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The Space-Terrestrial Integrated Network can leverage the complementary strengths of satellite communication and terrestrial mobile networks to significantly enhance network coverage, emerging as a key evolutionary trend for 6G. To validate satellite-terrestrial links and interference scenarios under the DTC mode, this paper examines the factors that influence the quality of satellite-terrestrial transmission. Taking GEO satellites as an example, this paper presents a comprehensive analysis of link budgets and interference mechanisms, quantifying their impacts on system performance. The research methodology is aligned with state-of-the-art industrial capabilities and international standards. The findings provide critical theoretical foundations for DTC system design, the formulation of interference mitigation strategies, and the planning of NTN frequency resources.

Millimeter wave fixed wireless systems in future backhaul and access network applications can be affected by weather conditions. The losses caused by rain attenuation and antenna misalignment due to wind-induced vibrations have greater impacts on the link budget reduction at E-band frequencies and higher. The current International Telecommunications Union Radiocommunication Sector (ITU-R) recommendation has been widely used to estimate rain attenuation, and the recent Asia Pacific Telecommunity (APT) report provides the model to estimate the wind-induced attenuation. This article provides the first experimental study of the combined rain and wind effects in a tropical location using both models at a frequency in the E band (74.625 GHz) and a short distance of 150 m. In addition to using wind speeds for attenuation estimation, the setup also provides direct antenna inclination angle measurements using the accelerometer data. This solves the limitation of relying on the wind speed since the wind-induced loss is dependent on the inclination direction. The results show that the current ITU-R model can be used to estimate the attenuation of a short fixed wireless link under heavy rain, and the addition of wind attenuation via the APT model can estimate the worst-case link budget during high wind speeds.

Optical Wireless Communications (OWCs) are capable of handling large data rates in the Internet of Underwater Things (IoUT) at low latency to be suitable for real-time image and video applications. This paper presents communication link feasibility via link budget to determine the link communication range for three types of line-of-sight link configurations: point-to-point, diffused, and modulating retro-reflector link. The main aim of this paper is to present a more realistic power link budget which is developed to take into account the following: LED Photo Source Lambertian radiation model, Beer-Lambert pass loss model that includes absorption and scattering effects of water types, Spherical wave propagation model, photodetector which is modeled by active area model, transmitter projection optics (PO) gain and receiver collection optics (CO) gain. Moreover, this paper considers the effects of aquatic channels ‘scattering and absorption by using intensity modulation direct detection IM-DD OOK, LED and LD–PS based transmitter, and SiPM-PD based receiver. The impact of different underwater environments, transmitter, and receiver parameters will be investigated on the communication link range. Its communication range on the order of tens of meters could be achieved by the three-link configurations. It is concluded from the analysis; that the line-of-sight point-to-point provides more communication range than a diffused line of sight. A diffused line of sight is used when it is required to multicast from a node to several nodes. Modulating retro-reflector provides moderate communication range and it is used when one party has more resources than the other one on the communication link. Medium distances are achieved by up to a hundred meters by placing multiple relay nodes between the source node and the destination node. The communication range is increased as increasing the active physical area of the photodetector and the transmitted power of the photo source. The communication range in both clear sea water and clear ocean water is higher than turbid water which is less since optical water suffers from higher attenuation. By using the multi-hop concept, an extended communication link range can be achieved.

In this paper, we present the design of a millimeter-wave 1 × 4 linear MIMO array antenna that operates across multiple resonance frequency bands: 26.28–27.36 GHz, 27.94–28.62 GHz, 32.33–33.08 GHz, and 37.59–39.47 GHz, for mm-wave wearable biomedical telemetry application. The antenna is printed on a flexible substrate with dimensions of 11.0 × 44.0 mm2. Each MIMO antenna element features a modified slot-loaded triangular patch, incorporating ‘cross’-shaped slots in the ground plane to improve impedance matching. The MIMO antenna demonstrates peak gains of 6.12, 8.06, 5.58, and 8.58 dBi at the four resonance frequencies, along with a total radiation efficiency exceeding 75%. The proposed antenna demonstrates excellent diversity metrics, with an ECC < 0.02, DG > 9.97 dB, and CCL below 0.31 bits/sec/Hz, indicating high performance for mm-wave applications. To verify its properties under flexible conditions, a bending analysis was conducted, showing stable S-parameter results with deformation radii of 40 mm (Rx) and 25 mm (Ry). SAR values for the MIMO antenna are calculated at 28.0/38.0 GHz. The average SAR values for 1 gm/10 gm of tissues at 28.0 GHz are found to be 0.0125/0.0079 W/Kg, whereas, at 38.0 GHz, average SAR values are 0.0189/0.0094 W/Kg, respectively. Additionally, to demonstrate the telemetry range of biomedical applications, a link budget analysis at both 28.0 GHz and 38.0 GHz frequencies indicated strong signal strength of 33.69 dB up to 70 m. The fabricated linear MIMO antenna effectively covers the mm-wave 5G spectrum and is suitable for wearable and biomedical applications due to its flexible characteristics.

