Change search
Refine search result
1234567 1 - 50 of 1006
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    ABBASI, MUHAMMAD MOHSIN
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Solving Sudoku by Sparse Signal Processing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sudoku is a discrete constraints satisfaction problem which is modeled as an underdetermined linear

    system. This report focuses on applying some new signal processing approaches to solve sudoku and

    comparisons to some of the existing approaches are implemented. As our goal is not meant for

    sudoku only in the long term, we applied approximate solvers using optimization theory methods. A

    Semi Definite Relaxation (SDR) convex optimization approach was developed for solving sudoku. The

    idea of Iterative Adaptive Algorithm for Amplitude and Phase Estimation (IAA-APES) from array

    processing is also being used for sudoku to utilize the sparsity of the sudoku solution as is the case in

    sensing applications. LIKES and SPICE were also tested on sudoku and their results are compared with

    l1-norm minimization, weighted l1-norm, and sinkhorn balancing. SPICE and l1-norm are equivalent

    in terms of accuracy, while SPICE is slower than l1-norm. LIKES and weighted l1-norm are equivalent

    and better than SPICE and l1-norm in accuracy. SDR proved to be best when the sudoku solutions are

    unique; however the computational complexity is worst for SDR. The accuracy for IAA-APES is

    somewhere between SPICE and LIKES and its computation speed is faster than both.

  • 2.
    Aguilar Pérez, David
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Designing schedules and Filter for cooperative localization2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In scheduled cooperative localization, devices in a network transmit pulses in a predetermined order. Every node measures inter-arrival time between received pulses to localize other nodes in the network. This thesis has looked into a few aspects of schedule based cooperative localization.First part of the thesis discusses constraints on schedule construction and algorithm to construct a schedule. An algorithm is proposed to design all possible schedules for any number of nodes.The second part of this thesis discusses designing a filter to process inter-arrival times to estimate position of all other nodes in the network. Every node runs a Kalman fi lter. Simulation results are presented for a fi lter model. Complexity of implementing the designed fi lter is discussed. A comparison is made between various ways to invert the matrix by QR decomposition. And finally, increase in fi lter complexity at every node with increase in number of nodes in network is discussed.

  • 3. Ahmed, Zakir
    et al.
    Bhardwaj, Krishna
    Krishnan, Ramesh
    Yajnanarayana, Vijaya
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Estimation of Sample Clock Frequency Offset Using Error Vector Magnitude2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A low complexity system and method for operating a receiver in order to estimate an offset between the actual sample clock rate 1/TS' of a receiver and an intended sample clock rate 1/TS. The receiver captures samples of a received baseband signal at the rate 1/TS', operates on the captured samples to generate an estimate for the clock rate offset, and fractionally resamples the captured samples using the clock rate offset. The resampled data represents an estimate of baseband symbols transmitted by the transmitter. The action of operating on the captured samples involves computing an error vector signal and then estimating the clock rate offset using the error vector signal. The error vector signal may be computed in different ways depending on whether or not carrier frequency offset and carrier phase offset are assumed to be present in the received baseband signal.

  • 4. Ahmed, Zakir
    et al.
    Yajnanarayana, Vijaya
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Blind mechanism for the joint estimation of frequency offset and phase offset for QAM modulated signals2010Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A mechanism for jointly correcting carrier phase and carrier frequency errors in a demodulated signal. A computer system may receive samples of a baseband input signal (resulting from QAM demodulation). The computer system may compute values of a cost function J over a grid in a 2D angle-frequency space. A cost function value J(theta,omega) is computed for each point (theta,omega) in the grid by (a) applying a phase adjustment of angle theta and a frequency adjustment of frequency omega to the input signal; (b) performing one or more iterations of the K-means algorithm on the samples of the adjusted signal; (c) generated a sum on each K-means cluster; and (d) adding the sums. The point (thetae,omegae) in the 2D angle-frequency space that minimizes the cost function J serves an estimate for the carrier phase error and carrier frequency error.; The estimated errors may be used to correct the input signal.

  • 5. Ahmed, Zakir
    et al.
    Yajnanarayana, Vijaya
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Maximizing the Viterbi Winning Path Metric to Estimate Carrier Frequency and Phase Offsets in Continuous Phase Modulated Signals2012Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A system and method for estimating carrier frequency offset Δf and carrier phase offset φ0 inherent in a received CPM signal. Samples of a continuous phase modulated (CPM) signal are received. A maximum of an objective function J is determined over a two-dimensional region parameterized by frequency offset v and phase offset w. The coordinates vmax and wmax of a maximizing point in the region represent estimates of the carrier frequency offset Δf and the carrier phase offset φ0. To evaluate the objective function J at a point (v, w), apply a frequency shift of amount −v and a phase shift of amount −w to the received samples to obtain modified samples, and perform Viterbi demodulation on the modified samples to obtain a winning path metric value at a final time. The winning path metric value is the objective function value J(v, w). 

  • 6.
    Ahmed, Zakir
    et al.
    Motorola India Electron. Ltd., Bangalore .
    Yajnanarayana, Vijaya
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Sancheti, Nirmal Kumar
    A time domain based efficient block decision algorithm for audio coders2007In: International Symposium on Communications and Information Technologies, 2007. ISCIT '07, IEEE Press, 2007, 1077-1081 p.Conference paper (Refereed)
    Abstract [en]

    In typical audio encoders the block decision is done either using time-domain techniques like energy computation or frequency domain techniques like temporal noise shaping (TNS) [1], [2]. The time-domain energy computation based decisions are less effective for detecting many of the stringent scenarios presented by test cases like castanets and fatboy. The frequency domain based algorithms have better decision making capabilities, however they are inherently complex as they require the computation of the FFT, additionally in case of TNS the computation of LPC (Linear Prediction coding) in the frequency domain. An improved time-domain technique with better block decision capability compared to TNS and with lesser computational complexity is proposed in this paper.

