• 대한임베디드공학회논문지
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• 제12권1호
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• pp.43-62
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• 2017

Mobile pulse scanning Light Detection And Ranging (LIDAR) are essential components of intelligent vehicles capable of autonomous travel. Obstacle detection functions of autonomous vehicles require very low failure rates. With the increasing number of autonomous vehicles equipped with scanning LIDARs to detect and avoid obstacles and navigate safely through the environment, the probability of mutual interference becomes an important issue. The reception of foreign laser pulses can lead to problems such as ghost targets or a reduced signal-to-noise ratio. This paper will show the probability that any two scanning LIDARs will interfere mutually by considering spatial and temporal overlaps. We have conducted four experiments to investigate the occurrence of the mutual interference between scanning LIDARs. These four experimental results introduced the effects of mutual interference and indicated that the interference has spatial and temporal locality. It is hard to ignore consecutive mutual interference on the same line or the same angle because it is possible the real object not noise or error. It may make serious faults because the obstacle detection functions of autonomous vehicle rely on heavily the scanning LIDAR.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1415-1435
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• 2018

Resource allocation in device-to-device (D2D) aided cellular systems, in which the proximity users are allowed to communicate directly with each other without relying on the intervention of base stations (BSs), is investigated in this paper. A new uplink resource allocation policy is proposed by exploiting the relationship between D2D-access probability and channel gain among variant devices, such as cellular user equipments (CUEs), D2D user equipments (DUEs) and BSs, etc., under the constraints of their minimum signal to interference-plus-noise ratio (SINR) requirements. Furthermore, the proposed resource-allocation problem can be formulated as the cost function of "maximizing the number of simultaneously activated D2D pairs subject to the SINR constraints at both CUEs and DUEs". Numerical results relying on system-level simulations show that the proposed scheme is capable of substantially improving both the D2D-access probability and the network throughput without sacrificing the performance of conventional CUEs.

• 한국통신학회논문지
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• 제33권11A호
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• pp.1079-1086
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• 2008

본 논문을 통해 GAS-CP-CDMA(우수한 자기상관 특성의 시퀀스를 사용하는 순한확장 CDMA) 시스템이 제안되었고 그 시스템의 상향링크의 신호대 잡음비 성능이 분석되었다. 다른 사용자를 구분하기 위해 위상이 편이된 시퀀스가 사용된다. GAS-CP-CDMA 시스템의 신호는 좋은 자기상관 특성 덕분에 동일 셀내의 다른 사용자 신호와 거의 간섭을 일으키지 않는다. 그러나 인접셀의 사용자 신호는 간섭을 일으킨다. CDMA 시스템에서 주파수 재사용율은 0.6 정도이다. 따라서 기존 CDMA 방식에서 인접셀로 부터 유입되는 간섭은 전체 간섭의 40% 정도가 된다. 수치분석은 주파수 재사용율에 대한 신호대 잡음비와, 사용자 수에 따른 신호대 잡음비 성능에 대해 수행되었으며, GAS-CP-CDMA 시스템은 기존 CDMA 시스템보다 우수한 성능을 가지는 것으로 분석되었다. 제안된 시스템의 상향링크 사용자 용량은 기존 CDMA 시스템의 약 2배로 증가됨을 확인하였다.

• Journal of the Optical Society of Korea
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• 제14권4호
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• pp.357-362
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• 2010

The joint transform correlator (JTC) has been the best known technique for pattern recognition and identification. This paper proposes a new technique of fringe adjustment by adopting a sinusoidal amplitude-modulated iterative filter convolved with an interference fringe pattern in the joint power spectrum (JPS) domain. The comparison of our new technique and other techniques is presented to show that the newly proposed technique can successfully improve both the correlation peaks and the peak signal-to-noise ratio (PSNR). Simulated results of enhanced interference fringes are also presented.

• ETRI Journal
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• 제41권5호
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• pp.637-647
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• 2019

Separating highly correlated users can reduce the loss caused by spatial correlation (SC) in multiuser multiple-input multiple-output (MU-MIMO) systems. However, few accurate analyses of the loss caused by SC have been conducted. In this study, we define signal-to-interference-plus-noise ratio (SINR) loss to characterize it in multiuser multiple-input single-output (MU-MISO) systems, and use coefficient of correlation (CoC) to describe the SC between users. A formula is deduced to show the accurate relation between SINR loss and CoC. Based on this relation, we propose a user selection method that utilizes CoC to minimize the average SINR loss of users in massive MU-MISO systems. Simulation results verify the correctness of the relation and show that the proposed user selection method is very effective at reducing the loss caused by SC in massive MU-MISO systems.

