• Journal of Computing Science and Engineering
• /
• 제6권4호
• /
• pp.310-319
• /
• 2012

Next generation wireless receivers demand low computational complexity algorithms with high computing power in order to perform fast signal detections and error estimations. Several signal detection and estimation algorithms have been proposed for next generation wireless receivers which are primarily designed to provide reasonable performance in terms of signal to noise ratio (SNR) and bit error rate (BER). However, none of them have been chosen for direct implementation as they offer high computational complexity with relatively lower computing power. This paper presents a low-complexity power-efficient algorithm that improves the computing power and provides relatively faster signal detection for next generation wireless multiuser receivers. Measurement results of the proposed algorithm are provided and the overall system performance is indicated by BER and the computational complexity. Finally, in order to verify the low-complexity of the proposed algorithm we also present a formal mathematical proof.

• Journal of Communications and Networks
• /
• 제18권5호
• /
• pp.677-687
• /
• 2016

Multi-way relay networks (MWRNs) allow multiple users to exchange information with each other through a single relay terminal. MWRNs are often incorporated with capacity achieving lattice codes to enable the benefits of high-rate signal constellations to be extracted. In this paper, we analytically characterize the symbol error rate (SER) performance of a functional decode and forward (FDF) MWRN in the presence of channel estimation errors. Considering M-ary quadrature amplitude modulation (QAM) with square constellations as an important special case of lattice codes, we obtain asymptotic expressions for the average SER for a user in FDF MWRN. The accuracy of the analysis at high signal-to-noise ratio is validated by comparison with the simulation results. The analysis shows that when a user decodes other users with better channel conditions than itself, the decoding user experiences better error performance. The analytical results allow system designers to accurately assess the non-trivial impact of channel estimation errors and the users' channel conditions on the SER performance of a FDF MWRN with M-QAM modulation.

• ETRI Journal
• /
• 제28권5호
• /
• pp.688-691
• /
• 2006

This letter addresses the superimposed pilot aided multiuser channel estimation for the uplinks of multi-input multi-output orthogonal frequency-division multiplexing systems. To mitigate the embedded-data effects on the performance of channel estimation, a novel combining algorithm is proposed. Optimal pilot symbols are developed with respect to the least square channel estimate's mean square error. The averaged sum-capacity lower bound is derived and simulated. Simulation results show that on a low signal-to-noise ratio regime, our proposed scheme achieves better performance and higher capacity than the conventional pilot aided approach.

• Journal of Electrical Engineering and Technology
• /
• 제13권1호
• /
• pp.445-450
• /
• 2018

Reliable detection and parameter estimation of a radar cross section(RCS) fluctuating target have been known as a difficult task. To reduce the effect of RCS fluctuation, various diversity techniques have been considered. This paper presents a new method for synthesizing a covariance matrix applicable to a coherent multi-input multi-output(MIMO) radar with frequency diversity. It is achieved by efficiently combining covariance matrices corresponding to different carrier frequencies such that the signal-to-noise ratio(SNR) in the combined covariance matrix is maximized. The value of a synthesized covariance matrix is assessed by examining the phase curves of its entries and the improvement on direction of arrival(DOA) estimation.

• 한국ITS학회 논문지
• /
• 제7권5호
• /
• pp.90-96
• /
• 2008

본 논문은 텔레메틱스 단말용 음성인식을 위한 음성향상 단일 칩 알고리듬을 제시한다. 제안된 방법은 잡음제거와 에코제거의 두 단계로 구성되어 있으며, 첫 단계로 크로스 스펙트럼 추정에 기반한 적응필터를 통해 에코를 제거하고, 두번째 단계로 Generalized Gamma분포기반의 LSA 음성추정 방식 추정을 통해 외부 배경잡음을 제거하여 음성의 음질을 향상시킨다. 적은 계산량이 요구되는 제안된 알고리즘을 토대로 구현된 단일 칩의 성능은 다양한 잡음환경에서 신호 대잡음비율과 음성인식 평가에서 기존의 방법보다 향상된 결과를 나타내었다.

• 한국통신학회논문지
• /
• 제21권12호
• /
• pp.3033-3045
• /
• 1996

In this paper, we propse an object-oriented coding method in low bit-rate channels using pyramid structure and residual image compensation. In the motion estimation step, global motion is estimated using a set of multiresolution images constructed in a pyramid structure. We split an input image into two regions based on the gradient value. Regions with larte motions obtain observation points at low resolution level to guarantee robustness to noise and to satisfy a motion constraint equation whereas regions with local motions such as eye, and lips get observation points at the original resolution level. Local motion variations and intesity variations of an image reconstructed by the golbal motion are compensated additionally by using the previous residual image component. Finally, the model failure (MF) region is compensated by the pyramid mapping of the previous displaced frame difference (DFD). Computer simulation results show that the proposed method gives better performance that the convnetional one in terms of the peak signal to noise ratio (PSNR), compression ratio (CR), and computational complexity.