  • 7.
    Ainomäe, Ahti
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Tallinn Univ. of Technol., Tallinn, Estonia.
    Trump, Tõnu
    Tallinn Univ. of Technol., Tallinn, Estonia.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Diffusion LMS based Energy Detection2014In: Proceedings of 6th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), 2014, 2014, 176-183 p.Conference paper (Refereed)
    Abstract [en]

    Cognitive radio (CR) is seen as a promising technology to make radio spectrum usage more effective by providing an opportunistic access for secondary users to the licensed spectrum areas. CR systems need to detect the presence of a primary user (PU) signal by continuously sensing the spectrum area of interest. Radiowave propagation effects like fading and shadowing often complicate sensing of spectrum holes because the PU signal can be weak in a particular area. Cooperative spectrum sensing is seen as a prospective solution to enhance the detection of PU signals. This paper studies distributed spectrum sensing in a cognitive radio context. We investigate distributed energy detection schemes without using any fusion center. We propose the usage of distributed, diffusion least mean square (LMS) type of power estimation algorithms. In this paper an Adapt and Combine (ATC) diffusion based power estimation scheme is proposed and the performance is compared with the Combine and Adapt (CTA) and ring-around schemes in a common framework. The PU signal is assumed to be slowly fading. We analyse the resulting energy detection performance and verify the theoretical findings through simulations.

  • 8.
    Ainomäe, Ahti
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Department of Radio and Telecommunication Engineering, Tallinn University of Technology, Tallinn, Estonia .
    Trump, Tõnu
    Tallin University of Technology.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Recursive Energy Detection2014In: Proceedings of Wireless Communications and Networking Conference (WCNC), 2014, IEEE Communications Society, 2014, 1242-1247 p.Conference paper (Refereed)
    Abstract [en]

    Recent studies have shown that, while the available licensed radio spectrum becomes more occupied, the assigned spectrum is significantly underutilized. To alleviate the situation, cognitive radio (CR) technology has been proposed to provide an opportunistic access to the licensed spectrum areas. CR systems are able to serve the secondary users for detecting and utilizing so called spectrum holes by sensing and adapting to the environment without causing harmful effects or interference to the licensed primary users (PU). CR systems need to detect the presence of a primary user by continuously sensing the spectrum area of interest. Radiowave propagation effects like fading and shadowing often complicate sensing of spectrum holes because the PU signal can be weak in a particular area. Cooperative spectrum sensing is seen as a prospective solution to enhance the detection of PU signals. This paper studies distributed spectrum sensing in a cognitive radio context. We investigate a distributed energy detection scheme without using any fusion center. Due to reduced communication such a topology is more energy efficient. The PU signal is assumed to be in slow fading. A recursive distributed power estimation and detection scheme is proposed. The theoretical findings are verified through simulations.

  • 9. Al Ismaeil, Kassem
    et al.
    Aouada, Djamila
    Mirbach, Bruno
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bilateral Filter Evaluation Based on Exponential Kernels2012Conference paper (Refereed)
    Abstract [en]

    The well-known bilateral filter is used to smooth noisy images while keeping their edges. This filter is commonly used with Gaussian kernel functions without real justification. The choice of the kernel functions has a major effect on the filter behavior. We propose to use exponential kernels with L1 distances instead of Gaussian ones. We derive Stein's Unbiased Risk Estimate to find the optimal parameters of the new filter and compare its performance with the conventional one. We show that this new choice of the kernels has a comparable smoothing effect but with sharper edges due to the faster, smoothly decaying kernels.

  • 10.
    Alam, Assad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Asplund, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Behere, Sagar
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Björk, Mattias
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Garcia Alonso, Liliana
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Khaksari, Farzad
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Khan, Altamash
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Kjellberg, Joakim
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Liang, Kuo-Yun
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Lyberger, Rickard
    Scania CV AB.
    Mårtensson, Jonas
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Pettersson, Henrik
    Scania CV AB.
    Pettersson, Simon
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Stålklinga, Elin
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Cooperative driving according to Scoop2011Report (Other academic)
    Abstract [en]

    KTH Royal Institute of Technology and Scania are entering the GCDC 2011 under the name Scoop –Stockholm Cooperative Driving. This paper is an introduction to their team and to the technical approach theyare using in their prototype system for GCDC 2011.

  • 11.
    Alayon Glasunov, Andrés
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Prasad, S.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Experimental characterization of the propagation channel along a very large virtual array in a reverberation chamber2014In: Progress in Electromagnetics Research B, ISSN 1937-6472, no 59, 205-217 p.Article in journal (Refereed)
    Abstract [en]

    We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array inside a reverberation chamber. A multidimensional characterization of the channel was performed at 40 antenna positions with spacing of 0:233λ at 1 GHz. The average power, the Ricean K-factor, the coherence bandwidth, the r.m.s. delay spread, the mean delay, the beamforming power angle spectrum and array antenna correlation have been studied for different arrangements in the reverberation chamber. The analysis shows that the joint average over time and frequency channel behavior is, as expected, rather homogeneous along the very large array. However, individual realizations of the channel present a pronounced selective behavior in space, time and frequency with parameters varying along the positions of the virtual array suggesting that a heterogeneous behavior of the radio channels can be emulated in reverberation chambers. An important application of the presented study comprises testing of antenna array designs and algorithms in multipath environments. Further development may lead to Over The Air testing of Multiple Input Multiple Output antenna systems of various sizes, i.e., from small to very large arrays.

  • 12.
    Alayon Glazunov, Andres
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Prasad, Sathyaveer
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bolin, Thomas
    Prytz, Kjell
    Impact of Scattering Within a Multipath Simulator Antenna Array on the Ricean Fading Distribution Parameters in OTA Testing2014In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 0096-1973, Vol. 62, no 6, 3257-3269 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the unwanted scattering that exists within the multipath simulator (MPS) array antennas employed in over the air (OTA) testing of mobile terminals. The impact of scattering is evaluated in terms of the measurement uncertainty of the average received power and the Ricean K-factor. The maximum ratio combining diversity is investigated for a generic device under test comprising two half-wavelength dipole antennas. We provide closed-form expressions for the uncertainties of the average received power and the Ricean K-factor for a uniform circular array of MPS antennas and a 2-D uniformly distributed angle-of-arrival spectrum. We also derive the maximum number of MPS antennas and the minimum ring radius of the MPS system as a function of the separation between the most distant antenna elements if the device under test employs a uniform linear array. As a result, we provide design guidelines for MPS array in terms of the number antennas, the radius of the MPS array and the wavelength of the carrier frequency.

