• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.988-995
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• 2019

In this paper, we propose the Tile Based Frequency Hopping - Chirp Spread Spectrum(TBFH-CSS) technique, which has excellent Low Probability of Intercept(LPI)/Anti-Jamming(AJ) performance. Conventional Frequency Hopping - Chirp Spread Spectrum(FH-CSS) technique uses only single chirp signal, that makes the follower jammer easy to find and jam. However, proposed TBFH-CSS uses various kind of chirp signals which are generated according to the structure of basis tile, it is composed the basis time unit and the basis bandwidth unit. The TBFH-CSS signal has variety signal period and signal bandwidth. Therefore, the follower jammer hard to find and difficult to jam the TBFH-CSS signal. We analysis the LPI/AJ performance of the TBFH-CSS technique when the follow jamming attack exist and compared with the performance of the conventional FH-CSS technique. From the analysis, we can see the proposed TBFH-CSS technique has better LPI/AJ performance than conventional technique.

• Journal of Advanced Navigation Technology
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• v.17 no.4
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• pp.386-395
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• 2013

This paper proposes a root-assisted MUSIC algorithm which uses a combination of the MUSIC and the root-MUSIC algorithm. This algorithm consists of two steps. Firstly, a coarse DOA is computed by the root-MUSIC algorithm. Secondly, a precise DOA estimation is carried out by the MUSIC algorithm in the reduced searching range. This paper analyzes the accuracy and the resolution performance of the proposed DOA estimation method using a software simulation platform.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.152-161
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• 2009

As follow jamming signals in a FHSS system cause malfuctioning in the code tracking circuits using early-late gates, we need a code tracking circuit that is robust against the follow jamming signals. In this paper, we propose a code tracking circuit using a linear clipper-Gaussian filter algorithm to remedy the malfunctioning due to the follow jamming signals in FHSS systems. We investigate the mechanism of the malfunctioning of the code tracking circuit and verify that the proposed linear clipper-Gaussian filter metigates the problem through mathematical analysis and computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1410-1413
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• 2016

Array beamforming for anti-jamming means that jamming signals are superposed destructively, while superposing information signals constructively at a receiver. However, according to channel state variation, the anti-jamming performance of the beamforming can be degraded because of large beamwidth of the sidelobe and lower selectivity of the mainlobe. To mitigate this problem, we introduce a beamformed decoy signal which uses frequency band distinguished from the information signal to make the jammer concentrate its jamming power to a wrong target under limited feedback. In this paper, we show that the performance of the proposed scheme can approach that of optimal one with perfect feedback.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.205-213
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• 2012

In this paper, we propose a new channel hopping scheme based on IEEE 802.11h as a good countermeasure against jamming attacks in IEEE 802.11 wireless networks. 802.11h Dynamic Frequency Selection (DFS) is a mechanism which enables hopping to a best channel with full channel measurement, not a randomly chosen channel, when the current link quality degradation occurs due to interferers such as military radars. However, under jammer attacks, this needs a time for full channel measurement before a new channel hopping and due to link disconnection during the time network performance degradation is inevitable. In contrast, our proposed schemes make an immediate response right after a jammer detection since every device is aware of next hopping channel in advance. To do this, a next hopping channel is announced by Beacon frames and the channel is selected by full channel measurement within Beacon intervals. Simulation results show that proposed scheme minimizes throughput degradation and keeps the advantages of DFS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1728-1735
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• 2011

In this paper, satellite data link waveform is proposed which is based on the waveform of Link-16 but LDPC code is studied instead of CCSK code in order to be optimized to satellite nonlinear channel environment and transmission characteristics. And the DSM (Demux, Selective CH switch, and Mux) transponder structure is suggested which can remove all of the jamming signal out of the transmission signal band and convert uplink hopping frequency to desired ones of downlink. The results of BER and anti-jamming performance analysis shows that the required Eb/No and processing gain in the worst case partial band jammer of the proposed waveform are 2.5dB and 52dB respectively and the anti-jamming capacity improvement of DSM transponder is maximum 2dB.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.9-13
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• 2022

In this paper, the tracking error of monopulse radar caused by cross-eye jamming using terrain bounce is analyzed. Cross-eye jamming is a method of generating an error in a radar tracking system by simultaneously transmitting two signals with different phases and amplitudes. When the monopulse radar receives the cross-eye jamming signal generated by the terrain bounce, a tracking error occurs in the elevation direction. In the presence of multipath, this signal is a combination of the direct target return and a return seemingly emanating from the target image beneath the terrain surface. Terrain bounce jamming has the advantage of using a single jammer, but the space affecting the jamming is limited by the terrain reflection angle and the degree of scattering of the terrain. This study can be usefully used to protect ships from low-altitude missiles or aircraft in the sea.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.3
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• pp.45-55
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• 2002

중거리 유도무기 체계가 탄도탄과 같이 기동이 심한 표적과 교전할 때에는 지상 레이더는 표적 및 유도탄 위치정보를 보다 빈번하게 전송하여야 하지만, 자신의 임무를 수행해야 하므로 유도탄 및 교전 표적에 대한 정보를 필요이상으로 자주 전송할 수 없다. 이러한 상황에서 탐색기가 자체적으로 표적의 거리, 속도, 방향을 측정함으로서 지상레이더에 추가 부담을 지우지 않고 우수한 추적 정밀도로 교전성능을 향상할 시킬 수 있는 고반복 펄스열을 사용하는 PRF 변조방식을 제안한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.2
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• pp.232-237
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• 2011

This paper analyzed the J/S of the GPS receiver in sea environment from GPS satellite and GPS jammer. Through the analysis, the operational range and effective radiation power of the GPS jammer could be estimated. In the case of the jammer effective radiation power is higher than the specific value, jammer height mainly resolves the jammer operational range.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.8
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• pp.837-845
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• 1992

This paper shows the performance of FH /BFSK communication systems under worst case Jamming interference. The channel Is modeled with ratio-threshold technique, and as a lamming signal the tone Jamming and Gaussian Jamming are used. The performance is analyzed by using the channel capacity which is the code rate and bit signal-to-Jammer ratio, and we show that the performance degration becomes large as background noise Is big and obtain the best performance when the threshold level f is about 1.5.