• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.114-118
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• 2014

In this paper, we analyze the performance of a concatenated code with two different inner decoding schemes. One is the error-detecting inner decoding, and the other is the error-detecting-and-correcting inner decoding scheme. We compare the performances of the two decoding schemes for finite and infinite block length cases when the concatenated code is applied to slow frequency-hopping spread-spectrum multiple access (FH-SSMA) communication systems.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.771-776
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• 2014

In this paper, an agile programmable chirp spread spectrum generator for wideband frequency-jamming applications from 20 MHz to 3 GHz is proposed. A frequency-mixing architecture using two voltage-controlled oscillators is used to achieve a wideband operating frequency range, and the direct digital synthesizer (DDS)-based chirping method with a two-point modulation technique is employed to provide a programmable and consistent chirp bandwidth. The proposed signal generator provides the various programmable FM signals from 20 MHz to 3 GHz with a modulation bandwidth from 0 to 400 MHz. The prototype successfully demonstrates arbitrary sequential jamming operation with a fast band-to-band hopping time of < 10 ${\mu}sec$.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.819-827
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• 2013

Compared to legacy frequency hopping communications, future radio communications are required the secure and high data rate, ad-hoc network communication. In this paper, we have designed the network communication structure on the frequency hopping mode, and analyzed the performance of synchronization on the frequency hopping network radio systems. The design results are shown the initial sync. phase of approximately 9 hops and the traffic packet phase of approximately 30 hops. Also, we have simulated the performance on the communication conditions which are carrier bandwidth of 50kHz, user data rate of 64kbps and OQPSK modulation scheme in AWGN. In the simulation, we analyzed the correlation and the performance of synchronization success. The result of simulation show 99% probability for synchronization success at $E_b/N_o$ -4dB.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.472-473
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• 2021

The frequency-hopping sequence is a type of user-specific code that has been used in various ways in military communication, Bluetooth, and ultra-wideband communications. In a practical communication environment, a frequency-hopping sequence with an alphabet and a length suitable for the number of available frequencies and transmission period is required. Therefore, the design of the frequency-hopping sequence having various parameters is a very important problem in frequency-hopping spread-spectrum communication. To this end, this paper explores a method of synthesizing a sequence of a new length through the synthesis of existing frequency-hopping sequences. As a result, it is possible to present the possibility of frequency-hopping sequences applicable to various environments of communications.

• Electronics and Telecommunications Trends
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• v.16 no.5 s.71
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• pp.101-112
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• 2001

여러 가지 확산방식 가운데 2.4GHz 대역에서 블루투스, 무선 LAN 등에 적용되고 있는 FHSS(Frequency Hopping Spread Spectrum) 방식을 사용하는 무선기기들에 대하여 미국과 유럽 그리고 일본에서 정하고 있는 기술기준 또는 표준에 관하여 개괄적으로 살펴보았다. 지역별로 정하고 있는 기술기준과 연계하여 각각의 기술기준 또는 표준의 항목들이 의미하는 바를 측정의 관점에서 기술하였으며, 다양한 측정 방법들이 갖는 기술적인 내용에 대하여도 포괄적으로 분석하였다. 마지막으로 최근 국내에서도 FHSS 방식을 사용하는 무선기기들에 대한 기술기준이 개정 고시됨에 따라 국내의 기술기준의 개정 배경과 의미를 외국 기술기준의 내용과 비교하여 설명하였으며, 그 측정 방법에 내포된 의미와 차이점들을 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1357-1365
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• 1991

This paper proposes the generation of several classes of frequency hopping patterns. which are derived by permutation, for an asynchronous frequency hopping spread spectrum multiple accecss system (FH/SSMA). The first class of hopping patterns is obtained by using a Latin square. The second class of hopping patterns is derived by generalizing the first class which is designed by using a permutation technique. The third class of hopping patterns is designed by using a rotational base of elements. We evaluate the hit property of the proposed classes of hopping patterns when these patterns are nutually shifted in an FH/SSMA system. Compared to the Reed Slolmon sequences generated by the conventional method, the sequence obtained by the permutation technique can reduce the number of hits among hopping frequencies in asynchronous time/frequency shift.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.215-222
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• 2019

A frequency hopping(FH) signal can change its carrier frequency during transmission and has spread-spectrum characteristics in these frequency bands. Therefore, FH signals are widely used in applications that require low-probability-of-intercept(LPI) and anti-jamming (AJ) abilities in wireless communication environments. In this study, the authors propose a method for generating hopping information (HI), which includes start time, dwell time, and hopping frequency for unknown FH signals. The proposed blind HI generation method produces signal detection information based on the spectrum data and then extracts HI using operational procedures for estimating the target FH signal's status, such as appearance, maintenance, and termination. Further, simulation results demonstrate that the proposed method provides accurate HI without detection omissions for various FH signals.

• The Journal of the Acoustical Society of Korea
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• v.7 no.2
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• pp.51-64
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• 1988

The frequency synthesizer thar has very short transient time is the key to construct the Fast Frequency Hopping(FFH) system. A Direct Digital Frequency Synthesizer(DDFS) whose transient time is in the nS range has been implemented and the performance of which has been examined through this paper. And by considering the hopping characteristic it is confirmed that the DDFS is suitable for the FFH system. Finally an improvement method which can greatly enhances the SNR with the state-of-the-art techniques and simplifies the system design is presented.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.85-90
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• 2010

In this paper, a blind hop timing and duration estimation scheme for FHSS (Frequency Hopping Spread Spectrum) systems based on digital frequency discriminator and wavelet transform is proposed. The proposed scheme not only requires the lower hardware complexity but also shows superior estimation performance compared to the previously proposed temporal correlation function based hop timing estimation scheme.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1987.04a
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• pp.191-195
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• 1987

When a 160QAM receiver in the band of spread spectrum system is interfered with a pseudo-random frequency-hopp-ing signal the interference signal has the form of the pulse amplitude probability density function. Each interfrering pulse amplitude probability density function Each interfering pulse amplitude is dependent upon theprobability density function of hopping frequency and the selectivity characteristic of 16QAM system in this paper the error rate equation of a system performance has been derived in the above condition which are interfrerence form and impulsive noise environmensts. The results of system analysis show us that the system performance is de-graded by impulsive noise and interference power, which improved as the frequency hopping bandsidth increases whit respect to receiver bandwidth