Young-Jun Chong

Implementation and performance evaluation of mmWave channel sounding system

This paper introduces mBECS(millimeter wave Band Exploration and Channel Sounder), also known as channel sounder, to explore mmWave channel characteristic. We present engineering parameters for implementation of the mmWave channel sounder to use swept time delay cross-correlation(STDCC) technique and show the measurement results of system response obtained from performance evaluation test. The dynamic range above 45 dB was obtained at 28GHz.

Channel Correlation Analysis using MIMO Channel Measurement Parameters at Domestic 700MHz band

In the next generation of mobile communication systems, high data rates and high capacity will be possible if multiple antennas are used at new frequencies. This paper presents the correlations between channel parameter path loss (PL), delay spread (DS), angular spread (AS) and K-factor established based on channel measurements. To avoid interference from Korean DTV broadcasting, we measured the channel characteristics in urban/rural/suburban areas on Jeju Island using a channel sounder and antennas. The correlations between channel parameter show that the wireless channel characteristics can be determined and effective communication system design can be produced for use in similar environments.

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.

Protection ratio between DVB-T2 and LTE system

The protection ratio between DVB-T2 and LTE is acquired by 1~2M Hz step, and modified in order to take into account the effect of LTE UE and BSs out of band emission based on 3GPP TS 36.101 and 36.104 specification, respectively. The result of this study will be used to determine precisely the guard band when the guard band between DVB-T 2 and LTE was smaller than 1~2 channel bandwidth of DVB-T2.

Design of an absorptive structure for WCDMA band

In this paper, an absorptive structure based on a periodic structure is presented and its absorption performance is examined. This is a single-layer planar resonant structure, and a lossy periodic surface is used for enhancing the absorption characteristic instead of the conventional resistive layer. Using well known structure, we propose a design technique to determine the important design parameter by using a simple equivalent circuit and analytical method. In addition, the method for accurately measuring the reflectivity of the structure is presented, and through measured result the design is verified. The measured result for the proposed absorptive structure, showing a broadband reflectivity response with a fractional bandwidth of approximately 91% below -10 dB, is presented along with other computational results to confirm the function of the structure.

The design and implementation of TV tuner for digital terrestrial broadcasting

The DTV tuner for 8-VSB modulation was developed with satisfying the requirements of the ATSC. The double frequency conversion and the active tracking filter in the front-end were used for the cancellation of the interferences between adjacent channels and multi-channels by suppressing IF beat and image band. However, it was impossible to get frequency mapping between the tracking filter and the first VCO in the existing DTV tuner structure differing from the NTSC tuner. This paper, therefore, suggests the available structure and a new method for automatic frequency selection by obtaining the mapping of frequency characteristic over the tracking voltage and the combined hardware which is composed of a microcontroller, EEPROM, D/A, op amp and switch driver.

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.

Enhanced Analysis Method of MIMO Channel Characteristics with Antenna Correlation at 781MHz

In this paper, the measurement data is analyzed and channel characteristics are derived through MIMO Channel measurements at 781MHz considering antenna correlation. 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 quite a different part of the existing research has demonstrated. In addition, the signal procedure of the channel characteristics, considering the correlation of the antenna, for a more accurate prediction research is needed. To avoid interference with Korean DTV broadcasting, we measured channel characteristics in urban areas of Jeju island by channel sounder and antenna. Channel characteristics with antenna correlation were derived based on the measured data in the urban area.

The implementation of a base station transceiver for WLL system based on wideband CDMA

The implementation of a BTS (base station transceiver) for a WLL system using a wideband CDMA (W-CDMA) method is presented. It consists of three boards; receiver, transmitter, and RF controller. Some RF parameters are considered and simulated by the RF simulation software using commercial and customized component specifications. The implemented transceiver of 5 MHz RF channel bandwidth satisfies the system requirements of a transceiver such as dynamic range, receiver sensitivity, and spurious emission suppression in the transmitter. At the receiver, the experimental measurement showed a noise figure (NF) of 2.86 dB and a dynamic range of above 60 dB in AGC locking. At the transmitter, the -49.34 dBc of spurious emission suppression is attained when the output power of the transmitter is 34.3 dBm. These results are good enough to meet standard performance specifications.

Permittivity Measurements of various Materials in 13-28GHz Band

Abstract This paper presents the results of permittivities of various materials by measurements of the dielectric properties for the materials in millimeter-wave band. Since the advantages of millimeter wave band include the miniaturization, weight reduction of component and a lot of information transfer, its study has received increasing attention of researches. Also, because of the characteristics of the band have the superior straightness and the small diffractive, in the band, the analysis for the reflection and transmission characteristics of the materials will be very important. Moreover, a low interference is one of characteristics of the band due to the fact that the millimeter wave is absorbed in the materials. Therefore, in this paper, the reflection and transmission characteristics of materials are measured in the band by using the free space method. Based on the presented result, the permittivities of the materials are derived by the calculation of Nicolson-Ross Weir method.