• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.75-78
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• 2004

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the data rate and the reliability of communications by a channel code, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve a performance in multi-path fading channel environment.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.775-784
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• 2010

In this paper we propose a design method of X band frequency hopping synthesizer in terms of phase noise and settling time with DDS driven PLL architecture, which has the advantages of high frequency resolution, fast settling time and small size. In addition, a noble method is proposed to remove the synthesizer output spurious signals due to superposition effect of DDS. The spurious signal which depend on its normalized frequency of DDS, can be dominant if they occur within the PLL loop bandwidth. We verify that the sources of that spurious signals are quasi-amplitude modulation and superposition effect, and suggest that such signals can be eliminated by intentionally creating frequency errors in the developed synthesizer.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.2
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• pp.222-231
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• 2011

In this paper, we have proposed a method which can make it possible to stably transmit and receive data like the ARC-164 radio frequency hopping environment as a S/W packet modem with PSK modulation. This is a method that the S/W packet modem with PSK digital modulation and the use of PC sound cards change over from data to voice signals and then transmit/receive data. We confirmed not only that it is possible to solve the slow speed communication with the use of sending data through multi-channels and PSK modulation that has the ability to methodically improve transmission rates, but also that it is possible to send the state of frequency hopping stably. In conclusion, we've confirmed both tactical values that though the transmission rate may be a tad slow, a state of frequency hopping of more than 94% confidence plus voice and data can be sent via radio at the same time. In this paper, the proposed S/W packet modem is only an implemented S/W component, so when we apply it to aircraft that we don't consider EMC problems with, then we have the advantage of a wider use of conventional UHF/VHF/HF radio that is possible to voice communication. If we recognize these operational requirements, we can apply for a lot of field equipment efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.7B
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• pp.1021-1033
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• 2001

본 논문에서는 초광대역 시간 도약 임펄스 무선 전송 (ultra wideband time hopping impulse radio) 다원 접속 시스템을 위한 잡음 부호 기반의 새로운 시간 도약 시퀀스를 제안한다. 임펄스 무선 전송 시스템에 대한 지금까지의 연구에서는 대부분 이상적인 랜덤 시간 도약 시퀀스를 사용하여 여러 사용자가 다원 접속한다고 가정하였다. 본 논문에서는 동일 차수의 다수 m-시퀀스와 십진화기를 이용하여 구현 가능한 시간 도약 시퀀스를 제안하고, 여러 사용자의 동기식 및 비동기식 접속 상황에 대한 모의 실험을 통해 이상적인 랜덤 시퀀스와 유사한 우수한 비트오율 성능을 얻을 수 있음을 확인하였다. 또한 제안된 시간 도약 시퀀스를 사용하는 경우 좀 더 일반적인 상황인 비동기식 다원 접속이 동기식 다원 접속에 비해 우수한 성능을 얻을 수 있음을 분석한다.

• ETRI Journal
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• v.35 no.5
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• pp.748-756
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• 2013

This paper addresses the problem of online hop timing detection and frequency estimation of multiple frequency-hopping (FH) signals with antenna arrays. The problem is deemed as a dynamic one, as no information about the hop timing, pattern, or rate is known in advance, and the hop rate may change during the observation time. The technique of particle filtering is introduced to solve this dynamic problem, and real-time frequency and direction of arrival estimates of the FH signals can be obtained directly, while the hop timing is detected online according to the temporal autoregressive moving average process. The problem of network sorting is also addressed in this paper. Numerical examples are carried out to show the performance of the proposed method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.139-147
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• 2003

In this paper we proposed system parameter values of M-ary PPM/TH(Pulse Position Modulation/Time Hopping) ultra-wideband systems having data rate of 100 Mbps for the frequency band, which is allocated by Federal Communications Commission(FCC). We also analyzed performance of the proposed system in the AWGN channels. According to the results of performance analysis, It is observed that available pulse duration is very limitative for this system. In case of constant data rate, if M and the pulse repetition numbers are increased, then the system performance is improved and the user number is decreased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.11A
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• pp.1672-1681
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• 2000

초광대역 시간 도약 이전 임펄스 무전 전송 시스템의 성능 평가 1672 최근 들어 실내 무선 LAN(local area network)이나 군용 무선 통신 시스템을 위한 새로운 대역 확산 전송방식으로서 초광대역 시간 도약 임펄스 무선 전송(ultra wideband time hopping impulse radio; 이하 IR) 기술이 큰 관심을 모으고 있다. 신호 전송을 위해 연속적인 정현파를 이용하는 기존의 무선 전송 시스템과는 달리 IR 시스템은 1 nese 이하의 매우 짧은 펄스폭의 펄스 위치 변조(pulse position modulation)된 가우시안 모노사이클 멀스 열을 이용하므로서 매우 작은 크기의 수 GHz에 이르는 초광대역 스펙트럼을 가지며 기존의 통신 시스템에 거의 간섭을 미치지 않으며 사용 가능하다. 본 논문에서는 동기식 이진 (synchronous binary) IR 시스템의 성능 분석 및 평가 결과를 제시하고자 한다.이를 위해 의사 잡음 부호 발생기와 decimator로 구성된 시간 도약 패턴을 사용 하여 다원 접속 간섭 이 배제되는 동기식 이진 IR 시스템의 비트 오율에 대한 closed form 결과를 유도하고, 유도된 이론적인 성능 결과를 부가성 백색 가우시안 잡음 채널에 대한 모의 실험을 통해 확인하였다. 또한 모의 실험을 통해 상관 복조기에서 발행한 렌덤 타이밍 지터에 대해 IR 시스템의 강인한 특성을 확인하였다.

• Journal of Communications and Networks
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• v.10 no.1
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• pp.63-70
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• 2008

Narrow-band interference (NBI) from the coexisting narrow-band services affects the performance of ultra wideband (UWB) systems considerably due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals may interfere with UWB systems significantly. In this paper, we suggest a novel NBI suppression technique based on singular value decomposition (SVD) algorithm in time hopping UWB (TH-UWB) systems. SVD is used to approximate the interference which then is subtracted from the received signals. The algorithm precision and closed-form bit error rate (BER) expression are derived in the wireless multipath channel. Comparing with the conventional suppression methods such as a notch filter and a RAKE receiver, the proposed method is simple and robust and especially suitable for UWB systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1374-1389
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• 1994

In this paper, a novel M-ary orthogonal CDMA scheme which utilizes time hopping codes and binary orthogonal sequences is proposed for personal communication system. Its modulated output signal has the characteristics of greater bandwidth occupancy and lower spectral density level as well. So this scheme is useful for spectrum overlay with existing narrowband communication systems which occupy current radio frequency channels. This paper investigates system characteristics through the analysis of modulated output signal power spectrum, and demonstrates the possibility of spectrum overlay.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.603-610
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• 2008

In this paper, analytical methods for calculating the average probability of bit error of direct sequence pulse amplitude modulation ultra wideband (DS-PAM UWB) system and time hopping pulse position modulation ultra wideband (TH-PPM UWB) system are given. For the multi-user DS-PAM UWB system, the bipolar pulse amplitude modulation is used in order to achieve better performance. As we know, more attention is paid to the TH-PPM UWB systems recently. In this paper. we first introduce the accurate BER calculation methods of the multi-user DS-PAM UWB and TH-PPM UWB systems and then give the performance analysis over the ideal AWGN channel and a correlation receiver. Furthermore, we also introduce their applications in image transmission and data transmission and give the simulation results. The analytical method yields simple and exact formulas relating the performance to the system parameters.