  • 13.
    Alayon Glazunov, Andres
    et al.
    TeliaSonera.
    Wang, Ying
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Experimental Evaluation of CW MIMO Channel Capacity in Urban Multicell Environment2006Conference paper (Refereed)
  • 14.
    Aldayel, Omar
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Evaluation of MIMO Non- Stationarity2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The transmission performance of MIMO systems can be highly improved under stationary channel conditions where the channel statistics are constant. Unfortunately, mobile radio channels are not stationary all the time. Instead, they are stationary for finite time durations, so-called the stationarity regions. If these stationarity regions are relatively large, then the channel statistics can be utilized during each stationarity region to enhance the transmission performance. Therefore, it is necessary to examine the stationarity of mobile channels and characterize the stationarity regions. This thesis investigates the non-stationarity of measured MIMO channels and proposes some stationarity metrics to measure it. These metrics are: the CMD proposed by [], NCMD and DES. Each one of the metrics is relevant to different types of transmission schemes and scenarios. The CMD may not be accurate for some transmission scenarios; therefore, the NCMD, which is a normalized version of CMD, is proposed. Theoretically, the NCMD can be at most 100% higher than the CMD for a 4x4 MIMO system. For beamforming scenario, the DES metric can be used to describe the non-stationarity of few eigenvectors taken from the channel variance. Under the measured MIMO channels, it was found that the CMD overestimates the stationarity regions compared to the NCMD and DES metrics particularly under the NLOS routes.

  • 15.
    Aldayel, Omar
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. King Saud University, Saudi Arabia.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Alshebeili, Saleh A.
    King Saud University, Saudi Arabia.
    Evaluation of MIMO channel non-stationarity2013In: 2013 Proceedings of the 21st European Signal Processing Conference (EUSIPCO), IEEE , 2013, 6811769- p.Conference paper (Refereed)
    Abstract [en]

    Several MIMO processing algorithms have been proposed that exploit long-term channel statistics, relaying on the critical assumption that this long-term information is valid long enough. In this paper, we consider the Correlation Matrix Distance (CMD) method previously proposed for the evaluation of MIMO channel non-stationarity. We highlight a couple of problems with the CMD measure and propose two new metrics that are more appropriate for non-stationarity evaluation. The performance of the CMD method and new correlation matrix distance metrics is investigated using measured 4×4 MIMO channels. Both Line-of-Sight (LOS) and Non-LOS (NLOS) environments are considered.

  • 16.
    Alenezi, Ali
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Evaluation of Precoder Designs Using Measured MIMO Channels2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    MIMO transceiver designs rely mainly on the knowledge of channel state information (CSI) at the transmitter and receiver sides of a communication link. In most  practical scenarios due to the fast fading channels, the transmitter side can only have statistical (or long-term) information about the channel. This thesis investigates and compares five MIMO transceiver designs over a measured 8x4 MIMO channel obtained from ERICSSON in terms of Bit-Error-Rate. Three of the algorithms use statistical channel information (CSI) at the transmitter side and instantaneous channel information at the receiver side, one of the algorithms uses instantaneous channel information at both the transmitter and receiver sides, and one algorithm uses no channel information at the transmitter and instantaneous channel information at the receiver side. The main target of this study is a recently long-term precoder design proposed in [1] which previously has showed good performance compared to other long-term precoder designs on a simulated channel. In the evaluation of the precoder designs on the measured MIMO channel, the precoder in [1] outperformed others long-term precoders and performed near to performance the short-term precoder in [5] on the slow and line-of-sight (LOS) channels. On the fast channels the long-term precoder in [1] works better than the long-term precoders but relatively far from the performance of the short-term precoder.

  • 17.
    Al-Ghazu, Nader
    KTH, School of Electrical Engineering (EES), Signal Processing.
    A Study of the Next WLAN Standard IEEE 802.11ac Physical Layer2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis studies the Physical Layer (PHY) of the new IEEE 802.11acWireless Local Access Network (WLAN) standard. The 11ac is built basedon the 11n successful standard. The standard is expected to be completedby the end of 2013. And it promises a Very High Throughput (VHT),and robust communication. In order to achieve that, the 11ac uses morebandwidth, it employs higher numbers of Multiple-Input Multiple-Output(MIMO) spatial streams, and higher orders of modulations. The 11ac PHYframe structure is studied in details. The transmitter and receiver blocks areexplained and implemented by MATLAB. Bit Error Rate (BER) and ErrorVector Magnitude (EVM) simulations of the PHY were run. The effectof different Modulation and Coding Scheme (MCS), and bandwidths werestudied. The performance of MIMO and Space-Time Block Coding (STBC)was investigated. The simulation results shows how the 11ac benefits fromthe new employed features. The created MATLAB simulation program canbe used for further tests and research.

  • 18. Ali Khan, N.
    et al.
    Ali, S.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Direction of arrival estimation using adaptive directional time-frequency distributions2016In: Multidimensional systems and signal processing, ISSN 0923-6082, E-ISSN 1573-0824, 1-19 p.Article in journal (Refereed)
    Abstract [en]

    Time-frequency distributions (TFDs) allow direction of arrival (DOA) estimation algorithms to be used in scenarios when the total number of sources are more than the number of sensors. The performance of such time–frequency (t–f) based DOA estimation algorithms depends on the resolution of the underlying TFD as a higher resolution TFD leads to better separation of sources in the t–f domain. This paper presents a novel DOA estimation algorithm that uses the adaptive directional t–f distribution (ADTFD) for the analysis of close signal components. The ADTFD optimizes the direction of kernel at each point in the t–f domain to obtain a clear t–f representation, which is then exploited for DOA estimation. Moreover, the proposed methodology can also be applied for DOA estimation of sparse signals. Experimental results indicate that the proposed DOA algorithm based on the ADTFD outperforms other fixed and adaptive kernel based DOA algorithms.

