• Title/Summary/Keyword: SNR Degradation

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Interference Neutralization for Small-Cell Wireless Networks (스몰셀 무선망 간섭 상쇄 기법 연구)

  • Jeon, Sang-Woon;Jung, Bang Chul
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.12
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    • pp.1117-1124
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    • 2013
  • As the recently soaring wireless traffic, small-cell techniques have been actively studied in order to support such a wireless demand for cellular wireless networks. This paper focuses on the inter-cell interference neutralization to resolve the main barrier for implementing small-cell cellular networks. Assuming that each message is delivered to the final destination by the help of base stations or relays, ergodic interference neutralization is proposed, which exploits the time-varying nature of wireless channels. The previous approach based on amplify-and-forward (AF) suffers from severe performance degradation in the low signal-to-noise (SNR) regime due to noise amplification. On the other hand, the proposed interference neutralization based on recently developed compute-and-forward (CF) fixes such a problem and improves the performance in the low SNR regime.

ML Frame Synchronization for Gaussian Channel with Co-channel Interference (가우스 잡음과 CO-CHANNEL 간섭이 존재하는 채널에서의 최대추정 프레임 동기)

  • 문병현;우홍체;김신환;이채욱
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.5
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    • pp.643-649
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    • 1993
  • The problem of locating a periodically inserted frame synchronization pattern in random data for a binary pulse amplitude modulated (PAM) digital communication system over a additive white Gaussian noise(AWGN) channel with co-channel interference is considered. The performance degradation of frame synchronization for the correlation rule due to the presence of co-channel interference is shown. The maximum likelihood(ML) decision rule for the frame synchronization over an AWGN channel with co-channel interference is derived. For the entire range of SNR considered, the ML frame synchronization rule obtains about 1dB signal energy gain over the correlation rule. Specially, the ML rule obtains as much as 2dB gain over the correlation rule when the SNR is greater than 0dB.

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An Adaptation Method in Noise Mismatch Conditions for DNN-based Speech Enhancement

  • Xu, Si-Ying;Niu, Tong;Qu, Dan;Long, Xing-Yan
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.10
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    • pp.4930-4951
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    • 2018
  • The deep learning based speech enhancement has shown considerable success. However, it still suffers performance degradation under mismatch conditions. In this paper, an adaptation method is proposed to improve the performance under noise mismatch conditions. Firstly, we advise a noise aware training by supplying identity vectors (i-vectors) as parallel input features to adapt deep neural network (DNN) acoustic models with the target noise. Secondly, given a small amount of adaptation data, the noise-dependent DNN is obtained by using $L_2$ regularization from a noise-independent DNN, and forcing the estimated masks to be close to the unadapted condition. Finally, experiments were carried out on different noise and SNR conditions, and the proposed method has achieved significantly 0.1%-9.6% benefits of STOI, and provided consistent improvement in PESQ and segSNR against the baseline systems.

Performance of Spectrum Sensing Using AF Cooperative Relay for Cognitive Radio System (인지 무선 통신에서 AF 협력 릴레이를 이용한 스펙트럼 센싱 성능)

  • Lee, Mi-Sun;Kim, Yoon-Hyun;Kim, Jin-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.12 no.4
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    • pp.31-36
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    • 2012
  • In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Premises equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (Cognitive Radio) system, and simulation results show comparison of the sensing performance.

Maximum Likelihood Sequence Estimation of TFM with Decision Feedback Equalization in the Correlative Coded Digital FM System (상관 부호화된 디지털 FM 시스템에서 결정 궤환을 이용한 TFM의 최대 근사 추정)

  • 송형규;강민구;강창언
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.5 no.3
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    • pp.22-35
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    • 1994
  • To improve the bandwidth efficiency in the environment of digital mobile communications, a correlative coded FM system is designed. The signal of this system has continuous phase and high power efficiency due to the constant envelope. But this signal also has a little loss of the SNR and some degradation of the BER. In this paper, a modified MLSE method which uses correlative coded signal is adopted to improve the performance of the receiver. The MLSE method improved the BER performance in the used channel. Without the decision feedback, the receiver performance was improved by 2dB and with it, by 4dB Particularly, the MLSE method and the decision feedback showed better performance in bad channels than in a stable telephone channel.

