LOS Components Research Articles

Performance Evaluation of CAM Broadcast Message and Vehicle Safe Distance Under Nakagami-m Radio Channel Conditions

Many potentials exist in the 5G era for effectively managing vehicle safety on the road. The European Telecommunications Standards Institute (ETSI) 5G C-V2X standards for Cooperative Aware Messages for Intelligent Transport Systems (ITS) provide necessary upper-layer requirements for safety message distribution between vehicles using Cooperative Aware Messages (CAM). In addition, the Long Term Evolution (LTE) mobile radio technology in Release-14 has two modes of communication, mode 3 and mode 4, to facilitate vehicle-to-vehicle communications. The focus of this study is on vehicle communications in a mode 3 environment, in which the cellular network chooses and manages the radio services utilised by vehicles for direct vehicle-to-vehicle communication. The performance modelling of Safety Avoidance Time (AT) and safety CAM message broadcast for vehicle-to-vehicle communication in LTE C-V2X under the Nakagami-m radio channel, which has two components, LOS and NLOS, is studied in this thesis. Under the Nakagami-m radio channel, the LOS and NLOS components will affect the CAM message disseminating to other vehicles within safe time gaps. Therefore, the aim of this study is to look into the various radio channel characteristics in a vehicle-to-vehicle communication environment that are related to CAM message dissemination and vehicle safe distance, as well as to evaluate the performance of the relationship between PDR, throughput, and transmit power proportional to safe time gaps under the Nakagami-m radio channel with various setting shape factors.

UAVs Assisted Intelligent Reflecting Surfaces SWIPT System With Statistical CSI

This paper investigates an intelligent reflecting surface (IRS) assisted simultaneous wireless information and power transfer (SWIPT) system. Multiple IRSs deployed on unmanned aerial vehicles (UAVs) and ground building are considered in the proposed system for enhancing transmission of information and energy simultaneously. The optimization problem is formulated to maximize the average achievable rate over <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> time slots by jointly optimizing power splitting (PS) ratio, transmit beamforming, phase shifts and trajectories of UAVs. To tackle the non-convex optimization problem which can be decomposed into different subproblems, block successive upper bound maximization/minimization (BSUM) method is proposed for optimizing subproblems alternately. Considering the difficulty brought by LoS components in optimizing UAVs’ trajectories, double iteration algorithm is proposed which BSUM with fixed LoS components is applied in the inner layer and LoS components are updated in the outer layer. Meanwhile, feasible initial trajectories of UAVs are also analyzed for improving the efficiency in optimizing UAVs’ trajectories by using successive convex approximation (SCA). In order to provide theoretical foundation for further study, perfect channel state information (CSI) is considered firstly in solving the non-convex optimization problem. Furthermore, considering the limited ability in acquiring CSI at both IRSs and UAVs, optimization problem under statistical CSI is reformulated. Accordingly, with the aid of Jensen's inequality, double iteration algorithm can be also applied to tackle the optimization problem. Simulation results are provided to evaluate performances of proposed designs under different setups.

The effect of a daytime 60-min nap opportunity on postural control in highly active individuals.

Although napping is commonly used as a strategy to improve numerous physical and cognitive performances, the efficacy of this strategy for improving postural balance has not yet been elucidated. Thus, the aim of this study was to conduct a comprehensive examination of the effect of a 60 min nap opportunity (N60) on different components of postural control. Ten highly active individuals (age = 27 ± 3.5 y, height = 1.75 ± 0.52 m, weight = 66.02 ± 8.63 kg) performed, in a randomized order, two afternoon test sessions following no nap (NN) and N60. Postural balance was assessed using the sensory organisation test (SOT), the unilateral stance test (UST), and the limits of Stability Test performed on NeuroCom® Smart Balance Master. The subjective rating of sleepiness before and after the nap conditions was also assessed. Compared to NN, N60 improved the composite balance score (p < 0.05, ES = 0.75, Δ = 5.3%) and the average and maximum percentage balance in the most challenging postural conditions of the SOT (p < 0.05 for SOT-4 and 5 and p < 0.0005 for SOT-6; ES range between 0.58 and 1.1). This enhanced postural balance in N60 was accompanied with improved visual (p < 0.05; ES = 0.93; Δ = 8.9%) and vestibular (p < 0.05; ES = 0.81; Δ = 10.5%) ratios and a reduced level of sleepiness perception (p < 0.001, ES = 0.87). However, no significant differences were found in any of the UST and LOS components’ scores (p > 0.05). Overall, a 60 min post lunch nap opportunity may be viable for improving static balance, although further work, involving larger samples and more complex motor activities, is warranted.

