• Title, Summary, Keyword: sub-Nyquist sampling

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Cooperative Spectrum Sensing Utilizing Sub-Nyquist Sampling in Cognitive Radio Networks (인지 무선 네트워크에서 Sub-Nyquist 샘플링을 활용한 협력 스펙트럼 센싱 기법)

  • Jung, Honggyu;Kim, Kwangyul;Shin, Yoan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.7
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    • pp.1234-1238
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    • 2015
  • We propose cooperative spectrum sensing schemes based on sub-Nyquist sampling. As compressed sensing has recently attracted great attention, sparsity order estimation techniques also has been widely investigated. Thus, assuming that the sparsity order of channel occupancy can be obtained, we mathematically analyze the detection performance of sub-Nyquist sampling schemes according to various sampling rates and cooperative spectrum sensing schemes. Simulation results verify the performance of the proposed schemes.

Sub-Nyquist Nonuniform Sampling and Perfect Reconstruction of Speech Signals (음성신호의 Sub-Nyquist 비균일 표준화 및 완전 복구에 관한 연구)

  • Lee, He-Young
    • Speech Sciences
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    • v.12 no.2
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    • pp.153-170
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    • 2005
  • The sub-Nyquist nonuniform sampling (SNNS) and the perfect reconstruction (PR) formula are proposed for the development of a systematic method to obtain minimal representation of a speech signal. In the proposed method, the instantaneous sampling frequency (ISF) varies, depending on the least upper boundary of spectral support of a speech signal in time-frequency domain (TFD). The definition of the instantaneous bandwidth (IB), which determines the ISF and is used for generating the set of samples that represent continuous-time signals perfectly, is given. Also, the spectral characteristics of the sampled data generated by the sub-Nyquist nonuniform sampling method is analyzed. The proposed method doesn't generate the redundant samples due to the time-varying property of the instantaneous bandwidth of a speech signal.

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Perfect Reconstruction in Sub-Nyquist Nonuniform Sampling of Signals with Known upper Time-frequency Boundary (비 균일 표본화 신호의 완전 복구에 관한 연구)

  • 이희영;정현권
    • Proceedings of the IEEK Conference
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    • pp.9-12
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    • 2002
  • The problem of sub-Nyquist nonuniform sampling for the perfect reconstruction of signals with time-varying spectral contents is studied. The signals are assumed to have a known instantaneous bandwidth in time-frequency domain. As the function of time, the nonuniform sampling pattern of a given signal, that is, the instantaneous sampling frequency is determined by the observation of instantaneous bandwidth based on time-frequency analysis. The proposed sampling pattern guarantees the perfect reconstruction of nonuniform sampled signals under Nyquist-sampling rate in average.

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Low-Sampling Rate UWB Channel Characterization and Synchronization

  • Maravic, Irena;Kusuma, Julius;Vetterli, Martin
    • Journal of Communications and Networks
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    • v.5 no.4
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    • pp.319-327
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    • 2003
  • We consider the problem of low-sampling rate high-resolution channel estimation and timing for digital ultrawideband (UWB) receivers. We extend some of our recent results in sampling of certain classes of parametric non-bandlimited signals and develop a frequency domain method for channel estimation and synchronization in ultra-wideband systems, which uses sub-Nyquist uniform sampling and well-studied computational procedures. In particular, the proposed method can be used for identification of more realistic channel models, where different propagation paths undergo different frequency-selective fading. Moreover, we show that it is possible to obtain high-resolution estimates of all relevant channel parameters by sampling a received signal below the traditional Nyquist rate. Our approach leads to faster acquisition compared to current digital solutions, allows for slower A/D converters, and potentially reduces power consumption of digital UWB receivers significantly.

A 1.8V 50-MS/s 10-bit 0.18-um CMOS Pipelined ADC without SHA

  • Uh, Ji-Hun;Kim, Won-Myung;Kim, Sang-Hun;Jang, Young-Chan
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.143-146
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    • 2011
  • A 50-MS/s 10-bit pipelined ADC with 1.2Vpp differential input range is proposed in this paper. The designed pipelined ADC consists of eight stage of 1.5bit/stage, one stage of 2bit/stage, digital error correction block, bias & reference driver, and clock generator. 1.5bit/stage is consists of sub-ADC, DAC and gain stage, Specially, a sample-and hold amplifier (SHA) is removed in the designed pipelined ADC to reduce the hardware and power consumption. Also, the proposed bootstrapped switch improves the Linearity of the input analog switch and the dynamic performance of the total ADC. The reference voltage was driven by using the on-chip reference driver without external reference. The proposed pipelined ADC was designed by using a 0.18um 1-poly 5-metal CMOS process with 1.8V supply. The total area including the power decoupling capacitor and power consumption are $0.95mm^2$ and 60mW, respectively. Also, the simulation result shows the ENOB of 9.3-bit at the Nyquist sampling rate.

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Front-End Design for Underwater Communication System with 25 kHz Carrier Frequency and 5 kHz Symbol Rate (25kHz 반송파와 5kHz 심볼율을 갖는 수중통신 수신기용 전단부 설계)

  • Kim, Seung-Geun;Yun, Chang-Ho;Park, Jin-Young;Kim, Sea-Moon;Park, Jong-Won;Lim, Young-Kon
    • Journal of Ocean Engineering and Technology
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    • v.24 no.1
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    • pp.166-171
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    • 2010
  • In this paper, the front-end of a digital receiver with a 25 kHz carrier frequency, 5 kHz symbol rate, and any excess-bandwidth is designed using two basic facts. The first is known as the uniform sampling theorem, which states that the sampled sequence might not suffer from aliasing even if its sampling rate is lower than the Nyquist sampling rate if the analog signal is a bandpass one. The other fact is that if the sampling rate is 4 times the center frequency of the sampled sequence, the front-end processing complexity can be dramatically reduced due to the half of the sampled sequence to be multiplied by zero in the demixing process. Furthermore, the designed front-end is simplified by introducing sub-filters and sub-sampling sequences. The designed front-end is composed of an A/D converter, which takes samples of a bandpass filtered signal at a 20 kHz rate; a serial-to-parallel converter, which converts a sampled bandpass sequence to 4 parallel sub-sample sequences; 4 sub-filter blocks, which act as a frequency shifter and lowpass filter for a complex sequence; 4 synchronized switches; and 2 adders. The designed front-end dramatically reduces the computational complexity by more than 50% for frequency shifting and lowpass filtering operations since a conventional front-end requires a frequency shifting and two lowpass filtering operations to get one lowpass complex sample, while the proposed front-end requires only four filtering operation to get four lowpass complex samples, which is equivalent to one filtering operation for one sample.

Quickest Spectrum Sensing Approaches for Wideband Cognitive Radio Based On STFT and CS

  • Zhao, Qi;Qiu, Wei;Zhang, Boxue;Wang, Bingqian
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.3
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    • pp.1199-1212
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    • 2019
  • This paper proposes two wideband spectrum sensing approaches: (i) method A, the cumulative sum (CUSUM) algorithm with short-time Fourier transform, taking advantage of the time-frequency analysis for wideband spectrum. (ii)method B, the quickest spectrum sensing with short-time Fourier transform and compressed sensing, shortening the time of perception and improving the speed of spectrum access or exit. Moreover, method B can take advantage of the sparsity of wideband signals, sampling in the sub-Nyquist rate, and it is more suitable for wideband spectrum sensing. Simulation results show that method A significantly outperforms the single serial CUSUM detection for small SNRs, while method B is substantially better than the block detection based spectrum sensing in small probability of the false alarm.

Performance Analysis of Compressed Sensing Given Insufficient Random Measurements

  • Rateb, Ahmad M.;Syed-Yusof, Sharifah Kamilah
    • ETRI Journal
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    • v.35 no.2
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    • pp.200-206
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    • 2013
  • Most of the literature on compressed sensing has not paid enough attention to scenarios in which the number of acquired measurements is insufficient to satisfy minimal exact reconstruction requirements. In practice, encountering such scenarios is highly likely, either intentionally or unintentionally, that is, due to high sensing cost or to the lack of knowledge of signal properties. We analyze signal reconstruction performance in this setting. The main result is an expression of the reconstruction error as a function of the number of acquired measurements.

A Calibration-Free 14b 70MS/s 0.13um CMOS Pipeline A/D Converter with High-Matching 3-D Symmetric Capacitors (높은 정확도의 3차원 대칭 커패시터를 가진 보정기법을 사용하지 않는 14비트 70MS/s 0.13um CMOS 파이프라인 A/D 변환기)

  • Moon, Kyoung-Jun;Lee, Kyung-Hoon;Lee, Seung-Hoon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.43 no.12
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    • pp.55-64
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    • 2006
  • This work proposes a calibration-free 14b 70MS/s 0.13um CMOS ADC for high-performance integrated systems such as WLAN and high-definition video systems simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs signal insensitive 3-D fully symmetric layout techniques in two MDACs for high matching accuracy without any calibration. A three-stage pipeline architecture minimizes power consumption and chip area at the target resolution and sampling rate. The input SHA with a controlled trans-conductance ratio of two amplifier stages simultaneously achieves high gain and high phase margin with gate-bootstrapped sampling switches for 14b input accuracy at the Nyquist frequency. A back-end sub-ranging flash ADC with open-loop offset cancellation and interpolation achieves 6b accuracy at 70MS/s. Low-noise current and voltage references are employed on chip with optional off-chip reference voltages. The prototype ADC implemented in a 0.13um CMOS is based on a 0.35um minimum channel length for 2.5V applications. The measured DNL and INL are within 0.65LSB and l.80LSB, respectively. The prototype ADC shows maximum SNDR and SFDR of 66dB and 81dB and a power consumption of 235mW at 70MS/s. The active die area is $3.3mm^2$.

Compressive Sensing Recovery of Natural Images Using Smooth Residual Error Regularization (평활 잔차 오류 정규화를 통한 자연 영상의 압축센싱 복원)

  • Trinh, Chien Van;Dinh, Khanh Quoc;Nguyen, Viet Anh;Park, Younghyeon;Jeon, Byeungwoo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.6
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    • pp.209-220
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    • 2014
  • Compressive Sensing (CS) is a new signal acquisition paradigm which enables sampling under Nyquist rate for a special kind of signal called sparse signal. There are plenty of CS recovery methods but their performance are still challenging, especially at a low sub-rate. For CS recovery of natural images, regularizations exploiting some prior information can be used in order to enhance CS performance. In this context, this paper addresses improving quality of reconstructed natural images based on Dantzig selector and smooth filters (i.e., Gaussian filter and nonlocal means filter) to generate a new regularization called smooth residual error regularization. Moreover, total variation has been proved for its success in preserving edge objects and boundary of reconstructed images. Therefore, effectiveness of the proposed regularization is verified by experimenting it using augmented Lagrangian total variation minimization. This framework is considered as a new CS recovery seeking smoothness in residual images. Experimental results demonstrate significant improvement of the proposed framework over some other CS recoveries both in subjective and objective qualities. In the best case, our algorithm gains up to 9.14 dB compared with the CS recovery using Bayesian framework.