  • 19.
    Ali, Sadiq
    et al.
    Universitat Autònoma de Barcelona (UAB),.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Seco-Granados, Gonzalo
    Universitat Autònoma de Barcelona (UAB),.
    López-Salzedo, José A.
    Universitat Autònoma de Barcelona (UAB),.
    Novel collaborative spectrum sensing based on spatial covariance structure2013In: 2013 Proceedings of the 21st European Signal Processing Conference (EUSIPCO), 2013, 6811678- p.Conference paper (Refereed)
    Abstract [en]

    In collaborative spectrum sensing, spatial correlation in the measurements obtained by sensors can be exploited by adopting Generalized Likelihood Ratio Test (GLRT). In this process the GLRT provides a test statistics that is normally based on the sample covariance matrix of the received signal samples. Unfortunately, problems arise when the dimensions of this matrix become excessively large, as it happens in the so-called large-scale wireless sensor networks. In these circumstances, a huge amount of samples are needed in order to avoid the ill-conditioning of the GLRT, which degenerates when the dimensionality of data is equal to the sample size or larger. To circumvent this problem, we modify the traditional GLRT detector by decomposing the large spatial covariance matrix into small covariance matrices by using properties of the Kronecker Product. The proposed detection scheme is robust in the case of high dimensionality and small sample size. Numerical results are drawn, which show that the proposed detection schemes indeed outperform the traditional approaches when the dimension of data is larger than the sample size.

  • 20.
    Alizadeh, Mahmoud
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. Univ Gavle, Sweden.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing. Univ Gavle, Sweden.
    Ronnow, Daniel
    Measurement and Analysis of Frequency-Domain Volterra Kernels of Nonlinear Dynamic 3 x 3 MIMO Systems2017In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 7, 1893-1905 p.Article in journal (Refereed)
    Abstract [en]

    Multiple-input multiple-output (MIMO) frequencydomain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and the phase of the kernels are Kramers-Kronig consistent. The self-kernels and cross-kernels have different symmetries, and the kernels are therefore determined and analyzed in different regions in the 3-D frequency space. By analyzing the properties along certain paths in the 3-D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for the third-order kernels. The device under test is an MIMO transmitter for radio frequency signals.

  • 21.
    Alizadeh, Mahmoud
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    ATM, University of Gävle.
    Measurement and analysis of frequency-domainVolterra kernels of nonlinear dynamic 3x3 MIMO systems2016In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662Article in journal (Refereed)
    Abstract [en]

    Multiple-input multiple-output (MIMO) frequency-domain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and phase of the kernels areKramers-Kronig consistent. The self- and cross-kernels have different symmetries and the kernels are therefore determined and analyzed in different regions in the 3D frequency space. By analyzing the properties along certain paths in the 3D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for third-order kernels. The device under test is a MIMO transmitter for radio frequency signals.

  • 22.
    Alizadeh, Mahmoud
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    A two-tone test for characterizing nonlinear dynamic effects of radio frequency amplifiers in different amplitude regions2016In: Measurement, ISSN 0263-2241, Vol. 89, 273-279 p.Article in journal (Refereed)
    Abstract [en]

     A new two-tone test method for radio frequency power amplifiers is presented. The test signal is a two-tone probing-signal superimposed on large-signals of different amplitude. The amplifier is, thus, excited in different amplitude regions. The amplitude and phase of the 3rd order intermodulation (IM) products are measured vs. frequency spacing and probing-signal amplitude in each region. The IM magnitude is a measure of the nonlinearity, while the frequency dependence and asymmetry are measures of the memory effects in the different regions. A Doherty and a class-AB amplifier were tested. For both amplifiers the IM magnitude increased by ~15 dB from the lowest to the highest amplitude region. For the Doherty amplifier the behavior of the IM products vs. frequency spacing was similar in all regions, indicating similar memory effects. For the class-AB amplifier the IM vs. frequency spacing was significantly different in the different regions, which indicates different memory effects.

  • 23.
    Alli Idd, Pazi
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Channel estimation in mobile wireless systems2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The demands of multimedia services from mobile user equipment (UE) for achieving high data rate, high capacity and reliable communication in modern mobile wireless systems are continually ever-growing. As a consequence, several technologies, such as the Universal Mobile Telecommunications System (UMTS) and the 3rd Generation Partnership Project (3GPP), have been used to meet these challenges. However, due to the channel fading and the Doppler shifts caused by user mobility, a common problem in wireless systems, additional technologies are needed to combat multipath propagation fading and Doppler shifts. Time-variant channel estimation is one such crucial technique used to improve the performance of the modern wireless systems with Doppler spread and multipath spread.

    One of vital parts of the mobile wireless channel is channel estimation, which is a method used to significantly improve the performance of the system, especially for 4G and Long Term Evolution (LTE) systems. Channel estimation is done by estimating the time-varying channel frequency response for the OFDM symbols. Time-variant channel estimation using Discrete Prolate Spheroidal Sequences (DPSS) technique is a useful channel estimation technique in mobile wireless communication for accurately estimating transmitted information. The main advantage of DPSS or Slepian basis expansion is allowing more accurate representation of high mobility mobile wireless channels with low complexity. Systems such as the fourth generation cellular wireless standards (4G), which was recently introduced in Sweden and other countries together with the Long Term Evolution, can use channel estimation techniques for providing the high data rate in modern mobile wireless communication systems.

    The main goal of this thesis is to test the recently proposed method, time-variant channel estimation using Discrete Prolate Spheroidal Sequences (DPSS) to model the WINNER phase II channel model. The time-variant sub-carrier coefficients are expanded in terms of orthogonal DPS sequences, referred to as Slepian basis expansions. Both Slepian basis expansions and DPS sequences span the low-dimensional subspace of time-limited and band-limited sequences as Slepian showed. Testing is done by using just two system parameters, the maximum Doppler frequency Dmax v and K, the number of basis functions of length N = 256.

    The main focus of this thesis is to investigate the Power spectrum and channel gain caused by Doppler spread of the WINNER II channel model together with linear fitting of curves for both the Slepian and Fourier basis expansion models. In addition, it investigates the Mean Square Error (MSE) using the Least Squares (LS) method. The investigation was carried out by simulation in Matlab, which shows that the spectrum of the maximum velocity of the user in mobile wireless channel is upper bounded by the maximum normalized one-sided Doppler frequency. Matlab simulations support the values of the results. The value of maximum Doppler bandwidth vDmax  of the WINNER model is exactly the same value as DPS sequences. In addition to the Power spectrum of the WINNER model, the fitting of Slepian basis expansion performs better in the WINNER model than that of the Fourier basis expansion.

