Young-Keun Yoon

Measurements of path loss in MM-wave for indoor environments

In the indoor environment, millimeter wave channel will be probably limited in the indoor environment due to severe attenuations by furniture, partitions, walls, and floors for non line of sight (NLOS). Therefore, in order to analysis a radio system at millimeter wave bands we need to measure path loss characteristics of a millimeter wave indoor channel, the influence of geometry on this phenomenon. In this paper, the path loss model using the statistical method based on the measurement was proposed. This model consists of three parts, free space path loss, attenuation factor and excess loss. To estimate the propagation characteristics has been measured path loss in the indoor environments using omni and horn antenna for line of sight (LOS) and non line of sight (NLOS). From the measurements results, we are proposed attenuation factor and standard deviation. Also, we compare the proposed attenuation factor with other reference model and analyze the delay characteristics for MM -wave

The multipath delay spread model for the LOS case

A rapid growth of radio services leads to the deficiency of frequency resource, but the utilization of the radio service at M/W band is very low, relatively. Therefore, wideband characteristics at 8 GHz band, is requested to solve the deficiency of frequency resources. The wideband characteristic such as the delay spread of multipath signals was measured with a channel sounder under LOS environment. And, the delay spread model was proposed from the measured results. The model was compared with ITU-R model and they were agreed well at similar conditions. But, it needs more measurements and analysis of some environments such as suburban areas and non-LOS conditions. After then, the delay spread model will be completed and it could be grasped a characteristics of M/W band according to radio environments.

28GHz Wideband Characteristics at Urban Area

Wideband characteristics in the 28GHz band were measured at various environments using narrow beamwidth antennas. In this paper, we present delay spreads of urban low-rise area with two line of sight cases, one is a face-to-face and the other is non-face-to-face between antennas. Also, we present a distance characteristic of delay spread based on measured data.

Modeling of Adjacent Channel Interference in Heterogeneous Wireless Networks

This letter proposes a new model for the aggregate adjacent channel interference (ACI) received from nearby terminal stations (TSs) of heterogeneous wireless networks. It is well known that lognormal distribution approximates the aggregate received signal, but we found that it does not perform well for ACI-modeling among coexisting TSs. We propose a weighted sum of lognormals-based approximation (WSLA) where the probability density function (PDF) of the aggregate ACI appears in the form of a weighted sum of lognormals. The closed-form downlink outage probabilities with both lognormal approximation and WSLA are also derived. Through simulations, we demonstrate that the proposed approximation outperforms the lognormal one. The WSLA can also be applied to a dual slope channel model and extended to model the aggregate interference in inter-cells or sensor networks.

MIMO Radio Channel Measurement and Analysis at 781MHz

Abstract In this paper, the measurement data is analyzed and channel parameters are derived through MIMO Channel measurements at 781MHz considering outdoor multi-path environment. 781MHz frequency band currently operates the DTV system. However, it will be allocated new mobile communication frequency band. The channel characteristics at 781MHz seem to be similar existing mobile communication system at 900MHz but a study on channel characteristics of signal transfer process is necessary because there is incomplete study in mobile networks at 781MHz. To avoid interference with Korean DTV broadcasting, we measured channel characteristics in city/suburban areas of Jeju island by channel sounder and 4×4 antenna of the ETRI(Korea Electronics and Telecommunications Research Institute). Path Loss, Delay Spread, Angular Spread and K-factor were derived based on measured data. Key Words : MIMO, Path Loss, Delay Spread, Angular Spread, K-factor * 준회원, 충북대학교 전파공학과 ** 준회원, 한국전자통신연구원 전파기술연구부 ***

Enhancement approach of ray-tracing algorithm for propagation prediction at the MM-wave band

The reflection characteristics of building materials at the millimeter (MM) wave band are needed for development MM-wave application such as Giga-bytes indoor communication systems. Because reflection characteristics in the MM-wave band is dependent on the condition of measurement environments and has so little measurement data. To enhance these problems, we have studied propagation characteristics in the MM-wave band. In this paper, we set up the measurement system and measured the propagation characteristics of samples with periodic and random rough surfaces. Their results compared with measurement and simulation results at the 60 GHz. We have numerical simulation for dependence of electrical property. Also, the energy estimation of scattered reflection according to the rough surfaces simulated. Finally, we propose the simple approach (2 ray path model) for ray-tracing algorithm. This approach can be directly applied to the estimation of multipath signal strength in ray tracing by weighting factor for propagation prediction.

