• Journal of electromagnetic engineering and science
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• 제12권3호
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• pp.223-225
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• 2012

In this paper, we develop a symbol/frame time and carrier frequency synchronization scheme for multi-carrier signaling in wireless mobile channels. The proposed scheme achieves simultaneous time synchronization and carrier frequency offset estimation. Simulation results show that the frequency offset of multiple sub-carrier spacings can be estimated and that performance is improved with robustness regardless of the cyclic prefix length.

• 한국통신학회논문지
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• 제30권8A호
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• pp.656-663
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• 2005

본 논문에서는 IEEE 802.15.3 High-Rate WPAN (Wireless Personal Area Network) 환경에서 다중 채널을 사용하여 향상된 성능의 MAC 프로토콜을 제안한다. IEEE 802.15.3 High-Rate WPAN은 10m 내외의 거리에서 실시간 비디오 및 대용량 파일 전송을 목적으로 설계된 MAC과 PHY의 표준을 말한다. 현재 표준의 MAC 프로토콜은 하나의 무선 채널을 piconet 내의 모든 DEV가 공유하여 사용한다. 이 중 PNC(Piconet Coordinator)는 TDMA(Time Division Multiple Access)방식으로 DEV들에게 채널타임을 할당한다. 이런 경우 piconet내의 통신하는 DEV의 수가 많아지게 되면 superframe의 길이가 길어져 전송되는 데이터의 aggregate throughput이 떨어지고 QoS(Quality of Service)를 보장하지 못한다. 본 논문에서 하나의 piconet이 여러 개의 채널을 동시에 사용하여 aggregate throughput을 향상시키고 QoS를 보장하는 다중채널 MAC 프로토콜을 제안하고 시뮬레이션을 통해 향상된 성능을 증명한다.

• 한국멀티미디어학회논문지
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• 제10권12호
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• pp.1632-1644
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• 2007

Wireless Mesh Networks aim to attain large connectivity with minimum performance degradation, as network size is increase. As such, scalability is one of the main characteristics of Wireless Mesh Networks that differentiates it from other wireless networks. This characteristic creates the need for bandwidth efficiency strategies to ensure that network performance does not degrade as the size of the network increase. Several researches have been done to realize mesh networks. However, the researches conducted were mostly focused on a per TCP/IP layer basis. Also, the studies on bandwidth efficiency and bandwidth improvement are usually dealt with as separate issues. This paper aims to simultaneously study bandwidth efficiency and improvement. Aside from optimizing the bandwidth given a fixed capacity, the capacity is also increased using results of physical layer studies. In this paper, the capacity is improved by using the concept of non-overlapping channels for wireless communication. A channel allocation scheme is conceptualized to choose the transmission channel that would optimize the network performance parameters with consideration of chosen Quality of Service (QoS) parameters. Network utility maximization is used to optimize the bandwidth after channel selection. Furthermore, a routing scheme is proposed using the results of the network utilization method and the channel allocation scheme to find the optimal path that would maximize the network gain.

• 정보통신설비학회논문지
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• 제8권4호
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• 한국전자파학회논문지
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• 제12권3호
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• pp.470-477
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• 2001

Multucarrier code-division multiple access(MC-CDMA) is one of the promising technique for high capacity wireless communication. Hower the carrier phase error and frequency offest cause the performance degradation of MC-CDMA due to the inter-carrier interference. In this work, downlink performance of the partially coherent MC-CDMA is analytically derived in Rayleigh fading channels. The bit error rate sensitivity by combining method, Maxiaml ratio combining (MRC)and Equal gain combining(EGC), is compared as functions of phase errors. multi-user interference, and received signal-to-noise ratio. The results show that the susceptibility for the performance degradation of EGc and MRC is negligible for loop SNR's of above 15 dB and above 10 dB, respectivtely.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.12-16
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• 2008

In this paper, we study precoding techniques for co-channel interference suppression in multiuser MIMO systems. DPC is optimal techniques to achieve the system capacity of multiuser MIMO downlink channels. DPC is not proper in practical wireless systems because complexity is very high. So block diagonal precoding for multiuser MIMO downlink channel is studied. The block diagonal precoding is used to suppress co-channel interference between multiuser. Block diagonal precoding method, whose complexity is reduced by modified null space operation, change multiuser MIMO channel to multiple single-user MIMO channel. We also use V-BLAST decoder in receiver. V-BLAST decoder can achieve increased system capacity in proportion to the number of users. We show improved system performance by using computer simulation.

