• Title/Summary/Keyword: interference cancellation

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A signal Detection Technique based on Compressed Sensing for Full-Duplex Generalized Spatial Modulation Systems (전 이중방식 일반화된 공간변조 시스템을 위한 압축센싱기반 신호검출기법)

  • Park, Jeonghong;Ban, Tae-Won;Jung, Bang Chul
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2015.05a
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    • pp.43-46
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    • 2015
  • Recently, full-duplex communications has been considered as one of the most promising techniques for net-generation mobile communication system. In this paper, we propose a compressed sensing based signal detection technique for full-duplex generalized spatial modulation (FD-GSM) systems. In FD-GSM systems, some antennas are used for signal transmission according to input data and the otehrs are used for detecting signals received over the same frequency band. The self-interference (SI) is assumed to be completely removed by help for the recently proposed SI cancellation techniques. The proposed signal detection technique significantly outperforms the conventional ones in terms of symbol error rate (SER). We will investigate the optimal number of used antennas in FD-GSM systems.

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Performance of the CDMA Receiver with PN Sequence Orthogonal Reception Process (PN 부호의 직교 수신 방식을 이용한 CDMA 수신기 성능)

  • Hyun, Kwang-Min;Yoon, Dong-Weon;Park, Sang-Kyu
    • 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.

A New Carrier frequency Offset Estimation Using CP-ICA Scheme in OFDM Systems (OFDM 시스템에서 CP-ICA 기법을 이용한 새로운 주파수 옵셋 추정)

  • Kim, Jong-Deuk;Byun, Youn-Shik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.12C
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    • pp.1257-1264
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    • 2006
  • The carrier frequency offset causes loss of orthogonality between sub-carriers, thus leads to inter-carrier interference (ICI) in the OFDM symbol. This ICI causes severe degradation of the BER performance of the OFDM receiver. In this paper, we propose a new ICI cancellation algorithm which estimates frequency offset at the time-domain by using CP-ICA method to the received sub-carriers phase rotation. This algorithm is based on a statistical blind estimation method, which mainly utilizes the EVD, rotating phase and the $4^{th}-cumulants$. Since our scheme does not need any training and pilot symbol in estimation, we can expect enhanced bandwidth efficiency in OFDM systems. Simulation results show that the proposed frequency offset estimator is more accurate than the other estimators in $0.0<\varepsilon<1.0$.

An Adaptive K-best Algorithm Based on Path Metric Comparison for MIMO Systems (MIMO System을 위한 Path Metric 비교 기반 적응형 K-best 알고리즘)

  • Kim, Bong-Seok;Choi, Kwon-Hue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.11A
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    • pp.1197-1205
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    • 2007
  • An adaptive K-best detection scheme is proposed for MIMO systems. The proposed scheme changes the number of survivor paths, K based on the degree of the reliability of Zero-Forcing (ZF) estimates at each K-best step. The critical drawback of the fixed K-best detection is that the correct path's metric may be temporarily larger than K minimum paths metrics due to imperfect interference cancellation by the incorrect ZF estimates. Based on the observation that there are insignificant differences among path metrics (ML distances) when the ZF estimates are incorrect, we use the ratio of the minimum ML distance to the second minimum as a reliability indicator for the ZF estimates. So, we adaptively select the value of K according to the ML distance ratio. It is shown that the proposed scheme achieves the significant improvement over the conventional fixed K-best scheme. The proposed scheme effectively achieves the performance of large K-best system while maintaining the overall average computation complexity much smaller than that of large K system.

Reduction of Conducted Emission in Interleaved RPWM Buck Converter (인터리브드 RPWM Buck 컨버터의 전도성 노이즈 감소에 대한 연구)

  • Lee, Seunghyun;Lee, Keunbong;Nah, Wansoo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.4
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    • pp.298-308
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    • 2017
  • This paper presents a Interleaved Buck Converter(IBC) system with Random PWM to reduce electromagnetic noise by harmonics. Swithced mode power supply generally controlled by high switching frequency have a electromagnetic interference(EMI) issue due to the high-voltage/high-current switching to regulate the voltage in buck converter. To solve the problem. we present a novel IBC system with PRBS. IBC system has two active switches with 180 phase difference that controll the cicuit with two PWM signal. IBC system may be disadventageous for the cost due to the addtion of one set of switch, but it has adventages of power distribution, current ripple cancellation, fast transient response, and passive component size reduction. To verify the validity of study, simulation program has been bulit using PSIM and the experimental results of IBC system using RPWM was compared with the conventinal PWM and randomized PWM.

An Adaptive Microphone Array with Linear Phase Response (선형 위상 특성을 갖는 적응 마이크로폰 어레이)

  • Kang, Hong-Gu;Youn, Dae-Hui;Cha, Il-Hwan
    • The Journal of the Acoustical Society of Korea
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    • v.11 no.3
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    • pp.53-60
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    • 1992
  • Many adaptive beamforming methods have been studied for interference cancellation and speech signal enhancement in telephone conference and auditorium. Main aspect of adaptive beamforming methods for speech signal processing is different from radar, sonar and seismic signal processing because desire output signal should be apt to the human ear. Considering that phase of speech is quite insensible to the human ear, Sondhi proposed a nonlinear constrained optimization technique whose constraint was on the magnitude transfer function from the source to the output. In real environment the phase response of the speech signal affects the human auditorium system. So it is desirable to design linear phase system. In this paper, linear phase beamformer is proposed and sample processing algorithm is also proposed for real time consideration Simulation results show that the proposed algorithm yields more consistent beam patterns and deep nulls to the noise direction than Sondhi's.

