International Journal of Communication Systems最新文献

Future wireless connections may rely heavily on multiple-input multiple-output (MIMO) devices as a major supporting technology. Nevertheless, it is not clear whether there are performance drops in MIMO circuits as a result of interference. As a relatively recent addition to the multiaccess family, nonorthogonal multiple access (NOMA) is expected to play a significant role in 5G wireless systems. The opportunity for increasing spectral effectiveness and improving wireless connectivity for more people with an amalgamation of NOMA and multiantenna MIMO is substantial. The gain of massive MIMO NOMA over other techniques increases linearly by a factor of M both with the number of users and with the number of antennas at the BS. The suggested approach organizes individuals in a NOMA group into a single group or multiple ones to increase the network's sum-throughput by taking use of the channel gain disparities among them. Then, we calculate the best power distribution strategy that increases the network's bandwidth by maximizing its sum-throughput each NOMA clustering for a specific set of NOMA nodes.

The purpose of this research is to develop an efficient and scalable communication framework for 3D Wireless Network-on-Chip (WiNoC) systems by introducing dynamic, power-aware routing and intelligent flow management techniques. Traditional routing approaches often suffer from high power consumption, congestion, and limited adaptability, which hinder the performance and energy efficiency of densely integrated, multi-layer chip architectures. To overcome these limitations, this work proposes DynaQ-NoC, an intelligent and scalable communication framework that leverages reinforcement learning to enable routers to make autonomous, context-aware routing decisions based on local traffic, thermal, and power conditions. At its core, DynaQ-NoC employs a Q-learning-based dynamic routing algorithm integrated with adaptive flow control mechanisms to balance network load, mitigate thermal hotspots in real-time, and ensure energy-efficient communication. Intelligent routing decisions are made dynamically to avoid congested or overheated regions, improving latency and reliability. Furthermore, DynaQ-NoC introduces energy-saving features such as sleep-mode activation for idle links and efficient link utilization policies, which significantly contribute to reduced static energy consumption. The proposed system was implemented using Python and evaluated with a cycle-accurate 3D WiNoC simulator using realistic traffic patterns. Results demonstrate that DynaQ-NoC reduces power consumption by up to 30% compared to baseline methods and achieves an average power consumption of 82.3 mW. It also reduces latency by approximately 16% and maintains a routing decision accuracy of up to 92%. The system sustains a packet delivery ratio of over 95% under moderate traffic loads while ensuring high throughput scalability. These results validate DynaQ-NoC's potential for enhancing system reliability, thermal stability, and energy efficiency in next-generation multi-core and 3D integrated circuits.

Wearable antennas are essential for the deployment of Internet of Things (IoT) applications in the fields of smart textiles, e-healthcare, and wireless body area networks (WBANs). This study presents the design, fabrication, and performance analysis of a microstrip patch antenna with an overall physical size of 42 × 40 mm² (≈0.34λ₀ × 0.32λ₀ at 2.4 GHz) utilizing four flexible substrates: leather, cotton, denim, and Dyneema, with a focus on 2.4-GHz ISM band applications. The methodology involves both simulation and experimentation using CST Studio Suite to evaluate parameters such as reflection coefficient, operational bandwidth, gain, and radiation efficiency. Among the investigated substrates, the leather-based antenna exhibits the best overall performance, achieving a measured operational bandwidth of 2.26–2.63 GHz (370 MHz) with a minimum reflection coefficient of −36 dB at 2.41 GHz, along with a simulated radiation efficiency of 90% and a simulated gain of 2 dBi. Parametric optimization of leather further enhanced its characteristics. Furthermore, low detuning and reliable impedance matching are observed during bending analysis performed both in free space (off-body) and on-body (including the author's arm, leg, and chest), demonstrating the robustness of the design for real-world applications. Specific absorption rate (SAR) analysis with values (1 g avg: 0.393 W/kg on the arm; 10 g avg: 0.0619 W/kg on the chest) confirms compliance with IEEE and ICNIRP safety standards. The link budget analysis (LBA) for data rates (0.5, 1, and 10 Mbps) confirms the reliable connectivity for short-range wearable smart applications. As compared with state-of-the-art designs, the leather substrate antenna exhibits enhanced flexibility, efficiency, and durability, making it an ideal candidate for deploying high-performance, safety-compliant wearable systems.

This work introduces a new SCMA-OTFS (Sparse Code Multiple Access–Orthogonal Time Frequency Space) with index modulation (IM) for coordinated multipoint vehicular communication systems. The system is modeled as an uplink CoMP system with remote radio head and baseband unit. Users' messages are divided into data bits and index bits. The SCMA codebook encodes the data bits, while index bits specify active resources. Each data bit is converted into SCMA codewords using a variational transformer autoencoder with manifolds learning (VAE-MFL)-based codebook mapping. The SCMA-IM aims to enhance spectrum efficiency and throughput by combining index modulation with the SCMA method. It uses the codebook index to encode information, allowing for extra information representation. The system uses SCMA and index modulation to encode data, identifying users by sparse codewords and index locations. The system then transforms the delay-Doppler domain signal into the time domain to obtain a time domain symbol vector. These vectors travel across the wireless channel to a remote ratio head (RRH) mounted on road infrastructure. The RRHs wirelessly connect to a centralized baseband unit (BBU) after receiving signals from every user. The time-domain symbol is estimated using a time-domain LMMSE (linear minimum mean squared error)-based OTFS detection technique. The delay-Dopper domain received symbol is acquired, and user bits are recovered using SCMA decoding. A probabilistic recurrent-based SCMA decoder is introduced to precisely recover user bits. As a result, ABER values of 2.00E-05 for proposed bound and 2.25E-05 for proposed Simulation are achieved with the proposed transmission power of 31 dBm.

