA; power line; resource sharing;

JEEVAN ONLINE HEALTH APPLICATION

The importance of health care is immense in society and over the past years, this sector has been evolving to produce a more efficient and computerized system. On our health service website, we try to develop software in which a patient registers on the website. then the patient is introduced to different features of the website such as health care tips, medication tips,pandemic awareness, nearest hospital location, blood availability and blood availability, and many more. Our software even allows patients to book a bed in a hospital and also allows the patient to buy blood from the nearest blood bank. Moreover, our software provides clear and actionable information for all users. This application maintains the entire data in a centralized and secured database server to maintain consistency in report generation and allows users to access it from any location. This is an online application that allows multi-user access to the system and to track or manage the data simultaneously. Various roles and authentications have been provided and access to various areas in the tool is restricted according to the role given to users. This system design is modularization into various categories. This system has enriched UI so that a novice user did not feel any operational difficulties. This system mainly concentrated on designing various reports requested by the users as well as higher with export to excel options.