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  • 151.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Detecting Lane Markers in Complex Urban Environments2010In: 2010 IEEE 7th International Conference on Mobile Adhoc and Sensor Systems (MASS), 2010, p. 727-732Conference paper (Refereed)
    Abstract [en]

    In this paper, we present a new methodology for detecting lane markers that is able to withstand many challenging situations like scattered shadows, illumination changes, and presence of neighboring vehicles to name a few. At first, the input image undergoes a perspective removal followed by a color space conversion. Then, the core elements consisting of template matching, lane region merging, and elliptical projections are explained. Finally, the developed system showed good results when tested on 15 minutes of real-world driving videos containing variations in illumination, traffic, and road surface conditions.

  • 152.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lane Detection and Tracking Using a Layered Approach2009In: ADVANCED CONCEPTS FOR INTELLIGENT VISION SYSTEMS, PROCEEDINGS / [ed] BlancTalon, J; Philips, W; Popescu, D; Scheunders, P, 2009, p. 474-484Conference paper (Refereed)
    Abstract [en]

    A new night-time lane detection system that extends the idea of a Layered Approach [1] is presented in this document. The extension includes the incorporation of (1) inverse Perspective Mapping (IPM) to generate a bird's-eye view of the road surface, (2) application of Random Sample Consensus (RANSAC) to rid outliers from the data., and (3) Kalman filtering to smooth the output of the lane tracker. Videos of driving scenarios on local city roads and highways were used to test the new system. Quantitative analysis shows higher accuracy in detecting lane markers in comparison to other approaches.

  • 153.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Polar Randomized Hough Transform For Lane Detection Using Loose Constraints of Parallel Lines2011In: 2011 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, 2011, p. 1037-1040Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a new methodology for detecting lane markers that exploits the parallel nature of lane boundaries on the road. First, the input image is pre-processed and filtered to detect lane marker features. Then, using the Polar Randomized Hough Transform that is introduced in this paper, lines are fitted through the detected features and the orientation of each line is evaluated. By finding near parallel lines separated by a constraint specified distance, false signalling caused by artifacts in the image is greatly reduced. The proposed system was tested using a real world driving videos and showed good results despite the presence of neighboring vehicles, shadows, and irregularities on the road surface.

  • 154.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Robust Lane Detection and Tracking With Ransac and Kalman Filter2009In: 2009 16TH IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING, VOLS 1-6, 2009, p. 3225-3228Conference paper (Refereed)
    Abstract [en]

    In a previous paper, a simple approach to lane detection using the Hough transform and iterated matched filters was described [1]. This paper extends this work by incorporating an inverse perspective mapping to create a bird's-eye view of the road, applying random sample consensus to help eliminate outliers due to noise and artifacts in the road, and a Kalman filter to help smooth the output of the lane tracker.

  • 155.
    Borkar, Amol
    et al.
    Georgia Institute of Technology.
    Hayes, Monson
    Georgia Institute of Technology.
    Smith, Mark T.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Pankanti, Sharath
    IBM T.J. Watson Research Center.
    A Layered Approach to Robust Lane Detection at Night2009In: CIVVS 2009: 2009 IEEE WORKSHOP ON COMPUTATIONAL INTELLIGENCE IN VEHICLES AND VEHICULAR SYSTEMS, 2009, p. 51-57Conference paper (Refereed)
    Abstract [en]

    A layered approach is designed to address many of the real-world problems that an inexpensive lane detection system would encounter. A region of interest is first extracted from the image followed by an enhancement procedure to manipulate the shape of the lane markers. The extracted region is then converted to binary using an adaptive threshold. A model based line detection system hypothesizes lane position. Finally, an iterated matched filtering scheme estimates the final lane position. The developed system shows good performance when tested on real-world data that contains fluctuating illumination and a variety of traffic conditions.

  • 156.
    Brandt, Rasmus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Coordinated Precoding for Multicell MIMO Networks2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Enabling multiple base stations to utilize the spatial dimension in a coordinated manner has been shown to be a fruitful technique for improving the spectral efficiency in wireless interference networks. This thesis considers multicell systems where base stations and mobile stations are equipped with multiple antennas. The base stations coordinate their spatial precoding, but individually serve their mobile stations with data. For such coordinated precoding systems, interference alignment (IA) is a useful theoretical tool, due to its ability to serve the maximum number of interference-free data streams. Three topics related to interference alignment and coordinated precoding are studied.

    First, the feasibility of IA over a joint space-frequency signal space is studied. A necessary condition for space-frequency IA feasibility is derived, and the possible gain over space-only IA is analyzed. An upper bound on the degree of freedom gain is shown to increase in the number of subcarriers, but decrease in the number of antennas. Numerical studies, using synthetically generated channels and real-world channels obtained from indoors and outdoors channel measurements, are used for sum rate performance evaluation. The results show that although a degree of freedom gain is noticeable due to the space-frequency precoding, the sum rate of the system is mainly improved due to a power gain.