Performance Analysis of UAV‐Assisted Wireless Powered Sensor Network over Shadowed κ − μ Fading Channels

In this work, we analyze performances of the unmanned aerial vehicle‐ (UAV‐) assisted wireless powered sensor communication, where sensor transmission ability is supported by the UAV. Harvested energy from the UAV‐broadcasted signal is further used at the sensor nodes for uplink information transmission to the UAV, over assumed shadowed κ − μ fading channels. Here, we observe a general scenario in which due to the flight conditions of the UAV, the channel’s content include the LOS components affected by the shadowing effect, modeled by the general shadowed κ − μ channel model, which can be reduced to other well‐known channel models as its special cases. We derive closed‐form expressions for the outage probability (OP) of such wireless sensor network (WSN) operating in shadowed κ − μ fading environments. Further, we analyze the optimization of time allocation to minimize OP subjected to UAV’s energy constraints. The impact of channel parameters on observed performance measures is analyzed, and obtained results are numerically validated.

Multi-Cell MMSE Combining Over Correlated Rician Channels in Massive MIMO Systems

This letter investigates the uplink of massive MIMO systems using multi-cell MMSE (M-MMSE) combining that was shown to yield unbounded capacity in Rayleigh fading. All intra and inter-cell channels are correlated with distinct per-user Rician factors and channel correlation matrices, pilot contamination and imperfect channel estimation. First, a closed-form approximation of the spectral efficiency (SE) is derived thus enabling to demonstrate that, under certain conditions on the correlation matrices, M-MMSE generates unbounded SE in Rician fading. Second, the impact of inter-cell LoS components is examined in favorable propagation conditions, and, interestingly, shown to be more beneficial in terms of SE than when these interfering links are entirely scattered.

Analysis of nonline-of-sight visible light communications

We analyze the channel properties of a nonline-of-sight (NLOS) ceiling-to-device and device-to-device visible light communication systems by considering various receivers' orientation and variable fields of view (FOVs). Analyses based on the recursive indoor channel model show that for a particular transmitter configuration, the pure NLOS path can offer higher 3-dB channel bandwidth (up to 14 MHz) compared with the link with LOS and NLOS components. We also show how the receiver rotation (orientation) influences the probability of receiving signals via the NLOS path compared with the LOS and NLOS paths. Moreover, based on the experimental campaign, we demonstrate that shadowing observed at the receiver due to people’s movement results in decreased received power level (up to 1.8 dB), thus resulting in reshaping of the probability density function of received power.

Mm-wave 26 GHz Channel Characterization for Future Wireless Communications

In this work, mm-wave 26 GHz channel characteristics are analyzed based on experimental channel measurements performed for both LOS and NLOS scenarios. Specifically, channel parameters like power delay profiles (PDPs), rms delay spread, path loss and shadow fading are analyzed. Results show that the LOS components dominant over other multipath components in this band. Rms delay spreads are larger in the LOS case than those in the NLOS case, as the LOS measurement positions are much further in the measurements. Radio wave propagates like in free space in LOS case, as the path loss exponent is quite close to free space value of 2. Shadow fading (in decibels) fits well with normal distributions. These results can provide useful information for the design of future wireless communication systems.

Investigating channel frequency selectivity in indoor visible‐light communication systems

Channel characterisation for indoor visible-light communication systems is revisited. The purpose of this study is to evaluate the channel frequency selectivity, or in other words, the significance of inter-symbol interference (ISI) at the receiver and the necessity of channel equalisation to recover the transmitted data. The authors focus on the effect of the indoor channel by assuming no bandwidth constraint on the light-emitting-diodes and by considering a simple intensity modulation technique, excluding discrete multi-tone modulation. The channel impulse response (CIR) is first simulated using the iterative site-based method. Then, conventional metrics for evaluating channel frequency selectivity, that is, the root-mean-square delay spread and channel frequency response are investigated and their practical interest is discussed. The authors also consider the signal-to-ISI ratio (SIR), which they define based on the sampled (i.e. discrete-time) signal at the receiver, and demonstrate its usefulness in determining the necessity of channel equalisation at the receiver. They consider several link scenarios in a medium-size and a large room, and show the significance of the LOS components of CIR in determining the channel frequency selectivity. They also discuss the choice of the receiver filter and explain how it affects the SIR.

