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  • 51.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    An application of the singular value decomposition to OFDM channel estimation1996In: Proceedings of the 1996 SNRV and NUTEK Conference on Radio Sciences and Telecommunications in Luleå and Kiruna June 3-6, 1996: RVK 96 / [ed] Lars H. Zetterberg, Luleå: Luleå tekniska universitet, 1996, p. 678-682Conference paper (Refereed)
    Abstract [en]

    A new approach to low-complexity channel estimation in orthogonal-frequency division multiplexing (OFDM) systems is described. A low-rank approximation is applied to a linear minimum mean-squared error (LMMSE) estimator that uses the frequency correlation of the channel. By using the singular-value decomposition (SVD) an optimal low-rank estimator is derived, where performance is essentially preserved - even for low computational complexities. A fixed estimator, with nominal values for channel correlation and signal-to-noise ratio (SNR), is analysed. Analytical mean-squared error (MSE) and symbol-error rates (SER) are presented for a 16-QAM OFDM system.

  • 52.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Analysis of DFT-based channel estimators for OFDM1996Report (Other academic)
    Abstract [en]

    In this paper we analyze the performance of three low-complexity channel estimators, based on the discrete Fourier-transform (DFT), for orthogonal frequency-division multiplexing (OFDM) systems. Estimators of this type have been analyzed for discrete-time channels, and we extend this analysis to continuous-time channels. We present analytical expressions for their mean-squared error (MSE) and evaluate their complexity versus symbol-error rate (SER) for 16-QAM. The analysis shows that this type of estimators may experience an irreducible error floor at high SNRs. However, in one of the three estimators the error floor can be eliminated while the complexity stays low and the performance is maximized.

  • 53.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    OFDM channel estimation by singular value decomposition1996In: Mobile technology for the human race: 1996 IEEE 46th Vehicular Technology Conference, Atlanta, Georgia, USA, April 28 - May 1, 1996 / [ed] Jim Worsham, Piscataway, NJ: IEEE Communications Society, 1996, p. 923-927Conference paper (Refereed)
    Abstract [en]

    A new approach to low-complexity channel estimation in orthogonal-frequency division multiplexing (OFDM) systems is proposed. A low-rank approximation is applied to a linear minimum mean-squared error (LMMSE) estimator that uses the frequency correlation of the channel. By using the singular-value decomposition (SVD) an optimal low-rank estimator is derived, where performance is essentially preserved - even for low computational complexities. A fixed estimator, with nominal values for channel correlation and signal-to-noise ratio (SNR), is analysed. Analytical mean-squared error (MSE) and symbol-error rates (SER) are presented for a 16-QAM OFDM system.

  • 54.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    OFDM channel estimation by singular value decomposition1996Report (Other academic)
    Abstract [en]

    In this report we present and analyse low-rank channel estimators for orthogonal frequency-division multiplexing (OFDM) using the frequency correlation of the channel. Low-rank approximations based on the discrete Fourier transform (DFT) have been proposed but they suffer from poor performance when the channel is not sample-spaced. We apply the theory of optimal rank-reduction to linear minimum mean-squared error (LMMSE) estimators and show that these estimators, when using a fixed design, are robust to changes in channel correlation and signal-to-noise ratio (SNR). The performance is presented in terms of uncoded symbol-error rate (SER) for a system using 16-QAM.

  • 55.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per-Ola
    Luleå tekniska universitet.
    OFDM channel estimation by singular value decomposition1998In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 46, no 7, p. 931-939Article in journal (Refereed)
  • 56.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Landström, Daniel
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    An introduction to orthogonal frequency-division multiplexing1997Report (Other academic)
    Abstract [en]

    This report is an introduction to orthogonal frequency-division multiplexing (OFDM). The focus is on signal processing areas pursued by our research group at Luleå University of Technology. We present an historical background and some frequently used system models. Typical areas of applications are also described, both wireless and wired. In addition to the general overview, the addressed areas include synchronization, channel estimation and channel coding. Both time and frequency synchronization are described, and the effects of synchronization errors are presented. Different types of channel estimators are described, where the focus is on low-complexity algorithms, and in this context, advantages and disadvantages of coherent and differential modulation are also discussed. Channel coding is described, both for wireless and wired systems, and pointers are included to evaluation tools and bitloading algorithms. An extensive bibliography is also included.

