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Block-Mode Lattice Reduction for Low-Complexity MIMO Detection
최권휴,Hannah Kim,김수영,Young-Il Kim 한국전자통신연구원 2012 ETRI Journal Vol.34 No.1
We propose a very-low-complexity lattice-reduction (LR) algorithm for multi-input multi-output detection in time-varying channels. The proposed scheme reduces the complexity by performing LR in a block-wise manner. The proposed scheme takes advantage of the temporal correlation of the channel matrices in a block and its impact on the lattice transformation matrices during the LR process. From this, the proposed scheme can skip a number of redundant LR processes for consecutive channel matrices and performs a single LR in a block. As the Doppler frequency decreases, the complexity reduction efficiency becomes more significant.
Design of A Grand Alliance VSB HDTV Demodulator
최권휴,정민수,이원호,전경훈,임형수,이동훈 에스케이텔레콤 (주) 1998 Telecommunications Review Vol.8 No.2
In this paper, we describe the design and hardware test results of a demodulator satisfying the US Grand-Alliance VSB HDTV standard. Novel algorithms that offer satisfactory performance with efficient hardware implementation are developed and employed in the prototype hardware. Satisfactory performance of the implemented prototype was verified and the demodulator is currently in the ASIC fabrication stage. Main algorithms of interest in this paper are the segmentation and symbol timing synchronization, FPLL polarity detection and compensation, phase/gain tracking loops and channel equalization.
Lattice Reduction-aided Detection with Out-of-Constellation Point Correction for MIMO Systems
최권휴(Kwonhue Choi) 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.12A
MIMO 시스템을 위한 Lattice Reduction (LR) aided 검출 방법의 중요한 단점의 해결책으로 심벌 판별의 신뢰도가 의심되는 경우 추가적인 보정을 해주면서, 계산양은 매우 작은 개선된 LR-aided 검출방법을 제안한다. LR 검출방법의 오류들은 주로, 마지막 lattice 역 변환 단계에서, lattice point들이 constellation point의 바깥으로 벗어날 때 발생한다는 것을 발견하였다. 이를 기반으로, 제안된 기법에서는 LR-aided 검출방법을 통해 얻어진 lattice point들이 constellation의 바깥쪽에 있는지를 확인하고, 바깥쪽에 있는 경우, 모든 constellation point들이 아닌, 얻어진 lattice point의 이웃하는 point들에 대해서만 ML(Maximum Likelihood) 검출을 수행한다. 제안된 기법을 사용함으로, 검출 성능은 ML에 근접하면서, 계산양은 아주 작은 효과를 기대할 수 있다. An important drawback in Lattice Reduction (LR) aided detectors has been investigated. For the solution, an improved LR aided detection with ignorable complexity overhead is proposed for MIMO system, where the additional correction operation is performed for the case of unreliable symbol decision. We found that LR aided detection errors mainly occur when the lattice points after the inverse lattice transform in the final step fall outside the constellation point set. In the proposed scheme, we check whether or not the lattice point obtained through LR detection is out of constellation. Only for the case of out of constellation, we additionally perform ML search with reduced search region restricted to the neighboring points near to the obtained lattice points. Using this approach, we can effectively and significantly improve the detection performance with just a slight complexity overhead which is negligible compared to full searched ML scheme. Simulation results show that the proposed scheme achieves the detection performance near to that of the ML detection with a lower computational complexity.
Wi-Fi 신호를 사용하지 않고 보행자 궤적과 건물내 지도 특성만을 이용한 스마트폰 실내 위치 측정 시스템
라동준,최권휴 대한임베디드공학회 2014 대한임베디드공학회논문지 Vol.9 No.6
In this paper, we proposed indoor positioning system with improved accuracy. The proposed indoor location measurement system is based pedestrian location measurement method that use the embedded sensor of smartphone. So, we do not need wireless external resources, such as GPS or WiFi signals. The conventional methods measure indoor location by generating a movement route of pedestrian by step and direction recognition. In this paper, to correct the direction sensor error, we use the common feature of the normal indoor floor map that the indoor path is lattice-structured. And we quantize moving directions depending on the direction of indoor path. In addition, we propose moving direction measuring method using geomagnetic sensor and gyro sensor to improve the accuracy. Also, the proposed step detection method uses angle and accelerometer sensors. The proposed step detection method is not affected by the posture of the smartphone. Direction errors caused by direction sensor error is corrected due to proposed moving direction measuring method. The proposed location error correction method corrects location error caused by step detection error without the need for external wireless signal resources.