Multiple Access Research Articles

Semantic Feature Division Multiple Access for Digital Semantic Broadcast Channels

Semantic Feature Division Multiple Access for Digital Semantic Broadcast Channels

Enhancing outage performance and sum capacity in multi-user environments through IOS-aided hybrid NOMA under imperfect SIC

Abstract This study investigates the potential of integrating passive intelligent omni surface (IOS) technology to enhance wireless communication within a hybrid non-orthogonal multiple access (NOMA) system. Through a comprehensive analysis, three user pairing schemes - near-near, far-far (NN-FF) pairing, odd-even (O-E) pairing, and near-far (N-F) pairing - are meticulously investigated. Analytical expressions for outage probability are derived for each of the three pairing schemes. The proposed IOS-assisted hybrid NOMA with N-F pairing demonstrates a significant signal-to-noise ratio (SNR) improvement, achieving gains of $$\sim$$ ∼ 48 dB to $$\sim$$ ∼ 52 dB compared to reconfigurable intelligent surface (RIS)-assisted hybrid NOMA and conventional hybrid NOMA systems. The N-F pairing strategy excels with the IOS-assisted hybrid NOMA, delivering superior performance over other pairing strategies. However, it results in a complex system, whereas NN-FF pairing exhibits a low-complexity system. Furthermore, the power allocation factors are optimized to maximize the sum capacity across all users. This work also explores the impact of imperfect successive interference cancellation (iSIC) on system performance. The proposed IOS-assisted hybrid NOMA system with N-F pairing demonstrates significant improvements in sum capacity. The N-F pairing achieves a minimum of $$\sim$$ ∼ 4% increase in sum capacity over other pairing strategies, even with a 1% SIC error rate. The proposed schemes with optimal power fractions improve sum capacity (bps/Hz) from $$\sim$$ ∼ 8.64 to $$\sim$$ ∼ 10.46 compared to conventional systems. The proposed system demonstrates significant improvements in sum capacity and outage probability performance, providing essential insights for the advancement of next-generation networks.

A Semantic Approach to Successive Interference Cancellation for Multiple Access Networks

A Semantic Approach to Successive Interference Cancellation for Multiple Access Networks

A Randomized Controlled Trial of a Telehealth Group Intervention to Reduce Perinatal Depressive Symptoms: A Mixed Methods Analysis

A Randomized Controlled Trial of a Telehealth Group Intervention to Reduce Perinatal Depressive Symptoms: A Mixed Methods Analysis

CAPACITY ANALYSIS IN ORTHOGONAL MULTIPLE ACCESS CELLULAR SYSTEMS

This paper provides a comprehensive analysis of capacity in orthogonal multiple access systems. In the coverage planning section, the focus is on cell radius and signal to noise ratio (SNR) at the cell boundary. The static channel allocation section examines capacity from the perspectives of signal to interference ratio (SIR), reuse distance, number of channels, cluster size, and group size. The guaranteed service-based capacity analysis section evaluates capacity based on signal to interference plus noise ratio (SINR) and cluster size, while the traffic-based capacity analysis section analyzes parameters such as relative traffic load, assignment failure rate, and blocking probability. The best-effort data services section assesses capacity in terms of data rates, and the interruption-based capacity analysis section looks at SINR and interruption probability. Finally, the directional antennas and sectorization section investigates capacity using directional antennas. These comprehensive analyses provide valuable insights into optimizing the performance of cellular systems and better understanding their capacity.

Risk factors for prolonged urine leakage following pediatric percutaneous nephrolithotomy: A comparative study of lithotripsy techniques

