하향링크 직교주파수분할다중접속 셀룰러 시스템을 위한 부반송파 기반 핸드오버 기법

왕한호,이성은,홍대식,Wang, Han-O,Lee, Sung-Eun,Hong, Dae-Sik 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol.45 No.2

본 논문에서는 직교주파수분할다중접속(Orthogonal Frequency Division Multiple Access) 하향링크 시스템에서 부반송파 별 채널 이득(channel gain)이 다름을 이용하여 시스템의 용량을 향상시킬 수 있는 핸드오버 기법을 제안한다. 제안하는 기법에서 핸드오버 중인 사용자는 소스 기지국(source base station)과 타겟 기지국(target base station)에서 할당 받은 부반송파 중 강한 채널이득을 가진 부반송파를 선택해 줌으로써 이득을 얻는다. 부반송파 선택 과정에서 탈락한 부반송파에 대한 정보는 기지국으로 피드백(feedback)되어 사용하지 않도록 하여 시스템 전체의 간섭(interference)량을 줄인다. 제안하는 기법은 핸드오버하고 있는 사용자의 오수신 확률을 22% 줄였으며, 이에 따라 시스템 전체의 전송률이 향상된다. In this paper, a new subcarrier-based handover scheme which exploits different channel gains of subcarriers in downlink OFDMA cellular systems. In this handover scheme, mobile users can obtain diversity gain by subcarrier selection. Feedback for unselected subcarriers reduces interference. The capacity enhancement by the handover scheme is originated from the following two characteristics of OFDMA systems. One is that interference per subcarrier is proportional to the traffic load. The other is that every subcarrier has different channel gain ?? 새 the Rayleigh fading channel. Therefore, selecting subcarriers with stronger channel gains results in diversity gain. Simulation results confirm that the proposed handover scheme improves the capacity of the OFDMA systems by reducing 24 percentage of the outage probability.

하향링크 직교주파수분할다중접속 셀룰러 시스템을 위한 부반송파 기반 핸드오버 기법

왕한호,홍대식,이성은 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol. No.

In this paper, a new subcarrier-based handover scheme which exploits different channel gains of subcarriers in downlink OFDMA cellular systems. In this handover scheme, mobile users can obtain diversity gain by subcarrier selection. Feedback for unselected subcarriers reduces interference. The capacity enhancement by the handover scheme is originated from the following two characteristics of OFDMA systems. One is that interference per subcarrier is proportional to the traffic load. The other is that every subcarrier has different channel gain ?? 새 the Rayleigh fading channel. Therefore, selecting subcarriers with stronger channel gains results in diversity gain. Simulation results confirm that the proposed handover scheme improves the capacity of the OFDMA systems by reducing 24 percentage of the outage probability. 본 논문에서는 직교주파수분할다중접속(Orthogonal Frequency Division Multiple Access) 하향링크 시스템에서 부반송파 별 채널 이득(channel gain)이 다름을 이용하여 시스템의 용량을 향상시킬 수 있는 핸드오버 기법을 제안한다. 제안하는 기법에서 핸드오버 중인 사용자는 소스 기지국(source base station)과 타겟 기지국(target base station)에서 할당 받은 부반송파 중 강한 채널이득을 가진 부반송파를 선택해 줌으로써 이득을 얻는다. 부반송파 선택 과정에서 탈락한 부반송파에 대한 정보는 기지국으로 피드백(feedback)되어 사용하지 않도록 하여 시스템 전체의 간섭(interference)량을 줄인다. 제안하는 기법은 핸드오버하고 있는 사용자의 오수신 확률을 22% 줄였으며, 이에 따라 시스템 전체의 전송률이 향상된다.

Performance Evaluation of Pilotless Channel Estimation with Limited Number of Data Symbols in Frequency Selective Channel

왕한호 한국콘텐츠학회 2018 International Journal of Contents Vol.14 No.2

In a wireless mobile communication system, a pilot signal has been considered to be a necessary signal for estimating a changing channel between a base station and a terminal. All mobile communication systems developed so far have a specification for transmitting pilot signals. However, although the pilot signal transmission is easy to estimate the channel,(Ed: unclear wording: it is easy to use the pilot signal transmission to estimate the channel?) it should be minimized because it uses radio resources for data transmission. In this paper, we propose a pilotless channel estimation scheme (PCE) by introducing the clustering method of unsupervised learning used in our deep learning into channel estimation.(Ed: highlight- unclear) The PCE estimates the channel using only the data symbols without using the pilot signal at all. Also, to apply PCE to a real system, we evaluated the performance of PCE based on the resource block (RB), which is a resource allocation unit used in LTE. According to the results of this study, the PCE always provides a better mean square error (MSE) performance than the least square estimator using pilots, although it does not use the pilot signal at all. The MSE performance of the PCE is affected by the number of data symbols used and the frequency selectivity of the channel. In this paper, we provide simulation results considering various effects(Ed: unclear, clarify).

