Jongho Kim

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

Analysis of space-time block codes OFDM systems with the number of antennas and various mobile speeds

We design STBC-OFDM systems with multiple-input multiple-output (MIMO) by applying several STBC schemes to the OFDM system and show their comparative analysis results obtained with the various mobile speeds, under Rayleigh fading environments, considering the effects of channel estimation error. There is no systematic comparative analysis for those STBC techniques, considering the 4th generation mobile system environments with various mobile speeds. Therefore it is very important to derive the optimum STBC-OFDM for 4G mobile system environments. We finally compare and analyze the BER performances of the STBC-OFDM systems according to the mobile speeds and the number of antennas.

Study on the Measurement System for MIMO Channel Considering Urban Environment at Microwave Frequencies

In this paper, the development of wideband MIMO channel sounder and a pilot measurement result is described for research on the multi antenna radio propagation characteristics considering urban environment at microwave frequencies. We developed MIMO(BW:100 MHz) channel sounder using the high speed switching mechanism and periodic pseudo random binary signals method considering next generation mobile communication system. A pilot measurement campaign at the urban area of Bundang is presented for confirmation of system performance. From the analysis of measurement data, wideband path loss exponent of 3.7 and 8 GHz band is 1.79 and 1.76. Average RMS delay spread is 200 ns and 42 ns respectively. From the experiment results, operation of this measurement system is confirmed considering research for a coverage, SNR and channel capacity in urban environment at microwave frequencies.

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.

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.

Intelligent ray tracing for the propagaiton prediction

This paper describes the accelerated ray tracing method in order to improve simulation speed. Ray tracing estimation uses the preprocessing scheme and backward tracing with volumetric ray tube and image method. Finally, results of ray tracing estimation are given and the comparison results between ray tracing estimation and measurement at millimeter wave band are shown.

Measurement and simulation for delay spread on the T-type hallway in indoor office building environment

The 60GHz band has made great interest [1–3] rather than UHF bands [4–5] because of its large bandwidth allocated for future dense wireless local communications, particularly as relates to large wireless LAN bridges, and wireless high quality video conferencing. Channel characterizations at these millimeter wave frequencies have made using the measurement [2] and high-frequency asymptotic approaches such as ray tracing (RT) method for modeling the channels. The measurement can be expensive (especially in the millimeter wave bands) as compared to electromagnetic modeling approach. RT methods have the capability to solve electrically large problems relatively fast and, as such, they become an obvious candidate for the extraction of channel parameters. This paper describes the measurement and a ray tracing method for extracting the root mean square (r.m.s) delay spread at 60GHz. A validation of the ray tracing method with our in-office hallway measurement in non line-of-sight (NLOS) environment is also presented. And, theoretical channel capacity from mean r.m.s delay spread is derived.

KA and Ray tracing approximation on the surface roughness

This paper is given the results compared Kirchhoff with ray tracing method for scattering characteristics due to the roughness on the periodic surface. Analysis method used first order Kirchhoff approximation and ray tracing based on viewing volume tube. Finally, there is proved that the provided approximation methods are possible to support to extract practical scattering characteristics.

Improving the acceleration of ray tracing estimation in an urban environment

In this paper, we present the advanced ray path search method. The proposed method can be applied to complex urban environments with arbitrary building layouts and heights.