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The correct installation of antenna-feeder devices on board a small spacecraft and the choice of their parameters make it possible to ensure the solution of target problems with high quality. The main problematic issues of placement of antenna-feeder devices of the on-board equipment of the radio link for the transmission of target information on the SSC “AIST-2T” and the adopted design solutions are considered.

This paper presents an effective method to boost the RSSI, the received signal strength on a moving path of LoRa wireless networking without change in digital circuitry or power amplifiers. Replacing the wire antenna as the conventionally used sensor by a printed Yagi-Uda antenna as a novel one designed to have a higher gain signifies increments of the RSSI at distant positions in the LoRa system with the same battery. The electromagnetic properties of the novel antenna are given by observing its beam-patterns in the anechoic chamber following the design procedures and fabrication. And the field-test for the radio link is conducted to see the proposed antenna enhance the RSSI at positions along the street of a wide-open area for LoRa communication. The RSSI has risen by more than 10 dB at distances from 200m to 700m with DLP-RFS1280 as the LoRa device in comparison to the conventional configuration in the device.

Measurement of water vapor (WV) in the lower troposphere on a continuous temporal basis would improve our knowledge of the atmospheric dynamics and the performance of numerical weather prediction models. In recent studies, a new measurement concept, the normalized differential spectral attenuation (NDSA) approach, was proposed. It is based on measurements of differential attenuation at 18.8 and 19.2 GHz performed along a tropospheric radio link. While NDSA measurement at a fixed elevation angle provides information on integrated WV (IWV), measurements at different elevation angles allow to retrieve the vertical WV content profile. A prototype NDSA demonstrator, which consists of two units, a synthesized transmitter and a software-defined radio receiver, has been designed and implemented. The system was accurately characterized through several laboratory tests, and then a first experimental campaign was conducted at fixed elevation angle along a ground-to-ground radio link. Obtained results confirm the sensitivity of the NDSA measurements to the IWV along such link with a good agreement with the existing ground-based and satellite data products. [ABSTRACT FROM AUTHOR]

Low-speed autonomous transport of passengers and goods is expected to have a strong, positive impact on the reliability and ease of travelling. Various advanced functions of the involved vehicles rely on the wireless exchange of information with other vehicles and the roadside infrastructure, thereby benefitting from the low latency and high throughput characteristics that 5G technology has to offer. This work presents an investigation of 5G millimeter-wave communication links for a low-speed autonomous vehicle, focusing on the effects of the antenna positions on both the received signal quality and the link performance. It is observed that the excess loss for communication with roadside infrastructure in front of the vehicle is nearly half-power beam width independent, and the increase of the root mean square delay spread plays a minor role in the resulting signal quality, as the absolute times are considerably shorter than the typical duration of 5G New Radio symbols. Near certain threshold levels, a reduction of the received power affects the link performance through an increased error vector magnitude of the received signal, and subsequent decrease of the achieved data throughput.

The research process was based on the design of a desktop application for indoor and outdoor coverage testing of wireless links in the 2.4 GHz frequency band with the use of free software, which allows capturing, processing, analysing, calculate and generate a real-time statistical type mathematical model of the media access control (MAC) hardware embedded in a laptop's wireless network card that detects power level, carriers, and other variables within frames of information transmitted by base stations. The methodology is experimental. First, different propagation models are analysed, next existing test tools are studied, and then hardware and software technologies and tools are compared. The programming language is selected and finally the code and the graphical interface of the application are generated in order to visualize the mathematical model expressed through the use of least squares with the Levenberg- Marquardt algorithm and then compare it with recognized propagation models. [ABSTRACT FROM AUTHOR]

A superheterodyne transmission scheme is adopted and analyzed in a 300 GHz wireless point-to-point link. This was realized using two different intermediate frequency (IF) systems. The first uses fast digital synthesis which provides an IF signal centered around a carrier frequency of 10 GHz. The second involves the usage of commercially available mixers, which work as direct up- and down-converters, to generate the IF input and output. The radio frequency components are based on millimeterwave monolithic integrated circuits at a center frequency of 300 GHz. Transmission experiments over distances up to 10 m are carried out. Data rates of up to 60 Gbps using the first IF option and up to 24 Gbps using the second IF option are achieved. Modulation formats up to 32QAM are successfully transmitted. The linearity of this link and of its components is analyzed in detail. Two local oscillators (LOs), a photonics-based source and a commercially available electronic source are employed and compared. This work validates the concept of superheterodyne architecture for integration in a beyond-5G network, supplying important guidelines that have to be taken into account in the design steps of a future wireless system. [ABSTRACT FROM AUTHOR]

In LTE and NR, the user equipment initiates a recovery procedure when a radio link failure (RLF) is declared. A shorter RLF timer T312 is introduced to speed up the recovery from an RLF and lower the outage time during a handover. However, T312 cannot remove the outage time completely and guarantee a successful recovery. In this letter, an event-based faster RLF trigger scheme is proposed to remedy the shortcomings of T312. The simulation results show that the proposed scheme can almost fully remove the outage time and reduce the interruption time caused by the recovery procedure, outperforming T312. [ABSTRACT FROM AUTHOR]