ObjectiveThis study aimed to identify the risk factors associated with prolonged urine leakage (PUL) following pediatric percutaneous nephrolithotomy (PCNL) with a specific focus on the impact of lithotripter type.MethodsData from 847 pediatric PCNL patients treated between August 1997 and February 2024 were collected. Patients were categorized into two groups based on the urine leakage time: prolonged leakage (> 24 h) and normal leakage. Logistic regression analysis was used to identify determinants of prolonged urine leakage.ResultsThe study found that the use of laser lithotripters (LL) significantly increased the risk of prolonged urine leakage compared with pneumatic lithotripters (PL) (OR, 3.1; 95% CI: 1.68–5.76, p < 0.001). Additionally, larger access diameters (≥ 26 Fr), larger stone sizes (> 350 cc), and younger age (< 6 years) were associated with an increased risk of PUL. Patients who underwent procedures with multiple accesses were also at a higher risk of PUL. Despite this, conservative management without the use of DJ stents is effective in most cases.ConclusionThe use of PL in pediatric cases is associated with a lower risk of PUL than LL. Factors such as the access diameter, stone size, and patient age can predict the likelihood of PUL. Conservative management is recommended in most patients to avoid increased morbidity.

Design of AR-based general computer technology experiment demonstration platform

Abstract In order to improve the experimental demonstration effect of computer technology, this article combines virtual reality technology and intelligent reflective surface-assisted perception and communication technology to build a general computer experiment demonstration platform. Based on sparse code division multiple access, this article proposes an intelligent reflector-assisted joint multi-user information reliable access and environmental reflector sensing scheme. Moreover, this article extracts the information about the environmental reflector in the received signal by means of computational imaging. In addition, this article iteratively optimizes the performance of multi-user information access and environment awareness through the relationship between the information of the environmental reflector and the received signal. The experimental research shows that the augmented reality-based general computer technology experimental demonstration platform proposed in this article has good effects and can effectively promote the computer technology experimental demonstration effect.

Implementation of LoRa TDMA-Based Mobile Cell Broadcast Protocol for Vehicular Networks

With increasing vehicle density and growing demands on transport infrastructure, there is a need for resilient, low-cost communication systems capable of supporting safety-critical applications, especially in situations where primary channels like Wi-Fi or LTE are unavailable. This paper proposes a novel, real-time vehicular network protocol that functions as an emergency fallback communication layer using long-range LoRa modulation and off-the-shelf hardware. The core contribution is a development of Mobile Cell Broadcast Protocol that is implemented using Long-Range modulation and time-division multiple access (TDMA)-based cell broadcast protocol (LoRA TDMA) capable of supporting up to six dynamic clients to connect and exchange lightweight cooperative awareness messages. The system achieves a sub-100 ms node notification latency, meeting key low-latency requirements for safety use cases. Unlike conventional ITS stacks, the focus here is not on full-featured data exchange but on maintaining essential communication under constrained conditions. Protocol has been tested in laboratory to check its ability to ensure real-time data exchange between dynamic network nodes having 14 bytes of payload per data packet and 100 ms network member notification latency. While focused on vehicular safety, the solution is also applicable to autonomous agents (robots, drones) operating in infrastructure-limited environments.

A novel approach for peak-to-average power ratio reduction and spectral efficiency enhancement in 5G and beyond networks

High peak-to-average power ratio (PAPR), interference, and inefficient power allocation can severely limit the capacity of a filtered Non-Orthogonal Multiple Access (NOMA) system. This paper presents a novel structurally modified filtered NOMA system integrated with a Decomposed-based Selective Mapping (D-SLM) technique, to reduce high PAPR, and thereby increase spectral efficiency and enable effective spectrum sharing. The proposed f-NOMA-D-SLM (filtered Non-Orthogonal Multiple Access Decomposed-based Selective Mapping) system follows a process similar to that of the transmitter side of filtered NOMA, up to the encoding stage. After that, it incorporates three key components: (i) Walsh–Hadamard Transform (WHT), a mathematical technique that orthogonally transforms the superimposed signal into a non-sinusoidal form, (ii) D-SLM, and (iii) physical layer for dynamic spectrum access (PHYDYAS) filter, a prototype filter designed to minimize unnecessary signal distortion and dynamically mitigate undesired effects through improved frequency domain localization. At the receiver side, Successive Interference Cancelation (SIC) is applied to decode the signals for each user sequentially. The evaluation of the f-NOMA-D-SLM system is done at the receiver side under two scenarios: (i) without relaying and (ii) with cooperative diversity relaying. The performance demonstrates that f-NOMA-D-SLM handles interference better, thereby increasing system capacity and throughput, thus suiting advanced 5G and beyond networks.