With growing demand for fast, reliable, and flexible communication, free-space optical (FSO) systems have seen significant advancements. However, weather and altitude have a significant impact on their performance, which requires an optimum system design. Using OptiSystem simulations, this research compares four hybrid techniques using three different multiplexings: space division multiplexing (SDM), wavelength division multiplexing (WDM), and polarization division multiplexing (PDM). With a maximum quality factor (Q-factor) of 149.47 and 0% bit error rate (BER) in clear circumstances, the WDM and SDM hybrid system performs the best among the evaluated setups. In ideal conditions, the more complicated WDM, SDM, and PDM configurations perform competitively, but interchannel interference causes them to suffer under high attenuation. WDM and SDM system maintain a Q-factor of 20 and are the most robust in severe weather conditions like fog and torrential rain. All things considered, the WDM and SDM system provides the best balance between performance, complexity, and practical dependability for FSO communication. While the proposed system model 1 introduces a scalable, forward-looking architecture, it also offers trade-offs between capacity and robustness that can be fine-tuned for future high-performance FSO networks.

Traditional orthogonal frequency division multiplexing (OFDM) systems face significant performance degradation under dynamic channel conditions due to fixed channel estimation and static transmission parameters. Existing autoencoder-based OFDM models improve end-to-end learning but lack adaptive mechanisms to handle varying SNR and multipath fading effectively. In this manuscript, dynamic autoencoder-based framework for performance enhancement in OFDM systems using CNN and attention mechanisms (DAF-OFDM-CNN) is proposed. This paper proposes a dynamic autoencoder-based framework to enhance the performance and reliability of OFDM systems under fluctuating signal-to-noise ratio (SNR) conditions. The framework integrates convolutional neural networks (CNN) and an attention mechanism within autoencoder architecture to improve feature extraction, channel estimation, and adaptive transmission. The system dynamically prioritizes important signal features, enabling effective data recovery and robust communication in multipath fading environments. Simulation results demonstrate that the proposed model significantly improves error rates, throughput, and latency compared to conventional OFDM systems, confirming its potential for next-generation wireless communication networks.

A novel microstrip line-fed super wideband antenna associated with quadruple notched band properties is demonstrated in this article. The antenna configuration is based on a partial ground back plane with a curved end and a decagon geometric patch. The physical volume of the proposed design is $��22�\times �26�\times �1.57��{\mathrm{mm}}^3�$. Three split-ring slots are etched onto the patch surface to produce three notched bands (3.65–4.6, 5.42–5.94, and 6.97–8 GHz). Additionally, a “T”-shaped stub resonator placed beside the feed line introduces a fourth notched band at 9.47–10.85 GHz. The functional impedance bandwidth (VSWR ≤ 2) of the constructed antenna spans from 2.8 to 28 GHz exhibiting percentage bandwidth of 163%. The suggested antenna prototype is constructed and successfully measured using standard microwave measuring techniques and compared with simulated findings. The peak gain of the antenna is measured as 6.25 dBi and the gains of the four notched bands are found as −8.2, −5.4, −3.5 and −1.1 dBi, respectively. The developed antenna may be utilized for broadband wireless communication to mitigate C-band satellite links, higher WLAN, X-band satellite downlink communications, and amateur radio applications.

This article introduces a compact quad-port wideband MIMO antenna intended for the globally popular 5G n77/78 NR bands. The proposed MIMO antenna is dedicated for densely packed 5G smart devices and beyond. A simple printed monopole antenna with a U-shaped slot and a slit positioned at the second radiating edge is used as the antenna unit element (29.72 × 29.72 mm²) for the 2 × 2 MIMO. The proposed antenna has an overall dimension of 67.21 × 67.21 mm², fabricated using the commercial FR4 substrate of thickness 1.57 mm. The orthogonally fed radiators in MIMO demonstrate polarization-diverse feature responding to dual linear polar component (dual LP) (horizontal and vertical). The spatial diversity nature of the proposed four-port MIMO is met through the novel hash-like shaped metamaterial-inspired rotationally symmetric decoupling element (DE). The DE, through its meticulous design and positioning at the functional plane (co-plane) of the MIMO radiator, helped maintain a minimal port isolation (s_ij, where i ≠ j) of > 20 dB throughout the −10-dB impedance bandwidth of 1.66 GHz (2.58–4.24 GHz), centering the popular 5G NR band of 3.5 GHz. The DE even aided improvement in reflection coefficient (s_ij, where i = j) from −19.87 to −44.01 dB, along with improved maximum radiation gain of 4.28 dBi at 3.5 GHz, with negligible impact toward the antenna efficiency metrics. The associated MIMO metrices, such as envelope correlation coefficient (ECC) (< 0.0001) and diversity gain (DG) (> 9.99 dB), estimated from far field results also complied to the acceptable range. Above all, the measured outcomes of the proposed antenna comparably mimic the simulation results carried out using Computer Simulation Technology (CST). In addition, equivalent circuit model for the complete four-port MIMO with the DE realized in Advanced Design System (ADS) is also reported in this article. Further, the proposed MIMO antenna is also verified for its viability to real-world device integration and specific absorption rate (SAR) analysis in the CST simulator.