No abstract

No abstract

No abstract

No abstract

No abstract

This paper introduces, investigates, and proposes power‐efficient equalization jamming attacks against the orthogonal frequency division multiplexing (OFDM) and possible countermeasures. Signals known a priori, called pilot tones, are employed in the conventional OFDM‐based systems to estimate the channel response and perform equalization. Attacks against these pilot tones can hamper equalization and degrade target's performance. This paper begins with noise‐based pilot tone jamming and moves onto pilot nulling attack. The paper embraces two mitigation strategies of randomizing the pilot tones. The paper presents mathematical model of effective noise per symbol and simulation results for OFDM systems with conventional and randomized pilot‐tones under such attacks. The paper concludes that the noise‐based pilot tone attacks are power efficient than conventional attacks, and the pilot nulling is capable of doing the most damage, but in the expense of additional channel state information. The paper also claims that the mitigation strategies offer a remedy, but works relatively poorly when no jammer is present. Copyright © 2015 John Wiley & Sons, Ltd.

This paper explores a collocated overlappedmultiple-input multiple-output (MIMO) antenna architecture and a spectrum sharing algorithm via null space projection (NSP) for radar-communications coexistence. In the overlapped-MIMO architecture, the transmit array of a collocated MIMO radar is partitioned into a number of subarrays that are allowed to overlap. Each of the antenna elements has signals orthogonal to others in the same subarray and to the other subarrays. The proposed architecture not only improves sidelobe suppression to reduce interference to communications system, but also enjoys the advantages of MIMO radar without sacrificing the desirable characteristics such as beampattern and SNR gain. The radarcentric spectrum sharing then projects the radar signal onto the null space of the communications system's interference channel to avoid interference from the radar. Numerical results are presented that show the performance of the proposed design in terms of overall beampattern and sidelobe levels of the radar waveform and finally shows a comparison of the proposed system with existing collocated MIMO radar architectures.

This work describes a new method of designing an anti-jam communications system. The key insight is that many of the concepts learned from interference alignment (IA) in multiple antenna (MIMO) systems can be applied to the field of antijam and robust communications in the presence of intentional jammers. It provides a new fundamental technique of hiding a signal, similar to the mature techniques of frequency hopping or direct sequence spread spectrum. This paper considers a realistic jamming scenario and provides a precoding technique that allows a pair of two-antenna transceivers to communicate while being jammed by a malicious single-antenna node. The precoder uses a small amount of channel information to shape the signal to appear orthogonal to the jammer at the intended receiver. The novelty introduced in this paper is both the application of interference alignment (IA) to anti-jamming communications and a specific method that allows these IA techniques to be practically employed.