Characteristic analysis on UAV-MIMO channel based on normalized correlation matrix.

Based on the three-dimensional GBSBCM (geometrically based double bounce cylinder model) channel model of MIMO for unmanned aerial vehicle (UAV), the simple form of UAV space-time-frequency channel correlation function which includes the LOS, SPE, and DIF components is presented. By the methods of channel matrix decomposition and coefficient normalization, the analytic formula of UAV-MIMO normalized correlation matrix is deduced. This formula can be used directly to analyze the condition number of UAV-MIMO channel matrix, the channel capacity, and other characteristic parameters. The simulation results show that this channel correlation matrix can be applied to describe the changes of UAV-MIMO channel characteristics under different parameter settings comprehensively. This analysis method provides a theoretical basis for improving the transmission performance of UAV-MIMO channel. The development of MIMO technology shows practical application value in the field of UAV communication.

Multipath fading analysis of telemetry signals power fluctuations from Universitetsky microsatellite

The article deals with the results of the fading fluctuations analysis for telemetry signals in the 2 m and 70 cm bands from the first Moscow State University microsatellite better known as “Universitetsky”. Radio telemetry signals were received from the microsatellite for around 2 years, collecting and recording the power signal data of almost 7500 satellite overpasses. The received signals from about 2300 satellite overpasses had a very low signal to noise ratio (SNR) that caused high transmission losses. The rest of the signals had a SNR high enough to complete the transmission without losses. The main objective of this paper was to find the fading fluctuations caused both by diffusion and by the presence of Gaussian and non Gaussian noise in telemetry signal power data. The purpose was both to characterize the communication channel as well as to elaborate solutions both to improve the communication quality as well as to identify no homogeneous zones in the ionosphere environment. The signal power analysis was based in the observation of statistical characteristics from different power signal components, in particular the components influenced by diffusion and non Gaussian noise. The employed methodology follows the next steps: removing the power signal envelope; taking away the Gaussian noise; obtaining the statistical characteristics from non Gaussian noise, Gaussian noise and envelope; finally identifying the LOS and NLOS signal fading components. For this purpose, the wavelet technique was used to perform the signal decomposition. In particular, the discrete wavelet transform DWT was utilized to carry out the signal de-noising. Then, the results were statistically treated in order to obtain a diffusion index for Rician fading, which are associated with fading in atmosphere and ionosphere layers. In this way the communications channel among satellite and ground station was characterized and a BER parameter was obtained for every satellite overpass, which means an outstanding result when considering that just few papers describe such results for satellite systems. The obtained results are valid not only for satellite communications systems but also for wireless communications systems. These results are the basis for future communications system design, which in our case pursues to reduce the BER parameter in the satellite link. The referred system will employ adaptive error coding schemes as well as channel analyzer algorithms based in the theory exposed in this paper.

IMPROVEMENT OF BALANCE AFTER 12-WK OF BALANCE TRAINING IN OLDER ADULTS

The use of exercise interventions to improve balance in older adults has recently been drawing increasing attention from scientists and practitioners. PURPOSE To determine the effect of a balance exercise program (BEX) on balance in a group of Japanese older adults. METHODS Static balance (eyes closed standing on one foot [one-leg balance]), and dynamic balance (limits of stability [LOS] while moving one □fs center of gravity in a given direction) were assessed in all participants before and after the intervention. Components of LOS (endpoint excursion [EPE], maximum excursion [MXE], and directional control [DCL] were evaluated in forward, backward, right, and left direction by a computerized balance assessment device. Thirty volunteers were randomly divided into a training group (TR: 5 men and 10 women, 75 ± 3 yr) and a control group (CN, 7 men and 8 women, 75 ± 7 yr). The TR participate d in a 12- wk (2d/wk, 60 min/day) of supervised BEX (10 min of warm-up, 40 min of balance exercises [BX], and 10 min of cool-down). BX was performed while standing on the floor (first 4 wk) and then progressed to standing on foam pads of different compliances. Exercises included placing the feet in various positions and standing on one leg while moving the head, with or without the eyes open. The CN continued their normal daily physical activity. RESULTS After 12-wk of training, the TR demonstrated improvements (p < 0.05) in one-leg balance (72%); EPE backward (67%), right (27%), and left (32%); MXE backward (61%), right (24%), and left (17%); DCL backward (54%), right (16%), and left (17%). No significant changes were noted in LOS components in forward direction in TR, and in any of the measured variables in CN after the 12-week period. CONCLUSION These results indicate that balance training is effective in improving both the static and dynamic balance in older adults. These improvements could reduce their risk of suffering a fall. Supported by JSPS (Japan), Monbusho (Japan), and Hygenic Corporation grants.