  • 57.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Landström, Daniel
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    An introduction to orthogonal frequency-division multiplexing1997Report (Other academic)
    Abstract [en]

    This report is an introduction to orthogonal frequency-division multiplexing (OFDM). The focus is on signal processing areas pursued by our research group at Luleå University of Technology. We present an historical background and some frequently used system models. Typical areas of applications are also described, both wireless and wired. In addition to the general overview, the addressed areas include synchronization, channel estimation and channel coding. Both time and frequency synchronization are described, and the effects of synchronization errors are presented. Different types of channel estimators are described, where the focus is on low-complexity algorithms, and in this context, advantages and disadvantages of coherent and differential modulation are also discussed. Channel coding is described, both for wireless and wired systems, and pointers are included to evaluation tools and bitloading algorithms. An extensive bibliography is also included.

  • 58.
    Eriksson, Mats
    et al.
    Arctos Labs Scandinavia AB.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Rural 5G: Oxymoron or Opportunity?2015In: IEEE ComSoc Technology News, no NovemberArticle in journal (Other (popular science, discussion, etc.))
  • 59.
    Gavrilovska, Liljana M.
    et al.
    Ss. Cyril and Methodius University, Skopje.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Xie, Yong
    Huawei Technologies, Chengdu.
    Lidström, Erik
    Huawei Technologies, Stockholm.
    Riihijärvi, Janne
    RWTH Aachen University.
    Mähönen, Petri H.
    RWTH Aachen University.
    Atanasovski, Vladimir M.
    Ss. Cyril and Methodius University, Skopje, Faculty of Electrical Engineering, Ss. Cyril and Mehtodius, Skopje.
    Denkovski, Daniel
    Faculty of Electrical Engineering, Ss. Cyril and Mehtodius, Skopje.
    Rakovic, Valentin
    Faculty of Electrical Engineering, Ss. Cyril and Mehtodius, Skopje.
    Enabling LTE in TVWS with radio environment maps: from an architecture design towards a system level prototype2014In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 53, p. 62-72Article in journal (Refereed)
    Abstract [en]

    This paper reports recent prototyping efforts that show the feasibility of the radio environmental map to enable efficient exploitation of TV white spaces by a cellular LTE system. We describe a flexible REM backend implementation, fully integrated with standard-compliant operational LTE base station equipment. Simulations results indicate that REMs enhance white-space detection by their means to incorporate accurate and local channel propagation information, while experimental laboratory results illustrate the feasibility and performance of transmitter localization capabilities in a REM.

  • 60.
    Idzikowski, Filip
    et al.
    Poznan University of Technology, Faculty of Electronics and Telecommunications.
    Chiaraviglio, Luca
    University of Rome Tor Vergata.
    Liu, William
    Auckland University of Technology.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Future Internet Architectures and Sustainability: An Overview2018Conference paper (Refereed)
    Abstract [en]

    The Internet Protocol (IP) traffic is constantly growing. The annual global IP traffic is estimated to reach 2.3 Zettabyte per year by 2020 according to the recent Cisco forecasts. New Internet infrastructures are required to handle the emerging Big Data. Several pilot initiatives have proposed Future Internet (FI) architectures. We provide an overview of the FI architectures from the perspective of sustainable development.

  • 61.
    Landström, Anders
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Transmitter Localization for 5G mmWave REMs by Stochastic Generalized Triangulation2016In: 23rd International Conference on Telecommunications (ICT 2016), Piscataway, NJ: IEEE Communications Society, 2016, p. 789-793, article id 7500413Conference paper (Refereed)
    Abstract [en]

    Future mobile networks will need new tools to deal with the challenges of emerging technologies. In particular, more flexible networks will require localization of transmitters in the networks. In this work we present a novel method for transmitter localization, suitable for rich multipath mmWave 5G scenarios such as dense urban environments. Our work combines stochastic estimation of Radio Environmental Maps (REMs) with the well known concept of triangulation, generalizing the latter into a method for localization in anisotropic propagation environments. It can be considered a conceptual bridge from classical distance-based triangulation into a generalized version where the propagation environment is taken into account. The result is a highly flexible tool for network planning in general and transmitter localization in particular.

  • 62.
    Landström, Anders
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Simonsson, Arne
    Ericsson Research AB.
    Thurfjell, Magnus
    Ericsson Research AB.
    Ökvist, Peter
    Ericsson Research AB.
    Measurement-Based Stochastical mmWave Channel Modeling2016In: 2016 IEEE Globecom Workshops (GC Wkshps), Piscataway, NJ: IEEE Communications Society, 2016, article id 7848959Conference paper (Refereed)
    Abstract [en]

    Emerging mmWave technology will require newchannel models. Compared to the lower frequency bands,mmWaves will be more reflected and absorbed but less diffracted.Hence, placement of individual physical structures in the en-vironment will affect the propagation much more than before,providing a challenge for channel modeling. At the same time,however, an increasing amount of information about the topologyof the physical environment, in particular for buildings, is madeavailable through better measurement equipment and servicesfor obtaining 3D data. We propose a Monte-Carlo approachfor channel modeling where interactions between mmWaves andthe surrounding small-scale environment can be included, givena stochastic representation. This method is not only suitablefor assessment of basic effects such as material reflection andabsorption, but can also in the future be extended to variousadditional effects such as weather, traffic, foliage, etc. Theframework is verified against 15 GHz measurements from anurban environment, demonstrating how major reflection pathscan be replicated by modeling the closest buildings.IndexTerms

  • 63.
    Landström, Daniel
    et al.
    Luleå tekniska universitet.
    Arenas, Julia Martinez
    Ecole Nationale Supérieure des Télécommunications.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Boucheret, Marie-Laure
    Ecole Nationale Supérieure des Télécommunications.
    Ödling, Per
    Luleå tekniska universitet.
    Time and frequency offset estimation in OFDM systems employing pulse shaping1997In: Bridging the way to the 21st century: 1997 IEEE 6th International Conference on Universal Personal Communications record ; 12 - 16 October 1997, Hotel Del Coronado, San Diego, CA, USA ; conference record, Piscataway, NJ: IEEE Communications Society, 1997, p. 279-283Conference paper (Refereed)
    Abstract [en]

    Time and frequency offset estimation is addressed in an OFDM system that uses a cyclic prefix and pulse shaping. Earlier work has presented a method that avoids the use of pilots by exploiting the inherent correlation in the cyclically extended OFDM symbol. In this paper this technique is extended to include systems with pulse shaping. The joint Maximum Likelihood estimator of time and frequency offsets for such systems is presented and evaluated. An implementable structure of the extended estimator is given. Simulations show that it is possible to maintain the performance when introducing pulse shaping into an OFDM system.

  • 64.
    Landström, Daniel
    et al.
    Department of Electrosciences, Lund Institute of Technology.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Ödling, Per
    Department of Electrosciences, Lund Institute of Technology.
    Börjesson, Per Ola
    Symbol time offset estimation in coherent OFDM systems1999In: IEEE International Conference on Communications: ICC '99, Piscataway, NJ: IEEE Communications Society, 1999, Vol. 1, p. 500-505Conference paper (Refereed)
    Abstract [en]

    This paper presents a symbol time offset estimator for coherent OFDM systems. This estimator exploits both the redundancy in the cyclic prefix and the pilot symbols used for channel estimation. The estimator is robust against frequency offsets and is suitable for use in dispersive channels. We base the estimator on the ML estimator for the AWGN channel. Simulations of an example system indicate a system performance as close as 0.3 dB to a perfectly synchronized system. Compared to an estimator not using pilots, our estimator's performance could allow a shorter cyclic prefix and thus a more spectrally efficient system

  • 65.
    Landström, Daniel
    et al.
    Department of Electrosciences, Lund Institute of Technology, Luleå tekniska universitet, Department of Applied Electronics, Lund University.
    Ödling, Per
    Department of Applied Electronics, Lund University.
    Börjesson, Per Ola
    Lunds universitet, Luleå tekniska universitet, Lund Institute of Technology, Department of Applied Electronics.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Uplink OFDM synchronization of future multiuser radio systems1999In: Proceedings of radiovetenskap och kommunikation: Karlskrona 14-17 juni 1999 / RVK 99 / [ed] Jan-Olof Gustafsson, Karlskrona: Högskolan i Karlskrona/Ronneby , 1999Conference paper (Refereed)
  • 66.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Novel Transmitter Architecture for Spectrally-Precoded OFDM2018In: IEEE Transactions on Circuits and Systems Part 1: Regular Papers, ISSN 1549-8328, E-ISSN 1558-0806, Vol. 65, no 8, p. 2592-2605Article in journal (Refereed)
    Abstract [en]

    Frequency nulling spectral precoding is an approachthat suppresses the out-of-band emission in OFDM systems.In this paper, we discuss the transmitter architecture of thespectrally precoded OFDM systems. We design a novel precoderthat matches the practical implementation of the OFDM modulator.We show that spectral precoding can relax the analog lowpass filtering requirements of the OFDM system transmitter. Weexamine the effect of spectral precoding on the PAPR as wellas the effect of the PA on the spectral precoding suppressionperformance. We also study the compliance of the spectrallyprecoded OFDM transmitter with the 3GPP standardizationmeasures and analyze its computation complexity. At the receiverside, we analyze the in-band interference and BER performanceof the suggested precoding approach.

  • 67.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An analysis of out-of-band emission and in-band interference for precoded and classical OFDM systems2015In: European Wireless 2015: 21th European Wireless Conference, 20-22 May 2015, Budapest, Hungary, Piscataway, NJ: IEEE Communications Society, 2015, article id 7147703Conference paper (Refereed)
    Abstract [en]

    In this paper we present analytical expressions for the out-of-band (OOB) emission and in-band interference of two different OOB suppressed OFDM-systems; classical low-pass filtered and precoded. Then, we analytically compare their performance in terms of OOB emission suppression and introduced level of in-band interference. We analyse the fact that the in-band interference introduced by the filter depends on the length of the cyclic prefix as well as the behavior of the channel while that of the precoded OFDM does not. The analysis confirms that edged subcarriers suffer higher in-band interference than central subcarriers. Moreover, frequency precoders, for a specific choice of notching frequencies, can outperform time precoders.

  • 68.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Minimum-EVM N-continuous OFDM2016In: 2016 IEEE International Conference on Communications (ICC): Kuala Lumpur, 22-27 May 2016, Piscataway, NJ: IEEE Communications Society, 2016, article id 7511164Conference paper (Refereed)
    Abstract [en]

    The N-continuous precoder for the suppression ofOOB emission in OFDM systems that minimizes the EVM isintroduced. We show that the minimum in-band interference dueto the introduced precoding approach is 3 dB less than the inbandinterference of existing N-continuous precoders. Moreover,we introduce a novel practical block precoder that approachesthe performance of the suggested optimal precoder. We analyzethe spectrum of the OFDM signal after block precoding, the inbandinterference due to block precoding and the effect of blockprecoding on the BER. The price to pay for block precoding isthe computational complexity that grows linearly with the blocksize.

  • 69.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    N-smooth OFDMIn: Article in journal (Refereed)
    Abstract [en]

    This paper introduces a new multicarrier system - a practical alternative for N-continuous OFDM: N-smooth OFDM. N-smooth OFDM improves the spectral compactness of practical OFDM systems by suppressing OOB emission. The higher spectral compactness of N-smooth OFDM allows the system to relax requirements of the digital to analog converter (DAC) construction filter. Moreover, it decreases the signal's self interference that results from spectral precoding as well as precoder's computational complexity. 

  • 70.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An SDR-based prototype of spectrally-precoded OFDM2017In: EuCNC 2017: European Conference on Networks and Communications, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7980758Conference paper (Refereed)
    Abstract [en]

    Spectrally precoded OFDM is a recent approach that aims for the suppression of the OOB, as well as the in-band gap, emissions in OFDM systems. Theoretically, the technique shows High suppression of the OOB and the in-band gap emissions. Although, practically hardware impairments may limit the precoder's performance. Yet, this demonstration shows that despite the hardware impairments, implemented spectrally precoded OFDM generates emissions tens of decibels less than that of plain OFDM. Therefore, the demonstration proves that communications links are less vulnerable to interference coming from spectrally precoded OFDM signals than to interference coming from plain OFDM signals

  • 71.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Spectrally-Precoded OFDM for 5G Wideband Operation in Fragmented sub-6GHz SpectrumArticle in journal (Refereed)
    Abstract [en]

    We consider spectrally-precoded OFDM waveforms for 5G wideband transmission in sub-6GHz band. In this densely

    packed spectrum, a low out-of-band (OOB) waveform is a critical 5G component to achieve the promised high spectral

    efficiency. By precoding data symbols before OFDM modulation, it is possible to achieve extremely low out-of-band

    emission with very sharp spectrum transition enabling an efficient and flexible usage of frequency resources. Spectrallyprecoded

    OFDM shows promising results for reaching 5G targets in high-data rate enhanced mobile broadband and ultrareliable

    low-latency communications use cases. Spectral precoding is particularly efficient for wideband transmission

    enabling short-time transmission, which will often require flexible fragmented spectrum usage.

  • 72.
    Mohamad, Medhat
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Taheri, Tayebeh
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Subspace-precoded OFDM with low Out-of-Band Emissions:it will workManuscript (preprint) (Other academic)
    Abstract [en]

    Today’s multicarrier transmitters, deployed in essentially all communications radio equipment we use(phones, TV’s, computers, etc.), contain means to avoid undesired out-of-band power emissions. Standards and regulations typically restrict the levels of these emissions in order to allow for an efficient use of the radio spectrum. Radio vendors deploy well-established algorithms such as low-pass filtering or windowing to satisfy these regulations. A new approach, specifically applicable to OFDM systems, known as spectralprecoding, has been studied during the last decade. In particular, subspace precoding has attracted theinterest of academia, for its elegance, and despite a few adamant disadvantages. Recent advances now provide a breakthrough: subspace precoding is now a viable alternative to today’s algorithms.

  • 73.
    Nilsson, Rickard
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Channel Measurements in an Open-pit Mine using USRPs: 5G – Expect the Unexpected2016In: 2016 IEEE Wireless Communications and Networking Conference: WCNC 2016, Doha, Qatar, 3-7  April 2016, 2016, p. 212-217, article id 7564672Conference paper (Refereed)
    Abstract [en]

    In this paper, we describe and analyze the results of a radio channel measurement campaign in an extreme industrial environment; a large open-pit copper mine targeted by next generation’s highly voiced device communications. We present a practical and efficient method to perform robust and high-sensitivity impulse response measurements without a common clock reference using the widely spread USRP hardware. With this technique, we performed channel sounding on a large number of locations within the mine. One important observation is that the radio channel’s impulse response in an open-pit mine can often be more than 10 microseconds long, and much unlike the responses normally associated with Wi-Fi and mobile cellular radio systems, which poses serious design challenges for future 5G radio systems.

  • 74.
    Perotti, Alberto G.
    et al.
    Huawei Technologies Sweden.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems. Huawei Technologies Sweden.
    Popovic, Branislav M.
    Huawei Technologies Sweden.
    Downlink Overloaded Multiple Access Based on Constellation Expansion2015In: 2014 IEEE Globecom Workshops: GC Wkshps 2014, Austin, 8-12 December 2014, Piscataway, Nj: IEEE Communications Society, 2015, p. 977-982Conference paper (Refereed)
    Abstract [en]

    A new overloaded multiple access scheme for the downlink of wireless systems is presented. It performs simultaneous transmission of multiple data streams intended for users experiencing similar signal-to-noise ratios (SNR). The proposed scheme performs stream multiplexing by mapping the coded bits of each stream onto the labels of an expanded constellation according to a time-varying pattern designed for providing the same level of protection against errors to all streams. Using this scheme, multiple data streams can be concurrently transmitted on the same time-frequency resource blocks of OFDMA systems, thus achieving a higher aggregate spectral efficiency and tighter delay constraints.

  • 75.
    Pirinen, Pekka
    et al.
    Oulu University.
    Saarnisaari, Harri
    Oulu University.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Matinmikko-Blue, Marja
    Oulu University.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Latva-aho, Matti
    Oulu University.
    Wireless Connectivity for Remote and Arctic Areas – Food for Thought2019Conference paper (Refereed)
  • 76.
    Pitaval, Renaud-Alexandre
    et al.
    Huawei Technologies Sweden AB.
    Popović, Branislav M.
    Huawei Technologies Sweden AB.
    Van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    N-continuous SC-FDMA and its Polarized Transmission and Reception2017In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 65, no 11, p. 4911-4925Article in journal (Refereed)
    Abstract [en]

    This paper investigates the application of N -continuous spectral projection precoding design to single-carrier frequency-division multiple access (SC-FDMA). It first considers a general orthogonal projection-based precoded system with an improved iterative receiver and analyzes its ultimate performance in an additive white Gaussian noise channel, both in terms of achievable throughput and symbol-error rates. For N -continuous SC-FDMA, the distribution of the symbol errors is very much asymmetric; a few base pulses carry the lion share of the self-induced interference, resulting in a zero throughput. We show that an optimized transmission and reception scheme based on a polarized use of the base pulses can satisfactorily deal with this asymmetry, and the end-to-end throughput can be recovered to be close to optimal. Applying a similar scheme to N -continuous OFDM enables also an improved performance in the high-SNR regime, where the interference effect strikes the most.

