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  • 1. Abu-Shaban, Zohair
    et al.
    Mehrpouyan, Hani
    M. R., Bhavani Shankar
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Reduced complexity satellite broadcast receiver with interference mitigation in correlated noise2018Ingår i: International Journal of Satellite Communications and Networking, Vol. 36, nr 5, s. 402-415Artikel i tidskrift (Refereegranskat)
  • 2. Afzal, Hassan
    et al.
    Aouada, Djamila
    Mirbach, Bruno
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Full 3D Reconstruction of Non-Rigidly Deforming Objects2018Ingår i: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP), ISSN 1551-6857, E-ISSN 1551-6865, Vol. 14, nr 1s, s. 24-1Artikel i tidskrift (Refereegranskat)
  • 3.
    Ainomae, Ahti
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Bengtsson, Mats
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Trump, Tonu
    Tallinn Univ Technol, Dept Radio & Telecommun Engn, EE-12616 Tallinn, Estonia..
    Distributed Largest Eigenvalue-Based Spectrum Sensing Using Diffusion LMS2018Ingår i: IEEE TRANSACTIONS ON SIGNAL AND INFORMATION PROCESSING OVER NETWORKS, ISSN 2373-776X, Vol. 4, nr 2, s. 362-377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we propose a distributed detection scheme for cognitive radio (CR) networks, based on the largest eigenvalues (LEs) of adaptively estimated correlation matrices (CMs), assuming that the primary user signal is temporally correlated. The proposed algorithm is fully distributed, there by avoiding the potential single point of failure that a fusion center would imply. Different forms of diffusion least mean square algorithms are used for estimating and averaging the CMs over the CR network for the LE detection and the resulting estimation performance is analyzed using a common framework. In order to obtain analytic results on the detection performance, the exact distribution of the CM estimates are approximated by a Wishart distribution, by matching the moments. The theoretical findings are verified through simulations.

  • 4.
    Alizadeh, Mahmoud
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Characterisation, Modelling and Digital Pre-DistortionTechniques for RF Transmitters in Wireless Systems2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wireless systems have become an inevitable part of modern technologies serving humankind. The rapid growth towards large dimensional systems, e.g. 5th generation (5G) technologies, incurs needs for improving the performance of the systems and considering aspects to make them as far as possible environmentally friendly in terms of power efficiency, cost, and so on. One of the key parts of every wireless communication system is the radio frequency (RF) power amplifier (PA), which consumes the largest percentage of the total energy. Hence, accurate models of RF PAs can be used to optimize their design and to compensate for signal distortions. This thesis starts with two methods for frequency-domain characterisation to analyse the dynamic behaviour of PAs in 3rd-order non-linear systems. Firstly, two-tone signals superimposed on large-signals are used to analyse the frequency-domain symmetry properties of inter-modulation (IM) distortions and Volterra kernels in different dynamic regions of RF PAs in a single-input single-output (SISO) system. Secondly, three-tone signals are used to characterise the 3rd-order self- and cross-Volterra kernels of RF PAs in a 3 × 3 multiple-input multiple-output (MIMO) system. The main block structures of the models are determined by analysing the frequency-domain symmetry properties of the Volterra kernels in different three-dimensional (3D) frequency spaces. This approach significantly simplifies the structure of the 3rd-order non-linear MIMO model.

    The following parts of the thesis investigate techniques for behavioural modelling and linearising RF PAs. A piece-wise modelling technique is proposed to characterise the dynamic behaviour and to mitigate the impairments of non-linear RF PAs at different operating points (regions). A set of thresholds decompose the input signal into several sub-signals that drive the RF PAs at different operating points. At each operating point, the PAs are modelled by one sub-model, and hence, the complete model consists of several sub-models. The proposed technique reduces the model errors compared to conventional piece-wise modelling techniques.

    A block structure modelling technique is proposed for RF PAs in a MIMO system based on the results of the three-tone characterisation technique. The main structures of the 3rd- and higher-order systems are formulated based on the frequency dependence of each block. Hence, the model can describe more relevant interconnections between the inputs and outputs than conventional polynomial-type models.

    This thesis studies the behavioural modelling and compensation techniques in both the time and the frequency domains for RF PAs in a 3 × 3MIMO system. The 3D time-domain technique is an extension of conventional 2D generalised memory polynomial (GMP) techniques. To reduce the computational complexity, a frequency-domain technique is proposed that is efficient and feasible for systems with long memory effects. In this technique, the parameters of the model are estimated within narrow sub-bands. Each sub-band requires only a few parameters, and hence the size of the model for each sub-band is reduced.

