• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.661-669
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• 2000

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.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.98-100
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• 2010

본 논문에서는 주파수 선택적 페이딩(frequency selective fading) 채널에서 다중 사용자 MIMO-OFDM 시스템을 위한 자원 할당(resource allocation)을 연구한다. 다중 사용자의 신호를 검출하기 위해 기지국은 MMSE-SIC 수신기를 사용하고 이러한 조건에서 다중 사용자 MIMO-OFDM 시스템을 위한 최적화 문제를 도출하며 이를 위한 자원 할당 기법을 제안한다. 평균 채널 이득이 사용자마다 다른 환경에서의 컴퓨터 모의실험을 통해 제안된 자원 할당 기법의 성능을 알아본다. 모의 실험 결과 제안된 자원 할당 기법은 기존의 자원 할당 기법보다 더 높은 데이터 전송률(data rate)을 달성함을 보이고 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.1-6
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• 2012

In this paper, the performance comparison of the TR-UWB System using Wavelet Pulse, DPSS pulse, and second Gaussian pulse in multi-user environment is analyzed. The data signal and the reference signal is sent with some time intervals in TR-UWB system. At this time the two signals are through the same channel. In the receiver the reference signal is used as a template. This advantage results in demodulation without channel estimation and low complexity of it. However the conventional TR-UWB system based on a Gaussian signal in a multi-user environment has the disadvantage of poor performance due to the interferences between the users. To overcome this disadvantage, DPSS (Discrete Prolate Shperoidal Sequence) is used to reduce the interferences between the users. We propose the system with multiresolution function of orthogonal wavelet reducing the interferences, which has a better performance in multi-user environment when they are sent in transmission side.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.755-764
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• 2001

In this paper, we propose maximum likelihood (ML) decision feedback channel estimation (DFCE) for M-ary orthogonal modulation in direct sequence/code division multiple access (DS/CDMA) systems. The proposed DFCE uses the maximum combiner output in a RAKE receiver as decision feedback information, enabling M-ary orthogonal signals to be demodulated coherently and a RAKE receiver to use a em maximal ration combining (MRC) scheme. However, the performance of the proposed DFCE in the multiuser environment is severely degraded due to multiple access interference (MAI). To overcome this problem, a multistage parallel interference cancellation (PIC) scheme is combined with the proposed DFCE for multiuser environments. Accurate knowledge of the channel coefficient estimated by the proposed DFCE is used to regenerate the signal of each user for the multistage PIC scheme. According to the results of our simulations, the performance of coherent demodulation using the proposed system is significantly improved in comparison with conventional noncoherent demodulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.199-204
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• 2000

In this paper, we study single-user receiver, which applicable to DS-CDMA downlink. DS-CDMA downlink mainly use wallsh code, its orthogonality may be lost by the multiple access interference(MAI) caused by the multipath channel. In this paper, we use linear channel equalizer to eliminate the interference due to multipath channel and then to recover orthogonalit and use code-matched filter to detect transmitted data. Unlike existing research, which mainly assumed ideal channel information, we use pilot channel to estimate the channel coefficients. Especially we use guard symbols which are inserted periodically to estimate channel coefficients exactly without interference from user signal, and we accept an approximately ideal. The results show that improvement can be achieved using proposed detectors compared with that of that conventional RAKE receiver, especially when the user population is high we accepts excellent performance improvement.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.33-48
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• 2018

In this paper, we characterise the joint interference alignment and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with a blind interference alignment through staggered antenna switching on the receiver. We explore the power allocation and the feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired and interference signals to cancel the common interference signals, since the received signal must have a corresponding independent signal subspace. The sum capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.45-54
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• 2010

This paper studies the design of a multiuser multiple-input multiple-output (MIMO) system, where a base station (BS) transmits independent messages to multiple users. The remarkable "dirty paper coding (DPC)" result was first presented by Costa that the capacity does not change if the Gaussian interference is known at the transmitter noncausally. While several implementable DPC schemes have been proposed recently for single-user dirty-paper channels, DPC is still difficult to implement directly in practical multiuser MIMO channels. In this paper, we propose a network channel matrix triangulation (NMT) algorithm for utilizing interference known at the transmitter. The NMT algorithm decomposes a multiuser MIMO channel into a set of parallel, single-input single-output dirty-paper subchannels and then successively employs the DPC to each subchannel. This approach allows us to extend practical single-user DPC techniques to multiuser MIMO downlink cases. We present the sum rate analysis for the proposed scheme. Simulation results show that the proposed schemes approach the sum rate capacity of the multiuser MIMO downlink at moderate signal-to-noise ratio (SNR) values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.200-207
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• 2003

This paper proposes a CDMA receiver structure with time-shifted m-sequence orthogonal reception process, and analyzes the output SNR performance and the characteristics of the orthogonal receiver. This structure can be simply implemented with the converntional receiver adding an additional integrator path in parallel and an adder sums the conventional path and the new path output signals. The structure provides to reference user signal not only increment of signal component but also perfect orthogonal characteristic, canceling the accumulated cross-correlated value out to zero between the reference user and other user signals. Hence, the proposed structure can be applied for channel impulse response measurement, and used for multi-user interference signal cancellation and channel capacity increment by flexible structural inter-working operation of the added path, connection or disconnection, to conventional receiver structure.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.651-658
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• 2020

In the fifth generation (5G) mobile networks, the interactive mobile game users have increased tremendously, which induces correlated information sources (CIS). One of the promising 5G technologies is non-orthogonal multiple access (NOMA). In NOMA, the users share the channel resources, so that CIS affect each user's bit-error rate (BER) performance, which is not the case for orthogonal multiple access (OMA). In this paper, we derive the optimal receiver for NOMA with CIS, and then investigate the impact of CIS on each user's BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.271-278
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• 2003

In this paper, we propose a new MLP based detector which has low circuit complexity and fast adaptation capability for CDMA downlink in frequency selective fading, and is easy for parameter optimization. The simplified structure of the proposed MLP is designed by making use of transmission characteristics of downlinks such that all users signals transmitted over same propagation paths and the number of channelization codes are limited. Significant performance improvement over Rake receiver can be obtained with the proposed MLP and the efficiency of the proposed MLP was compared with that of conventional MLP.