  • 24. Alodeh, Maha
    et al.
    Chatzinotas, Symeon
    Ottersten, Björn E.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Spatial DCT-Based Channel Estimation in Multi-Antenna Multi-Cell Interference Channels2015In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, no 6, 1404-1418 p.Article in journal (Refereed)
    Abstract [en]

    This work addresses channel estimation in multiple antenna multicell interference-limited networks. Channel state information (CSI) acquisition is vital for interference mitigation. Wireless networks often suffer from multicell interference, which can be mitigated by deploying beamforming to spatially direct the transmissions. The accuracy of the estimated CSI plays an important role in designing accurate beamformers that can control the amount of interference created from simultaneous spatial transmissions to mobile users. Therefore, a new technique based on the structure of the spatial covariance matrix and the discrete cosine transform (DCT) is proposed to enhance channel estimation in the presence of interference. Bayesian estimation and least squares estimation frameworks are introduced by utilizing the DCT to separate the overlapping spatial paths that create the interference. The spatial domain is thus exploited to mitigate the contamination which is able to discriminate across interfering users. Gains over conventional channel estimation techniques are presented in our simulations which are also valid for a small number of antennas.

  • 25.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed.

    When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed.

    To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions.

    Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.

  • 26.
    Amin, Shoaib Amin
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Characterization and Linearization of Multi-channel RF Power Amplifiers2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The demands for high data rates and broadband wireless access require the development of wireless systems that can support wide and multi-band signals. To deploy these signals, new radio frequency (RF) front-ends are required which impose new challenges in terms of power consumption efficiency and sources of distortion e.g., nonlinearity. These challenges are more pronounced in power amplifiers (PAs) that degrade the overall performance of the RF transmitter. Since it is difficult to optimize the linearity and efficiency characteristics of a PA simultaneously, a trade-off is needed. At high input power, a PA exhibits high efficiency at the expense of linearity. On the other hand, at low input power, a PA is linear at the expense of the efficiency. To achieve linearity and efficiency at the same time, digital pre-distortion (DPD) is often used to compensate for the PA nonlinearity at high input power. In case of multi-channel PAs, input and output signals of different channels interact with each other due to cross-talk. Therefore, these PAs exhibit different nonlinear behavior than the single-input single-output (SISO) PAs. The DPD techniques developed for SISO PAs do not result in adequate performance when used for multi-channel PAs. Hence, an accurate behavioral modeling is essential for the development of DPD for multi-channel RF PAs. In this thesis, we propose three novel behavioral models and DPD schemes for nonlinear multiple-input multiple-output (MIMO) transmitters in presence of cross-talk. A study of the source of cross-talk in MIMO transmitters have been investigated to derive simple and powerful modeling schemes. These models are extensions of a SISO generalized memory polynomial model. A comparative study with a previously published MIMO model is also presented. The effect of coherent and partially non-coherent signal generationon DPD performance is also highlighted. It is shown experimentally that with partially non-coherent signal generation, the performance of the DPD degrades compared to coherent signal generation. In context of multi-channel RF transmitters, PA behavioral models and DPD schemes suffer from a large number of model parameters with the increase in nonlinear order and memory depth. This growth leads to high complexity model identification and implementation. We have designed a DPD scheme for MIMO PAs using a sparse estimation technique for reducing model complexity. This technique also increases the numerical stability when linear least square estimation model identification is used. A method to characterize the memory effects in a nonlinear concurrent dual-band PAs is also presented. Compared to the SISO PAs, concurrent dual-band PAs are not only affected by intermodulation distortions but also by cross-modulation distortions. The characterization of memory effects inconcurrent dual-band transmitter is performed by injecting a two-tone test signal in each input channel of the transmitter. Asymmetric energy surfaces are introduced for the intermodulation and cross-modulation products, which can be used to identify the power and frequency regions where the memory effects are dominant.

  • 27.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    ATM, University of Gävle.
    Digital Predistortion of Single and Concurrent Dual BandRadio Frequency GaN Amplifiers with Strong NonlinearMemory Effects2017In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 7, 2453-2464 p.Article in journal (Refereed)
    Abstract [en]

    Electrical anomalies due to trapping effects in gallium nitride (GaN) power amplifiers (PAs) give rise to long-term or strong memory effects. We propose novel models based on infinite impulse response fixed pole expansion techniques for the behavioral modeling and digital predistortion of single-input single-output (SISO) and concurrent dual-band GaN PAs. Experimental results show that the proposed models outperform the corresponding finite impulse response (FIR) models by up to 17 dB for the same number of model parameters. For the linearization of a SISO GaN PA, the proposed models give adjacent channel power ratios (ACPRs) that are 7-17 dB lower than the FIR models. For the concurrent dual-band case, the proposed models give ACPRs that are 9-14 dB lower than the FIR models.

  • 28.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Khan, Zain Ahmed
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Isaksson, Magnus
    Högskolan i Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Högskolan i Gävle.
    Concurrent Dual-band Power Amplifier Model Modification using Dual Two-Tone Test2016In: European Microwave Week 2016: "Microwaves Everywhere", EuMW 2016 - Conference Proceedings; 46th European Microwave Conference, EuMC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, 186-189 p., 7824309Conference paper (Refereed)
    Abstract [en]

    A dual two-tone technique for the characterization of memory effects in concurrent dual-band transmitters is revisited to modify a 2D-DPD model for the linearization of concurrent dual-band transmitters. By taking into account the individual nonlinear memory effects of the self- and cross-kernels, a new2D modified digital pre-distortion (2D-MDPD) model is proposed,which not only supersedes the linearization performance but also reduces the computational complexity compared to the 2DDPDmodel in terms of a number of floating point operations(FLOPs). Experimental results show an improvement of 1.7 dBin normalized mean square error (NMSE) and a 58% reduction in the number of FLOPs.

