UWB channel characterization in 28 ghz millimeter waveband for 5G cellular networks

The demands of high data rate transmission for future wireless communication technologies are increasing rapidly. The current bands for cellular network will not be able to satisfy these requirements. The millimeter wave (mm-wave) bands are the candidate bands for the future cellular networks. The 28 GHz band is the strongest candidate for 5G cellular networks. The large bandwidth at this band is one of the main parameters that make the mm-wave bands promising candidate for the future cellular networks. To know the wideband channel behavior in mm-wave bands, the wideband channel characterizations are required. In this paper, the 3D WINNER model is used to model the wideband channel at 28 GHz band. Based on this model, the time dispersion parameters at 28 GHz mm-wave band are investigated. The root mean square delay spread and the mean excess delay are the main parameters that can be used to characterize the wideband channel. Morever, the cumulative distribution function (CDF) is used to model the RMS delay spreads. The results show that the RMS delay spread varies between 4.1 ns and 443.7 ns

Window-based channel impulse response prediction for time-varying ultra-wideband channels

This work proposes channel impulse response (CIR) prediction for time-varying ultra-wideband (UWB) channels by exploiting the fast movement of channel taps within delay bins. Considering the sparsity of UWB channels, we introduce a window-based CIR (WB-CIR) to approximate the high temporal resolutions of UWB channels. A recursive least square (RLS) algorithm is adopted to predict the time evolution of the WB-CIR. For predicting the future WB-CIR tap of window wk, three RLS filter coefficients are computed from the observed WB-CIRs of the left wk-1, the current wk and the right wk+1 windows. The filter coefficient with the lowest RLS error is used to predict the future WB-CIR tap. To evaluate our proposed prediction method, UWB CIRs are collected through measurement campaigns in outdoor environments considering line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. Under similar computational complexity, our proposed method provides an improvement in prediction errors of approximately 80% for LOS and 63% for NLOS scenarios compared with a conventional method

Sequence analysis of the VSX1 and SOD1 genes in families with Keratoconus and a review of the literature

AbstractObjectiveKeratoconus (KC) is a non-inflammatory disorder of the cornea in which the cornea becomes thin and conical, inducing myopia and irregular astigmatism and resulting in mild to marked impairment of vision. The present study was designed to screen two candidate KC genes to identify pathogenic sequence variants responsible for KC in Saudi families.MethodsPeripheral blood samples from members of five Saudi families with KC from the Northern region were collected. Genomic DNA was isolated, and bidirectional sequencing was performed of all coding exons of VSX1 and SOD1 genes using Sanger sequencing.ResultsAll five of the KC families showed a pattern of autosomal recessive inheritance. Phenotyping of these families was performed by a senior ophthalmologist. Sequence analysis of the VSX1 and SOD1 genes failed to reveal any pathogenic sequence variant that could account for KC in the affected individuals.ConclusionOur failure to detect sequence variants in two of the known KC associated genes triggers an interest in other known KC candidate genes, including miR-184, DOCK9, IL1RN and SLC4A11. Future genotyping with dense SNP arrays followed by exome sequencing in these families will be a useful approach to identify the gene(s) underlying KC in this Saudi cohort, which may be different from those reported elsewhere

Design and validation of an adaptive CubeSat transmitter system

CubeSat in low earth orbit (LEO) primarily uses an amateur radio-band transmitter with a fixed specification. Nevertheless, the LEO satellite does not have an orbital velocity that equates to one sidereal day. Therefore, the ground station antenna views the satellite at different elevation angles which result in varied propagation path lengths. In this paper, an adaptive transmitter is designed to optimise the LEO satellite communication link and overcome the variability of the propagation path length issue due to different ground station elevation angles. A satellite communication link and operation analyses are performed to identify the relationship between the variation of the elevation angle so as to determine the optimum signal-to-noise ratio (SNR), improve data rate and increase the power efficiency of an adaptive link. Based on the results, a model is developed to control the adaptive configuration. The SNR and power consumption performance of the developed transmitter is compared with commercial transmitters. The results indicate that the transmitter output power is adjustable from 0.5 W to 1 W, and the data rate is selectable between 9600 bps and 19,200 bps. Compared to other CubeSat transmitters, the developed adaptive transmitter demonstrates more than 20% improvement in terms of SNR optimisation, additional throughput and power reduction

Comparative study of indoor propagation model below and above 6 GHz for 5G wireless networks

It has been widely speculated that the performance of the next generation based wireless network should meet a transmission speed on the order of 1000 times more than the current cellular communication systems. The frequency bands above 6 GHz have received significant attention lately as a prospective band for next generation 5G systems. The propagation characteristics for 5G networks need to be fully understood for the 5G system design. This paper presents the channel propagation characteristics for a 5G system in line of sight (LOS) and non-LOS (NLOS) scenarios. The diffraction loss (DL) and frequency drop (FD) are investigated based on collected measurement data. Indoor measurement results obtained using a high-resolution channel sounder equipped with directional horn antennas at 3.5 GHz and 28 GHz as a comparative study of the two bands below and above 6 GHz. The parameters for path loss using different path loss models of single and multi-frequencies have been estimated. The excess delay, root mean square (RMS) delay spread and the power delay profile of received paths are analyzed. The results of the path loss models show that the path loss exponent (PLE) in this indoor environment is less than the free space path loss exponent for LOS scenario at both frequencies. Moreover, the PLE is not frequency dependent. The 3GPP path loss models for single and multi-frequency in LOS scenarios have good performance in terms of PLE that is as reliable as the physically-based models. Based on the proposed models, the diffraction loss at 28 GHz is approximately twice the diffraction loss at 3.5 GHz. The findings of the power delay profile and RMS delay spread indicate that these parameters are comparable for frequency bands below and above 6 GH

Path loss model for outdoor parking environments at 28 GHz and 38 GHz for 5G wireless networks

It has been widely speculated that the performance of the next generation Internet of Things (IoT) based wireless network should meet a transmission speed on the order of 1000 times more than current wireless networks; energy consumption on the order of 10 times less and access delay of less than 1 ns that will be provided by future 5G systems. To increase the current mobile broadband capacity in future 5G systems, the millimeter wave (mmWave) band will be used with huge amounts of bandwidth available in this band. Hence, to support this wider bandwith at the mmWave band, new radio access technology (RAT) should be provided for 5G systems. The new RAT with symmetry design for downlink and uplink should support different scenarios such as device to device (D2D) and multi-hop communications. This paper presents the path loss models in parking lot environment which represents the multi-end users for future 5G applications. To completely assess the typical performance of 5G wireless network systems across these different frequency bands, it is necessary to develop path loss (PL) models across these wide frequency ranges. The short wavelength of the highest frequency bands provides many scatterings from different objects. Cars and other objects are some examples of scatterings, which represent a critical issue at millimeter-wave bands. This paper presents the large-scale propagation characteristics for millimeter-wave in a parking lot environment. A new physical-based path loss model for parking lots is proposed. The path loss was investigated based on different models. The measurement was conducted at 28 GHz and 38 GHz frequencies for different scenarios. Results showed that the path loss exponent values were approximately identical at 28 GHz and 38 GHz for different scenarios of parking lots. It was found that the proposed compensation factor varied between 10.6 dB and 23.1 dB and between 13.1 and 19.1 in 28 GHz and 38 GHz, respectively. The proposed path loss models showed that more compensation factors are required for more scattering objects, especially at 28 GHz

Microstructure, texture and tensile properties of ultrafine/nano grained magnesium alloy processed by accumulative back extrusion

An AZ31 wrought magnesium alloy was processed by employing multipass accumulative back extrusion process. The obtained microstructure, texture and room temperature tensile properties were characterized and discussed. Ultrafine grained microstructure including nano grains were developed, where the obtained mean grain size was decreased from 8 to 0.5 µm by applying consecutive passes. The frequency of both low angle and high angle boundaries increased after processing. Strength of the experimental alloy was decreased after processing, which was attributed to the obtained texture involving the major component lying inclined to the deformation axis. Both the uniform and post uniform elongations of the processed materials were increased after processing, where a total elongation of 68 pct was obtained after six-pass deformation. The contribution of different twinning and slip mechanism was described by calculating corresponding Schmid factors. The operation of prismatic slip was considered as the major deformation contributor. The significant increase in post uniform deformation of the processed material was discussed relying on the occurrence of grain boundary sliding associated with the operation of prismatic slip.Postprint (author's final draft

The origin of fracture in the I-ECAP of AZ31B magnesium alloy

Magnesium alloys are very promising materials for weight-saving structural applications due to their low density, comparing to other metals and alloys currently used. However, they usually suffer from a limited formability at room temperature and low strength. In order to overcome those issues, processes of severe plastic deformation (SPD) can be utilized to improve mechanical properties, but processing parameters need to be selected with care to avoid fracture, very often observed for those alloys during forming. In the current work, the AZ31B magnesium alloy was subjected to SPD by incremental equal-channel angular pressing (I-ECAP) at temperatures varying from 398 K to 525 K (125 °C to 250 °C) to determine the window of allowable processing parameters. The effects of initial grain size and billet rotation scheme on the occurrence of fracture during I-ECAP were investigated. The initial grain size ranged from 1.5 to 40 µm and the I-ECAP routes tested were A, BC, and C. Microstructures of the processed billets were characterized before and after I-ECAP. It was found that a fine-grained and homogenous microstructure was required to avoid fracture at low temperatures. Strain localization arising from a stress relaxation within recrystallized regions, namely twins and fine-grained zones, was shown to be responsible for the generation of microcracks. Based on the I-ECAP experiments and available literature data for ECAP, a power law between the initial grain size and processing conditions, described by a Zener–Hollomon parameter, has been proposed. Finally, processing by various routes at 473 K (200 °C) revealed that route A was less prone to fracture than routes BC and C

Diffuse duodenal nodular lymphoid hyperplasia: a large cohort of patients etiologically related to Helicobacter pylori infection

Abstract Background Nodular lymphoid hyperplasia of gastrointestinal tract is a rare disorder, often associated with immunodeficiency syndromes. There are no published reports of its association with Helicobacter pylori infection. Methods From March 2005 till February 2010, we prospectively followed all patients with diffuse duodenal nodular lymphoid hyperplasia (DDNLH). Patients underwent esophagogastroduodenoscopy with targeted biopsies, colonoscopy, and small bowel video capsule endoscopy. Duodenal nodular lesions were graded from 0 to 4 based on their size and density. Patients were screened for celiac sprue (IgA endomysial antibody), immunoglobulin abnormalities (immunoglobulin levels & serum protein electrophoresis), small intestine bacterial overgrowth (lactulose hydrogen breath test), and Helicobacter pylori infection (rapid urease test, and histological examination of gastric biopsies). Patients infected with Helicobacter pylori received sequential antibiotic therapy and eradication of infection was evaluated by 14C urea breath test. Follow up duodenoscopies with biopsies were performed to ascertain resolution of nodular lesions. Results Forty patients (Males 23, females 17; mean age ± 1SD 35.6 ± 14.6 years) with DDNLH were studied. Patients presented with epigastric pain, vomiting, and weight loss. Esophagogastroduodenoscopy showed diffuse nodular lesions (size varying from 2 to 5 mm or more) of varying grades (mean score ± 1SD 2.70 ± 0.84) involving postbulbar duodenum. Video capsule endoscopies revealed nodular disease exclusively limited to duodenum. None of the patients had immunoglobulin deficiency or small intestine bacterial overgrowth or positive IgA endomysial antibodies. All patients were infected with Helicobacter pylori infection. Sequential antibiotic therapy eradicated Helicobacter pylori infection in 26 patients. Follow up duodenoscopies in these patients showed significant reduction of duodenal nodular lesions score (2.69 ± 0.79 to 1.50 ± 1.10; p Helicobacter pylori infection showed no significant reduction of nodular lesions score (2.71 ± 0.96 to 2.64 ± 1.15; p = 0.58). Nodules partially regressed in score in 2 patients, showed no interval change in 10 patients and progressed in 2 patients. Conclusions We report on a large cohort of patients with DDNLH, etiologically related to Helicobacter pylori infection.</p