  • 77.
    Popović, Branislav M.
    et al.
    Huawei Technologies Sweden.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    User traffic multiplexing on OFDM downlink2004In: Proceedings of the 2004 IEEE International Symposium on Spread Spectrum Techniques and Applications: 30 August - 2 September 2004, Sydney, Australia, Piscataway, NJ: IEEE Communications Society, 2004, p. 429-433Conference paper (Refereed)
    Abstract [en]

    A user traffic multiplexing scheme for the downlink of an OFDM cellular system is proposed and evaluated. The scheme is based on the set of orthogonal time-frequency (T-F) patterns obtained from a generic Costas sequence. An inter-cell interference averaging method, based on randomly variable cyclic time offsetting of the whole set of orthogonal T-F patterns, is also part of the scheme. The time offset is changed for each transmission time interval, according to a cell-specific multi-level pseudo-random sequence. In such a way the inter-cell OFDM interference becomes limited and noise-like, while no resource planning on the system level is required

  • 78.
    Sandell, Magnus
    et al.
    Luleå tekniska universitet.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Timing and frequency synchronization in OFDM systems using the cyclic prefix1995In: Proceedings: 1995 International Symposium on Synchronization, Saalbau, Essen, Germany, December 14-15, 1995 / [ed] Kees A Schouhamer Immink ; A. J. Vinck, Shannon Foundation , 1995, p. 16-19Conference paper (Refereed)
    Abstract [en]

    We present a method for the joint estimation of timing and carrier-frequency offset in Orthogonal frequency-division multiplexing (OFDM) systems. We show that it is possible to generate these estimates without the use of pilots, by exploiting the cyclic prefix of OFDM frames. We derive the joint likelihood function of the offset-parameters given the received data. The performance of the resulting method can be improved considerably by averaging several likelihood functions before the peak detection. Simulations show that even without pilots the frequency estimator is capable of operating in a tracking mode and the timing estimation can be used in an acquisition mode.

  • 79.
    Sun, Guolin
    et al.
    Huawei Technologies Sweden.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A method of signaling precoder information for dynamical spectrum shaping2010In: 2010 6th International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM 2010): Chengdu City, China, 23 - 25 September 2010, Piscataway, NJ: IEEE Communications Society, 2010, article id 5600884Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a method for signalling precoder information in cognitive radio networks employing precoded OFDM. In this way, radio transmitters in said cognitive radio networks change their spectral occupancy from one time to another, characterized by the steps of 1. The network determines a suitable precoder uniquely characterized by a codebook index from a finite codebook of precoders, said codebook being known at both the network-side and by the mobile units. 2. The network informs the relevant mobile units about the precoder to use by broadcasting the codebook index Meanwhile, we propose several measurement based optimization methods for spectrum shaping to determine the suitable precoder from, for instance, a database of interference information, or feedback information from UEs about their current interference and noise environment, then notify the precoder information over a CPC. We could use a codebook of precoders each being designed for a certain radio scenario, this precoder jointly considering noise level and frequency band. We could use a codebook with precoders forcing the OFDM signal to be N-continuous and where said codebook index is directly related to the continuity order N. We also could use a codebook with precoders forcing the spectrum of the OFDM signal to be zero at pre-defined frequencies f 0...f M, and where said codebook index is directly related to the said frequencies. f 0...f M.

  • 80.
    Sun, Guolin
    et al.
    Huawei Technologies Sweden.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Simple distributed interference source localization for radio environment mapping2010In: 2010 IFIP Wireless Days (WD 2010): Venice, Italy, 20 - 22 October 2010, IEEE Communications Society, 2010, article id 5657755Conference paper (Refereed)
    Abstract [en]

    In order to construct a radio environmental map that can help navigating secondary communication in TV bands, we present a new method of interference source localization for cognitive radio networks. Our low-cost, high-precision localization method, operates without any prior knowledge of the interference source other than transmitter power. It can be divided into two steps: an estimation step at each sensor based on classical methods to estimate the angle of arrival and the received signal power, followed by an SNR-aided fusion. Simulation results show that tens of sensor nodes each having two antennas in a large-scale area setting are enough to achieve accurate location. The proposed location method is practical, economic and essential for blind interference source localization in cognitive radio networks