Time-reversal based power division multiple access

Time-reversal based power division multiple access

Evaluation of the capacity region for uplink multi user NOMA in fading environment

Abstract The ever-increasing demand for massive machine-type communication requires multiple communication channels to coexist simultaneously. Beyond the classical orthogonal multiple access (OMA), a promising emerging scheme is non-orthogonal multiple access (NOMA), which offers better bandwidth utilization. An important measure of efficiency is the achievable capacity region for the communicating channels, which defines the theoretical limits of any implementation. In the literature, this capacity region is usually presented only for two users. In this paper, we present a systematic method to determine the convex hull of the capacity region for any number of users in uplink NOMA communication. We also extend the discussion to cases where one or more users experience fading. We provide examples of capacity regions for some indicative cases and present the necessary formulas to apply our method in a general setting.

Multiplexed Internet of Things Data Transmission and Visualization Utilizing Wireless LAN Authentication and Privacy Infrastructure Protocol in Smart Factories.

In high-security environments, such as smart factories and power networks, secure and reliable data transmission and device access are crucial. This paper proposes a diversified Internet of Things (IoT) data transmission and visualization solution based on the Wireless LAN Authentication and Privacy Infrastructure (WAPI) protocol. First, we introduce the technical characteristics of the WAPI protocol and analyze network access solutions relevant to smart factories, along with their application requirements in power networks. Addressing gaps in the existing literature, we present a comprehensive solution that encompasses network deployment, device management, device testing, and data transmission, highlighting its completeness and effectiveness in real-world applications. Furthermore, we provide detailed experimental evidence demonstrating the WAPI protocol's effectiveness and security in supporting multiple terminal device access within high-security settings. The findings of this research not only fill critical gaps in existing work but also provide valuable technical support and reference for secure data management and real-time monitoring in smart-factory environments.

CARDIOVASCULAR PRE–REHABILITATION BEFORE CARDIAC SURGERY: OUR EXPERIENCE

CARDIOVASCULAR PRE–REHABILITATION BEFORE CARDIAC SURGERY: OUR EXPERIENCE

Rate-Splitting Multiple Access for Green Communications: A Survey and Robust Beamforming Design

Rate-Splitting Multiple Access for Green Communications: A Survey and Robust Beamforming Design

Improving Integrated Satellite-Terrestrial Cell-Free Massive MIMO Systems by Rate-Splitting Multiple Access

Improving Integrated Satellite-Terrestrial Cell-Free Massive MIMO Systems by Rate-Splitting Multiple Access

An Efficient Quantized Message Passing Receiver Design for SCMA Systems.

Sparse code multiple access (SCMA) has been considered as an efficient technique to provide both massive connectivity and high spectrum efficiency for future machine-type wireless networks. However, the conventional uniform quantization of the message passing algorithm (MPA) for the SCMA detection induces a significant bit error ratio (BER) performance degradation. In this sense, we propose a new quasi-uniform quantization scheme that can efficiently handle the dynamic range in the exchange of messages. To accelerate the convergence of conventional Max-log MPA, the Sub-log MPA is considered by using the latest updating messages at the current iteration. Simulation results show that the proposed quasi-uniform quantization method can significantly improve the BER performance of the SCMA decoder without modifying the resource nodes' and variable nodes' update rules in both the additive white Gaussian noise and the Rayleigh frequency selective channels, as compared to the uniform quantizer.