Epitope expression and partial structural characterization of F62 lipooligosaccharide (Los) of Neisseria gonorrhoeae: IgM monoclonal antibodies (3F11 and 1-1-M) recognize non-reducing termini of the los components

F62 LOS of Neisseria gonorrhoeae consists of two components. The higher molecular weight (MW) component is recognized by monoclonal antibody (MAb) 1-1-M and the smaller MW component by MAb 3F11. Epitope expression of the two LOS components and their partial structures were investigated by treating the F62 LOS with several glycosidases and then monitoring their antigenicity with the two mouse IgM MAbs. The 1-1-M-defined LOS component was cleaved with both β- N-acetylhexosaminidase and endo- β-galactosidase, and each cleavage resulted in the loss of expression of the 1-1-M-defined epitope. The N-acetylhexosamine (HexNAc) released by the hexosaminidase was found to be GalNAc, and the smaller oligosaccharide released by the endo enzyme was identified to be a dimer GalNAcβ → Gal. In contrast, the MAb 3F11-defined LOS component was not digested by the endo galactosidase, but it was cleaved with α and β-galactosidase, and expression of the MAb 3F11-defined LOS epitope expression of the MAb 3F11-denned LOS was abolished by the treatment with each of two exo enzymes. MAb 3F11 bound to the 1-1-M-defined LOS component resulting from the removal of the β-GalNAc residue, and the resulting LOS was further cleaved with β-galactosidase, but not with α-galactosidase. From these results, we conclude the following: (1) MAbs 1-1-M and 3F11 both recognize the non-reducing termini of the LOS components; (2) the 1-1-M-defined LOS component has the GalNAcβ → Galβ 1 → 4-Glc (or GlcNAc) structure, and the GalNAcβ → Gal residue is involved in the MAb 1-I-M-defined epitope; (3) the MAb 3F11-defined LOS component may not have a Galβ → 4GlcNAcβ 1 → Galβ → 4Glc structure within the molecule. However, it has β-Gal residue at its non-reducing terminus, and this residue is involved in the MAb 3F11-defined epitope; (4) the two LOS components share a similar antigenic structure, and the 3F11-defined epitope structure is present in the MAb 1-1-M-defined LOS component. Expression of this epitope within the 1-1-M-defined LOS molecule is blocked by the β -GalNAc residue; however, the β-GalNAc residue at the non-reducing end may be not the only structural difference between the two components.

Structural determination of oligosaccharides derived from lipooligosaccharide of Neisseria gonorrhoeae F62 by chemical, enzymic, and two-dimensional NMR methods

F62 LOS of Neisseria gonorrhoeae consists of two major LOS components; the higher and smaller molecular weight (MW) components were recognized by MAbs 1-1-M and 3F11 respectively. Base-line separation of the two major oligosaccharide (OS) components from F62 LOS was achieved by Bio-Gel P-4 chromatography after dephosphorylation of the OS mixture. The structures of the two major OSs were studied by chemical, enzymatic, and 2D NMR methods [double quantum filtered COSY (DQF-COSY), delayed COSY (D-COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), pure-absorption 2D NOE NMR] as well as methylation followed by GC/MS analysis. The OS component derived from the MAb 1-1-M defined LOS component was determined to have a V3-(beta-N-acetylgalactosaminyl)neolactotetraose structure (GalNAc is beta 1----3-linked to a neolactotetraose) at one of its nonreducing termini as shown below. The above pentaose is linked to a branched diheptose-KDO core in which a GlcNAc is alpha-linked. The OS component derived from the MAb 3F11 defined LOS component did not have a GalNAc residue. The rest of its structure was identical to that of the OS-1, and a neolactotetraose is exposed at its nonreducing terminus. [formula: see text]