    Second, distributed channel state information (CSI) acquisition techniques are proposed, which provide estimates of the information necessary to perform distributed coordinated precoding. The methods are based on pilot-assisted channel estimation in the uplink and downlink, and correspond to different tradeoffs between feedback and signaling, backhaul use, and computational complexity. Naively applying the existing WMMSE algorithm for distributed coordinated precoding together with the estimated CSI however results in poor performance. A robustification of the algorithm is therefore proposed, relying on the well known diagonal loading technique. An inherent property of the WMMSE solutions is derived and, when enforced onto solutions with imperfect CSI, results in diagonally loaded receive filters. Numerical simulations show the effectiveness of the proposed robustification. Further, the proposed robustified and distributed WMMSE algorithm performs well compared to existing state-of-the-art robust WMMSE algorithms. In contrast to our approach, the existing methods however rely on centralized CSI acquisition.

    Third, coordinated precoding systems with hardware impairments are studied. Assuming that impairment compensation techniques have been applied, a model is used to describe the aggregate effect of the residual hardware impairments. An iterative resource allocation method accounting for the residual hardware impairments is derived, based on an existing resource allocation framework. Numerical simulations show that the proposed method outperforms all benchmarks. In particular, the gain over impairments-aware time-division multiple access is substantial.

  • 157.
    Brandt, Rasmus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Coordination in Multiantenna Cellular Networks2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Wireless communications are important in our highly connected world. The amount of data being transferred in cellular networks is steadily growing, and consequently more capacity is needed. This thesis considers the problem of downlink capacity improvement from the perspective of multicell coordination. By employing multiple antennas at the transmitters and receivers of a multicell network, the inherent spatial selectivity of the users can be exploited in order to increase the capacity through linear precoding and receive filtering. For the coordination between cells, distributed algorithms are often sought due to their low implementation complexity and robustness. In this context, the thesis considers two problem domains: base station clustering and coordinated precoding.

    Base station clustering corresponds to grouping the cell base stations into disjoint clusters in order to reduce the coordination overhead. This is needed in intermediate-sized to large networks, where the overhead otherwise would be overwhelmingly high. Two solution methods for the clustering problem are proposed: an optimal centralized method, as well as a heuristic distributed method. The optimal method applies to a family of throughput models and exploits the structure of the model to find bounds that can be used to focus the search for the optimal clustering into promising territories. The distributed method instead uses notions from coalitional game theory, where the base stations are modelled as rational and intelligent players in a game. By letting the players make individual deviations that benefit them in the game, i.e.\@ switching clusters, a distributed coalition formation algorithm is obtained.

    Coordinated precoding is the act of finding the linear precoders and receive filters that maximize the network performance, given a base station clustering. Four specific challenges are studied in this problem domain. First, coordinated precoding under intercluster interference is considered. The channels of the intercluster links are not explicitly estimated due to overhead reasons, and these links thus lead to intercluster interference. By exploiting the known statistics of the intercluster channels, a robust and distributed coordinated precoding algorithm is developed. Second, coordinated precoding under imperfect channel state information is considered. Relying on the channel reciprocity under time-division duplex operation, a distributed estimation framework is proposed. Given the estimated channels, a robust and distributed coordinated precoding algorithm is then derived. Third, coordinated precoding under imperfect radio hardware is considered. By modelling the radio frequency distortion noises, a distributed coordinated precoding method that accounts for the imperfections is proposed. Fourth, joint coordinated precoding and discrete rate selection is considered. By bounding and linearizing an originally intractable optimization problem, a heuristic algorithm is derived which selects the transmit rate from a finite set and simultaneously forms the linear precoders and receive filters.

  • 158.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Asplund, Henrik
    Ericsson Research.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Interference Alignment in Frequency — a Measurement Based Performance Analysis2012In: 2012 19th International Conference on Systems, Signals and Image Processing, IWSSIP 2012, IEEE conference proceedings, 2012, p. 227-230Conference paper (Refereed)
    Abstract [en]

    The idea of interference alignment (IA) has shown great promise in many theoretical studies. Yet it is not clear under what operating conditions it will perform better than traditional multiple access schemes under realistic network conditions. Here, we use measured channels to evaluate a number of different IA schemes and related methods, focusing on wideband single-antenna transmission, using frequency extensions for the IA. The radio channels were measured jointly from three base station sites in an urban macrocell scenario, over a 20 MHz bandwidth, allowing to emulate a scenario with 3 interfering cells (i.e. 3 interfering transmit/receive pairs). The numerical results show clear gains using IA related methods, compared to frequency planning with frequency reuse 3 and to uncoordinated transmission, even at low to moderate SNR.

  • 159.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed CSI Acquisition and Coordinated Precoding for TDD Multicell MIMO Systems2016In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 65, no 5, p. 2890-2906Article in journal (Refereed)
    Abstract [en]

    Several distributed coordinated precoding methods exist in the downlink multicell MIMO literature, many of which assume perfect knowledge of received signal covariance and local effective channels. In this work, we let the notion of channel state information (CSI) encompass this knowledge of covariances and effective channels. We analyze what local CSI is required in the WMMSE algorithm for distributed coordinated precoding, and study how this required CSI can be obtained in a distributed fashion. Based on pilot-assisted channel estimation, we propose three CSI acquisition methods with different tradeoffs between feedback and signaling, backhaul use, and computational complexity. One of the proposed methods is fully distributed, meaning that it only depends on over-the-air signaling but requires no backhaul, and results in a fully distributed joint system when coupled with the WMMSE algorithm. Naively applying the WMMSE algorithm together with the fully distributed CSI acquisition results in catastrophic performance however, and therefore we propose a robustified WMMSE algorithm based on the well known diagonal loading framework. By enforcing properties of the WMMSE solutions with perfect CSI onto the problem with imperfect CSI, the resulting diagonally loaded spatial filters are shown to perform significantly better than the naive filters. The proposed robust and distributed system is evaluated using numerical simulations, and shown to perform well compared with benchmarks. Under centralized CSI acquisition, the proposed algorithm performs on par with other existing centralized robust WMMSE algorithms. When evaluated in a large scale fading environment, the performance of the proposed system is promising.

  • 160.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fast-Convergent Distributed Coordinated Precoding for TDD Multicell MIMO Systems2015In: Proc. IEEE Int. Workshop Computational Advances in Multi-Sensor Adaptive Process. (CAMSAP'15), 2015Conference paper (Refereed)
    Abstract [en]

    Several distributed coordinated precoding methods relying on over-the-air (OTA) iterations in time-division duplex (TDD) networks have recently been proposed. Each OTA iteration incurs overhead, which reduces the time available for data transmission. In this work, we therefore propose an algorithm which reaches good sum rate performance within just a few number of OTA iterations, partially due to non-overhead-incurring local iterations at the receivers. We formulate a scalarized multi-objective optimization problem where a linear combination of the weighted sum rate and the multiplexing gain is maximized. Using a well-known heuristic for smoothing the optimization problem together with a linearization step, the distributed algorithm is derived. When numerically compared to the state-of-the-art in a scenario with 1 to 3 OTA iterations allowed, the algorithm shows significant sum rate gains at high signal-to-noise ratios.

  • 161.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wideband MIMO Channel Diagonalization in the Time Domain2011In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), New York: IEEE , 2011, p. 1958-1962Conference paper (Refereed)
    Abstract [en]

    Methods for spatially diagonalizing wideband multiple-input multiple-output channels using linear finite impulse response (FIR) filters are investigated. The PSVD approach by applying the PQRD-BC algorithm for approximate singular value decomposition (SVD) of polynomial matrices is compared to the approach of performing a set of conventional SVDs in the Discrete Fourier Transform (DFT) domain, in terms of complexity and approximation error. Reduced order filters, based on the DFT-SVDs, are then obtained by optimizing the phases of the filters. Applying the phase optimized filters as linear filters then forms a benchmark on the accuracy attainable for any PSVD factorization, for the given filter length. Simulations show that the DFT-SVD method has significantly lower complexity than the PSVD by PQRD-BC, but results in higher order filters. On the other hand, the PSVD by PQRD-BC yields filters which are close to being perfectly unitary for all frequencies. To achieve good performance, the reduced order filters are around one order of magnitude longer than the channel impulse response length. Therefore there is no gain in performing time domain diagonalization using a polynomial SVD, compared to using a multicarrier solution.

  • 162.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björnson, Emil
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Weighted Sum Rate Optimization for Multicell MIMO Systems with Hardware-Impaired Transceivers2014Conference paper (Refereed)
    Abstract [en]

    Physical transceivers exhibit distortions from hardware impairments, of which traces remain even after compensation and calibration. Multicell MIMO coordinated beamforming methods that ignore these residual impairments may suffer from severely degraded performance. In this work, we consider a general model for the aggregate effect of the residual hardware impairments, and propose an iterative algorithm for finding locally optimal points to a weighted sum rate optimization problem. The importance of accounting for the residual hardware impairments is verified by numerical simulation, and a substantial gain over traditional time-division multiple access with impairments-aware resource allocation is observed.

  • 163.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mochaourab, Rami
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Interference Alignment-Aided Base Station Clustering using Coalition Formation2015In: Proceedings of the 49th Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, USA: IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    Base station clustering is necessary in large interference networks, where the channel state information (CSI) acquisition overhead otherwise would be overwhelming. In this paper, we propose a novel long-term throughput model for the clustered users which addresses the balance between interference mitigation capability and CSI acquisition overhead. The model only depends on statistical CSI, thus enabling long-term clustering. Based on notions from coalitional game theory, we propose a low-complexity distributed clustering method. The algorithm converges in a couple of iterations, and only requires limited communication between base stations. Numerical simulations show the viability of the proposed approach.