• 한국소음진동공학회논문집
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• 제16권11호
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• pp.1093-1099
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• 2006

In general, a measuring instrument of sound noise use only one wired channel by one sensor. Therefor the measuring instrument use wired cables as the number of channels are provided by instrument. In a point of observed target it needs data from multiple sensors and In case of measured point is a large numbers the environment of constitution would be complicated because that is in need of channel and cable. So we need the method that can improve the existing transmission channel and cable environment even the measured point is increased. If we use the Code Division Multiple Access(CDMA) we transmit a large numbers of sensor data by using a common transmission channel. We present the method that transmits data of multiple sensor to wireless by using CDMA. This method can simplify the measurement environment dramatically when collecting data by using multiple sensor. We expect this study to contribute the part of multiple access technology and relation technologies on the measuring environment.

• 대한전자공학회논문지TC
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• 제41권10호
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• pp.61-67
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• 2004

차세대 무선 통신 시스템은 현재보다 고속의 데이터 전송과 매우 큰 시스템 용량을 요구하며, 이와 같은 요구를 충족시키기 위해서 복수의 안테나를 사용하여 송수신을 하는 MIMO(Multiple Input Multiple Output) 기술이 널리 연구되고 있다. 이 논문은 하나의 송신기에서 복수의 수신기에게 각각 복수의 데이터 스트림을 동시에 전송하면서 동적 슬롯할당을 이용하여 성능을 향상시키는 동적 슬롯할당 공간분할 다중접속 MIMO 시스템을 제안한다. 제안하는 기술은 빔포밍 차원의 감소로 인한 성능 감소를 최소화하면서 다른 MIMO 기술보다 많은 수의 병렬 데이터를 전송할 수 있게 함으로써 시스템 용량을 크게 증가시키는 것이 가능하다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.133-137
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• 2006

In general, a measuring instrument of sound noise use only one wired channel by one sensor. Therefor the measuring instrument use wired cables as the number of channels are provided by instrument. In a point of observed target it needs data from multiple sensors and In case of measured point is a large numbers the environment of constitution would be complicated because that is in need of channel and cable. So we need the method that can improve the existing transmission channel and cable environment even the measured point is increased. If we use the Code Division Multiple Access(CDMA) we transmit a large numbers of sensor data by using a common transmission channel. We present the method that transmits data of multiple sensor to wireless by using CDMA. This method can simplify the measurement environment dramatically when collecting data by using multiple sensor. We expect this study to contribute the part of multiple access technology and relation technologies on the measuring environment.

• 한국정보통신학회논문지
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• 제9권8호
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• pp.1643-1648
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• 2005

MIMO (Multiple put Multiple Output) 시스템은 공간적으로 분리된 안테나를 이용하여 공간 다이버시티 이득을 제공하는 고성능, 고용량의 광대역 무선 접속 기술이다. 본 논문에서는 주파수 다이버시티의 이득을 제공하는 다중 반송파 부호 기술인 반송파 간섭 부호 (Carrier Interferometry Code)를 MIMO-OFDM 시스템에 적용하여 성능을 추가적으로 개선하는 반송파 간섭 부호 기반의 MIMO-OFDM 시스템을 제안한다. SPW 시뮬레이션 플랫폼을 이용한 시뮬레이션 분석 결과에 의하면 주파수 선택적 페이딩 채널 환경에서 기존의 MIMO-OFDM 시스템 보다 반송파 간섭 부호를 적용한 MIMO-OFDM 시스템의 성능이 높은 채널 지연 환경에서도 약 4dB까지 개선됨을 알 수 있었다.