• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.37-39
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• 2015

In this paper, we propose a distributed user scheduling with interference-aware power control (IAPC) to maximize signal to generating interference plus noise ratio (SGINR) in multi-cell uplink network. Assuming that the channel reciprocity time-division duplexing (TDD) system is used, the interference channel from users to other cell BSs is obtained at each user. In the proposed scheduling, each user reduces the transmit power if its generating interference to other BSs is larger than a predetermined threshold. Each BS selects the user with the largest SGINR among users. Simulation results show that the proposed technique significantly outperform the existing user scheduling algorithms.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.54-56
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• 2013

A subcarrier allocation scheme for base station (BS), relay station (RS) and mobile station (MS) can affect the performance of orthogonal frequency division multiple access (OFDMA) relay systems. In this paper, we propose a subcarrier allocation scheme with inter-cell interference and network coding in OFDMA relay systems. In the network coding zone, we consider an environment where RS can transmit a frame to BS and MS simultaneously. We divide an OFDMA frame into downlink zone, uplink zone, and network coding zone. The proposed scheme allocates subcarriers to BS, RS, and MS for each zone with consideration of inter-cell interference in OFDMA relay systems. We evaluate the performance of the proposed subcarrier allocation scheme through simulation.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.186-190
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• 2002

본 논문에서는 WCDMA/TDD시스템에서 실외 환경에 셀 간 간섭 모델과 빌딩내의 층 간 간섭 모델을 비교하여 성능을 분석하였다. 실내 빌딩 환경에서 층 간 간섭 분석 모델을 고려 시, 건축 자재에 의한 전파 투과손실로 인해 인접 셀로부터 오는 간섭의 영향이 작아짐으로 실외환경을 고려한 셀 간 간섭 모델에 비해 성능이 좋음을 알 수 있었다. 따라서 WCDMA/TDD시스템은 광범위한 교외지역이나 피코 셀로 설계된 도심지역보다 층 간 간섭 모델을 기반으로 둔 빌딩내 사무실 환경을 고려한 시스템 설계에 더 적합할 것이라 사료된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1986-1993
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• 2015

We investigate the optimal resource and power allocation for device-to-device (D2D) communications in a multicell environment. When D2D links reuse the cellular radio resources, each D2D user will interfere with a cellular link and other D2D links, in its own cell as well as in adjacent cells. Under such situation, we propose a coordinated resource allocation scheme that can handle the intercell interferences as well as the intracell interference. For a given resource allocation, we also formulate a power optimization problem and present an algorithm for finding the optimal solution. The resource and power allocation algorithms are designed to maximize the achievable rate of the D2D link, while limiting the generated interference to the cellular link. The performance of the proposed algorithms is evaluated through simulations in a multicell environment. Numerical results are presented to verify the coordination gain in the resource and power allocation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.477-483
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• 2016

In this paper, we propose a distributed user scheduling with interference-aware power control (IAPC) to maximize signal to generating interference plus noise ratio (SGINR) in uplink multi-cell networks. Assuming that the channel reciprocity time-division duplexing (TDD) system is used, the channel state information (CSI) can be obtained at each user from pilot signals from other BSs. In the proposed scheduling, to be specific, each user reduces the transmit power if its generating interference to other BSs is larger than a predetermined threshold. Each BS selects the user with the largest SGINR among users. Simulation results show that the proposed technique significantly outperforms the existing user scheduling algorithms. It is worth noting that the proposed technique operates with distributed manner without information exchange among cells. Hence, it can be easily applied to the practical wireless systems like 3GPP LTE without significant modifications of the specification.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.727-729
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• 2004

본 연구는 비정지궤도 이동위성 통신시스템에서 동일 셀과 인접 셀 내의 단말기들의 밀집도에 따른 채널용량을 비교 분석하였다. CDMA 셀룰라 시스템은 같은 시간에 같은 주파수를 모든 사용자들이 같이 사용하므로 자기 신호 외의 다른 사용자의 신호는 간섭으로 나타나 통신 품질에 영향을 미친다. 특히 동일 셀과 인접 셀에서 단말기의 분포 및 밀집도에 따라 통신link에서 간섭이 달라 질 수 있으며, 이는 곧 통신 채널에서 용량의 변화가 이루어 질 수 있다는 점으로 해석된다. 본 연구는 이동위성 통신시스템에서 간섭에 따른 효율적인 채널용량 분석에 유용하게 사용될 수 있을 것이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5C
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• pp.351-360
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• 2008

In cellular mobile radio systems with frequency reuse, the interference signals degrade the channel estimation and signal detection performance due to the low signal-to-interference ratio near coverage boundaries. When the preamble pilot sequences from different cells are orthogonal or located in disjointed positions, they can be used for multi-cell channel estimation and interference cancellation. In time-varying channels caused by Doppler spread, data pilot symbols are needed for channel estimations. However, data pilot symbols are usually located in identical positions for the overhead reduction, which degrades the channel estimation performance. In this paper, we demonstrate a significant amount of performance improvement is achieved by multiplying different pseudonoise(PN) sequences to the data pilot symbols from adjacent interference cells. In particular, for detection scheme using maximal ratio combining(MRC) and inter-cell spatial demultiplexing(ISD), quantitative performance gain of spectral efficiency for different values of Doppler frequency and interference power is presented.

• Journal of Advanced Navigation Technology
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• v.14 no.4
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• pp.521-529
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• 2010

In this paper, we propose a new scheduling algorithms in OFDM systems to reduce inter-cell interference. The proposed algorithm applies different subcarrier allocation sequences for different cells which is optimized through integer programming to minimize inter-cell interference. System level simulation is executed to derive the performance of the proposed algorithm. Simulation results show that the proposed scheduling algorithm improves user fairness as well as throughput compared with previous algorithms and therefore improves support of user QoS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.10
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• pp.937-945
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• 2014

As various services requiring high data rate are supported by introducing LTE/LTE-adv., mobile traffic increases rapidly. To cope with the continuous growth of traffic demand, small cell technology is considered as one of the most promising one. Small cell can increase system capacity by increasing the number of base stations with reduced cell radius. In this paper, we analyze the effect of cell densification with small cells in terms of SINR and average UE throughput considering cell split and the number of UE per unit area. As the cell becomes smaller, SINR degradation arises from high ICI(Inter Cell Interference) and we evaluate the effect of interference mitigation scheme in small cell environment where the proper interference mitigation technique is applied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.896-902
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• 2016

In this paper, we investigate a minimum mean-squared error based nonlinear successive precoding method as a practical solution of dirty paper coding for multiuser downlink channels where each user has more than one antenna in the presence of other cell interference (OCI). Unlike conventional zero-forcing (ZF) based methods, the proposed scheme takes the OCI plus noise into account when suppressing the inter-cell multiuser interference, which results in improvement of the received signal-to-interference-plus-noise ratio. Simulation results show that the proposed scheme outperforms conventional methods in terms of sum rate for various OCI configurations.