• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.1
• /
• pp.78-89
• /
• 1999

In this paper, to improve bandwidth amplitude fluctuation for the broadband signal in indoor propagation environment, we measured and analyzed broadband signal using a vertically polarized, horizontally polarized and circularly polarized antenna, conducting by frequency sweeping method in NLOS (Non-Line-of-Sight) environment. And, to investigate the optimum condition for the improvement of broadband propagation characteristics we also examined the effects of both human motions and transmission antenna height in the NLOS environment. As a result, in the case of NLOS environment, it was found that the amplitude deviation characteristics in frequency bandwidth can be improved by polarization diversity reception. Especially, we found that it is the best effective one to make polarization diversity reception branches, which install the circularly polarized antenna at transmitting end and install the polarized diversity branches received vertical or/and horizontal polarized wave at receiving end. The affection of a human motions is not so much in LOS and NLOS environment, but it can lead to the cause of burst error in indoor digital radio communications as the fade of signal strength become more deeper. And also, when raise the transmitting antenna up to the ceiling, the LOS and NLOS environment could be coexisted. In this case, it can be also inferred that frequency bandwidth amplitude deviation must be fundamentally improved by using polarization diversity reception technique to make the possibility of high transmission rate.

• Journal of Navigation and Port Research
• /
• v.26 no.1
• /
• pp.22-27
• /
• 2002

The 25 Watt hybrid MIC SSPA has been developed in the frequency rang from 1.6265 GHz to 1.6465 GHz for uplink of INMARST's earth station. To simplify the fabrication process, the whole system is designed of two parts composed of a friving amplifier and a power amplifier. The Motorolas MRF-6401 is used for driving part, the Motorolas MRF-16006 and MRF-16030 is used the power amplifier. We reduced weight and volume of high power amplifier through arranging the bias circuits in the same housing. The realized SSPA has more than 30 dB for gain within 20 MHz bandwidth, and the voltage standing wave ratios(VSWR) of input and output port are less than 1.7, respectively. The output power of 44 dBm is achieved at the 1 dB gain compression point of 106365 GHz These results reveal a high power amplifier of 25 Watt which is the design target. The Proposed SSPA manufacture techniques in this paper can be applied to the implementation of high power amplifiers for some radars and SCPC.

• Cartoon and Animation Studies
• /
• s.48
• /
• pp.271-310
• /
• 2017

This paper examines the composition and the content of media art which is an art education subject in a national curriculum of Australia; and discusses implications for Korean education curriculums. Media covered by Media Art subject in Australia are the multi types of general media including TV, movie, video, newspaper, radio, video game, the internet, and mobile media; and their contents. The purpose of ACARA's media art education curriculum is to improve creative use, knowledge, understanding, and technology of communication techniques for multiple purposes and the audiences. Through the Media Art subject, both the students and the community are able to participate in the actual communications with the rich culture surrounding them and to develop the knowledge and understanding of the 5 core concepts of language, technology, system, audience and re-creation while testing the culture. The implication of this study is as the following. ACARA's media art education curriculum has been developed as an independent educational program and has a special significance within Australian education curriculums. Although ACARA's media art education curriculum is formed as an independent subject, it is suggested within the curriculum to instruct in close connection with other subjects upon execution. Its organization and elaborateness in curriculum composition are very effective in terms of the teacher's teaching-learning design and as well as the evaluation. This seems to show a good model of leading media literacy curriculum. ACARA's media art education curriculum can be a great reference in introducing media literacy to Korean national education curriculums.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.9A
• /
• pp.1048-1057
• /
• 2004

WCDMA system is 3rd generation wireless mobile system specified by 3GPP. In WCDMA downlink, two power control schemes are operated. One is inner loop power control operated m every slot Another is outer loop power control based on one frame time. Base staion (BS) can estimate proper transmission power by these two power control schemes. However, because each MS's transmission power makes a severe effect on BS's performance, BS cannot give excessive transmission power to the speclfic user 3GPP defined Power Control Dynamic Range (PCDR) to guarantee proper BS's performance. In this paper, we propose Adaptive PCDR algorithm. By APCDR algorithm, Radio Network Controller (RNC) can estimate each MS's current state using received signal to interference ratio (SIR) APCDR algorithm changes MS's maximum code channel power based on frame. By proposed scheme, each MS can reduce wireless channel effect and endure outages in cell edge. Therefore, each MS can obtain better QoS. Simulation result indicate that APCDR algorithm show more attractive output than fixed PCDR algorithm.

• Journal of Korean Society of Transportation
• /
• v.26 no.6
• /
• pp.39-47
• /
• 2008

With dramatic development of IT technology and start of DMB service, installing the DMB equipment in a vehicle for watching TV programs and literal or pictorial traffic information are increasing. Watching the DMB during driving the vehicle could cause visual and cognitive distraction to drivers as much as eating food, operating radio and using mobile phone. However, there is not much empirical research for this topic and no research examined the effect of watching the DMB on driving behaviors in Korea. So, the present study examined the effect of watching the DMB on the driving behaviors with car simulator experiment. Within subject design was used in the study. That is, all subjects drove the vehicle both in the watching DMB condition and the non-watching DMB condition. The results indicated that subjects in the watching DMB condition took longer time to arrive at the destination and operated accelerator and brake pedal rapidly than subjects in the non-watching DMB condition. That is, their overall driving stability was lower than non-watching subjects'. Additionally, we examined the difference among the DMB control conditions (i.e., keypad condition, touch-pad condition and remote controller condition) in the driving behaviors. Finally, we discussed the limitations and the implications of the present study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.3 s.106
• /
• pp.307-316
• /
• 2006

