MB-OFDM UWB 시스템을 위한 샘플링 주파수 오프셋 추정기법
(Sampling Frequency Offset Estimation Schemes for MB-OFDM UWB Systems)
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초록
본 논문에서는 향후 초고속 W-PAN(Wireless Personal Area Network)을 위한 유력한 전송 기술로서 각광받고 있는 MB-OFDM UWB(Multi-Band Orthogonal Frequency Division Multiplexing Ultra Wide Band) 시스템의 동기화를 위한 효과적인 샘플링 주파수 오프셋 추정 기법을 제시하고 성능을 평가하였다. 이를 위해 PLCP 프리앰블(Physical Layer Convergence Procedure Preamble)내의 채널 추정 시쿼스를 이용하고 MB-OFDM UWB 시스템 기술 규격 및 주파수 운용 방식을 고려하였으며, 각 부반송파를 통해 얻어진 추정 결과들을 이용하여 최종적인 샘플링 주파수 오프셋을 추정하기 위해 최대우 추정 및 가중치 기반 조합 방식을 적용하였다. IEEE 802.15 Task Group 3a에서 제공하는 4가지 UWB 실내 채널 모델을 이용한 모의실험 결과, 잡음 영향 감소 및 주파수 선택적 페이딩에 대한 강인성을 제공하기 위하여 가각의 서브밴드들로부터 추정된 결과들에 대한 평균을 이용할 경우 모든 샘플링 주파수 오프셋 추정 기법들에 대하여 추정 성능이 개선됨을 볼 수 있으며 특히 본 논문에서 제안된 각 부채널에서의 수신 신호 평균 전력만을 반영하는 간단한 혀태의 가중치 기반 샘플링 주파수 오프셋 추정 기법의 성능이 기존 방법들에 비해 월등히 우수함을 확인하였다.
Abstract
In this paper, we propose and evaluate the sampling frequency offset estimation schemes based on the cahnnel estimation sequences in PLCP (Physical Layer Convergence Procedure) preamlble for the propoer and efficient synchreonization of the MB-OFDM UWB (Multi-Band orthogonal Frequency Division Multiplexing Ultra Wide Band) systems which have recently drawn explosive attention for future W-PAN(Wireless Personal Area Network) applications. After obtaining the sampling frequency offset estimates from all teh sub-carriers by comsidering technical specification and multi-band utilization of the MB-OFDM UWB, we also exploit the MLE(Maximum Likelihood Estimate)and the weighing fastoe vased schemes to efficiently combine these estimates and to determine the fianl sampling frequency offset estimate value. Simulation results using IEEE 802-15 Task Grop 3a UWB channel models reveal that perfomance improvement of the sampling frequency estimation for the MB-OFDM UWB systems can by achieved by averaging the estimates obtained from all the sub-bands. In particular, it is also obseved that the estimation scheme using the simple weighting fasctors based on easily-measurable reseiced signal power of each sub-channel show fairly good estimation perfomance as sompared to any other conventional estimation schemes.
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