  • 5.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Rönnow, Daniel
    University of Gävle.
    Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers2018Ingår i: 6th Telecommunications forum TELFOR 2018, Belgrade, Serbia, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a new approach is proposed to decompose the basis functions in a piece-wise modeling technique for nonlinear radio frequency (RF) power amplifiers. The proposed technique treats the discontinuity problem of the model output at the joint points between different operating points, whereas preserves the linear and nonlinear properties of the original model within each region. Experimental results show that the proposed technique outperforms the conventional piece-wise model in terms of model errors.

  • 6.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Rönnow, Daniel
    University of Gävle.
    Behavioural modelling and digital pre-distortion techniques for RF PAs in a 3x3 MIMO system2018Ingår i: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern telecommunications are moving towards (massive) multi-input multi-output systems in 5th generation (5G) technology, increasing the dimensionality of the system dramatically. In this paper, the impairments of radio frequency (RF)power amplifiers (PAs) in a 3x3 MIMO system are compensated in both time and frequency domains. A three-dimensional(3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of a system is split into several narrow sub-bands, and the parameters of the system are estimated for each subband. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test (DUT) consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioural modelling and digital pre-distortion(DPD) perspectives. The results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects by about 23.5 dB and 7 dB in terms of the normalized mean square error and adjacent channel leakage ratio, respectively.

  • 7.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Department of Electronics, Mathematics and Natural Sciences, University of Gävle (HiG), Gävle, Sweden.
    Rönnow, D.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Characterization of Volterra Kernels for RF Power Amplifiers Using a Two-Tone Signal and a Large-Signal2018Ingår i: 2018 12th International Conference on Communications, COMM 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 351-356, artikel-id 8430119Konferensbidrag (Refereegranskat)
    Abstract [en]

    The 3rd-order Volterra kernels of a radio frequency (RF) power amplifier (PA) are characterized using a large-signal and a two-tone probing-signal. In this technique, the magnitude and phase asymmetries of the kernels of the PA excited by the probing-signal are analyzed in different amplitude regions of the large-signal. The device under test is a class-AB PA operating at 2.14 GHz. The maximum sweeping frequency space of the probing-signal is 20 MHz. The results indicate that the Volterra kernels of the PA show different behaviors (frequency dependency and asymmetry) in different regions.

  • 8.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Rönnow, Daniel
    University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    A new Block-Structure Modeling Technique for RF Power Amplifiers in a 2×2 MIMO System2017Ingår i: 2017 13th International Conference on Advanced Technologies, Systems and Services in Telecommunications, TELSIKS 2017 - Proceeding, Nis, Serbia: IEEE, 2017, Vol. 2017, s. 224-227Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new block-structure behavioral model is proposed for radio frequency power amplifiers in a 2×2 multiple-input multiple-output system including input cross-talk. The proposed model forms kernels of blocks of different nonlinear order that correspond to the significant frequency response of measured frequency domain Volterra kernels. The model can therefore well describe the input-output relationships of the nonlinear dynamic behavior of PAs. The proposed model outperforms conventional models in terms of model errors.

  • 9. Alodeh, M.
    et al.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Energy-Efficient Symbol-Level Precoding in Multiuser MISO Based on Relaxed Detection Region2016Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 15, nr 5, s. 3755-3767Artikel i tidskrift (Refereegranskat)
  • 10. Alodeh, M.
    et al.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Symbol-Level Multiuser MISO Precoding for Multi-Level Adaptive Modulation2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 8, s. 5511-5524Artikel i tidskrift (Refereegranskat)
  • 11. Alodeh, M.
    et al.
    Spano, D.
    Kalantari, A.
    Tsinos, C. G.
    Christopoulos, D.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Symbol-Level and Multicast Precoding for Multiuser Multiantenna Downlink: A State-of-the-Art, Classification, and Challenges2018Ingår i: IEEE Communications Surveys and Tutorials, ISSN 1553-877X, E-ISSN 1553-877X, Vol. 20, nr 3, s. 1733-1757Artikel i tidskrift (Refereegranskat)
  • 12.
    Avula, Ramana R.
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Månsson, Daniel
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Privacy-preserving smart meter control strategy including energy storage losses2018Ingår i: Proceedings - 2018 IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT-Europe 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, artikel-id 8571537Konferensbidrag (Refereegranskat)
    Abstract [en]

    Privacy-preserving smart meter control strategies proposed in the literature so far make some ideal assumptions such as instantaneous control without delay, lossless energy storage systems etc. In this paper, we present a one-step-ahead predictive control strategy using Bayesian risk to measure and control privacy leakage with an energy storage system. The controller estimates energy state using a three-circuit energy storage model to account for steady-state energy losses. With numerical experiments, the controller is evaluated with real household consumption data using a state-of-the-art adversarial algorithm. Results show that the state estimation of the energy storage system significantly affects the controller's performance. The results also show that the privacy leakage can be effectively reduced using an energy storage system but at the expense of energy loss.