  • 164.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rami, Mochaourab
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Long-Term Base Station Clustering in Cellular Networks using Coalition Formation2016In: IEEE TRANSACTIONS ON SIGNAL AND INFORMATION PROCESSING OVER NETWORKS, ISSN 2373-776X, Vol. 2, no 3Article in journal (Refereed)
    Abstract [en]

    Interference alignment (IA) is a promising technique for interference mitigation in multicell networks due to its ability to completely cancel the intercell interference through linear precoding and receive filtering. In small networks, the amount of required channel state information (CSI) is modest and IA is therefore typically applied jointly over all base stations. In large networks, where the channel coherence time is short in comparison to the time needed to obtain the required CSI, base station clustering must be applied however. We model such clustered multicell networks as a set of coalitions, where CSI acquisition and IA precoding is performed independently within each coalition. We develop a long-term throughput model which includes both CSI acquisition overhead and the level of interference mitigation ability as a function of the coalition structure. Given the throughput model, we formulate a coalitional game where the involved base stations are the rational players. Allowing for individual deviations by the players, we formulate a distributed coalition formation algorithm with low complexity and low communication overhead that leads to an individually stable coalition structure. The dynamic clustering is performed using only long-term CSI, but we also provide a robust short-term precoding algorithm which accounts for the intercoalition interference when spectrum sharing is applied between coalitions. Numerical simulations show that the distributed coalition formation is generally able to reach long-term sum throughputs within 10 % of the global optimum.

  • 165.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rami, Mochaourab
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Globally Optimal Base Station Clustering in Interference Alignment-Based Multicell Networks2016In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 23, no 4, p. 512-516Article in journal (Refereed)
    Abstract [en]

    Coordinated precoding based on interference alignment is a promising technique for improving the throughputs in future wireless multicell networks. In small networks, all base stations can typically jointly coordinate their precoding. In large networks however, base station clustering is necessary due to the otherwise overwhelmingly high channel state information (CSI) acquisition overhead. In this work, we provide a branch and bound algorithm for finding the globally optimal base station clustering. The algorithm is mainly intended for benchmarking existing suboptimal clustering schemes. We propose a general model for the user throughputs, which only depends on the long-term CSI statistics. The model assumes intracluster interference alignment and is able to account for the CSI acquisition overhead. By enumerating a search tree using a best-first search and pruning sub-trees in which the optimal solution provably cannot be, the proposed method converges to the optimal solution. The pruning is done using specifically derived bounds, which exploit some assumed structure in the throughput model. It is empirically shown that the proposed method has an average complexity which is orders of magnitude lower than that of exhaustive search.

  • 166.
    Brandt, Rasmus
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Interference Alignment over a Combination of Space and Frequency2013In: 2013 IEEE International Conference on Communications Workshops, ICC 2013, IEEE Communications Society, 2013, p. 149-153Conference paper (Refereed)
    Abstract [en]

    Time or frequency extensions are integral in most information theoretic studies of interference alignment (IA), but a large majority of the more practically oriented studies have focused on narrowband space-only schemes. As wideband systems are now common, it is natural to investigate IA for frequency extended multiple antenna systems where precoding is performed over a combination of space and frequency dimensions. For this setting, we derive a necessary condition on IA feasibility using the properness framework and investigate the sum rate performance using simulations. Applying frequency extensions to multiple antenna systems allows for some additional users to be served interference-free, but our numerical results with synthetic channels indicate a practically more important improvement in terms of a power gain. Emulating a particular scenario using channel measurements, with real-world path losses and channel correlations, we see similar performance gains.

  • 167.
    Buendia, Ruben
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Harris, Matthew
    Phillips Research.
    Caffarel, Jeniffer
    Phillips Research.
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Hook Effect correction & resistance-based Cole fitting prior Cole model-based analysis: Experimental validation2010In: Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2010, IEEE Engineering in Medicine and Biology , 2010, p. 6563-6566Conference paper (Refereed)
    Abstract [en]

    The analysis of measurements of Electrical Bioimpedance (EBI) is on the increase for performing non-invasive assessment of health status and monitoring of pathophysiological mechanisms. EBI measurements might contain measurements artefacts that must be carefully removed prior to any further analysis. Cole model-based analysis is often selected when analysing EBI data and might lead to miss-conclusion if it is applied on data contaminated with measurement artefacts. The recently proposed Correction Function to eliminate the influence of the Hook Effect from EBI data and the fitting to the real part of the Cole model to extract the Cole parameters have been validated on experimental measurements. The obtained results confirm the feasible experimental use of these promising pre-processing tools that might improve the outcome of EBI applications using Cole model-based analysis.

  • 168.
    Bueno, Fermin
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Öberg, Johnny
    Kumar, Anshul
    Torkelsson, Mats
    Ericsson AB.
    High-Level Synthesis of a 1 Mbps Direct-Sequence Spread-Spectrum RAKE Receiver1996In: Workshop on Synthesis And System Integration, 1996, p. 170-177Conference paper (Refereed)
  • 169.
    Butt, M. M.
    et al.
    Interdisciplinary Center for Security, Trust and Reliability (SnT), University of Luxembourg, Luxembourg .
    Kapetanovic, D.
    Interdisciplinary Center for Security, Trust and Reliability (SnT), University of Luxembourg, Luxembourg .
    Ottersten, Björn
    Interdisciplinary Center for Security, Trust and Reliability (SnT), University of Luxembourg, Luxembourg .
    Maximizing Minimum Throughput Guarantees: The Small Violation Probability Region2013In: Wireless Communications Letters, ISSN 2162-2337, Vol. 2, no 3, p. 271-274Article in journal (Refereed)
    Abstract [en]

    Providing minimum throughput guarantees is one of the goals for radio resource allocation schemes. It is difficult to provide these guarantees without defining violation probability due to limited power budget and rapidly changing conditions of the wireless channel. For every practical scheduling scheme, there is a feasibility region defined by the minimum guaranteed throughput and the corresponding probability that the users fail to get the guaranteed throughput (violation probability). In this work, we focus on minimizing the violation probability specifically in the small probability region. We compare our results with major schedulers available in literature and show that our scheme outperforms them in the small violation probability region.

  • 170. Butt, M.Majid
    et al.
    Jorswieck, Eduard A.
    Ottersten, Björn
    Interdisciplinary Center For Security, Reliability and Trust (SnT) University of Luxembourg, Luxembourg.
    Maximizing energy efficiency for loss tolerant applications: The packet buffering case2013In: 2013 IEEE 24th International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), 2013, p. 2663-2667Conference paper (Refereed)
    Abstract [en]

    Energy efficient communication has emerged as one of the key areas of research due to its impact on industry and environment. Any potential degree of freedom (DoF) available in the system should be exploited smartly to design energy efficient systems. This paper proposes a framework for achieving energy efficiency for the data loss tolerant applications by exploiting the multiuser diversity and DoFs available through the packet loss pattern. For a real time application, there is a constraint on the maximum number of packets to be dropped successively that must be obeyed. We propose a channel-aware energy efficient scheduling scheme which schedules the packets such that the constraint on the average packet drop rate and the maximum number of successively dropped packets is fulfilled for the case when a finite number of unscheduled packets can be buffered. We analyze the scheme in the large user limit and show the energy gain due to buffering on the proposed scheme.

  • 171.
    Carlsson, Håkan
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Jaldén, Joakim
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    On-The-Fly Geometric Calibration of Inertial Sensor Arrays2017In: 2017 INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION (IPIN), 2017Conference paper (Refereed)
    Abstract [en]

    We present a maximum likelihood estimator for estimating the positions of accelerometers in an inertial sensor array. This method simultaneously estimates the positions of the accelerometers and the motion dynamics of the inertial sensor array and, therefore, does not require a predefined motion sequence nor any external equipment. Using an iterative block coordinate descent optimization strategy, the calibration problem can be solved with a complexity that is linear in the number of time samples. The proposed method is evaluated by Monte-Carlo simulations of an inertial sensor array built out of 32 inertial measurement units. The simulation results show that, if the array experiences sufficient dynamics, the position error is inversely proportional to the number of time samples used in the calibration sequence. Further, results show that for the considered array geometry and motion dynamics in the order of 2000 degrees/s and 2000 degrees/s(2), the positions of the accelerometers can be estimated with an accuracy in the order of 10(-6) m using only 1000 time samples. This enables fast on-the-fly calibration of the geometric errors in an inertial sensor array by simply twisting it by hand for a few seconds.

  • 172.
    Cavarec, Baptiste
    et al.
    KTH. Royal Inst Technol, Stockholm, Sweden..
    Bengtsson, Mats
    KTH.
    Pulse Design for Spectrally efficient Transmissions assuming Maximum Likelihood Detection2017In: 2017 Fifty-First Asilomar Conference on Signals, Systems, And Computers / [ed] Matthews, M B, IEEE Computer Society, 2017, p. 1754-1758Conference paper (Refereed)
    Abstract [en]

    In this paper, we analyse different spectrally efficient waveforming modulations under the framework of Gabor analysis. We derive a channel adaptive pulse design paradigm for such modulations under Maximum Likelihood (ML) detection at the receiver. The proposed pulse design is tested on a simulation scenario with high self-interference and compared with existing pulses at different spectral densities.

