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DS-CDMA 하향링크에서 파일럿지원 채널등화기를 이용한 단일사용자 수신기
남옥우,김재형,김응배 한국정보통신학회 2000 한국정보통신학회논문지 Vol.4 No.3
DS-CDMA 하향링크에서는 직교확산부호에 의하여 사용자들을 구분하는데 다중경로 페이딩(multhpath fading)에 의한 다중접속간섭(MAI)과 주파수 선택적 페이딩에 의하여 확산부호의 직교성은 깨어지게 되고 시스템의 성능열화를 가져온다. 따라서 본 논문에서는 선형 채널 등화기를 사용하여 다중경로 페이딩 채널을 등화 시킴으로써 직교부호의 직교성을 복구한 후 부호-정합 필터(code-matched filter)를 통하여 데이터를 복조하는 단일사용자 수신기를 제안하였다. 기존의 연구는 주로 이상적인 채널정보를 가정하였는데 본 논문에서는 채널추정 방법으로 병렬기준전송(transmission of a parallel reference)방법인 파일럿 채널지원(pilot channel assisted)방법을 사용하였으며, 특히 채널 추정의 정확도를 높이기 위하여 사용자 신호에 주기적으로 보호심볼(guard symbol)을 삽입하였다. 성능분석결과 정확한 채널추정으로 인하여 이상적인 채널정보를 사용한 경우에 비해 성능저하가 크지 않았으며, MMSE criterion에 의한 채널등화로 기존의 수신기에 비해 특히 사용자가 많을 경우에 우수한 성능을 보임을 알 수 있었다. DS-CDMA downlink distinguishes actual user by orthogonal spreading codes ,but its orthogonality may be lost by the multiple access interference(MAI) caused by the multipath channel. Therefore in this paper, we proposed the single-user receiver, which use linear channel equalizer to eliminate the interference due to multipath channel and to recover orthogonality and then use code-matched filter to detect transmitted data. Unlike existing research, which mainly assumed ideal channel information, we use pilot channel assisted methods that is a kind of transmission of a parallel reference method to estimate the channel coefficients. Especially we use guard symbols which are inserted periodically to estimate channel coefficients exactly without interference from user signal. The results show that we accepted an approximately ideal channel information and achieved excellent performance improvement using proposed receiver compared with the conventional receiver especially user populations are high.
제3세대 시스템을 위한 무선접속방식의 비교-Ⅰ : TDMA 및 CDMA 기반 무선접속기술
남옥우,이순규,김재형 창원대학교 산업기술연구소 2001 産技硏論文集 Vol.15 No.-
In this paper, we persents an overview of worldwide air interface research activities and result of performance comparison analysis which regards to CDMA and TDMA based multiple access schemes for third generation mobile communication named IMT-2000. Considering systems are CDMA based FRAMES FMA2 and CODIT and TDMA based FREAMES FMA1 and ATDMA. As a result of performance comparison analysis, CDMA and TDMA schemes show almost equal performance. But the decisive factor is advanced technique such as interference cancellation methods which applied to receiver.
남옥우,김재형 한국정보통신학회 2001 한국정보통신학회논문지 Vol.5 No.7
본 논문에서는 BWLL 상향링크에 적용할 수 있는 버스트 QPSK 수신기의 동기알고리즘을 설계하였다. 본 논문에서 설계한 버스트 수신기는 디지털 다운컨버터와 정합필터 그리고 동기회로로 구성되어 있다. 동기회로의 경우 심벌 타이밍 복구를 위하여 가드너 알고리즘을 사용하였고 반송파 주파수 복구를 위하여 4승법을 사용하였으며 반송파 위상 복구는 DD알고리즘을 사용하였다. 성능 분석을 위하여 제안된 알고리즘에 대한 시뮬레이션 결과와 VHDL로 코딩되어 FPGA에 구현된 실제회로의 결과를 비교, 분석하였다. 성능분석 결과 주파수 옵셋이 심벌율의 4.7% 까지 동기기가 잘 동작하였다. In this Paper we describe the design of synchronization algorithms for burst QPSK receiver, which are applicable to BWLL uplink. The demodulator consists of digital down converter, matched filter and synchronization circuits. For symbol timing recovery we ufo Gardner algorithm. And we use forth power method and decision directed method for carrier frequency recovery and phase recovery, respectively. For the sake of performance analysis, we compare simulation results with the board implemented by FPGA which is APEX20KE series chip for Alter. The performance results show it works quite well up to the condition that a frequency offset equal to 4.7% of symbol rate.
DS-CDMA 의 용량개선을 위한 다중사용자 복조시스템
남옥우,김재형 창원대학교 정보통신연구소 2001 精報通信論文集 Vol.5 No.-
In this paper, we research the concepts and classes of Multi-User Detection Systems. MUD holds much promise for improving DS-CDMA performance and capacity. Multiple access interference significantly limits the performance and capacity of conventional DS-CDMA systems. In MUD, code and timing information of multiple users is jointly used to better detect each individual user. The optimum multi-user sequence detector is known, and provides huge gains in performance and capacity over the conventional detector ; it also minimizes the need for power control. Unfortunately, it is too complex to implement for practical DS-CDMA systems. Many simpler suboptimal MUD have been proposed in the last few years, all of which have the potential to provide substantial performance and capacity gains over the conventional detector. Most of the detectors fall into two categories : linear and subtractive interference cancellation.
남옥우,김재형,김응배 國立 昌原大學校 産業技術硏究所 1997 産技硏論文集 Vol.11 No.-
Highway congestion, traffic-related pollution, and difficulty locating travel destinations are some of the mounting problems facing most Korean drivers on a regular basis. ITS (Intelligent Transportation Systems) is an integrated system aiming to improve the transportation efficiency of existing road infrastructure, enhance the safety of driving, and save the transportation cost in terms of mitigating the traffic congestion by using advanced information, telecommunication, sensing, and control technologies. In this study, we are intended to assess the properties and application method of wireless communications either existing commercial systems or none existing dedicated wireless systems (e.g., Paging, Wireless Data, Cellular Radio Communication, Personal Communication Systems, and FPLMTS) and provide solutions to select a possible communication method to realize the Intelligent Transportation Systems.