• Journal of Electrical Engineering and Technology
• /
• 제9권5호
• /
• pp.1753-1761
• /
• 2014

Due to the inherent inhomogeneous and anisotropy nature of the composite materials, the detection of internal defects in these materials with non-destructive techniques is an important requirement both for quality checks during the production phase and in service inspection during maintenance operations. The estimation of the time-of-arrival (TOA) and/or time-of-flight (TOF) of the ultrasonic echoes is essential in ultrasonic non-destructive testing (NDT). In this paper, we used split-spectrum processing (SSP) combined with matching pursuit signal decomposition (MPSD) to develop a dedicated ultrasonic detection system. SSP algorithm is used for Signal-to-Noise Ratio (SNR) enhancement, and the MPSD algorithm is used to decompose backscattered signals into a linear expansion of chirplet echoes and estimate the chirplet parameters. Therefore, the combination of SSP and MPSD (SSP-MPSD) presents a powerful technique for ultrasonic NDT. The SSP algorithm is achieved by using Gaussian band pass filters. Then, MPSD algorithm uses the Maximum Likelihood Estimation. The good performance of the proposed method is experimentally verified using ultrasonic traces acquired from three specimens of carbon fibre reinforced polymer multi-layered composite materials (CFRP).

• 한국통신학회논문지
• /
• 제38B권2호
• /
• pp.154-161
• /
• 2013

본 논문에서는 IEEE 802.16m WirelessMAN-Advanced 단말에서 SINR(Signal to Interference Plus Noise Ratio)을 측정하는 방법을 설명하고, 이를 구현 및 시험한 결과에 대해 기술하였다. IEEE 802.16m규격의 하향링크는 두 가지의 A-Preamble인 PA-preamble과 SA-preamble을 포함하는데, 이들을 이용하여 SINR을 측정하였다. 본 논문은 PA-preamble로부터 잡음전력을 구하고, SA-preamble을 이용해 신호전력과 간섭전력을 구하는 방법에 대해 설명하고 이 값들로부터 SINR값을 계산하는 과정을 설명한다. 특히 수신 신호와의 시간동기 오차로 인한 부반송파의 위상회전 영향을 해결하는 방법과 구현과정에서 고려해야하는 사항들에 대해 설명하고 전산 실험 및 하드웨어로 구현된 시험 결과에 대해 기술한다. 구현 결과물인 SINR 측정기는 ETRI가 구현한 IEEE 802.16m 시스템의 단말에 탑재되어 AMC(Adaptive Modulation and Coding) 적용 및 핸드오버의 판단 근거를 제공하며, 전산 실험과 시스템 시험에서도 우수한 측정 성능을 확인할 수 있었다.

• 방송공학회논문지
• /
• 제11권4호
• /
• pp.407-419
• /
• 2006

본 논문은 다시점 동영상 부호화를 위한 적응적인 조명변화 보상 방법을 제안한다. 다시점 비디오에서 카메라의 위치에 따라 조명의 차이가 발생할 수 있으며, 여러 대의 카메라가 물리적으로 완전히 동일한 특성을 가지도록 조정되지 못하여 각 카메라에서 촬영된 영상 간에 미세한 차이가 발생할 수 있다. 이러한 특성은 인접한 위치의 카메라로부터 획득된 영상을 참조하여 부호화하는 다시점 비디오 부호화의 성능을 저하시키는 요인이 된다. 제안하는 조명변화 보상 방법을 통하여 다시점 비디오 부호화의 압축 효율을 높일 수 있었으며, 조명변화 보상을 수행하지 않는 다시점 비디오 부호화와 비교하여 PSNR(Peak Signal-to-Noise Ratio)이 약 $0.1{\sim}0.6dB$ 정도 향상되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권7호
• /
• pp.3050-3065
• /
• 2016

Neural networks (NNs) are extensively used in applications requiring signal classification and regression analysis. In this paper, a NN based threshold selection algorithm for 60 GHz millimeter wave (MMW) time of arrival (TOA) estimation using an energy detector (ED) is proposed which is based on the skewness, kurtosis, and curl of the received energy block values. The best normalized threshold for a given signal-to-noise ratio (SNR) is determined, and the influence of the integration period and channel on the performance is investigated. Results are presented which show that the proposed NN based algorithm provides superior precision and better robustness than other ED based algorithms over a wide range of SNR values. Further, it is independent of the integration period and channel model.