  • 173.
    Cavarec, Baptiste
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Schedule based self localization of asynchronous wireless nodes with experimental validation2017In: 2017 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 5975-5979, article id 7953303Conference paper (Refereed)
    Abstract [en]

    In this paper we have proposed clock error mitigation from the measurements in the scheduled based self localization system. We propose measurement model with clock errors while following a scheduled transmission among anchor nodes. Further, RLS algorithm is proposed to estimate clock error and to calibrate measurements of self localizing node against relative clock errors of anchor nodes. A full-scale experimental validation is provided based on commercial off-the-shelf UWB radios under IEEE-standardized protocols.

  • 174. Cazzorla, Alessandro
    et al.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing.
    De Angelis, Guido
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Moschitta, Antonio
    Dionigi, Marco
    Alimenti, Federico
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Carbone, Paolo
    Localizzazione in ambienti chiusi mediante trasmissione di segnali a banda ultra larga ed elaborazione statistica2013Conference paper (Refereed)
  • 175. Chalermsook, Parinya
    et al.
    Cygan, Marek
    Kortsarz, Guy
    Laekhanukit, Bundit
    Manurangsi, Pasin
    Na Nongkai, Danupon
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Trevisan, Luca
    From Gap-ETH to FPT-Inapproximability: Clique, Dominating Set, and More2017In: 2017 IEEE 58th Annual Symposium on Foundations of Computer Science (FOCS), IEEE Computer Society, 2017, Vol. 2017, p. 743-754Conference paper (Refereed)
    Abstract [en]

    We consider questions that arise from the intersection between the areas of approximation algorithms, subexponential-time algorithms, and fixed-parameter tractable algorithms. The questions, which have been asked several times (e.g., [1], [2], [3]) are whether there is a non-trivial FPT-approximation algorithm for the Maximum Clique (Clique) and Minimum Dominating Set (DomSet) problems parameterized by the size of the optimal solution. In particular, letting OPT be the optimum and N be the size of the input, is there an algorithm that runs in t(OPT) poly(N) time and outputs a solution of size f(OPT), for any functions t and f that are independent of N (for Clique, we want f(OPT) = omega(1))? In this paper, we show that both Clique and DomSet admit no non-trivial FPT-approximation algorithm, i.e., there is no o(OPT)-FPT-approximation algorithm for Clique and no f(OPT)-FPT-approximation algorithm for DomSet, for any function f (e.g., this holds even if f is an exponential or the Ackermann function). In fact, our results imply something even stronger: The best way to solve Clique and DomSet, even approximately, is to essentially enumerate all possibilities. Our results hold under the Gap Exponential Time Hypothesis (Gap-ETH) [4], [5], which states that no 2(o(n))-time algorithm can distinguish between a satisfiable 3SAT formula and one which is not even (1 - epsilon)-satisfiable for some constant epsilon > 0. Besides Clique and DomSet, we also rule out non-trivial FPT-approximation for Maximum Balanced Biclique, the problem of finding maximum subgraphs with hereditary properties (e.g., Maximum Induced Planar Subgraph), and Maximum Induced Matching in bipartite graphs. Previously only exact versions of these problems were known to be W[1]-hard [6], [7], [8]. Additionally, we rule out k(o(1))-FPT-approximation algorithm for Densest k-Subgraph although this ratio does not yet match the trivial O(k)-approximation algorithm. To the best of our knowledge, prior results only rule out constant factor approximation for Clique [9], [10] and log(1/4+epsilon) (OPT) approximation for DomSet for any constant epsilon > 0 [11]. Our result on Clique significantly improves on [9], [10]. However, our result on DomSet is incomparable to [11] since their results hold under ETH while our results hold under Gap-ETH, which is a stronger assumption.

  • 176. Chan, Wai Ming
    et al.
    Kim, Taejoon
    Ghauch, Hadi
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Subspace Estimation and Hybrid Precoding for Wideband Millimeter-Wave MIMO Systems2016In: 2016 50th Asilomar Conference on Signals, Systems and Computers, IEEE Computer Society, 2016, p. 286-290, article id 7869043Conference paper (Refereed)
    Abstract [en]

    There has been growing interest in millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems, which would likely employ hybrid analog-digital precoding with large-scale analog arrays deployed at wide bandwidths. Primary challenges here are how to efficiently estimate the large-dimensional frequency-selective channels and customize the wideband hybrid analog-digital precoders and combiners. To address these challenges, we propose a low-overhead channel subspace estimation technique for the wideband hybrid analog-digital MIMO precoding systems. We first show that the Gram matrix of the frequency-selective channel can be decomposed into frequency-flat and frequency-selective components. Based on this, the Arnoldi approach, leveraging channel reciprocity and time-reversed echoing, is employed to estimate a frequency-flat approximation of the frequency-selective mmWave channels, which is used to design the analog parts. After the analog precoder and combiner design, the low-dimensional frequency-selective channels are estimated using conventional pilot-based channel sounding. Numerical results show that considerable improvement in data-rate performance is possible.

  • 177. Chang, Z.
    et al.
    Lei, L.
    Zhang, H.
    Ristaniemi, T.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Han, Z.
    Energy-Efficient and Secure Resource Allocation for Multiple-Antenna NOMA With Wireless Power Transfer2018In: IEEE Transactions on Green Communications and Networking, ISSN 2473-2400, Vol. 2, no 4, p. 1059-1071Article in journal (Refereed)
  • 178.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Flåm, John T.
    NTNU - Norwegian University of Science and Technology.
    Kansanen, Kimmo
    NTNU - Norwegian University of Science and Technology.
    Ekman, Tobjorn
    NTNU - Norwegian University of Science and Technology.
    On MMSE estimation: A linear model under Gaussian mixture statistics2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 7, p. 3840-3845Article in journal (Refereed)
    Abstract [en]

    In a Bayesian linear model, suppose observation y = Hx + n stems from independent inputs x and n which are Gaussian mixture (GM) distributed. With known matrix H, the minimum mean square error (MMSE) estimator for x , has analytical form. However, its performance measure, the MMSE itself, has no such closed form. Because existing Bayesian MMSE bounds prove to have limited practical value under these settings, we instead seek analytical bounds for the MMSE, both upper and lower. This paper provides such bounds, and relates them to the signal-to-noise-ratio (SNR).

  • 179.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Koniaris, Christos
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Kleijn, W. Baastian
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Auditory model based optimization of MFCCs improves automatic speech recognition performance2009In: INTERSPEECH 2009: 10TH ANNUAL CONFERENCE OF THE INTERNATIONAL SPEECH COMMUNICATION ASSOCIATION 2009, 2009, p. 2943-2946Conference paper (Refereed)
    Abstract [en]

    Using a spectral auditory model along with perturbation based analysis, we develop a new framework to optimize a set of features such that it emulates the behavior of the human auditory system. The optimization is carried out in an off-line manner based on the conjecture that the local geometries of the feature domain and the perceptual auditory domain should be similar. Using this principle, we modify and optimize the static mel frequency cepstral coefficients (MFCCs) without considering any feedback from the speech recognition system. We show that improved recognition performance is obtained for any environmental condition, clean as well as noisy.

  • 180.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Structured Gaussian Mixture model based product VQ2010In: 18th European Signal Processing Conference (EUSIPCO-2010), EUROPEAN ASSOC SIGNAL SPEECH & IMAGE PROCESSING-EURASIP , 2010, p. 771-775Conference paper (Refereed)
    Abstract [en]

    In this paper, the Gaussian mixture model (GMM) based parametric framework is used to design a product vector quantization (PVQ) method that provides rate-distortion (R/D) performance optimality and bitrate scalability. We use a GMM consisting of a large number of Gaussian mixtures and invoke a block isotropic structure on the covariance matrices of the Gaussian mixtures. Using such a structured GMM, we design an optimum and bitrate scalable PVQ, namely an split (SVQ), for each Gaussian mixture. The use of an SVQ allows for a trade-off between complexity and R/D performance that spans the two extreme limits provided by an optimum scalar quantizer and an unconstrained vector quantizer. The efficacy of the new GMM based PVQ (GMPVQ) method is demonstrated for the application of speech spectrum quantization.

  • 181.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    A mixed-split scheme for 2D-DPCM based LSF quantization2005In: TENCON 2005 - 2005 IEEE REGION 10 CONFERENCE, VOLS 1-5, 2005, p. 864-869Conference paper (Refereed)
  • 182.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Analysis of conditional PDF based split VQ2007In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 14, no 11, p. 781-784Article in journal (Refereed)
  • 183.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Analysis-by-synthesis based switched transform domain split VQ using Gaussian mixture model2009In: 2009 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, VOLS 1- 8, PROCEEDINGS, 2009, p. 4117-4120Conference paper (Refereed)
  • 184.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Comparison of prediction based LSF quantization methods using split VQ2006In: INTERSPEECH 2006 AND 9TH INTERNATIONAL CONFERENCE ON SPOKEN LANGUAGE PROCESSING, VOLS 1-5, 2006, p. 237-240Conference paper (Refereed)
  • 185.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Computationally efficient optimum weighting function for vector quantization of LSF parameters2007In: 2007 9TH INTERNATIONAL SYMPOSIUM ON SIGNAL PROCESSING AND ITS APPLICATIONS, VOLS 1-3  Pages: 732-735, 2007Conference paper (Refereed)
  • 186.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Gaussian mixture model based switched split vector quantization of LSF parameters2007In: 2007 IEEE INTERNATIONAL SYMPOSIUM ON SIGNAL PROCESSING AND INFORMATION TECHNOLOGY, VOLS 1-3, 2007, p. 704-709Conference paper (Refereed)
  • 187.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Joint inter-frame and intra-frame predictive coding of LSF parameters2007In: 2007 9TH INTERNATIONAL SYMPOSIUM ON SIGNAL PROCESSING AND ITS APPLICATIONS, VOLS 1-3, 2007Conference paper (Refereed)
    Abstract [en]

