Young-Bin Chang

Proposal on Millimeter-Wave Channel Modeling for 5G Cellular System

This paper presents 28 GHz wideband propagation channel characteristics for millimeter wave (mmWave) urban cellular communication systems. The mmWave spectrum is considered as a key-enabling feature of 5G cellular communication systems to provide an enormous capacity increment; however, mmWave channel models are lacking today. The paper compares measurements conducted with a spherical scanning 28 GHz channel sounder system in the urban street-canyon environments of Daejeon, Korea and NYU campus, Manhattan, with ray-tracing simulations made for the same areas. Since such scanning measurements are very costly and time-intensive, only a relatively small number of channel samples can be obtained. The measurements are thus used to quantify the accuracy of a ray-tracer; the ray-tracer is subsequently used to obtain a large number of channel samples to fill gaps in the measurements. A set of mmWave radio propagation parameters is presented based on both the measurement results and ray-tracing, and the corresponding channel models following the 3GPP spatial channel model (SCM) methodology are also described.

A novel dual-slope mm-Wave channel model based on 3D ray-tracing in urban environments

To solve mobile traffic crunch, the usage of enormous bandwidth in millimeter wave (mm-Wave) is under discussion. In this paper, we investigate radio channel characteristics of mm-Wave frequency in the downtown area of Ottawa using 3D ray-tracing technique. In the results, important parameters of the radio channel model, such as path loss exponent, shadow fading, delay spread and angle spread, are provided. Especially, in case of path loss model in non-line of sight, a novel dual-slope approach is proposed for two conventional deployment scenarios. Comparing to traditional single-slope path loss model, the proposed method has smaller RMS errors in terms of local mean of path loss observations. We believe that the proposed method is appropriate to evaluate performance of the mm-Wave system in dense urban environments.

Novel OFDM transmission scheme to overcome caused by multipath delay longer than cyclic prefix

This paper proposes the novel OFDM transmission scheme that can effectively overcome ISI by adjusting CP length. As a way of combating ISI caused by multipath delay longer than guard interval, interference canceller or powerful channel coding has been proposed. Such approaches may reduce ISI, but it needs much complex computation or considerably decreases transmission efficiency to completely eliminate ISI. In our proposed scheme, CP length can be adaptively controlled by simply adjusting sampling rate. Hence it does neither much increase receiver complexity nor decrease effective data rate, compared to the conventional schemes. Our simulation results show that by employing the proposed OFDM transmission scheme, ISI can be effectively avoided in mobile environment with various multipath delays.

3-Dimensional Large-Scale Channel Model for Urban Environments in mmWave Frequency

From the results of the ray-tracing simulation of 28 GHz frequency band over downtown of Ottawa and New York University campus, we propose 3D large-scale channel models for urban city which are applicable to a mmWave version of 3D spatial channel model. Due to the change of geographical topology dimension from 2D to 3D, the height information of the transmitter should be reflected to the parameters of the channel model such as line-of-sight probability, Ricean K factor, path loss and shadow fading accordingly. In the simulation results, the line-of-sight probability depends on the height of the transmitter compared to the 2D model. The dual-slope path loss model is still appropriate in 3D channel model. We also propose the linear standard deviation function of the shadow fading, which shows a large standard deviation and an increasing trend with the distance.

Characterization of crystallographic properties of SMC poly Si using electron backscattered diffraction

Crystallographic properties of silicide mediated crystallization (SMC) polycrystalline silicon (poly Si) and excimer laser annealing (ELA) poly Si were studied by electron backscattered diffraction. Large‐grain sized poly Si with a large fraction of low‐angle grain boundaries was acquired by SMC, and small‐grain sized poly Si with high‐angle grain boundaries especially around 60° was acquired by ELA. The thin film transistor (TFT) device characteristics were investigated in view of short‐range crystallinity (pattern quality) and long‐range crystallinity (misorientation distribution) of the specimens. Short‐range crystallinity did not significantly affect the TFT device characteristics, and long‐range crystallinity considering the low energy level of special boundaries could be better related to the TFT device characteristics of poly Si.

