• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.17-22
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• 2005

This paper presents our investigation for the effect of symbol timing errors in orthogonal frequency division multiple access (OFDMA) uplink systems. We express the symbol timing errors between users as the symbol timing misalignments with respect to the desired user. Then, we derive an explicit expression of the average effective signal-to-interference-plus-noise ratio. (SINR) as a function of the maximum value of the symbol timing misalignments. Based on the resulting SINR degradation, we evaluate the SINR gain with guard subcarriers in order to mitigate the effect of the symbol timing misalignments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.3 s.94
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• pp.270-276
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• 2005

This paper presents an analytical analysis about neighboring UWB interferences in a S-DMB receiver. We first derive the C/N$_{o}$ of a S-DMB receiver, based on its specifications and present the theoretical description of its effect to UWB interferences in terms of C/(N$_{o}$+ I) and I/N$_{o}$. Using the calculated C/(N$_{o}$+ I) and I/N$_{o}$, we derive the separation distance for a S-DMB receiver not to be interfered by UWB interferences. Finally, we propose an UWB emission limit at minimum separation distance under which a S-DMB is free of UWB interferences and compare it with the value appeared in FCC proposal.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.97-103
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• 2005

본 고에서는 전력선통신 기술동향을 분석하고 국내 기술기준에서 어떻게 규제를 받는지 분석하였다. 전력선통신은 초기에 전기 이용기기의 원격 제어용으로 비교적 적은 데이터를 송수신하는데 이용되었다. 그러나 광대역 통신 요구에 따라서 전력선을 이용한 고속 전력선모뎀 기술이 개발되어 인터넷 등과 같은 고속 데이터 통신을 할 수 있게 되었다. 그러나 전력선통신은 기존 전선로를 사용하므로 높은 주파수의 신호를 전송하면 전파 방사에 의해서 다른 무선설비에 영향을 줄 수 있다. 현재 30MHz 이하의 대역을 사용하고 있으나 이 대역은 해상, 항공 등 인명 안전을 위한 중요 통신에서 이용하고 있다. 그러므로 전력선모뎀이 기존 무선설비에 간섭을 주지 않으면서 주파수 대역을 공유하기 위해서는 간섭을 최소화할 수 있는 spread spectrum이나 OFDM과 같은 기술을 활용해서 설계되어야 한다. 이미 이러한 기술들을 활용한 전력선 모뎀이 상용화되어 있으며 옥내 뿐 만 아니라 옥외까지 용도를 확장하기 위해서 간섭 완화기술 및 방법 등이 활발히 연구되고 있다. 본 고에서는 전력선통신의 고속화를 위한 기술 동향 및 간섭 완화 방법 기술을 분석하고, 구현된 시스템이 다른 무선설비와 간섭 없이 사용될 수 있도록 규정하고 있는 관련 기술기준을 분석하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1674-1683
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• 2003

The performance of a packet data multiplexer with stop­and­wait ARQ protocols under Markovian interruption is considered in this work It is assumed that the input process, into the system is Poisson process, and that the output channel is divided into a series of time slots and a data packet can be transmitted in a slot time. In this system the round­trip propagation delay is defined to be the frame time. It is modeled that the output channel can be blocked by some Markevian interruption, whose state change between the blocking and non­-blocking states is given by Markov process. The overall system has been analyzed by constructing a relationship, taking the Markovian interruption into account, about the buffer behavior between the successive frames of slots. The validity of this analytical results has been verified by computer simulation.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.13-20
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• 2013

Currently, SEAMCAT has been widely used as a tool to evaluate the effects of interference among wireless communication systems. In the previous work, we have incorporated the ITU-R P.526 pathloss model to the existing SEAMCAT in order to support the capability of interference evaluation taking into account any specific terrain characteristics. Along with this, we have implemented a terrain display function based on the Google map. However, the two-dimensional Google map based display is not effective in helping users to figure out some terrain features including the elevation variation in a given region. In order to alleviate this difficulty, we have incorporated the three-dimensional terrain display using the API of the Google earth to the existing SEAMCAT and provided the capability of viewing the positions of the associated communication systems, the variation of the carrier intensity and interference intensity in location, shadow region indication, and line-of-sight analysis and presented an example of interference evaluation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.752-760
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• 2010

This paper investigates the performance of EPCglobal Generation-2(Gen-2) radio frequency identification(RFID) protocol under reader-to-reader interfering environments. We establish a modified discrete-time Markov chain(DTMC) model for the Gen-2 and accordingly obtain quantitative results of query success rate(QSR) and tag identification speed (TIS). Extensive simulations validate our theoretical analysis and demonstrate that the number of tags over 100 has little impact on the performance. TIS linearly decreases by 10 tags/sec/reader as the number of interfering readers increases. Our model for Gen-2 protocol is also useful to study the performance of other RFID protocols.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.663-668
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• 2008

Recently, World Radio Conference(WRC)-2007 approved the ultrawide bandwidth of 500 MHz for the use of spaceborne synthetic aperture radar in X-band for the EESS(Earth Exploration Satellite Service) in order to improve the SAR imaging resolution. It is concerned about the interference impact from the spaceborne SAR that may cause to most of ground radars due to the extended ultra wideband. In this paper, in order to predict the interference impact of the ground-based radar from the spaceborne radar, radar interference model is presented using radar characteristic parameters by taking into account the operating environments of the spaceborne and ground based radar in the time, space, and spectrum domains. Using the spaceborne SAR model of TerraSAR-X and ground radar model of meteorological radar recommended by ITU-R, the interference impact was assessed through the computer simulation to see the possible interference impact of the ground based radar operating in the Korean peninsula.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.125-133
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• 2007

In this paper, the frequency sharing issue between cellular time division duplex-orthogonal frequency division multiple access (TDD-OFDMA) Systems and terrestrial Fixed Systems has been studied. The conventional advanced minimum coupling loss (A-MCL) includes only the formulation to calculate the interference from one interfering system. Therefore, A-MCL must be modified to assess the aggregated interference from base stations(BS) and mobile stations(MS). By applying the modified model, the coexistence analysis are done according to the average number of MS per sector, BS-to-BS distance, and the main beam direction of the terrestrial fixed system. In the case of 20 MS per sector, the BS-to-BS distance and the minimum distance between a terrestrial fixed system and BS are 5.8 km and 2.5 km, respectively. It is about 25dB that the difference between maximum and minimum interference signal power which varies with the main beam direction of the terrestrial fixed system. Moreover, for 40% of the main beam direction of the terrestrial fixed system, interference signal power is less than the maximum permissible interference.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.653-660
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• 2000

In this paper, an adaptive interference excision scheme with multiple adaptive filter bank using an adaptive algorithm is proposed. This scheme suppresses interference in the wavelet packet transform domain for the direct spread spectrum communication systems. Using the Monte-Carlo simulation, we analyze the performance of the direct spread spectrum communication systems with this excision scheme using LMS and RLS adaptive algorithms in AWGN and interference channel.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.67-68
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• 2012

전이중(full-duplex) 양방향 중계 네트워크는 전이중 방식을 사용하는 중계기에서 물리 계층 네트워크 부호화(physical layer network coding) 혹은 중첩 부호화(superposition coding)을 사용하여 기존 반이중(half duplex) 중계기를 사용하는 양방향 중계 네트워크에 비해 높은 주파수 효율을 제공한다. 본 논문에서는 전이중 양방향 중계 네트워크를 고려하여 전이중 방식에서 필연적으로 발생하는 루프간섭 신호의 영향을 살펴보았다. 여기에서 사용자 및 중계기는 루프간섭 신호를 제거하기 위해 루프간섭 신호를 추정한다. 하지만 루프간섭 신호를 추정할 때 추정 오류가 발생하여 수신 신호에서 루프간섭 신호를 완벽하게 제거하기는 어렵다. 모의실험에서는 이로 인해 발생할 수 있는 성능 변화를 불능 확률을 통해 분석하였다.