Mobile Edge Computing (MEC) has received much attention from the research community in recent years. A significant part of the published work has studied the telecom-centric MEC architecture, which assumes that the computing resource is located at the edge of the mobile access network (e.g., the Evolved Packet Core or ePC), typically at the first aggregation level. Many of these studies make a silent assumption that the latency at this stage of the network is negligible. We show not only that this assumption is false, but that in some common cases the latency of the first aggregation stage dominates the end-to-end latency. We further show that common probing metrics can easily fail when used to select the service site for an application and discuss possible improvements to server-selection reliability. [ABSTRACT FROM AUTHOR]

This paper examines the possibility of joint reception of radio reflections from the same meteor trails simultaneously at two spaced receivers. A refined simulation of a joint reception area (JRA) of meteor radio reflections on the basis of a diffraction theory of oblique scattering of radio waves off ionized meteor trails is performed for radio links of moderate (500 km) and medium (1000 km) lengths. The obtained results may be particularly useful for territory planning of meteor burst communication (MBC) networks with the spatial division of subscribers (SDMA technology). The simulated JRAs also characterize an interception probability of messages. This knowledge is especially important in designing highly secure MBC, such as meteor key distribution systems, intended for the creation of two identical copies of a shared secret key at both sides of the meteor radio link. [ABSTRACT FROM AUTHOR]

Abstract Development of spatial multiplexing techniques and co-channel operation of different wireless systems require a way to assess the mutual influence of emitted signals. This paper focuses on the signal level evaluation as a function of the path loss that depends on the parameters of a transmitting and receiving antenna in the multipath propagation conditions. The developed procedure uses a multi-elliptical propagation model to estimate a power angular spectrum, which is the basis for evaluation of the received signal power. This procedure provides adaptation of the close-in free space reference distance path loss propagation model by considering parameters of directional parameters. Simulation studies are the basis for assessing the impact of the antenna parameters on the path loss and consequently on the received signal power. The results of these studies show the influence of the width of the main lobe and, most importantly, the direction of the antennas on the level and angular dispersion of the received signals. A comparison of the results for multi-path and free-space propagation conditions demonstrates the viability of the developed procedure for the purposes of predicting power distribution and reception direction. [ABSTRACT FROM AUTHOR]

Several different waveform processing techniques have been studied and proposed for the 5G new radio (NR) physical layer, to support new mixed numerology and asynchronous services. The evaluation and comparison of these different techniques is commonly based on matched waveform processing in the transmitter and receiver units. In this article, it is shown that different techniques can be flexibly mixed, making it possible to separately optimize complexity-performance trade-offs for transmitter and receiver implementations. Mixing different waveform processing techniques is possible by setting adequate requirements for transmitter and receiver baseband processing allowing transparent design. We provide the basic framework of how transmitter and receiver units can be independently applied and evaluated in the context of transparent design and an extensive set of examples of the achievable radio link performance with unmatched transmitter and receiver waveform processing. The discussed approach and solutions simplify standardization, improve transparent transmitter and receiver coexistence, and enable a futureproof evolution path for performance improvements in 5G NR physical layer hardware and algorithm design. [ABSTRACT FROM AUTHOR]

A new application of utilizing ultra-wideband (UWB) technology to sense wind turbine blade deflections is introduced in this paper for wind energy cost reduction. The lower UWB band of 3.1–5.3 GHz is applied. On each blade, there will be one UWB blade deflection sensing system, which consists of two UWB antennas at the blade root and one UWB antenna at the blade tip. The detailed topology and challenges of this deflection sensing system are addressed. Due to the complexity of the problem, this paper will first realize the on-blade UWB radio link in the simplest case, where the tip antenna is situated outside (and on the surface of) a blade tip. To investigate this case, full-blade time-domain measurements are designed and conducted under different deflections. The detailed measurement setups and results are provided. If the root and tip antenna locations are properly selected, the first pulse is always of sufficient quality for accurate estimations under different deflections. The measured results reveal that the blade tip-root distance and blade deflection can be accurately estimated in the complicated and lossy wireless channels around a wind turbine blade. Some future research topics on this application are listed finally.

Abstract Recently, spectrum optimization solutions require mobile phones to obtain precise, accurate and fine-grained estimates of the radio link data rate. In particular, the effectiveness of anticipatory schemes depends on the granularity of these measurements. In this paper we use a reliable LTE control channel sniffer (OWL) to extensively compare mobile phone measurements against exact LTE radio link data rates. We also provide a detailed study of latencies measured on mobile phones, the sniffer, and a server to which the phone is connected. In this study, we show that mobile phones can accurately (if slightly biased) estimate the physical radio link data rate. We highlight the differences among measurements obtained using different mobile phones, communication technologies and protocols. We also provide detailed instructions on how to replicate our measurements and describe alternative measurement setups and their tradeoffs. [ABSTRACT FROM AUTHOR]