  • 13.
    Avula, Ramana Reddy
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Chin, Jun-Xing
    Power Systems Laboratory, ETH Zurich, Switzerland.
    Hug, Gabriela
    Power Systems Laboratory, ETH Zurich, Switzerland.
    Smart Meter Privacy Control Strategy Including Energy Storage Degradation2019Ingår i: 2019 IEEE Milan PowerTech, IEEE, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a degradation-aware privacy control strategy for smart meters by taking into account the capacity fade and energy loss of the battery, which has not been included previously. The energy management strategy is designed by minimizing the weighted sum of both privacy loss and total energy storage losses, where the weightage is set using a trade-off parameter. The privacy loss is measured in terms of Bayesian risk of an unauthorized hypothesis test. By making first-order Markov assumptions, the stochastic parameters of energy loss and capacity fade of the energy storage system are modelled using degradation maps. Using household power consumption data from the ECO dataset, the proposed control strategy is numerically evaluated for different trade-off parameters. Results show that, by including the degradation losses in the design of the privacy-enhancing control strategy, significant improvement in battery life can be achieved, in general, at the expense of some privacy loss.

  • 14.
    B. da Silva Jr., Jose Mairton
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Nätverk och systemteknik.
    Ghauch, Hadi
    Fodor, Gabor
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Smart Antenna Assignment is Essential in Full-Duplex Communications2019Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Full-duplex communications have the potential to almost double the spectralefficiency. To realize such a potentiality, the signal separation at base station’s antennasplays an essential role. This paper addresses the fundamentals of such separationby proposing a new smart antenna architecture that allows every antenna to beeither shared or separated between uplink and downlink transmissions. The benefitsof such architecture are investigated by an assignment problem to optimally assignantennas, beamforming and power to maximize the weighted sum spectral efficiency.We propose a near-to-optimal solution using block coordinate descent that divides theproblem into assignment problems, which are NP-hard, a beamforming and powerallocation problems. The optimal solutions for the beamforming and power allocationare established while near-to-optimal solutions to the assignment problems are derivedby semidefinite relaxation. Numerical results indicate that the proposed solution isclose to the optimum, and it maintains a similar performance for high and low residualself-interference powers. With respect to the usually assumed antenna separationtechnique and half-duplex transmission, the sum spectral efficiency gains increase withthe number of antennas. We conclude that our proposed smart antenna assignment forsignal separation is essential to realize the benefits of multiple antenna full-duplexcommunications.

  • 15. Bahnsen, Alejandro Correa
    et al.
    Aouada, Djamila
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Example-dependent cost-sensitive decision trees2015Ingår i: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 42, nr 19, s. 6609-6619Artikel i tidskrift (Refereegranskat)
  • 16. Bahnsen, Alejandro Correa
    et al.
    Aouada, Djamila
    Stojanovic, Aleksandar
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Feature engineering strategies for credit card fraud detection2016Ingår i: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 51, s. 134-142Artikel i tidskrift (Refereegranskat)
  • 17.
    Bao, Jinchen
    et al.
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 611756, Sichuan, Peoples R China..
    Ma, Zheng
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 611756, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Tsiftsis, Theodoros A.
    Jinan Univ, Sch Elect & Informat Engn, Zhuhai 519070, Peoples R China..
    Zhu, Zhongliang
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 611756, Sichuan, Peoples R China..
    Bit-Interleaved Coded SCMA With Iterative Multiuser Detection: Multidimensional Constellations Design2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 11, s. 5292-5304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the constellation/codebook design of a promising uplink multiple access technique, sparse code multiple access (SCMA), proposed for the fifth generation mobile networks. The application of bit-interleaved coded modulation with iterative multiuser detection is considered for uplink SCMA over fading channels. Extrinsic information transfer chart is used to aid the analysis and the design of multidimensional constellations, and the design criteria for multidimensional constellations and labelings optimization are thus established. Furthermore, a new and simple approach of multi-stage optimization for the multidimensional constellation design is proposed for SCMA, to improve the bit-error rate performance and alleviate the complexity of turbo multiuser detection. Numerical and simulation results are also provided to demonstrate the performance and verify the efficiency of the proposed scheme, compared with the state of the art.

  • 18.
    Bassi, German
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Univ Paris Sud, CNRS, Cent Supelec, Lab Signaux & Syst,L2S,UMR 8506, F-91192 Gif Sur Yvette, France.
    Piantanida, Pablo
    Shamai (Shitz), Shlomo
    The Wiretap Channel With Generalized Feedback: Secure Communication and Key Generation2019Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 65, nr 4, s. 2213-2233Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is a well-known fact that feedback does not increase the capacity of point-to-point memoryless channels, however, its effect in secure communications is not fully understood yet. In this paper, an achievable scheme for the wiretap channel with generalized feedback is presented. This scheme, which uses the feedback signal to generate a shared secret key between the legitimate users, encrypts the message to be sent at the bit level. New capacity results for a class of channels are provided, as well as some new insights into the secret key agreement problem. Moreover, this scheme recovers previously reported rate regions from the literature, and thus it can be seen as a generalization that unifies several results in the field.

  • 19.
    Bassi, Germán
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Piantanida, Pablo
    Shamai, Shlomo
    The Secret Key Capacity of a Class of Noisy Channels with Correlated Sources2019Ingår i: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 21, nr 8, artikel-id 732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the problem of secret key generation over a wiretap channel when the terminals observe correlated sources. These sources are independent of the main channel and the users overhear them before the transmission takes place. A novel outer bound is proposed and, employing a previously reported inner bound, the secret key capacity is derived under certain less-noisy conditions on the channel or source components. This result improves upon the existing literature where the more stringent condition of degradedness is required. Furthermore, numerical evaluation of the achievable scheme and previously reported results for a binary model are presented; a comparison of the numerical bounds provides insights on the benefit of the chosen scheme.

  • 20.
    Bassi, Germán
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Piantanida, Pablo
    Lossy Communication Subject to Statistical Parameter Privacy2018Ingår i: 2018 IEEE International Symposium on Information Theory (ISIT) - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 1031-1035, artikel-id 8437690Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate the problem of sharing (communi-cating) the outcomes of a memoryless source when some of its statistical parameters must be kept private. Privacy is measured in terms of the Bayesian statistical risk according to a desired loss function while the quality of the reconstruction is measured by the average per-letter distortion. We first bound -uniformly over all possible estimators- the expected risk from below. This information-theoretic bound depends on the mutual information between the parameters and the disclosed (noisy) samples. We then present an achievable scheme that guarantees an upper bound on the average distortion while keeping the risk above a desired threshold, even when the length of the sample increases.

  • 21.
    Cao, Le Phuong
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Optimal Transmit Strategies for Multi-antenna Systems with Joint Sum and Per-antenna Power Constraints2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Trådlös kommunikation har idag kommit att bli en viktig del av våra dagliga liv. Under det senaste decenniet har både antalet användare och deras efterfrågan på trådlös data ökat enormt. Att utöka antalet antenner i sändare och mottagare är lovande strategier för att möta det ständigt ökande trafikbehovet. I den här avhandlingen studerar vi optimala transmissionsstrategier för multi-antennsystem med avancerade effektbegränsningar. Mer specifikt antas sammanlänkade begränsningar på total effekt och effekt per antenn. Vi fokuserar på tre olika modeller, nämligen multi-antenn punkt-till-punkt kanaler, wiretap-kanaler samt s.k. massiv MIMO (eng. multiple-input multiple-output) scenarier. Lösningar ges antingen i form av slutna matematiska uttryck, alternativt genom effektiva iterativa algoritmer redo att implementeras i praktiska system.

    Den första delen av avhandlingen studerar optimala transmissionsstrategier för punkt-till-punkt MISO (eng. multiple-input single-output) samt MIMO-kanaler med sammanlänkade begränsningar på total effekt och effekt per antenn. För Gaussiska MISO-kanaler härleds en sluten karakterisering av en optimal ’beamforming’ -strategi. Vi visar att det alltid går att hitta en optimal ’beamforming’-strategi som allokerar den maximala totaleffekten med faser matchade till de komplexa kanalkoefficienterna. En intressant egenskap hos den optimala effektallokeringen är att närhelst den optimala effektallokeringen med enbart total effektbegränsning endast överskrider de individuella begränsningarna för specifika antenner, erhålls en optimal lösning genom att allokera maximal per-antenn effekt till just dessa antenner. