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Gerhard Fettweis - One of the best experts on this subject based on the ideXlab platform.

  • low complexity gfdm receiver based on sparse Frequency Domain Processing
    Vehicular Technology Conference, 2013
    Co-Authors: Ivan Gaspar, Nicola Michailow, Ainoa Navarro, Eckhard Ohlmer, Stefan Krone, Gerhard Fettweis
    Abstract:

    Generalized Frequency division multiplexing (GFDM) is a multi-carrier modulation scheme. In contrast to the traditional orthogonal Frequency division multiplexing (OFDM), it can benefit from transmitting multiple symbols per sub-carrier. GFDM targets block based transmission which is enabled by circular pulse shaping of the individual sub- carriers. In this paper we propose a low complexity design for demodulating GFDM signals based on a sparse representation of the pulse-shaping filter in Frequency Domain. The proposed scheme is compared to receiver concepts from previous work and the performance is assessed in terms of bit error rates for AWGN and Rayleigh multipath fading channels. The results show, that for high-order QAM signaling, the error performance can be significantly improved with interference cancellation at reasonable computational cost.

  • VTC Spring - Low Complexity GFDM Receiver Based on Sparse Frequency Domain Processing
    2013 IEEE 77th Vehicular Technology Conference (VTC Spring), 2013
    Co-Authors: Ivan Gaspar, Nicola Michailow, Ainoa Navarro, Eckhard Ohlmer, Stefan Krone, Gerhard Fettweis
    Abstract:

    Generalized Frequency division multiplexing (GFDM) is a multi-carrier modulation scheme. In contrast to the traditional orthogonal Frequency division multiplexing (OFDM), it can benefit from transmitting multiple symbols per sub-carrier. GFDM targets block based transmission which is enabled by circular pulse shaping of the individual sub- carriers. In this paper we propose a low complexity design for demodulating GFDM signals based on a sparse representation of the pulse-shaping filter in Frequency Domain. The proposed scheme is compared to receiver concepts from previous work and the performance is assessed in terms of bit error rates for AWGN and Rayleigh multipath fading channels. The results show, that for high-order QAM signaling, the error performance can be significantly improved with interference cancellation at reasonable computational cost.

  • Comparison of Time and Frequency Domain Processing of a Multi‐Carrier Spread‐Spectrum System
    European Transactions on Telecommunications, 2000
    Co-Authors: J. Kuhne, A. Nahler, Gerhard Fettweis
    Abstract:

    Multi-carrier spread-spectrum (MC-SS) modulation is a new kind of spread-spectrum modulation[1],[2]. The spreading code is designed in the Frequency Domain. Hence, the system is dual to a direct-sequence spread-system (DS-SS) where the spreading code is given in the time Domain. There exist two different views: the OFDM view and the DS-SS view. Many publications deal with the Frequency Domain Processing. Transmitter and receiver structures are similar to OFDM. Therefore all these implementations use a guard interval to avoid ISI. The disadvantage of this guard interval is the higher hardware complexity and the waste of symbol energy. In the following paper the effect of ISI on a MC-SS system is investigated. Both types of implementation (time or Frequency Domain) are compared and the dependencies of the performance from the spreading code are demonstrated. It is shown that with proper code selection and a time Domain implementation without guard interval (RAKE receiver) it is possible to outperform equivalent Frequency Domain receivers with guard interval (MRC).

R Niederjohn - One of the best experts on this subject based on the ideXlab platform.

  • ICASSP - An investigation of several Frequency-Domain Processing methods for enhancing the intelligibility of speech in wideband random noise
    ICASSP '78. IEEE International Conference on Acoustics Speech and Signal Processing, 1
    Co-Authors: R Curtis, R Niederjohn
    Abstract:

    This paper describes results of a study of several Frequency-Domain Processing methods for enhancing the intelligibility of speech in wideband random noise. Five categories of Processing methods are explored. These include the INTEL technique, a technique based upon minimum mean square filtering, several techniques based upon subtraction of the estimated spectrum of the noise from the spectrum of the speech plus noise, spectrum squaring, and techniques based upon pitch Frequency analysis. The results of this study have provided considerable insight into the individual Processing methods and into the use of Frequency-Domain Processing methods in general. A major conclusion of this work is that all successful techniques investigated are similar in that they are an attempt to emphasize spectral components as a function of the amount by which they exceed the noise. A second conclusion is that unless the spectral weighting within a time-window is relatively smooth, it will introduce conspicuous background distortion.

Jurgen Peissig - One of the best experts on this subject based on the ideXlab platform.

  • Frequency Domain Processing for synchronization and channel estimation in oqam ofdm systems
    International Workshop on Signal Processing Advances in Wireless Communications, 2013
    Co-Authors: Christoph Thein, Martin Fuhrwerk, Jurgen Peissig
    Abstract:

    In this work the design of a Frequency-Domain synchronization and channel estimation scheme for OQAM-OFDM systems is presented and evaluated. The need for signal Processing schemes for wireless communication systems, that are processed solely in the Frequency Domain results from the desire to build Frequency-agile radios. Driven by the transition from exclusive spectrum resource allocation towards a dynamic usage of the spectrum a non-contiguous spectrum utilization in fragmented spectrum is needed. Well-known time-Domain algorithms severely suffer from encapsulated spectral components not belonging to the non-contiguous OQAM-OFDM waveform. We show that Frequency-Domain Processing can achieve similar system performance as comparable time-Domain methods over a wide range of Frequency offsets while offering a new degree of freedom in preamble design for FBMC systems.

  • SPAWC - Frequency-Domain Processing for synchronization and channel estimation in OQAM-OFDM systems
    2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2013
    Co-Authors: Christoph Thein, Martin Fuhrwerk, Jurgen Peissig
    Abstract:

    In this work the design of a Frequency-Domain synchronization and channel estimation scheme for OQAM-OFDM systems is presented and evaluated. The need for signal Processing schemes for wireless communication systems, that are processed solely in the Frequency Domain results from the desire to build Frequency-agile radios. Driven by the transition from exclusive spectrum resource allocation towards a dynamic usage of the spectrum a non-contiguous spectrum utilization in fragmented spectrum is needed. Well-known time-Domain algorithms severely suffer from encapsulated spectral components not belonging to the non-contiguous OQAM-OFDM waveform. We show that Frequency-Domain Processing can achieve similar system performance as comparable time-Domain methods over a wide range of Frequency offsets while offering a new degree of freedom in preamble design for FBMC systems.

  • practical spectrum sensing with Frequency Domain Processing in cognitive radio
    European Signal Processing Conference, 2012
    Co-Authors: Hanwen Cao, Jurgen Peissig
    Abstract:

    The imperfections of practical receivers such as nonwhite noise floor, noise power uncertainty and spurs normally have large influence on the performance and stability of spectrum sensing. However, in most of the literatures about spectrum sensing, part of or all of theses imperfections are ignored and only addictive white Gaussian noise (AWGN) is assumed in many cases. In this paper, two spectrum sensing algorithms are proposed using Frequency-Domain Processing. The first one is a blind detection and the second one takes the known power spectrum density (PSD) of the target signal as a template. Analysis and simulations show that they are equivalent or similar to some reported spectrum sensing algorithms. The advantage of the proposed ones is that the imperfections can be easily mitigated at nearly no cost of extra complexities, which makes it more feasible to low-cost implementations.

  • EUSIPCO - Practical spectrum sensing with Frequency-Domain Processing in cognitive radio
    2012
    Co-Authors: Hanwen Cao, Jurgen Peissig
    Abstract:

    The imperfections of practical receivers such as nonwhite noise floor, noise power uncertainty and spurs normally have large influence on the performance and stability of spectrum sensing. However, in most of the literatures about spectrum sensing, part of or all of theses imperfections are ignored and only addictive white Gaussian noise (AWGN) is assumed in many cases. In this paper, two spectrum sensing algorithms are proposed using Frequency-Domain Processing. The first one is a blind detection and the second one takes the known power spectrum density (PSD) of the target signal as a template. Analysis and simulations show that they are equivalent or similar to some reported spectrum sensing algorithms. The advantage of the proposed ones is that the imperfections can be easily mitigated at nearly no cost of extra complexities, which makes it more feasible to low-cost implementations.

R Curtis - One of the best experts on this subject based on the ideXlab platform.

  • ICASSP - An investigation of several Frequency-Domain Processing methods for enhancing the intelligibility of speech in wideband random noise
    ICASSP '78. IEEE International Conference on Acoustics Speech and Signal Processing, 1
    Co-Authors: R Curtis, R Niederjohn
    Abstract:

    This paper describes results of a study of several Frequency-Domain Processing methods for enhancing the intelligibility of speech in wideband random noise. Five categories of Processing methods are explored. These include the INTEL technique, a technique based upon minimum mean square filtering, several techniques based upon subtraction of the estimated spectrum of the noise from the spectrum of the speech plus noise, spectrum squaring, and techniques based upon pitch Frequency analysis. The results of this study have provided considerable insight into the individual Processing methods and into the use of Frequency-Domain Processing methods in general. A major conclusion of this work is that all successful techniques investigated are similar in that they are an attempt to emphasize spectral components as a function of the amount by which they exceed the noise. A second conclusion is that unless the spectral weighting within a time-window is relatively smooth, it will introduce conspicuous background distortion.

Fang Zhu - One of the best experts on this subject based on the ideXlab platform.

  • direct sequence spreading uwb systems Frequency Domain Processing for enhanced performance and throughput
    International Conference on Communications, 2003
    Co-Authors: C R Nassar, Fang Zhu
    Abstract:

    In this work, we propose an innovative high performance, high throughput direct sequence spreading (DSS) ultra wideband (UWB) system. Our proposed system employs a novel multi-carrier pulse waveform at the UWB transmit side: At the receiver side, the received DSS UWB pulse is decomposed into its subcarriers and recombined to (1) exploit diversity in the Frequency Domain and (2) provide resistance to inter symbol interference (ISI) and/or multi-access interference (MAI). As a direct result, the proposed Frequency-based UWB DSS system is shown to significantly outperform time-based DSS UWB systems, offering significant gain in throughput (up to 32 fold) without performance degradation, or, alternatively, avoiding error floors due to MAI that limit the performance of time-based systems.

  • Performance comparison of Frequency Domain Processing and time Domain Processing in ultra wideband links
    The 2002 45th Midwest Symposium on Circuits and Systems 2002. MWSCAS-2002., 1
    Co-Authors: Fang Zhu, Carl R. Nassar
    Abstract:

    Ultra-Wideband (UWB) systems are considered excellent candidates for future-generation short-range, high-throughput wireless communications. Today, UWB transmit strategies include equally-spaced pulse positioning, time-hopping, and direct-sequence spreading. In this work, we begin by comparing the BER performance of all three UWB architectures in multi-path fading channels. We then propose a multi-carrier pulse waveform (named the Carrier Interferometry (CI) waveform) for UWB systems: When employing the Cl waveform at the transmitter, UWB receivers utilize a Frequency-Domain Processing to exploit available Frequency diversity gains (improving both performances and throughput). We compare the BER performance of equally-spaced pulse positioning, time-hopping, and direct sequence spreading UWB systems using traditional time-Domain and the proposed Frequency-Domain Processing. Simulation results suggest that Frequency-Domain Processing in UWB systems leads to very significant gains in performance and/or throughput relative to time-Domain Processing.

  • Ultra wideband time hopping systems: performance and throughput enhancement via Frequency Domain Processing
    Conference Record of the Thirty-Sixth Asilomar Conference on Signals Systems and Computers 2002., 1
    Co-Authors: Fang Zhu, Carl R. Nassar
    Abstract:

    In this work, the authors introduce a high performance, high throughput ultrawideband (UWB) time hopping system based on a multicarrier pulse waveform. Specifically, the authors propose the multicarrier UWB waveform referred to as the carrier interferometry (CI) waveform: the CI waveform corresponds to the superpositioning of N orthogonal subcarriers. At the receiver side, the received UWB pulse is decomposed into its subcarriers and recombined to exploit diversity in the Frequency Domain. The receiver's Frequency Domain Processing also provides resistance to inter symbol interference. As a result, the proposed Frequency-based time-hopping UWB system is shown to support increased throughputs and higher performances when compared to traditional time-based UWB time hopping.

  • High performance ultra-wide bandwidth systems via novel pulse shaping and Frequency Domain Processing
    2002 IEEE Conference on Ultra Wideband Systems and Technologies (IEEE Cat. No.02EX580), 1
    Co-Authors: Fang Zhu, Carl R. Nassar
    Abstract:

    Ultra-wide bandwidth (UWB) systems have emerged as a strong candidate for high-throughput short range wireless communications. Because of the UWB systems' fine time resolution properties, a large path diversity gain can be exploited. However, to exploit this path diversity gain while avoiding inter symbol interference between data bits, the repetition period of data-modulated pulses must be larger than the time delay spread of multipath fading channels. This significantly reduces the throughput of UWB systems (making it spectrally inefficient, e.g., 0.05 b/s/Hz). If a larger throughput is desired (e.g.. a throughput requiring information-bearing pulses separated by less than the time delay spread), the BER performance degrades rapidly. In this work, we propose a novel pulse waveform referred to as the carrier interferometry (CI) pulse waveform for use in UWB systems: CI supports significant increases fit throughput with negligible performance loss. Specifically, the CI pulse waveform corresponds to the superpositioning of N orthogonal subcarriers. At the receiver side, the received pulse is decomposed into its subcarriers and recombined to exploit diversity in the Frequency Domain. This Frequency Domain Processing provides resistance to inter symbol interference (from data-modulated pulses positioned within the delay spread of the channel). As a direct result, much higher throughput is supported with small performance loss when CI pulse waveforms are employed. Simulation results over indoor channels confirm that the novel CI-UWB system is capable of significantly outperforming current UWB systems: at a fixed BER performance level of 10/sup -3/, the proposed system can provide up to 64 times the data rate of current time Domain UWB systems.

  • ICC - Direct sequence spreading UWB systems: Frequency Domain Processing for enhanced performance and throughput
    IEEE International Conference on Communications 2003. ICC '03., 1
    Co-Authors: Carl R. Nassar, Fang Zhu
    Abstract:

    In this work, we propose an innovative high performance, high throughput direct sequence spreading (DSS) ultra wideband (UWB) system. Our proposed system employs a novel multi-carrier pulse waveform at the UWB transmit side: At the receiver side, the received DSS UWB pulse is decomposed into its subcarriers and recombined to (1) exploit diversity in the Frequency Domain and (2) provide resistance to inter symbol interference (ISI) and/or multi-access interference (MAI). As a direct result, the proposed Frequency-based UWB DSS system is shown to significantly outperform time-based DSS UWB systems, offering significant gain in throughput (up to 32 fold) without performance degradation, or, alternatively, avoiding error floors due to MAI that limit the performance of time-based systems.