In this paper the analytical method, namely advanced minimum coupling loss(A-MCL), was proposed in order to analyze the coexistence of OFDM-based systems beyond 3G(B3G) with point-to point(PP) fixed service(FS) microwave systems. Our proposed method is based on a power spectral density(PSD) analysis. So it can be easily applicable to analyze the coexistence of OFDM-based systems B3G using flexible spectrum usage(FSU) with other systems, where the conventional MCL method cannot allocate transmit power partially to some subcarriers which overlap the band of a victim system. By applying the conventional MCL method and the A-MCL method, interfering power levels at the receiver of a interfered system are respectively calculated. A-MCL can calculate interference power more accurately than MCL by the maximum value of 4.5 dB. Therefore it can be concluded that our prosed method, namely A-MCL, is applicable to a sharing analysis of OFDM-based systems B3G.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.5
• /
• pp.1-9
• /
• 2000

In this paper, for the reverse link of a imperfect power controlled DS/CDMA cellular system when a mobile radio channel is a Rayleigh distributed multipath fading channel, A extended DS/CDMA blocking probability formula considering both shadowing and multipath fading is derived. Erlang capacity and equivalent channel number considering shadowing are analyzed and compared with those considering both shadowing and multipath fading, respectively. The DS/CDMA blocking probability is calculated based on the analysis method that obtains Erlang capacity and ICF(interference correction factor) using the median value of $E_{b(i)}$/ $I_{0}$ corresponding to each reverse link user Assuming that the blocking probability set 2%, it is observed that the Erlang capacity is 19.97 Erlang at the data rate $R_{b}$=9.6 kbps and 11.67 Erlang at the data rate $R_{b}$=14.4 kbps and then is less 16% and 19% than the Erlang capacity considering shadowing only, respectively. It is also shown that the effect of multipath fading must not be ignored and then exact Erlang capacity and equivalent channel numbers that the DS/CDMA cellular system can support are provided.d.d.d.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.4
• /
• pp.428-435
• /
• 2004

With the rapid and wide-spread use of cellular telephones much attention has been focussed on propagation in the urban area crowed with buildings and houses. It is often surrounded by hills, forests, and mountains. The importance of surface scattering intereference between transmitters and receivers on the rough surfaces has been interested and investigated. Therefore, a prediction method is necessary to estimate the influence of rough surfaces on microwave radio propagation. Moreover, most of the mobile communications are performed based on the digital communication system rather than the analog one. In this case, we must pay more careful attention to the signal delay caused by the phase delay due to the multi-path propagation. In this paper we have analyzed numerically scattering of electromagnetic waves from building walls by using FVTD(Finite Volume Time Domain) method. We consider three different types of rough surfaces such as periodic, random, and composite structures. We calculate the bistatic normalized radar cross section (NRCS) for horizontal and vertical polarization, and we take account of the conventional optical reflection which corresponds to the n-th Bragg reflection for periodic structures. In addition, we investigated what conditions are needed in order to be able to ignore the higher order Bragg reflection for the periodic structures.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.4
• /
• pp.894-900
• /
• 2004

There are many types of circularly polarized(CP) microstrip antenna elements, which are used as a good unit radiator. Since an advantage of CP antenna is no strict alignment requirements between Rx and Tx system, the printed antennas with circular polarization are very often used in numerous satellite and mobile radio systems. In order to realize the broad bandwidth of 3 dB axial ratio and impedance of CP microstrip antenna, complex feed structure and tri-plate patch element have been researched. This paper describes a design of wideband microstrip cross slot array antennas with circular polarization. The proposed antenna is composed of an open-ended microstrip feed line as a feeder and a cross slot as a radiator for circular polarization. To realize the wide bandwidth, tri-plate structure are considered and cross slot is electromagnetically coupled with feed line. Optimum parameters of 1-element cross slot antenna are analyzed and designed by method of moments. These parameters are also applied to may antennas design considered the mutual coupling between radiating elements. Right hand circular polarization(RHCP) and left hand circular polarization(LHCP) of the proposed antenna are easily controlled by asymmetrical cross slot structure and slot position. In 1-element and 15-element cross slot array antenna, the good axial ratio of 1 dB below and the broad bandwidth characteristics of antenna are obtained.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.7
• /
• pp.1804-1820
• /
• 1997

In this paper, an efficient call control procedure is presented for next generation wireless ATM networks and its performance is mathematically analyzed using the open queueing network. This procedure is based on a new scheme called as the cell clustering. When we use the cell clustering scheme, at the time that a mobile connection is admitted to the network, a virtual cell is constructed by choosing a group of neighboring base stations to which the call may probabilistically hand over and by assigning to the call a collection of virtual paths between the base stations. Within a microcell/picocell environment, it is seen that the cell clustering can support effectively a very high rate of handovers, provides very high system capacity, and guarantees a high degree of frequency reuse over the same geographical region without requiring the intervention of the network call control processor each time a handover occurs. But since mobiles, once admitted, are free to roam within the virtual cell, overload condition occurs in which the number of calls to be handled by one base station to exceed that cell site's capacity of radio channel. When an overload condition happens, the quality of service is abruptly degraded. We refer to this as the overload state and in order to quantify the degree of degradation we define two metrics, the probability of overload and the normalized average time spent in the overload state. By using the open network queueing model, we derive closed form expressions for the maximum number of calls that can be admitted into the virtual cell such that the two defined metrics are used as the acceptance criteria for call admission control.