• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.718-723
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• 2017

We propose a pilot hopping scheme that improves the limited system capacity due to pilot contamination in multi-cell environment with large-scale antenna arrays at a base station, assuming the infinite number of antennas. In the conventional fixed pilot scheme, each user obtains the same signal-to-interference ratio (SIR) over a long period of time. Therefore, a user with strong interference has continuously low SIR which degrades its service quality. In the proposed pilot hopping scheme, different pilot signals are used for each time slot, and different amounts of interference are received every time. When such a pilot hopping technique is applied, the SIR fluctuates at every time slot. When the Hybrid Automatic Repeat & reQuest (HARQ) technique is applied in such a channel, the outage probability and transmission rate are improved. We show that there is the performance gain of the proposed scheme over the conventional scheme through computer simulations.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.11-14
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• 2003

본 논문에서는 다중안테나 시스템(Multiple-Input Multiple-Output : MIMO)과 다중코드(Multicode)를 사용하는 코드분할 다중접속(Code Division Multiple Access : CDMA) 시스템의 하향링크(from the base station to the mobile) 환경하에서 채널응답의 중요한 요소인 전송지연시간(Propagation Delay Time)이 기존의 단일안테나(Single-Input Single-Output : SISO) 채널 환경에서 다중안테나 채널 환경으로 바뀌어 적용되었을 때 발생할 수 있는 환경 변화를 찾아보고 그러한 환경이 코드 동기 성능에 미치는 영향과 그러한 문제점을 해결할 수 있는 효율적인 파일롯(Pilot) 전송 기법을 제안 하였다. 또한 모의 실험을 통하여 도착 시간 지연 차이의 분산(variance)값이 검파 성능에 미치는 영향을 확인 하였다.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.167-173
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• 2003

We treat the problem of channel estimation and interference cancellation in multiuser ultra-wide-band (UWB) communication systems over multipath fading channels. The UWB system under consideration employs a random time-hopping impulse radio format. We develop a channel estimation method based on linear weighted algorithm. An iterative channel estimation and interference cancellation scheme is proposed to successively improve the receiver performance. We also consider systems employing multiple transmit and/or receive antennas. For systems with multiple receive antennas, we develop a diversity receiver for the wellseparated antennas. For systems with multiple transmit antennas, we propose to make use of Alamouti’s space-time transmission scheme, and develop the corresponding channel estimation and interference cancellation receiver techniques. Simulation results are provided to demonstrate the performance of various UWB receiver techniques developed in this paper.