  • 29.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ladin, Per N.
    ATM, University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    ATM, University of Gävle.
    2D Extended Envelope Memory Polynomial Model forConcurrent Dual-band RF Transmitters2016In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787Article in journal (Refereed)
    Abstract [en]

    The paper presents a 2D extended envelope memory polynomial (2D-EEMP) model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital pre-distortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error (NMSE) of -51.7/-51.6dB and adjacent channel error power ratio (ACEPR) of -63.1/-63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are 3 times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio (ACPR) of -55.8/ -54.6 dB for channel 1/2 and is 7-10 dB lower than those resulted with the 2D-DPD model and2-4 dB lower compared to the DB-GMP model.

  • 30.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Högskolan i Gävle.
    Landin, Per
    Chalmers University of Technology.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Högskolan i Gävle.
    Behavioral modeling and linearization of crosstalk and memory effects in RF MIMO transmitters2014In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 62, no 4, 810-823 p.Article in journal (Refereed)
    Abstract [en]

    This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2 x 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 x 2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of 30 dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3-4 dB between coherent and partially noncoherent signal generation.

  • 31.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Van Moer, Wendy
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    Characterization of a Concurrent dual-band Power Amplifier using a dual-tone excitation signals2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456Article in journal (Other academic)
  • 32.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Van Moer, Wendy
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    University of Gävle.
    Characterization of concurrent dual-band Power Amplifiers using a dual two-tone excitation signal2015In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, no 99Article in journal (Refereed)
    Abstract [en]

    A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two tone test for power amplifiers to concurrent dual band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation products but also by cross-modulation products. In one frequency band, the transmitter is excited by a two tone signal which frequency separation is swept. In the second band the transmitter is concurrently excited by an other two tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two tone test is made at different power levels. The upper and lower third-order inter- and cross-modulation products are measured. The asymmetry between the upper and lower third-order inter- and cross-modulation products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order intermodulation products than in the cross modulation products. An error analysis and system calibration was performed and measurement results for two different devices are presented.

  • 33.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zenteno, Efrain
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Landin, Per
    Dept. Electronics, Mathematics and Natural Sciences, Faculty of Engineering and Sustainable Development,University of Gävle .
    Rönnow, Daniel
    Dept. Electronics, Mathematics and Natural Sciences, Faculty of Engineering and Sustainable Development,University of Gävle .
    Isaksson, Magnus
    Dept. Electronics, Mathematics and Natural Sciences, Faculty of Engineering and Sustainable Development,University of Gävle .
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Noise Impact on the Identification of DigitalPredistorter Parameters in the Indirect LearningArchitecture2012In: Swedish Communication Technologies Workshop (Swe-CTW), 2012, IEEE conference proceedings, 2012, 36-39 p.Conference paper (Refereed)
    Abstract [en]

    The indirect learning architecture (ILA) is the mostused methodology for the identification of Digital Pre-distorter(DPD) functions for nonlinear systems, particularly for highpower amplifiers. The ILA principle works in black box modelingrelying on the inversion of input and output signals of thenonlinear system, such that the inverse is estimated. This paperpresents the impact of disturbances, such as noise in the DPDidentification. Experiments were performed with a state-of-artDoherty power amplifier intended for base station operationin current telecommunication wireless networks. As expected,a degradation in the performance of the DPD (measured innormalized mean square error (NMSE)) is found in our experiments.However, adjacent channel power ratio (ACPR) canbe a misleading figure of merit showing improvement in theperformance for wrongly estimated DPD functions.

  • 34. Andersen, O.
    et al.
    Wisell, David
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Keskitalo, N.
    Stenvard, P.
    Cost effective high performance modular instrumentation, signal generation and signal analysis for future mobile communication systems2007In: 2007 IEEE Autotestcon, IEEE , 2007, 660-668 p.Conference paper (Refereed)
    Abstract [en]

    A decrease in life cycle cost is a key issue for testing of mobile communication systems. The rapid development and edge technology requires high performance instruments and state of the art measurement technology. It is desired to use virtual/synthetic instruments and put the measurement technology in software independent of hardware, i.e. software driven measurements. Increased flexibility and modularization, both in hardware and software, are requirements to support the cost decrease. The hardware basis is signal generation and signal analysis. In this paper state of the art signal generation and signal analysis capabilities are demonstrated in a modular and flexible architecture. A direct IF synthesis is used to generate 1 WideBand Code-Division Multiple Access (WCDMA) carrier with more than 72 dB Adjacent Carrier Leakage Ratio (ACLR) 2 carrier with more than 68 dBc ACLR over a total bandwidth of 100 MHz. The signal analysis capabilities, ACLR performance, for a WCDMA carrier is better than -70 dBc and for a continuous wave better than -85 dBc over a bandwidth of 42.5 MHz. The critical down converter in the set up doesn't degrade the performance.

  • 35.
    Andersson, Fredrik
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Grafisk utvecklingsplattform för signalbehandling - Design och implementation2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We have different kinds of signal processing everywhere around us in our everyday life, in our cellphones, when we are listening to music, watching TV etc. This makes signal processing a very interesting and important technical area, where the demand of skilled engineers sets the limit of what is possible.

    Working with signal processing requires in-depth knowledge in areas such as mathematics, physics, electronics, and other related areas. For this, it has traditionally been demanded by a talented developer to also master the advanced programming languages such as C / C + + and Assembler.

    This has begun to change; today there are several companies that offer graphical development environments for signal processing, environments where programming skills are not needed anymore, and the focus can be on signal processing instead.

    The goal with this project is to build a corresponding graphical development environment to reach an understanding of what is required of these systems, and also to grasp what opportunities that are available within graphic programming. Inspiration for the work has partly arise from some of the tools available on the market, and partly from previous theses that have been written about graphic programming.

    The challenge lies in creating a program that can execute signal diagrams in real time from given signal blocks, and be able to handle feedback loops in an efficient way and to do so at the lowest "cost" in terms of clock cycles as possible. This should also be compared against to code, compile and run a complete signal diagram directly.

    To increase the usability it should also be possibility to externally manage in real time the parameters of the signal diagram during execution.

    The interface is a separate program, which is to some extent similar to Matlab Simulink, where a signal diagram is drawn up graphically by connecting wires between different signal blocks. This signal scheme is then executed in an additional program that serves as a runtime environment. In this report, the term "signal engine" is used for this program.

    Signal engine is equivalent to the program that should have been run directly into a standalone DSP (Digital Signal Processor) if a more classic design had been selected, but now runs as a separate process in Windows.

  • 36.
    Andersson, Helene
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Twente, Netherlands .
    Van Den Berg, A.
    From LOC to LIC: Using individual cells as experimentation platforms2005In: Nanobiotechnology, ISSN 1551-1286, Vol. 1, no 3, 319-321 p.Article in journal (Refereed)
    Abstract [en]

    There are many efforts today trying to mimic the properties of single cells in order to design chips that are as efficient as cells. However, cells are nature's nanotechnology engineering at the scale of atoms and molecules. Therefore, it might be better to vision a microchip that utilizes a single cell as experimentation platform. A novel, so-called Lab-in-a-Cell (LIC) concept is described, where advantage is taken of micro/nanotechnological tools to enable precise control of the biochemical cellular environment and possibility to analyze the composition of single cells.

  • 37.
    Andersson, Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    IEEE standard 1057, Cramer-Rao bound and the parsimony principle2006In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, Vol. 55, no 1, 44-53 p.Article in journal (Refereed)
    Abstract [en]

    This paper deals with some fundamental properties of the sine-wave-fit algorithm included in IEEE Standards 1057 and 1241. Asymptotic Cramer-Rao bounds (CRBs) for three and four model parameters are derived under the Gaussian assumption. Further, the sine-wave-fitting properties of the algorithm are analyzed by the parsimony principle. A decision criterion whether to use the three- or four-parameter model is derived. It is shown that a three-parameter sine-wave fit produces a better fit than the four-parameter fit if the frequency is known to be within an interval related to the number of samples and the signal-to-noise ratio. By a numerical analysis, the theoretical results are shown to be also valid for the uniform noise model of quantization.

  • 38.
    Andersson, Tomas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Multiple-tone estimation by IEEE standard 1057 and the expectation-maximization algorithm2003In: IMTC/O3: PROCEEDINGS OF THE 20TH IEEE INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE, 2003, 739-742 p.Conference paper (Refereed)
    Abstract [en]

    The aim of this work is to present an efficient algorithm for multiple-tone parameter estimation. The algorithm is inspired by the expectation-maximization algorithm, and it utilizes the IEEE standard 1057 for single tone parameter estimation. In the derivation of the algorithm it is assumed that the number of tones are known and that the frequencies are well separated The algorithm is evaluated using data consisting of multiple real-valued tones. The performance of the frequency estimator is studied and compared with the asymptotic Cramer-Rao bound (CRB). It is shown that the algorithm produces statistically efficient frequency estimates at high signal to noise ratios, that is the variance of the estimates reaches the CRB. Finally, it is shown that the algorithm can produce efficient estimates independent of the number of tones in the input signal.

  • 39.
    Andersson, Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Multiple-tone estimation by IEEE standard 1057 and the expectation-maximization algorithm2005In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, Vol. 54, no 5, 1833-1839 p.Article in journal (Refereed)
  • 40.
    Andersson, Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robustness of wave-fitting with respect to uncertain parameter values2005In: Instrumentation and Measurement Technology Conference, 2005. IMTC 2005. Proceedings of the IEEE, 2005, Vol. 1, 662-665 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a criterion for model order selection. By usage of the parsimony principle the mean sum-squareerror is evaluated for models subject to imperfections inparameter values. In particular, model imperfections in different sinewavefitting scenarios have been analyzed. The analysis is carried out considering linear models. The obtained result is generalized to models incorporating non-linear parameters. Numerical illustrations are provided in order to gain insight of the behavior of model imperfections, as well as to numerically verify the theoretical results. The main contributions include a general result for linear signal models, as well as some novel results on sinewave-fitting. 

  • 41. Andersson, Tomas
    et al.
    Skoglund, Mikael
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Frequency estimation by 1-bit quantization and table look-up processing2000In: Proceedings European Signal Processing Conference, 2000, 1807-1810 p.Conference paper (Refereed)
  • 42.
    Anton-Haro, Caries
    et al.
    Centre Tecnolo`gic de Telecomunicacions de Catalunya (CTTC, Spain).
    Svedman, Patrick
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Alexiou, Angeliki
    Bell Laboratories, Lucent Technologies (United Kingdom).
    Gameiro, Atilio
    University of Aveiro/Istituto de Telecomunicações (Portugal).
    Cross-layer scheduling for multi-user MIMO systems2006In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 44, no 9, 39-45 p.Article in journal (Refereed)
    Abstract [en]

    The increasing demand of wireless services associated with the scarcity of the radio spectrum and the trend to provide end-to-end QoS in emerging and future applications calls for the design of spectrally efficient systems with QoS support. To fulfill these two requirements of spectral efficiency and QoS provision in the highly dynamic environment of mobile radio requires the collaboration of several layers in the system as well as the use of multiple transmit and receive antennas. In a packet network, one important component to achieve the aforementioned efficiency goals is a properly designed scheduling algorithm. Using an information-theoretic framework, we present an overview of the issues associated with the design of packet scheduling algorithms and review several proposed solutions. The article focuses on the advantages of a cross-layer approach to the resource allocation problem and identifies the trade-offs associated with the increased signaling needs. Also, we thoroughly discuss the additional degrees of freedom that multiple transmit and receive antennas can provide.

  • 43. Anttila, L
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mylläri, O
    Valkama, M
    Recursive learning-based joint digital predistorter for power amplifier and I/Q modulator impairments2010In: International Journal of Microwave and Wireless Technologies, ISSN 1759-0787, Vol. 2, no 2, 173-182 p.Article in journal (Refereed)
    Abstract [en]

    The main implementation impairments degrading the performance of direct-conversion radio transmitters are in-phase/quadrature (I/Q) mismatch, local oscillator (LO) leakage, and power amplifier (PA) nonlinear distortion. In this article, we propose a recursive least-squares-based learning algorithm for joint digital predistortion (PD) of frequency-dependent PA and I/Q modulator impairments. The predistorter is composed of a parallel connection of two parallel Hammerstein (PH) predistorters and an LO leakage compensator, yielding a predistorter which as a whole is fully linear in the parameters. In the parameter estimation stage, proper feedback signal from the transmitter radio frequency (RF) stage back to the digital parts is deployed, combined with the indirect learning architecture and recursive least-squares training. The proposed structure is one of the first techniques to explicitly consider the joint estimation and mitigation of frequency-dependent PA and I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficiency of the proposed PD technique. In general, the obtained results demonstrate linearization and I/Q modulator calibration performance clearly exceeding the performance of current state-of-the-art reference techniques.