    We explore the performance of two dimensional (2-D) prediction based LSF quantization method for both wide-band and telephone-band (narrow-band) speech. The 2-D prediction based method exploits both the inter-frame and intra-frame correlations of LSF parameters. We show that a 4th order 2-D predictor provides optimum prediction gain as well as improved quantization performance at various choices of frame shift for both wide-band and telephone-band speech. Existing one dimensional (1-D) predictive method, exploiting only inter-frame correlation, results in poor performance at larger frame shifts; whereas proposed 2-D predictor provides lower spectral distortion as well as lower number of outliers compared to existing memory-based and memory-less methods.

  • 188.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Low complexity wide-band LSF quantization using GMM of uncorrelated Gaussian Mixtures2008Conference paper (Refereed)
  • 189.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Normalized two stage SVQ for minimum complexity wide-band LSF quantization2007In: INTERSPEECH 2007: 8TH ANNUAL CONFERENCE OF THE INTERNATIONAL SPEECH COMMUNICATION ASSOCIATION, VOLS 1-4, 2007, p. 261-264Conference paper (Refereed)
  • 190.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Optimum switched split vector quantization of LSF parameters2008In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 88, no 6, p. 1528-1538Article in journal (Refereed)
  • 191.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Optimum transform domain split VQ2008In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 15, p. 285-288Article in journal (Refereed)
  • 192.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Predicting VQ performance bound for LSF coding2008In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 15, p. 166-169Article in journal (Refereed)
  • 193.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Reduced complexity two stage vector quantization2009In: Digital signal processing (Print), ISSN 1051-2004, E-ISSN 1095-4333, Vol. 19, no 3, p. 476-490Article in journal (Refereed)
  • 194.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Sequential split vector quantization of LSF parameters using conditional PDF2007In: 2007 IEEE International Conference on Acoustics, Speech, and Signal Processing, Vol IV, Pts 1-3, 2007, p. 1101-1104Conference paper (Refereed)
  • 195.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Switched conditional PDF-based split VQ using Gaussian mixture model2008In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 15, p. 91-94Article in journal (Refereed)
  • 196.
    Chatterjee, Saikat
    et al.
    Indian Institute of Science.
    Sreenivas, T.V.
    Indian Institute of Science.
    Two stage transform vector quantization of LSFs for wideband speech coding2006In: INTERSPEECH 2006 AND 9TH INTERNATIONAL CONFERENCE ON SPOKEN LANGUAGE PROCESSING, VOLS 1-5, 2006, p. 233-236Conference paper (Refereed)
  • 197.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Look ahead orthogonal matching pursuit2011In: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, 2011, p. 4024-4027Conference paper (Refereed)
  • 198.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skolglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust matching pursuit for recovery of Gaussian sparse signal2011In: 2011 Digital Signal Processing and Signal Processing Education Meeting, DSP/SPE 2011 - Proceedings, 2011, p. 420-424Conference paper (Refereed)
    Abstract [en]

    For compressive sensing (CS) recovery of Gaussian sparse signal, we explore the framework of Bayesian linear models to achieve a robust reconstruction performance in the presence of measurement noise. Using a priori statistical knowledge, we develop a minimum mean square error (MMSE) estimation based iterative greedy search algorithm. Through experimental evaluations, we show that the new algorithm provides a robust CS reconstruction performance compared to an existing least square based algorithm.

  • 199.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skolglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Statistical post-processing improves basis pursuit denoising performance2010In: 2010 IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2010, 2010, p. 23-27Conference paper (Refereed)
  • 200. Chatzinotas, S.
    et al.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Cognitive interference alignment between small cells and a macrocell2012In: 2012 19th International Conference on Telecommunications, ICT 2012, IEEE , 2012, p. 6221210-Conference paper (Refereed)
    Abstract [en]

    Small cells have attracted large interest lately in the research community, mainly due to easy and quick deployment. In addition, a large number of small cells is in general more energy efficient than macrocells since less power is required to combat path loss and get across the wireless medium. However, in current network configurations these two types of cells have to coexist over the same spectrum because existing cellular systems are mainly based on macrocells and additional bandwidth for small cell deployments is scarce and too expensive to acquire. In this context, this contribution investigates an underlay cognitive communication technique which exploits interference alignment across multiple antennas in order to mitigate the interference of small cell User Terminals (UTs) towards the macrocell Base Station (BS). More specifically, three techniques for aligning interference are investigated, namely static, coordinated and un-coordinated. The system performance is evaluated and compared based on sum-rate capacity, primary rate protection ratio and primary to secondary rate ratio.

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