Kyung-Seok Kim

A CR Platform for Applications in TV Whitespace Spectrum

A cognitive radio platform for whitespace spectrum in UHF TV band is introduced. The purpose of the CR platform is to evaluate the feasibility of the unlicensed wireless service in the UHF TV band. The platform consists of RF, baseband modem and MAC including spectrum sensing function. The performance of the spectrum sensing function combined with wideband RF IC which is designed for mobile broadcasting service in multiple bands is presented.

MIMO Channel Measurement and Analysis for 4G Mobile Communication

MIMO channel model requires propagation channel measurements to estimate according channel parameters and is rarely done. This paper presents the measured radio propagation characteristics in outdoor environments for 4G mobile communication in the Jeju Island at 781 MHz frequency. 781MHz frequency band currently operates the DTV system, however, it will be allocated 4G mobile communication frequency band. So, we measure channel characteristics in urban/rural/suburban areas by 4×4 MIMO channel sounder. To analyses the frequency characteristics for a domestic propagation environment, we derive various propagation characteristic parameters.

Channel Allocation and Interference Analysis for DAB System in Frequency Band III Environment With Legacy T-DMB

For Eureka-147-based digital audio broadcasting (DAB) system, frequency band III has been generally used in many countries. However, in some countries, other legacy broadcasting services have been adopted in the same frequency band. Especially, in South Korea, T-digital multimedia broadcasting (DMB) service has been already broadcasted through the band III since early 2005. In this paper, to adopt the DAB system in band III, channel allocation method and interference analysis are investigated for Korea broadcasting environment with legacy T-DMB. To allocate DAB channel, actual FM radio broadcasting stations and geographical features are considered. Furthermore, interference analysis and evaluation are performed between co-channel broadcasting areas and adjacent channel broadcasting areas. These evaluation results provide the DAB service channel allocation method in broadcasting environment with legacy broadcasting system, and can be used as a reference to determine the DAB service channel allocation through the frequency band with existing broadcasting system.

Design and implementation of a novel emergency wake-up alert system within a conventional T-DMB service network

Existing emergency alert techniques of terrestrial-digital multimedia broadcasting (T-DMB) and digital audio broadcasting (DAB) can be executed only when the receivers are activated. To overcome the limitation of existing technique, a novel emergency wake-up alert system within a conventional T-DMB service network is proposed. The emergency wake-up alert signal is periodically generated by emergency transmission data unit (ETDU) and then transmitted through the conventional T-DMB/DAB station. After receiving the emergency wake-up alert signal, T-DMB/DAB receiver can be wake-up, activating and result in showing emergency broadcasting contents to people. To obtain frequency efficiency, the emergency wake-up alert signal is overlaid onto the conventional T-DMB frequency band using a direct sequence spread spectrum technique. To assess the performance of the developed ETDU, simple RF transmitter, test receiver and measurement equipment are used. The performance is checked with different values of emergency wake-up alert signal to T-DMB power ratio. The laboratory test results shows that the wake-up alert signal can be transmitted without degrading the existing T-DMB signal quality and can be detected at very low power emergency wakeup alert signal, e.g., as low emergency wake-up alert signal to T-DMB power ratio as -22.2dB.

The optimal placement of radio stations in coexisting DRM+ and analog FM systems

Currently in wireless communication technology, digital radio systems are replacing analog radio systems. The digital radio service provides better quality sound to receiver and uses frequency efficiently. However, digital radio has the potential to cause interference problem, since in-band digital radio systems occupy existing analog radio frequency bands. It is important to effectively analyze this interference for both digital radio receivers and analog radio receivers. This paper analyzes the interference between the DRM+ system used in in-band digital radio and the existing analog FM system, and derives the optimal separation distance needed to preclude interference. These results are able to supply basic information for digital radio system cell design.

Channel-Allocation Plan for National and Local T-DAB Services in VHF Band III

The digital audio broadcasting (DAB) system is mainly designed for large-area coverage and is suited for a single-frequency network (SFN) operating in Very High Frequency (VHF) Band III. To operate successfully, the SFN requires a different network-planning approach for multiple-frequency networks and should avoid self-interference. This paper focuses on nationwide SFN planning and DAB channel-allocation planning to replace all frequency-modulation (FM) services with terrestrial DAB services in VHF Band III. In South Korea, VHF Band III has been used for terrestrial digital multimedia broadcasting (T-DMB) services; thus, available frequencies should be investigated for T-DAB services and the nationwide SFN. An approach for broadcasting channel-interference analysis is proposed herein. For the interference analysis, the geographical features and the information for stations of legacy FM radio broadcasting and T-DMB, such as transmission parameters, are considered. The ratio of the interference area to the coverage is calculated via the channel-interference analysis. Areas affected by the self-interference in the nationwide SFN are investigated. The results of this paper provide insights regarding channel-allocation planning for T-DAB services and an approach for nationwide SFN planning.

Measurement and analysis for 3.5GHz small-cell environment with time and spatial ratio

Recently, researches regarding spectrum sharing has been underway due to the insufficiency of spectrum resources. Basically, it is necessary to solve the temporal or spatial environment in order to share the frequency. In this paper, we will introduce to our own channel sounder and we use this system to generate path loss modelling based on time and space ratio.

A wireless channel sounding system for 3.5GHz band small-cell environmental measurements

Recently, 3.5GHz band is determined as mobile communications frequency in IMT-2020. Basically, TD-LTE in small-cell environment and downlink supplement in hotspot area can be utilized in 3.5GHz band. According to this latest trends, channel sounder for 3.5GHz band is harmoniously implemented by universal devices such as NI equipment for baseband and transceiver and self-developed modules which are high power amplifier, RF switch, timing module and antenna. From this channel measurement system, we obtain the various measurement parameters through real wireless channel measurement in urban and suburban areas for 3.5GHz band.

Radio Propagation Analysis for Various Urban Sites on Ka-Band Satellite Communication

Propagation analysis of the transmitting and receiving environment is important for designing satellite communication systems. The satellite signal passes though the atmospheric layer and is affected by the resulting attenuation. Therefore, systematic analyses of the atmospheric characteristics and the receiving environment are needed. This study examined the propagation characteristics of a geostationary satellite using the Ka band. The atmospheric characteristics of the Ka band were analyzed, and the urban environment was modeled. A range of receiving environments was analyzed. The results of this paper are expected to assist in the design of satellite mobile communication systems in the Ka-band.

Performance enhancement approach of the Wiener beamforming in DS/CDMA systems

An efficient performance enhancement scheme using the persymmetric covariance matrix structure to enhance the performance of the Wiener beamforming in DS/CDMA systems is proposed. The main idea of the proposed scheme is to reduce the interference-plus-noise effect from the pre-correlation array covariance matrix using the persymmetric covariance matrix in a weight vector calculation for the Wiener beamforming. Generally, the persymmetric covariance matrix has the theoretical properties such as Toeplitz structure matrix or a positive semidefinite matrix. The persymmetric covariance matrix structure is obtained from the pre-correlation array covariance matrix using one of three methods, which are Toeplitz matrix approximation (TMA) method, forward/backward averaging (FBA) method and Toeplitz-plus-Hankel approximation (THA) method. Simulation results are shown with the various parameters that demonstrate the superiority of the proposed scheme. Copyright