인지 무선 통신 환경에서 임의접속 기법의 전송 효율 분석

왕한호,유화선,우중재,Wang, Han-Ho,Yoo, Hwa-Sun,Woo, Choong-Chae 한국융합신호처리학회 2012 융합신호처리학회 논문지 (JISPS) Vol.13 No.3

임의 접속(random access) 프로토콜은 기본적으로 센싱 기능을 가지고 있으며, 이것을 이용하여 분산형 무선 네트워크 시스템 구축에 적합한 특징을 가지고 있다. 이러한 기술적 특징은 중앙식 제어(centralized control)가 어려운 이기종 시스템들이 동작하는 인지 무선 통신 환경에 대하여 장점을 가지며, 인지 무선 통신 환경에서 임의 접속의 성능을 검증해 보아야 한다는 동기를 제공한다. 이 논문에서 우리는 인지 무선 통신 환경에서 CSMA/CA(carrier-sensing multiple access with collision avoidance)기법을 도입하고, 성능을 분석하는 기본 틀을 제공한다. Random access protocol takes advantage of constructing a decentralized wireless network due to its intrinsic spectrum sensing capability. Such technical feature goes well with cognitive radio networks consisting of heterogeneous wireless systems, in which a centralized control between heterogeneous wireless systems is hard to be implemented. Motivated by the decentralized feature of the random access, we adopt the random access protocol in cognitive radio networks, and evaluate the performance of a CSMA-based cognitive radio network.

스몰 셀과 HetNet 전송용량

왕한호,류탁기,홍대식 대한전자공학회 2014 전자공학회지 Vol.41 No.12

이중 편파 안테나시스템의 오수신 확률 분석

왕한호(Hanho Wang),노고산(Gosan Noh),방승재(Seungjae Bahng),박윤옥(Youn Ok Park) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.12(통신이론)

M2M 어플리케이션 지원을 위한 무선 결합 전송 플랫폼의 전송률 분석

왕한호(Hanho Wang),우중재(Choongchae Woo) 대한전기학회 2014 전기학회논문지 P Vol.63 No.3

Various M2M applications have different quality-of-service(QoS) requirements to be implemented practically. QoS requirements are normally data rate and delay constraint. However, there are limited number of wireless communication chip solutions which cannot support QoS requirements for all M2M application. Hence, aggregated usage of plural wireless communication chip solutions should be needed to implement M2M applications. In this paper, we consider the case that two wireless communication chips using random access protocol work together to transmit data of an M2M application. In such case, data rate and delay performance are mathematically analyzed. In our results, practical data rate can be improved from 2.5 to 7 times while delay constraints are satisfied if we simply use two wireless communication chips together.

타 단말 신호를 이용하는 K-means 기반 채널 추정 기법

왕한호(Hanho Wang) 한국정보기술학회 2020 한국정보기술학회논문지 Vol.18 No.11

Pilotless channel estimation (PCE) without transmitting a pilot signal increases a substantial data rate by estimating a channel using only data symbols. However, the existing PCE techniques have had a problem that a channel can be normally estimated only when received data symbols are evenly distributed over all symbol positions on a constellation of a modulation scheme. This paper proposes a PCE technique that estimates the channel by receiving both the desired user’s signal and the signal of another terminal in the downlink. By receiving signals from two terminals together and increasing the actual number of data symbols used for the PCE, improved channel estimation performance can be obtained. According to the results of this paper, when estimating the channel of the desired terminal using data symbols modulated with 16QAM, it is confirmed that the mean squared error of the estimated channel can be reduced by estimating channel including other user’s signal.

편향된 QPSK를 이용한 머신 러닝 기반 채널 위상 추정에 대한 연구

왕한호(Hanho Wang),고균병(Kyunbyoung Ko) 한국콘텐츠학회 2023 한국콘텐츠학회 종합학술대회 논문집 Vol.2023 No.5

시변 채널에서 K-means 기반 채널 추정 기법의 성능 평가

왕한호(Hanho Wang) 한국정보기술학회 2022 한국정보기술학회논문지 Vol.20 No.1

PCE with a certain number of data symbols has superior mean squared error(MSE) performance compared to a least square(LS) channel estimator using pilot signal. However, in PCE studies conducted so far, only the channel estimation performance for the snapshot channel has been presented, but the performance in the time-varying channel has not been presented. Since the PCE is a channel estimator that estimates the channel based on the previous channel estimation, performance evaluation in the time-varying channel is essential. In this paper, the channel estimation performance of the PCE is evaluated in time-varying channel of a mobile communication environment. Through this evaluation, It is shown that the PCE has superior MSE performance with SNR gain between 4 and 6 dB compared to the LS channel estimator even in time-varying channels. In addition, mobility adaptive resource allocation scheme for the PCE is proposed, which makes the PCE provide the best MSE performance in a channel environment