• 한국통신학회논문지
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• 제37B권10호
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• pp.938-946
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• 2012

간섭정렬(Interference Alignment : IA)은 높은 신호 대 잡음 비(Signal to Noise Ratio : SNR)에서 다중 사용자 간섭 채널에서 도달 가능한 최대 자유도를 얻을 수 있는 데이터 전송 기법이다. 그러나 대부분의 간섭정렬에 대한 연구는 네트워크 내의 모든 채널의 정보를 송, 수신단에서 완벽하게 알아야 하는 비현실적인 가정에 기반을 둔다. 본 논문에서는 K 사용자 다중안테나 간섭채널에서 간섭정렬을 위한 채널 상태 정보 (Channel-State Information : CSI)의 궤환 량을 효율적으로 감소시킬 수 있는 CSI 궤환 구조를 제안한다. 기존의 IA기법은 K의 2차함수의 형태로 궤환 오버헤드가 증가하는 반면, 제안된 궤환 구조는 송, 수신 단 사이에서 계산된 IA 송신기의 순차적인 교환을 통하여 K에 선형적으로 증가하는 오버헤드를 갖는다. 또한, 주어진 궤환 구조 하에서 제한된 궤환 채널에 의한 잔여 간섭의 세기를 분석하였으며, 이 때 발생하는 잔여 간섭을 최소화 할 수 있는 IA 조건, 즉, 주어진 채널환경에 따라 각 수신단에서 잔여 간섭을 최소화할 수 있는 최적의 IA 쌍을 순차적으로 결정하는 알고리즘을 제안한다.

• 한국통신학회논문지
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• 제25권6B호
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• pp.1092-1099
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• 2000

An adaptive array system can effectively remove all received interferences by using adaptive algorithms even though the received signal condition is not known. The conventional adaptive array systems, however, cannot remove all interferences adaptively and converge very slowly when the eigenvalue spread of the input covariance matrix is large. In the paper, a new adaptive array system called an automatic gain controller (AGC) Applebaum array and its control algorithm are proposed to overcome the performance degradation of conventional Applebaum array in multiple interference conditions. The performance analysis of the proposed AGC Applebaum array is described under the condition of multiple narrowband interferences. Simulation results show the array output signal-to-noise ratio (SNR) of the AGC Applebaum array increases by 30dB compared to that of the conventional Applebaum array in the simulation condition. The gain of the AGC Applebaum array in the incident direction of a weaker interference is also shown to be lower than that of the conventional Applebaum array.

• 한국인터넷방송통신학회논문지
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• 제8권2호
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• pp.43-48
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• 2008

본 논문에서는 Cognitive Radio 환경에서의 사용자의 송신 전력에 대해 다루고자 한다. 사용자의 송신전력은 PU(Primary User)에 피해를 주지 않는 선에서 동작되어야 하며 이는 PU에서 측정된 SINR(Signal to Interference and Noise Ratio)로 고려 될 수 있다. SU는 비어 있는 주파수가 어떤 것인지 알아야 하는 정확한 스펙트럼 센싱이 요구 되며, 이는 실시간 변화 하므로 정확한 센싱을 한다 하더라도 일정시간 동안 동작을 반복해야 한다. 이를 직교성 인자를 이용하여 기존의 단점들을 감소시키고, PU의 SINR을 보장하는 선에서 동작도 가능하다는 것을 보이려 한다.

• ETRI Journal
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• 제42권1호
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• pp.17-25
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• 2020

Multiple-input multiple-output systems can achieve a full sum rate (SR) via full duplex (FD). However, its performance is degraded by self-interference (SI) that occurs between the transmitter and receiver at the same node and thus is constrained by error floors. Conversely, half duplex (HD) can avoid the SI albeit at lower spectral efficiency, and the slope of its error curve is determined by the diversity order. In this study, a link selection scheme based on switching between FD and HD is examined as a simple method to improve the bit error rate (BER) performance of FD systems. In the proposed link selection algorithm, either FD or HD is selected based on the received minimum distance and signal-to-interference plus noise ratio. Simulation results indicate that the proposed hybrid FD/HD switching system offers significant BER performance improvement when compared with that of the conventional FD and FD based on only the received minimum distance under the same fixed SR. Under relatively sufficient SI cancellation, it is demonstrated to outperform the HD with a diversity advantage in low and medium signal-to-noise ratio region.

• Journal of Information Processing Systems
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• 제10권3호
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• pp.384-394
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• 2014

The femtocell overlaid cellular network (FOCN) has been used to enhance the capacity of existing cellular systems. To obtain the desired system performance, both cross-tier interference and co-tier interference in an FOCN need to be managed. This paper proposes an interference management scheme that adaptively constructs a femtocell cluster, which is a group of femtocell base stations that share the same frequency band. The performance evaluation shows that the proposed scheme can enhance the performance of the macrocell-tier and maintain a greater signal to interference-plus-noise ratio than the outage level can for about 99% of femtocell users.