  • 81.
    Taheri, Tayebeh
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Mohamad, Medhat
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Joint spectral-spatial precoders in massive-MIMO OFDM transmittersIn: Article in journal (Refereed)
    Abstract [en]

    In this paper we propose novel joint spectral-spatial precoders for large-antennaOFDM systems that suppress both spatial multi-user interference and spectral out-ofbandpower emissions. We analyse the performance of the proposed precoder in termsof spectral characteristics, system sum-rate and transmitter complexity. We show inparticular that, interestingly, the proposed joint maximum-ratio precoder has a simpletransmitter structure of two separate and consecutive banks of spectral and spatialprecoders.

  • 82.
    Taheri, Tayebeh
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Asymmetric Transmit-windowing for low-latency and robust OFDM2016In: Globecom Workshops (GC Wkshps), 2016 IEEE, Piscataway, NJ: IEEE Communications Society, 2016, article id 7848842Conference paper (Refereed)
    Abstract [en]

    In the content of low-latency 5G systems we revisit in this paper the question of shortening the cyclic prefix in windowed OFDM system without sacrificing OOB power emissions or increasing the ISI and ICI. Based on interference power analysis we propose a new asymmetric window which provides 30 percent cyclic prefix length reduction without increasing adjacent-channel interference power or channel-induced ISI/ICI.

  • 83.
    Taheri, Tayebeh
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Quasi-Cyclic Symbol Extensions for Shaping the OFDM Spectrum2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 10, p. 7054-7066Article in journal (Refereed)
    Abstract [en]

    N-continuous orthogonal frequency division multiplexing (OFDM) is a promising solution to the outof- band (OOB) emission issue in OFDM systems where the Nth-order continuity between OFDM symbols leads to lower OOB emission than the plain OFDM, however, high self-interference in such systems is an obstacle. In this paper we propose a new class of quasi-cyclic symbol extensions which makes the OFDM system N- continuous. The new extension leads to low OOB emission while the additive interference is less than other N-continuous OFDM systems. Moreover, we propose a general analysis of the spectrum and interference that occurs in a linear precoded OFDM system. The framework is applicable to many N-continuous OFDM systems including our proposed method.

  • 84.
    Tayebeh, Taheri
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nilsson, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    van de Beek, Jaap
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hybrid spectral precoding/windowing for low-latency OFDM2017Conference paper (Refereed)
    Abstract [en]

    In this paper we present a joint precoded and windowed OFDM system. This new hybrid method provides flexibility to suppress the out-of band (OOB) emission in non-contiguous OFDM systems used in cognitive radio. This method also provides the possibility of shortening the cyclic prefix without sacrificing the OOB emission or increasing the additional interference which is the case in low-latency future systems.

  • 85.
    Wahlqvist, Mats
    et al.
    Telia Research.
    Östberg, Christer
    Telia Research.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Edfors, Ove
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    A conceptual study of OFDM-based multiple access schemes: Part 1: Air interface requirements1996Report (Other academic)
    Abstract [en]

    The multimedia era has started. The migration of computer (packet oriented) and telephony (circuit switched) networks in combination with an explosive development of new services, creates a mass market for public broadband communication. There are no reasons foreseen why these kinds of services should not go mobile. Future customers will not treat a mobile access differently than a fixed access to the network. The different types of services together with the demand of broadband mobile communication requires a new air interface. Limitations in the existing systems (flexibility and bit-rate) gives that they are not serious competitirs.

  • 86.
    Wahlqvist, Mattias
    et al.
    Telia Research.
    Östberg, Christer
    Telia Research.
    Ericsson, Mårten
    Olsson, Lennart
    Luleå tekniska universitet.
    Johansson, Magnus
    Ye, Wen
    Ödling, Per
    Edfors, Ove
    Luleå tekniska universitet.
    Landström, Daniel
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Arenas, Julia Martinez
    Description of Telias OFDM based proposal1997Report (Other academic)
    Abstract [en]

    This document gives an overview of Telias OFDM based proposal for UTRA and should be cinsidered as an input to the OFDM concept group within SMG 2. The document describes the fundamental frame structure, principles of the detection, modulation, coding and synchronization. Further, the channel structure, the resource management and handover principles are outlined

12 51 - 86 of 86
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