Solar scintillation refers to the rapid amplitude fluctuations of the radio signal passing through large-scale coronal irregularities. In this letter, the scintillation index model is first derived to characterize radio wave propagation in coronal turbulence during superior solar conjunction. The proposed model takes into account the non-Kolmogorov turbulence model with the Rytov approximation method. After that, the bit error rate (BER) performance is analyzed based on the proposed scintillation index model, which has instructional significance for deep space communication but still remains largely unexplored. Simulation results demonstrate that the coronal parameters have extensive effects on the scintillation index, and further affect the link BER performance. Our proposed scintillation index model also achieves better agreement with the observation data. [ABSTRACT FROM AUTHOR]

In this paper, we propose a distributed mobility robustness optimization algorithm to minimize handover failures due to radio link failures by adjusting time-to-trigger and offset parameters. According to the reason for failure, the algorithm classifies handover failure into three categories (too late, too early, and wrong cell), and simultaneously optimizes three handover parameters according to the dominant failure. Moreover, the algorithm considers handover failures to each neighboring cell and adjusts handover parameters individually. Via simulation, we show how the proposed algorithm adaptively optimizes the parameters and outperforms previous algorithms in various mobile environments. [ABSTRACT FROM PUBLISHER]

A control/user (C/U) plane-split network, where macro- and microevolved Node Bs (eNBs) are responsible for C/U-planes, respectively, is a potential 5G solution to address the problems experienced by high-speed railway communication systems such as frequent handovers (HOs), low system capacity, and low data rate. The C-plane transition occurs during an intermacro eNB HO to reduce the frequency of HOs. However, the intermacro-eNB HO in a C/U-plane-split network is prone to handover failures (HOFs) and long service interruption time similar to the traditional long-term evolution-advanced (LTE-A) HO without improvements because it is similar to an LTE-A HO between macro-eNBs from the perspective of C-plane transition. In this paper, we realize a C/U-plane-split network using the LTE-A dual-connectivity (DC) technique and propose a dc-based prevenient HO (PHO) scheme to improve the robustness of the intermacro-eNB HO. The proposed scheme specifically is an a priori method and uses the transmit diversity based on the dc technique to reduce the risk of HOFs and the long service interruption time. Further, we first develop the analytical expressions for HO performance for PHO and LTE-A HO, where HOFs are aligned with the LTE-A specifications such that they are defined as the association between the radio link monitor and HO processes. The analytical results are verified against simulation results. Through simulations, we compare PHO with LTE-A HO and the representative schemes of the previous literature in a variety of mobility performance metrics (such as the averages of the successful HO rate, the HOF rate, the radio link failure rate, the ping-pong rate, and the service interrupt time). The results confirm that the proposed scheme achieves superior performance in the key metrics of the successful HO rate and service interrupt time. [ABSTRACT FROM PUBLISHER]

Rain is the major source of attenuation for microwave propagation above 10 GHz. In tropical and equatorial regions where the rain intensity is higher, designing a terrestrial and earth-to-satellite microwave links is very critical and challenging at these frequencies. This paper presents the preliminary results of rain effects in a 23 GHz terrestrial point-to-point communication link 1.3km long. The experimental test bed had been set up at Skudai, Johor Bahru, Malaysia. In this area, a monsoon equatorial climate prevails and the rainfall rate can reach values well above 100mm/h with significant monthly and diurnal variability. Hence, it is necessary to implement a mitigation technique for maintaining an adequate radio link performance for the action of very heavy rain. Since we now know that the ULPC (Up Link Power Control) cannot guarantee the desired performance, a solution based on frequency band diversity is proposed in this paper. Here, a secondary radio link operating in a frequency not affected by rain (C band for instance) is placed parallel with the main link. Under no rain or light rain conditions, the secondary link carries without priority radio signals. When there is an outage of the main link due to rain, the secondary link assumes the priority traffic. The outcome of the research shows a solution for higher operating frequencies during rainy events.

A method for calculating and measuring antenna gain and factor over perfect ground is presented. The electromagnetic compatibility antenna factor is used to determine the spurious electric field of the device under evaluation. The radio link employed to calibrate the receiving antenna gain and factor will produce completely different values for the transmitting and receiving antennas, and the principle of reciprocity does not hold true, in this particular case, even if both antennas are identical. [ABSTRACT FROM AUTHOR]

An ultra-wideband (UWB) blade deflection sensing system with a tip antenna inside a blade is investigated in this paper. The lower UWB band of 3.1–5.3 GHz is utilized. This system composes of two UWB radio links between one antenna inside the blade tip and two antennas outside the blade root. Blade deflections are tracked via two radio links using delay-based distance estimation and triangulation. In order to build reliable radio links, time-domain pulse field distributions are simulated to optimize the in-blade tip antenna polarization and the locations of the two root antennas around the root surface. Full-blade time-domain measurements are proposed to verify the simulations and realize the blade deflection sensing with an in-blade tip antenna. With the optimized in-blade tip antenna polarization and two root antenna locations, an accuracy of 2 cm is achieved for the tip-root antenna distance estimation, and the sensing system can realize the deflection tracking with a maximum deviation of 0.21 m and a root mean squared error of 0.11 m. [ABSTRACT FROM PUBLISHER]