Comparison Analysis of Outdoor Channel Characteristics at 28 GHz and 2 GHz Using 3D Ray-Tracing Technique

Broadband wireless systems operating in millimeter wave (mmWave) frequency band has been used for short-range wireless communication and point-to- point wireless backhaul. Due to lack of research work on outdoor radio propagation characteristics in mmWave frequency band, the question of feasibility of cellular communication including long-range and non-line of sight (NLoS) environments in mmWave frequency band is unanswered. In this paper, we investigate the radio propagation characteristics at 28 GHz and 2 GHz using 3D ray-tracing simulation based on Manhattan-like grid model. LoS and NLoS results of outdoor radio propagation characteristics considering beamforming effects at 28 GHz are provided. Results of 2 GHz in the same geometry are also provided. In LoS environment, the radio propagation with 25 dBi beamforming gain at 28 GHz has similar characteristics with 2 GHz. In NLoS environment, even if the transmitter has 25 dBi beamforming gain at 28 GHz, the received power is 10 to 25 dB lower than 2 GHz. The received power loss because of narrow beam usage at 28 GHz is negligible in both LoS and NLoS environments.

Electron backscattered diffraction study of poly-Si by Ni-mediated crystallization of amorphous silicon using a SiO2 nanocap

Low-temperature polycrystalline silicon (poly-Si) is of increasing interest for the display on glass. Among several techniques for the low-temperature poly-Si the Ni-mediated crystallization of amorphous silicon (a-Si) is promising one. We studied the crystalline orientation of the disk-shaped grains in the poly-Si formed by Ni-mediated crystallization of a-Si using a SiO2 nanocap by electron backscattered diffraction measurements. A SiO2 nanocap layer was formed by O2 plasma treatment on a-Si and an ultrathin Ni layer was deposited on the nanocap. It was heated in a UV scan system for crystallization. The Ni atoms in a-Si diffused through the nanocap and formed NiSi2 crystallites. Disk-shaped grains were then grown from these nuclei. The size of disk-shaped grains in poly-Si increases from ∼6 to ∼20 μm when the thickness of nanocap on a-Si changes from 2.4 to 3.2 nm. On the other hand, without the nanocap layer, its size is ∼3.5 μm. The crystalline quality of poly-Si is improved by introducing a nanocap layer, which is due mainly to the increase of the grain size.Low-temperature polycrystalline silicon (poly-Si) is of increasing interest for the display on glass. Among several techniques for the low-temperature poly-Si the Ni-mediated crystallization of amorphous silicon (a-Si) is promising one. We studied the crystalline orientation of the disk-shaped grains in the poly-Si formed by Ni-mediated crystallization of a-Si using a SiO2 nanocap by electron backscattered diffraction measurements. A SiO2 nanocap layer was formed by O2 plasma treatment on a-Si and an ultrathin Ni layer was deposited on the nanocap. It was heated in a UV scan system for crystallization. The Ni atoms in a-Si diffused through the nanocap and formed NiSi2 crystallites. Disk-shaped grains were then grown from these nuclei. The size of disk-shaped grains in poly-Si increases from ∼6 to ∼20 μm when the thickness of nanocap on a-Si changes from 2.4 to 3.2 nm. On the other hand, without the nanocap layer, its size is ∼3.5 μm. The crystalline quality of poly-Si is improved by introducing a nanocap ...

Data burst transmission scheme to suppress audible noise in mobile handheld terminal

Audible noise caused by uplink periodic hulrt transmis.rion in mobile terminol can irritate a talking ziser. Such audible noise problem has heen resolved by harrlwure filtering. In tliis paper ~ , e propose a burst data transmi.wion scheme that can ef

A study on correlation properties of shadow fading of millimeter wave frequency spectrum

cientlv suppress the audible noise. Tl7rong17 the use ofthe proposed scheme, we cun considerahlv reduce die audible noire withoar !lie hardwore coni~~onents andfiltcring. Index Terms Audible noise, Data transmission, Hardware complexity, Mobile terminal

Opportunistic discovery scheme for device-to-device communication

Correlation properties of shadow fading are the essential part of a large-scale channel model to evaluate system-level performance. The recent interest on mmWave frequency band naturally requires the study of these correlation properties so that new cellular system based on the new spectrum on mmWave band can be identified to be feasible. To the best of our knowledge, the correlation study has been done in only legacy band, below 6 GHz, and the study of these correlation properties in mmWave channel is required. In this paper, we investigate the correlation of shadow fading in mmWave frequency band by comparing this with the results in conventional cellular frequency band, i.e., under 6 GHz. In detail, decorrelation distance and site-to-site correlation as the correlation parameters are obtained from the results of the ray-tracing simulation at 28 GHz and 2 GHz frequencies in the area of downtown of Ottawa. The simulation results show the similarity of the decorrelation distance which is statistically independent of frequency. Also, 28 GHz and 2 GHz have similar site-to-site correlation values to each other. From these results, we claim that the correlation parameters for mmWave frequency band can be adopted from the parameters of the conventional cellular frequency band.