Joint optimization of communication rates for multi-UAV relay systems

The multi-UAV relay system can rapidly deploy a temporary communication network in disaster emergency communication scenarios to enhance communication coverage and stability in the affected area and ensure the efficient transmission of rescue information. Aiming at the problems of insufficient real-time performance, low user fairness, and low utilization of communication resources in multi-UAV relay systems, this paper proposes a joint optimization method of communication rate based on Lexicographic Optimization (LO). The multi-UAV relay scenario using multi-carrier non-orthogonal multiple access (MC-NOMA) technology is modeled as a multi-objective optimization problem and solved in stages using the LO method. Specifically, the first stage maximizes the minimum user communication rate by jointly optimizing the user association, relay UAV transmit power and flight trajectory; the second stage optimizes the modulation order of the relay UAVs to maximize the communication rate between UAV base stations. Finally, the proposed algorithm is compared under different optimization schemes and different optimization algorithms. The simulation results show that the user communication rate of the proposed algorithm is 6.8×105bps/s higher than that of the static user association scheme, 6.7×106bps/s higher than that of the static UAV trajectory scheme, and 2.0×105bps/s higher than that of the traditional Jara algorithm, and 6.7×106bps/s higher than that of the K-mean based optimization algorithm. Moreover, this algorithm performs well in convergence and stability, effectively improves the user communication rate, the communication rate between UAV base stations, and the energy utilization of relay UAV, and enhances the adaptability of the system to the dynamic environment.

Endovascular rodent model using tail access and ultrasound guidance.

We have developed a cost-effective method to study the fate of stents, particularly flow diverter stents placed in the abdominal aorta, in a rat model. This technique utilizes (caudal) tail artery access,1-5 thereby avoiding the need for surgical exposure of the femoral or carotid arteries and reducing procedural invasiveness,6 7 aligning with the principles of refinement and reduction in animal research.7 This approach may be particularly beneficial for studies requiring multiple or iterative vascular access. The use of ultrasound guidance further reduces costs and infrastructure requirements by eliminating the need for specialized angiography suites.8 This makes this technique accessible to a broader range of research settings, promoting wider adoption and collaboration in the field of endovascular research. A detailed demonstration of this method is provided in the accompanying educational video (video 1).neurintsurg;jnis-2025-023444v1/V1F1V1Video 1-Technical video describing the tail artery access and flow diverter deployment using ultrasound guidance.

Design of Digital Simulation Monitoring System for High-Voltage Power Transmission Lines with Ad-hoc MAC Access

To realize the digital simulation monitoring for high-voltage transmission lines, a transmission line monitoring system based on the Media Access Control (MAC) mode of a wireless Ad-hoc network is studied. We analyze the transmission services of transmission lines comprehensively and adopt the Linear Hybrid Time Division Multiple Access (LHTDMA) hybrid access mode with logic integration and services to improve the resource utilization efficiency of the algorithm. In the optimization process of the routing algorithm, the optimization scheme based on deep Q-learning is selected to enhance the system life cycle and reduce the system delay. The algorithm of this study is verified by experiments. The experimental results confirm that the LHTDMA hybrid access method has higher data throughput and lower delay effect. Compared with other routing algorithms, under the same conditions, the time cost of this algorithm is lower than other comparison algorithms. As the size of the transfer file gradually increases, the advantages of this algorithm are more obvious for its more accurate iterative output results, which proves its superiority.

High-Capacity Optical Communication Systems using 4D Spatial-Wavelength-Zero Cross Correlation Encoding

Optical Code Division Multiple Access (OCDMA) is a technology used in optical communication systems to multiplex many signals onto a single optic line. Each signal in OCDMA is allocated a unique code, which the receiver decodes using a matching filter. In this paper, a novel 4 Dimensional Spatial-Wavelength-Zero Cross Correlation (SWZCC) encoding scheme for high-capacity optical communication system has been proposed. The system incorporates advanced multiplexing across 4D technique is a combination of polarization, spectral, temporal, and spatial to enhance data transmission efficiency and robustness. Primary light signals are generated by optical sources and encoded through 4D-SWZCC modulation with non-return-to-zero (NRZ) signal for transmission via Line-of-Sight (LOS) optical channel. The receiver converts the optical signal into electrical data by splitting it and decoding it with a photo detector. By using polarization multiplexing as well as wavelength division multiplexing (WDM), the proposed system minimizes crosstalk and signal degradation while maximizing spectral efficiency. Optical communication solutions for next-generation networks are demonstrated by this system by illustrating high performance and scalability. The proposed model outperforms the existing techniques, such as NOMA-VLC, WMZCC, RSMA-VLC respectively. Proposed method achieves a BER of 1.0%, which is 71.4% lower than NOMA-VLC of 3.5%, 60% lower than WMZCC of 2.5%, and 50% lower than RSMA-VLC of 2.0%.