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Efficient User Selection Algorithms for Multiuser MIMO Systems with Zero-Forcing Dirty Paper Coding

  • Wang, Youxiang;Hur, Soo-Jung;Park, Yong-Wan;Choi, Jeong-Hee
    • Journal of Communications and Networks
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    • v.13 no.3
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    • pp.232-239
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    • 2011
  • This paper investigates the user selection problem of successive zero-forcing precoded multiuser multiple-input multiple-output (MU-MIMO) downlink systems, in which the base station and mobile receivers are equipped with multiple antennas. Assuming full knowledge of the channel state information at the transmitter, dirty paper coding (DPC) is an optimal precoding strategy, but practical implementation is difficult because of its excessive complexity. As a suboptimal DPC solution, successive zero-forcing DPC (SZF-DPC) was recently proposed; it employs partial interference cancellation at the transmitter with dirty paper encoding. Because of a dimensionality constraint, the base station may select a subset of users to serve in order to maximize the total throughput. The exhaustive search algorithm is optimal; however, its computational complexity is prohibitive. In this paper, we develop two low-complexity user scheduling algorithms to maximize the sum rate capacity of MU-MIMO systems with SZF-DPC. Both algorithms add one user at a time. The first algorithm selects the user with the maximum product of the maximum column norm and maximum eigenvalue. The second algorithm selects the user with the maximum product of the minimum column norm and minimum eigenvalue. Simulation results demonstrate that the second algorithm achieves a performance similar to that of a previously proposed capacity-based selection algorithm at a high signal-to-noise (SNR), and the first algorithm achieves performance very similar to that of a capacity-based algorithm at a low SNR, but both do so with much lower complexity.

A Study on Adaptive Linear MMSE Detector for DS-CDMA Reverse Link in Rayleigh Fading Environment (레일리 페이딩 환경하에서 DS-CDMA 역방향 링크에 적용 가능한 적응 선형 MMSE 수신기의 연구)

  • 안태기;이병섭;김성락;이정구
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.9 no.2
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    • pp.131-140
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    • 1998
  • MAI(Multi-Access Interference) and fast channel variation due to the fading environment are the major problems in the mobile CDMA communication systems. Recently, interest has been increasing in applying the Adaptive Linear MMSE Detector to MAI cancellation in the CDMA reverse link. In this paper, we propose a modified Adaptive Linear MMSE Detector structure which can be used in Long-duration code CDMA system in the presence of independent Rayleigh fading. We use independent multiple tap-weight vector structure to cope with the variation of spreading sequence pattern between neighbor symbols because of the Long-duration code. In this case, more exact channel parameter estimation is required. To solve this problem, we use coherent CDMA structure which can track the channel parameters like amplitude and phase by employing the low power pilot channel in the CDMA reverse link.

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Differential LC VCO with Enhanced Tank Structure and LC Filtering Techniques in InGaP/GaAs HBT Technology (InGaP/GaAs HBT 공정을 이용하여 향상된 탱크 구조와 LC 필터링 기술을 적용한 차동 LC 전압 제어 발진기 설계)

  • Lee, Sang-Yeol;Kim, Nam-Young
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.18 no.2 s.117
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    • pp.177-182
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    • 2007
  • This paper presents the InGaP/GaAs HBT differential LC VCO with low phase noise performance for adaptive feedback interference cancellation system(AF-lCS). The VCO is verified with enhanced tank structure including filtering technique. The output tuning range for proposed VCO using asymmetric inductor and symmetric capacitors withlow pass filtering technique is 207 MHz. The output powers are -6.68 including balun and cable loss. The phase noise of this VCO at 10 kHz, 100 kHz and 1 MHz are -102.02 dBc/Hz, -112.04 dBc/Hz and -130.40 dBc/Hz. The VCO is designed within total size of $0.9{\times}0.9mm^2$.

A Buffer-Aided Successive Relaying Technique with a Priori Decoding Information (선행 복호 정보를 활용한 버퍼기반 연쇄적 중계 기법)

  • Lee, Byeong Su;Jung, Bang Chul;Ban, Tae-Won
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.2
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    • pp.275-280
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    • 2016
  • In this paper, we propose a novel relay selection technique which utilizes a priori decoding information at relays for buffer-aided successive relaying networks. In the conventional relaying schemes, a single relay pair is selected for receiving data from the source and transmitting data to the destination. In the proposed technique, however, all relays except the relay selected for transmitting data to the destination try to decode the received signal from the source, and they store the data if they succeed decoding. The proposed technique selects the relay such that it can succeed its own transmission and it maximizes the number of relays successfully decoding the data from the source at the same time. It is shown that the proposed relaying technique significantly outperforms the conventional buffer-aided relaying schemes in terms of outage probability through extensive computer simulations.