  • 44. Anttila, Lauri
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Valkama, Mikko
    Joint Mitigation of Power Amplifier and I/Q Modulator Impairments in Broadband Direct-Conversion Transmitters2010In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 58, no 4, 730-739 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a novel digital predistorter structure for joint mitigation of frequency-dependent power amplifier (PA) and in-phase and quadrature (I/Q) modulator impairments in direct-conversion radio transmitters. The predistorter is based on an extended parallel Hammerstein structure, yielding a predistorter that is fully linear in the parameters. In the parameter estimation stage, the indirect learning architecture is utilized. The proposed technique is the first technique in the literature to consider the joint estimation and mitigation of frequency-dependent PAand I/Q modulator impairments. Extensive simulation and measurement analysis is carried out to verify the operation and efficacy of the proposed predistortion structure. It is shown that the adjacent channel power ratio is increased by more than 20 dB in all experiments when using the proposed method, and that the performance of the reference techniques is clearly exceeded.

  • 45.
    Aquilanti, Claudia
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Sensor Fusion of GPS and speed information for low-cost automotive positioning and navigation2011Student paper other, 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Global navigation satellite systems, such as the Global Positioning System (GPS) are nowadays widespread in the consumer and professional fields. To guarantee the desired accuracy, availability, integrity and robustness performance, it is necessary to add to GPS receivers aiding systems, like extra sensors, which can be expensive. In order to reduce the expenses, a low-cost alternative aiding system is here presented. The main idea is to extract the information needed to support the GPS services from an easily measurable signal as the one provided by the power supply of a car. This signal has a frequency component related to the rpm speed of the engine, thus it can be used to estimate the speed, and related states, when the GPS service is unavailable for some reason. Unfortunately, the frequency component isequal to the speed measured by the GPS up to a scale factor dependent on the gear engaged, so it is necessary to estimate over time these scale factors in order to use the information. In this thesis project we implemented an off-line system which leads to the estimation over time of the scale factors. A sensor fusion solution has been used: training data consisting only of speed measurement provided by the GPS and measurements of the signal of interest are processed through a bench of five Kalman Filters (one for each gear) which leads to the estimation of the scale factors. Three measurement campaigns with three different cars have been conducted in order to collect an exhaustive amount of datasets necessary to calibrate and then validate the system.

  • 46.
    Arapoglou, Pantelis-Daniel
    et al.
    University of Luxembourg, Luxembourg.
    Shankar, M. R. Bhavani
    University of Luxembourg, Luxembourg.
    Panagopoulos, Athanasios
    University of Luxembourg, Luxembourg.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Gateway Diversity Strategies in Q/V Band Feeder Links2011In: Proceedings 17th Ka and Broadband Communications Conference, 2011Conference paper (Refereed)
  • 47. Aravanis, Alexis
    et al.
    Shankar Bhavani, M.R.
    Danoy, Gregoire
    Arapoglou, Pantelis-Daniel
    Cottis, Panayotis
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Power allocation in multibeam satellites: A hybrid-genetic algorithm approach2012Conference paper (Refereed)
  • 48.
    Arvidsson, Pontus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Channel Estimation Error Model for SRS in LTE2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In 3GPP long term evolution (LTE), sounding is used to gain a wideband estimate of the uplink channel. This channel estimate may then be used for several radio resource management related applications such as frequency selective scheduling and beam forming. Code division multiplexing (CDM) enables several users to broadcast sounding reference signals (SRS) simultaneously on the same time and frequency resource. As the multiplexed users may interfere with one another there is a trade-off between having users broadcast SRS as often as possible to get a frequent channel estimate and getting higher quality estimates with a lower periodicity. To assess this trade-off one must have a good understanding of what causes the errors in the channel estimate so that the sounding resource may be used as efficiently as possible. This thesis proposes a method to model the channel estimation error with sounding for use in a system simulator environment. The method consists of estimating a standard deviation with a per-resource-block resolution of the channel estimates as a function of received signal powers of interfering users as well as the target user and background noise. This estimated estimation error may then, in the system simulator, be applied to a known ideal channel estimate as noise. The main limiting source of error is shown to beinterference, both from sounding users in the same cell and in others as well as some effects of limited frequency resolution. Simulation results indicate that a cleverly designed sounding resource handler is needed to fully utilize the possible gains of sounding.

  • 49.
    Astély, David
    et al.
    Ericsson Research.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Spatio-Temporal Interference Rejection Combining2005In: Smart Antennas - State-of-the-Art / [ed] Kaiser, Thomas, Hindawi Publishing Corporation , 2005, 5-26 p.Chapter in book (Other academic)
  • 50. Bang, I.
    et al.
    Kim, Su Min
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Sung, D. K.
    Opportunistic user selection with adaptive jamming for secure communication in heterogeneous networks2015In: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, IEEE conference proceedings, 2015, 42-46 p.Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose an opportunistic user selection criterion to obtain a multiuser diversity gain for secure communication. At the same time, we also propose a strategy for utilizing a small base station in heterogeneous networks as a helper or a jammer adaptively. Our approach is to maximize the secrecy achievable rate based on an analytically derived lower bound instead of the original objective function due to its complexity. Based on a simple proposed user selection criterion considering both macro and small base stations, we propose two jamming strategies according to knowledge of eavesdropper's channel: adaptive jamming and probabilistic jamming strategies. Through simulations in two scenarios, it is shown that our proposed user selection and jamming schemes provide a good performance gain in terms of secrecy achievable rate.

1234567 1 - 50 of 1006
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf