• Journal of the Korean Institute of Telematics and Electronics
• /
• v.27 no.1
• /
• pp.1-9
• /
• 1990

This paper investigates the significance and the implication of the pointer scheme, which was recently adapted by CCITT as a standard synchronization method in the broadband network-node interface environment, and discusses the merits of the pointer scheme in comparison with the conventional positive justification method. It also analyzes the jitter performance of the communication system employing the pointer scheme based on the fact that the pointer scheme corresponds to a multiple-bit positive/zero/negative justification.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.30 no.3
• /
• pp.1-11
• /
• 2007

The purpose of this study is to predict promising Location Based Services under an ubiquitous environment based on their technical characteristics, which is strongly required in rapidly changing circumstances with ubiquitous computing and Broadband Convergence Network (BcN). To begin with, this study proposes a classification scheme of ubiquitous services and defines five technology factors required for ubiquitous services. Next, this study collects a number of ubiquitous services from previous researches and classified them according to the classification scheme of ubiquitous services. And then, technical importance of the collected ubiquitous services are evaluated in terms of technology factors by using service-technology metrics. Finally, a set of important Location Based Services under ubiquitous environments and the correlations between technology factors are identified by using the evaluation results.

• Journal of the Optical Society of Korea
• /
• v.18 no.5
• /
• pp.589-593
• /
• 2014

Terahertz (THz) communication has important applications in high-speed and ultra broadband wireless access networks. The THz modulator is one of the key devices in a THz communications system. Wavelength division multiplexing (WDM) can expand the capacity of THz communications systems, so research on multi wavelength THz modulators has significant value. By combining photonic-crystal and THz technology, a novel type of multi wavelength THz modulator based on a triple-lattice photonic crystal is proposed in this paper. Compared to a compound-lattice photonic crystal, a triple-lattice photonic crystal has a larger gap width of 0.196. Simulation results show that six beams of THz waves can be modulated simultaneously with high performance. This modulator's extinction ratio is as large as 34.25 dB, its insertion loss is as low as 0.147 dB, and its modulation rate is 2.35 GHz.

• Journal of Korea Society of Industrial Information Systems
• /
• v.12 no.4
• /
• pp.148-152
• /
• 2007

This paper develops an integrated optic transmitter/receiver based on ring-type WDM PON. The optic transmitter/receiver can transmit real-time images from the CCTV of a remote street without compression and transmit TCP/IP data using an optic fiber. This system can also perform remote controls of the CCTV camera. The developed optic transmitter/receiver can provide the monitoring service of an advanced image quality of remote traffic using a broadband technology.

• ETRI Journal
• /
• v.32 no.3
• /
• pp.475-478
• /
• 2010

A multiband meandered monopole antenna is proposed for digital video broadcasting handheld (DVB-H), global positioning system, personal communications service, wireless broadband (Wibro), and wireless local area network (WLAN) applications. The proposed antenna consists of a meandered line, a shorted length strip line, and a conductor strip between a meandered line and a microstrip feed line. By tuning a short strip and a conductor, a multiband impedance matching is achieved. The proposed antenna has an omnidirectional radiation and yields an antenna gain of greater than -3 dBi in the DVB-H band and 4.5 dBi in the Wibro and WLAN bands. Details of the proposed antenna design and experimental results are presented.

• Proceedings of the IEEK Conference
• /
• summer
• /
• pp.27-30
• /
• 2004

OFDMA is considered as one of the major candidates for broadband wireless access. The OFDMA signal is usually coherently demodulated, requiring the channel estimation which can be estimated using a known pilot signal. In multi-cell environment, the performance of channel estimation is mainly limited by intercell interference. It is desirable to use a pilot signal that can estimate the channel information robust to the intercell interference in the OFDMA uplink system. In this paper, we consider two types of pilot signal applicable to multi-cell OFDMA uplink systems: One is time-multiplexed pilot signal and the other is code­multiplexed pilot signal. Simulation results show that the code-multiplexed pilot is suitable for low mobility environment and time-multiplexed pilot is suitable for high mobility environment.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.675-678
• /
• 2006

IPTV (Internet Protocol Television) is an efficient system which serves various contents to subscribing consumers by using the IP over a broadband connection. The IPTV services can be multi-channel broadcasting service, VoD, T-Commerce, video conference, on-line game and so on. TV Anytime metadata provides various description tools for TV program contents by which TV program contents can serve more information. In this paper, we mention about the overview and feature of IPTV and TV Anytime metadata, propose the essential functions in the EPG program of IPTV and survey the description tools for the proposed functions in EPG. Finally, we show the authored metadata and the implementation of advanced EPG application.

• Journal of electromagnetic engineering and science
• /
• v.10 no.4
• /
• pp.263-269
• /
• 2010

Multiple input multiple output (MIMO) has been considered one of the key enablers of broadband wireless communications. The indoor environment is known to be favorable to ensure both high rank property and high signal-to-interference/noise ratio (SINR) to fully exploit MIMO spatial multiplexing (SM) gain. In this paper, we describe several practical deployment cases where repeater links (or relay links), such as those present with an indoor distributed antenna system (DAS), can act as keyholes to degenerate the rank property of MIMO communications. In this case, we cannot exploit MIMO SM gain in indoor environment. We propose a novel MIMO communication scheme which uses simple converter in the devices in repeater links to resolve the rank degeneration issue and to ensure MIMO SM gain in highly MIMO-favorable indoor environment. MIMO SM is possible over the indoor DAS with single cable line through use of simple converters, which enables practical deployment in real fields.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.10A
• /
• pp.1167-1176
• /
• 2004

This paper presents an adaptive MC-CDMA transmission for downlink in mobile satellite system and simulation results on Ka-band mobile satellite channel. The simulation results show that the proposed scheme support a throughput of several tens of Mbit/s and a spectral efficiency range of 1 bit/s/Hz to 4.7 bit/s/Hz according to channel environments due to the adaptive broadband satellite transmission.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.2023-2028
• /
• 2004

The effects of nozzle-lip thickness on the relationship between screech tone and broadband shock-associated noise were experimentally investigated using a convergent-divergent nozzle with a design Mach number of 2.0. Overall sound pressure levels (OASPL) and noise spectra were obtained at far-field locations. Schlieren optical system was used to visualize the flow-fields of supersonic jets. A baffle plate was installed at the exit of the nozzle and its size was varied to obtain different nozzle-lip thicknesses. Experiment was carried out over a wide range of nozzle pressure ratios from 2.0 and 18.0, which corresponds to over- and under-expanded conditions. The results obtained clearly show that the screech tones are influenced by the nozzle-lip thickness. It is found that the screech tone and its peak amplitude are strongly dependent on whether the jet is over-expanded and under-expanded at the nozzle exit.