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MIMO OFDM 시스템을 위한 향상된 채널 추정 기법
신명철,이학주,심세준,이충용,Shin Myeongcheol,Lee Hakju,Shim Seijoon,Lee Chungyong 대한전자공학회 2004 電子工學會論文誌-TC (Telecommunications) Vol.41 No.6
MIMO OFDM 시스템에서 comb형태의 훈련심볼을 사용하는 기존의 채널 추정방식은 가장자리 반송파 영역에서 채널 추정의 MSE(Mean Squared Error)가 큰 단점이 있다. 본 논문에서는 이러한 문제점을 해결하기 위해 순환구조를 갖는 comb형태 훈련심볼을 제안한다. 제안된 순환구조에서는 모든 종류의 comb 훈련심볼이 각 안테나로부터 순환 전송되며 수신 단에서는 각 comb 형태의 훈련심볼들을 이용해 채널을 추정한 후, MSE로부터 구해진 최적의 가중치를 곱함으로써 채널 주파수 응답을 추정한다 모의실험을 통해 제안된 방식이 기존의 comb 형태의 훈련심볼에 비해 높은 성능을 나타냄을 확인하였다. In MIMO-OFDM systems, conventional channel estimation techniques using comb type training symbols give relatively large mean squared errors(MSEs) at the edge subcarriers. To reduce the MSEs at these subcarriers, a cyclic comb type training structure is proposed. In the proposed cyclic training structure, all types of training symbols are transmitted cyclically at each antenna. At the receiver, the channel frequency responses that are estimated using each training symbol are averaged with weights obtained from the corresponding MSEs. Computer simulations showed that the proposed cyclic training structure gives more SNR gain than the conventional training structure.
TIM: TDD Remote Interference Management Solution
Okyoung Choi(최옥영),Myoung-Kwang Byun(변명광),Seijoon Shim(심세준) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
In time-division duplex (TDD) cellular systems, downlink (DL) and uplink (UL) are separated by a guard period that accommodates signal propagation delay from adjacent cells. However, certain atmospheric changes form an abnormal propagation condition for signals to travel much farther than the maximum propagation delay that the TDD system can absorb within the guard period. The DL-to-UL crosslink interference from remote TDD cells causes significant performance impacts. Unlike the typical inter-cell interference managements coping with a few adjacent cells, the TDD remote interference requires a very complicated mitigation since the crosslink interference should be managed over massive TDD cells in a wide area. In this paper, we propose a novel TDD remote interference management solution, so-called TIM (TDD Interference Manager), which periodically identifies aggressor-victim associations and adaptively mitigates interference among nationwide TDD cells. The proposed solution has been shown to effectively manage the TDD remote interference through successful commercial operations in massive LTE networks.