• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.6
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• pp.30-36
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• 1999

Jamming is an important factor in the military satellite communication system. In this paper, link capacity and jamming margin of the DS-CDMA(Direct Sequence-Code Division Multiple Access) military satellite communication system are analyzed and calculated under a multitone jamming. The analysis was performed with two types of transponders loaded on a geosynchronous satellite. Calculation methods for link capacity and jamming margin were obtained. The results of the analysis show that capacity of a transponder which does modulation/demodulation, decoding/encoding in addition to despreading/respeading is twice as much as that of a tranponder which does despreading /respreading only.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1149-1155
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• 2003

OFDM/SFH(orthogonal frequency division multiplexing/slow frequency hopping) system is the combination of OFDM communication system with frequency hopping(FH) method and OFDM/DS(orthogonal frequency division multiplexing/direct sequence) system combines the OFDM communication system with direct sequence(DS) method in terms of PN(pseudo noise) sequence. These two systems are also can be used for anti-jamming. In this study we analyze performances of OFDM/SFH system and OFDM/DS system with the equal information rate in partial band jamming and tone jamming channel. We find BER(bit error rate) in the variation of JFR(jamming fractional ratio) and JSR(jamming to signal power ratio) of the partial band jamming. Also, BER is found in the several JSR of the single tone or multi tone jamming. OFDM/DS system shows better performance than OFDM/SFH system in partial band jamming environment. OFDM/DS system has about 2.5 ㏈ SNR(signal to noise power ratio) gains than OFDM/SFH system when JFR=4/16 and JSR=0 ㏈ to meet BER=10$\^$-3/. However, OFDM/SFH system has about 3 ㏈ SNR gains than OFDM/DS system at single tone jamming of JSR=5 ㏈. In multi tone jamming, performance of OFDM/SFH system is considerably degraded than OFDM/DS system.

• Journal of Communications and Networks
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• v.17 no.5
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• pp.482-490
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• 2015

This article exploits spatial diversity for jamming to prevent wiretapping in the extreme case in which an eavesdropper is located near the source and a common jamming signal is unavailable. To address this challenge, the jamming signal is allowed to carry a random binary message. Then, it is proposed that the active intermediate node transmits this jamming signal and the decoding of this signal at both source and destination is physically secured as result of using the physical-layer security method. If the source and the destination securely and correctly decode this jamming message, the source transmits another message which is created from combining its information message and the decoded message using the network-coding method. Therefore, this method prevents the transmissions from being eavesdropped upon by the source-wiretapping.

• Journal of Industrial Technology
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• v.17
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• pp.153-160
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• 1997

This paper has analyzed the performance against a single tone jamming for the CPM DS-SS system with a Binary FSK Modulation. The CPM DS-SS system designed with the different phase shift of the same pseude-noise code has the advantage of reducing the jamming and interference effects on multi-users communication environment. Analytical results show that the system preformance improves by increasing parrallel users in the presence of the coherent single-tone, which is the worst interference since the jamming signal has the same frequency as a carrier.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3444-3457
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• 2021

In the field of anti-jamming based on dynamic spectrum, most methods try to improve the ability to avoid jamming and seldom consider whether the jammer would perceive the user's signal. Although these existing methods work in some anti-jamming scenarios, their long-term performance may be depressed when intelligent jammers can learn user's waveform or decision information from user's historical activities. Hence, we proposed a hidden anti-jamming method to address this problem by reducing the jammer's sense probability. In the proposed method, the action correlation between the user and the jammer is used to evaluate the hiding effect of the user's actions. And a deep reinforcement learning framework, including specific action correlation calculation and iteration learning algorithm, is designed to maximize the hiding and communication performance of the user synchronously. The simulation result shows that the algorithm proposed reduces the jammer's sense probability significantly and improves the user's anti-jamming performance slightly compared to the existing algorithms based on jamming avoidance.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.10a
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• pp.29-33
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• 1990

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.482-488
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• 2009

Mobile Ad-hoc Networks provide communication without a centralized infrastructure, which makes them suitable for communication in disaster areas or when quick deployment is needed. On the other hand, they are susceptible to malicious exploitation and have to face different challenges at different layers due to its open Ad-hoc network structure which lacks previous security measures. Denial of service (DoS) attack is one that interferes with the radio transmission channel causing a jamming attack. In this kind of attack, an attacker emits a signal that interrupts the energy of the packets causing many errors in the packet currently being transmitted. In harsh environments where there is constant traffic, a jamming attack causes serious problems; therefore measures to prevent these types of attacks are required. The objective of this paper is to carry out the simulation of the jamming attack on the nodes and determine the DoS attacks in OPNET so as to obtain better results. We have used effective anomaly detection system to detect the malicious behaviour of the jammer node and analyzed the results that deny channel access by jamming in the mobile Ad-hoc networks.

• Journal of Convergence for Information Technology
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• v.9 no.5
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• pp.125-129
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• 2019

This paper describes the jamming effect of phase-coded pulse compression(PCPC) radar. Barker code radar, a typical PCPC radar, separates transmission pulses into 13 or 31 small pulses and phase modulates and transmits each pulse signal to increase radar detection efficiency and reduce the influence of jamming. Generally, when the radar is subjected to jamming, the detection distance becomes shorter and the detection error rate becomes higher. In the case of noise jamming or carrier jamming on the PCPC radar, the jamming effect is very small for no phase-coded convergence. However, the jamming effect is large in the case of synchronous jamming using the pulse-coded signal as a jamming signal with DRFM. It can be seen that the jamming effect increases when the storage time of the pulse-coded signal is prolonged. This study is considered to be useful for PCPC radar and EW jamming system design.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.79-80
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• 2006

In this paper, we compare two different anti-jamming schemes, Subspace projection and SCORE algorithm. For multipath cancelation, nulling technique is applied to both anti-jamming schemes. It is noted that SCORE algorithm is more robust to the multipath interference. It is also noted that Subspace projection scheme requires nulling technique for multipath mitigation.