Interference Analysis for Coexistence Between UWB System and Portable Internet Service

This paper evaluates the impacts of interference by Ultra-wideband (UWB) system, and determines the tolerable UWB emission power spectral density (PSD) to the new deploying system, which is called portable internet service in Korea. It also proposes the interference analysis scheme that can evaluate the characteristics of the performance degradation for portable internet service according to the emission PSD of UWB systems at the specified frequency bands. The proposed scheme includes a multi-rate and data service environment to deal with the effects of interference to portable internet service. It is obtained from simulation results that the emission PSD of UWB system should be rigidly restricted by less 30dB than Federal Communications Commission (FCC) provisional limit for the coexistence between UWB and portable internet service, which is already allocated at 2.3GHz frequency bands in Korea.

Site specific analysis on mm-Wave radio propagation in commercial small urban

This paper describes R.M.S delay spread according to the TX-RX separation distance in commercial urban zone measurement at millimeter wave frequency. We found that small scale fading in our focus is caused by multipath due to a large number of reflective and diffractive characteristics in various urban environments. With the ray-optical site specific model presented in this paper, R.M.S delay spread predictions in urban hot-spot propagation environment gave reasonable accuracy.

Millimeter-wave delay spread measurement and simulation at LoS urban low-rise environments

Delay spread characteristics in the 28GHz band were measured at line of sight urban environments using narrow beamwidth antennas and simulated using ray-tracing with the same conditions. The channel sounder has 500MHz wide bandwidth at 28GHz, and using swept time delayed cross-correlation technique. The measurement environment is urban low-rise areas. The measurement and simulation results are compared to predict a delay spread with a line of sight condition.

Radio propagation characteristics in the large city and LTE protection from STL interference

This paper describes composite propagation effects of both the median pathloss and shadow fading in the large city. In general, the propagation characteristic for the power profile of received signal has the relative power reduction and fluctuation according to distance to the receivers location far away from the transmitter. The result of these channel propagation losses is due to the reduction of electric field in the air according to the separated distance between a transmitter and receiver, and due to the multipath effect such as the plane reflection and edge diffraction of the propagated radio signals at the plane of buildings and roads or vehicles etc. Propagated multipath radio signals via different paths may be simultaneously received to a target receiver with different field strength and phases. Actually, it is not easy to how to predict the optimum radio propagation characteristics in the large city from a transmitter to target receiver at the specific mobile or fixed communication link, because the outdoor environment have the different height of transceivers and various structure factors such as buildings, roads, and vehicles in the large city including the urban, suburban and rural area. Therefore, the measurement is currently candidate solution for predicting the radio propagation characteristics in the novel environments. In this paper, two different stations between a fixed and mobile station are considered. Measurement results are compared with the general radio propagation model of 3GHz frequency and lower. As another issue, we discuss and propose on the closed form of the interfering received signal strength intensity when two different stations like a fixed system as the repeater and a mobile system as Long Term Evolution coexist in the same area. In the coexisting environment, two different stations overlap the cell coverage and are assigned in the adjacent channel frequency. Therefore, the potential interference may cause to their reception each other. Here, it is important to analyze the interference impact to the victim station as a receiver from the interfering station as a transmitter to get out of the interference. In this paper, it is assumed that an interfering station as a transmitter is fixed repeater and a victim station as a receiver is a mobile Long Term Evolution system. For estimating interfering received signal strength intensity, it is issued to figure out a radio propagation characteristic. However, it is unknown for the available median pathloss model to apply for analyzing the performance of Long Term Evolution system from interfering fixed repeater in the large city with none line of sight in the coexisting environment. Finally, we propose the median pathloss characteristic from measuring the electric field strength of a fixed repeater as an interfering transmitter and calculated interfering received signal strength intensity to a victim station. Using both the measurement and the theoretic calculation results, the separated distance between an interfering transmitter and victim receiver is discussed for the protection of a victim station.