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Transmitted Reference UWB Systems Based on Block-Coded Modulation (블럭부호변조 기반의 Transmitted Reference 광대역 통신 시스템)

  • Min, Seungwook
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.3
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    • pp.289-293
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    • 2013
  • In the noncoherent methods for UWB-IR (ultra-wideband impulse radio), block coded modulation (BCM) is better than the transmitted reference (TR) systems in terms of the energy efficiency and data rate. However, even BCM suffers from the performance degradation in the presence of strong inter-frame interference and inter symbol interference. We propose the transmitted reference based on the BCM (TR-BCM) which is the hybrid system of TR and BCM. Performance evaluation shows that the performance of TR-BCM is better than that of BCM in the high SNR range.

Advanced Synchronization Scheme in the LR-UWB System (LR-UWB 시스템에서 개선된 동기 기법)

  • Kwon, Soon-Koo;Kim, Jae-Seok
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.7B
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    • pp.892-896
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    • 2011
  • This paper proposes a two-stage synchronization scheme using a serial search non-coherent correlator appropriate for the IEEE 802.15.4a system. The proposed method improved the synchronization performance by using multi-pulse signals unlike the conventional method using single-pulse signals. It also compensated for the degradation of performance at low SNR resulting from the use of fixed threshold by applying the adaptive threshold technique. The proposed method showed a detection probability that is higher by approximately 0.2-0.3 compared with the conventional method in the IEEE 802.15.4a channel model.

Performance of Spectrum Sensing Using Cooperative Relay for Cognitive Radio System (인지 무선 통신을 위한 협력 릴레이 센싱 성능)

  • Lee, Mi-Sun;Kim, Yoon-Hyun;Kim, Jin-Young
    • Journal of Satellite, Information and Communications
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    • v.7 no.1
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    • pp.7-12
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    • 2012
  • In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Primise equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (cognitive radio) system, and simulation results show comparison of the sensing performance between AF and DF.

A Study on Reconstruction of Degraded Signal using Wavelet Transform (웨이브렛 변환을 이용한 훼손된 신호의 복원에 관한 연구)

  • Kim Nam-Ho;Bae Sang-Bum;Ryu Ji-Goo
    • Journal of the Institute of Convergence Signal Processing
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    • v.6 no.1
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    • pp.33-38
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    • 2005
  • Degradation is generated by several causes in the process of digitalization or transmission of data. And its essential cause is noise. Therefore, researches for wavelet-based methods which reconstruct signal degraded by noise have continued. In AWGN(addtive white gaussian noise) environment, the general trend for denoising is to use the thresholding method. Reconstructed signal includes a lot of noise because these methods only consider statistical characteristic regarding noise. In this paper, we present a new method which uses the cumulation of wavelet detail coefficients. As a result, reconstruction of edges and denoising performance are improved. Also we compare existing methods using SNR(signal-to-noise ratio) as the standard of judgement of improvemental effect.

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Effect Analysis of Residual Frequency Offsets for Asynchronous MC-CDMA Uplink Systems (비동기 MC-CDMA 상향 링크 시스템에서의 잔류 주파수 옵셋 영향 분석)

  • Ko, Kyun-Byoung;Woo, Choong-Chae
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.8
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    • pp.9-15
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    • 2010
  • This paper presents an analysis of asynchronous multicarrier-code division multiple access (MC-CDMA) uplink systems over frequency-selective multipath fading channels when the frequency offsets (FOs) of all users are random variables and the frequency offset for the desired user is compensated. The effect of a residual frequency offset(RFO) on the average bit error rate (BER) is evaluated by the semi-analytical method, then the approximated BER performance is obtained as a closed-form expression. Moreover, the signal to noise ratio (SNR) loss caused by RFO is evaluated. Derived results show that the performance degradation due to RFO is negligible if the estimation error of RFO for the desired user is less than the normalized value of 0.1.