This article explores the convergence of artificial intelligence and its challenges for precise planning of LoRa networks. It examines machine learning algorithms in conjunction with empirically collected data to develop an effective propagation model for LoRaWAN. We propose decoupling feature extraction and regression analysis, which facilitates training data requirements. In our comparative analysis, decision-tree-based gradient boosting achieved the lowest root-mean-squared error of 5.53 dBm. Another advantage of this model is its interpretability, which is exploited to qualitatively observe the governing propagation mechanisms. This approach provides a unique opportunity to practically understand the dependence of signal strength on other variables. The analysis revealed a 1.5 dBm sensitivity improvement as the LoR’s spreading factor changed from 7 to 12. The impact of clutter was revealed to be highly non-linear, with high attenuations as clutter increased until a certain point, after which it became ineffective. The outcome of this work leads to a more accurate estimation and a better understanding of the LoRa’s propagation. Consequently, mitigating the challenges associated with large-scale and dense LoRaWAN deployments, enabling improved link budget analysis, interference management, quality of service, scalability, and energy efficiency of Internet of Things networks.

N owadays, Optical Wireless Communications provide high data rates and minimal delay, making them ideal for real-time video and image applications in the Internet of Underwater Things (IoUT). However, Line-of-Sight (LOS) communication may not always be feasible due to misalignment, obstacles, or the random orientation of transceivers, especially for underwater sensor nodes or mobile users, to mitigate this challenge, a non-LOS (NLOS) link configuration is established. This paper conducts a feasibility study of communication links using a link budget approach to determine the feasible NLOS communication range for two types of transmitters: light emitting diode photo source (LED-PS) and laser diode photo source (LD-PS), at two wavelengths. A more realistic power link budget is developed. This paper examines the effects of underwater channel scattering and absorption, LED and LD-PS-based transmitters, and SiPM-PD-based receivers. In addition, it investigates how underwater environments, transmitter, and receiver parameters impact the communication link range. The effect of different water types on communication range was analyzed. Various transmitter parameters such as beam divergence angle and optical power, as well as receiver parameters such as incident angle and PD active area, were explored. The impact of different Lambertian order values was also assessed. The contribution of this paper is knowing the value of the received power used to determine the communication distance, this power is compared to the required receiver sensitivity, and the resulting link margin is used to determine the feasibility of the communication link.

Currently, the ultra-wideband (UWB) technology commercialized in smartphones and smart keys is a high-rate pulse repetition frequency (HRP) UWB of the IEEE 802.15.4z standard, which aims to accurately determine the distance between UWB devices located within tens of meters using two-way ranging (TWR). However, in order for UWB ranging technology to be spread to various location-based services or positioning services, it must be able to measure the distance between UWB devices that are hundreds of meters apart. Fortunately, UWB technology can freely change physical layer parameters, as long as they comply with the UWB local regulations worldwide. Therefore, in this study, we analyzed the method of configuring the packet structure, length, and transmission power from the link budget perspective to enable longer UWB ranging of hundreds of meters within UWB local regulations. As a result of the analysis, we theoretically confirmed that UWB ranging is possible even at hundreds of meters by selecting the optimal physical layer parameters. In addition, the experimental results using the Qorvo DW3000 module were confirmed to be consistent with the results analyzed in this study. The results of this study can be used as basic data for the introduction of wide-area UWB technology and services in the future.

With the rapid development of multi-orbit satellite networks, efficient and reliable communication systems have become essential for ensuring the link connectivity. As digital modulation schemes play a critical role in the design and performance evaluation of satellite communication links, this paper aims to analyze the sensitivity of satellite link budgets to various digital modulation schemes, providing insights into their impact across different orbital configurations. The analysis was conducted by modeling multi-orbit satellite communication scenarios incorporating typical link parameters and evaluating their performance under varying conditions and bandwidth. Sensitivity analysis was carried out to assess the influence of modulation schemes on link margin in multi-orbit configurations. The insights provided in this paper serve as a guideline for system designers to balance capacity, power, and reliability requirements, contributing to the development of robust multi-orbit satellite communication systems.

A hybrid free-space optical (FSO) and radio frequency (RF) communication system has been considered an effective way to obtain a good trade-off between spectrum utilization efficiency and high-rate transmission. Utilizing artificial intelligence (AI) to deal with the switching and rate adaption problems between FSO/RF links, this paper investigated their modulation adapting mechanism based on a machine learning (ML) algorithm. Hybrid link budgets were estimated for different modulation types in various environments, particularly severe weather conditions. For the adaptive modulation (AM) scheme with different order PPM/PSK/QAM, a rate-compatible soft-switching model for hybrid FSO/RF links was established with a random forest algorithm based on ML. With a given target bit error rate, the model categorized a link budget threshold of the hybrid FSO/RF system over a training data set from local weather records. The switching and modulation adaption accuracy were tested over the testing weather data set especially focusing on rain and fog. Simulation results show that the proposed adaptive modulation scheme based on the random forest algorithm can have a good performance for soft-switching hybrid FSO/RF communication links.

This paper presents a compact wideband implantable antenna developed for wireless capsule endoscopy (WCE) functioning in the 2.4–2.48 GHz ISM band. The antenna’s miniaturized design is achieved through the integration of E - and L - shaped slots in the circular radiator, a shorting pin and defective ground structure with an inclined T – shaped slot. The final structure has compact dimension of and the Rogers RO3010 ( ) material serves as both substrate and superstrate. Performance was assessed in homogeneous muscle and heterogeneous human phantoms, and experimentally validated by implanting the device in minced pork. At 2.45 GHz the antenna delivered − 20.8 dBi gain, and a 44.02% impedance bandwidth. The specific absorption rate (SAR) values are recorded as 216.8 W/kg (1 – g) and 30.2 W/kg (10 – g). The study demonstrates that the antenna reliably supports wireless links beyond 10 m, maintaining a 10 dB margin at 2.45 GHz.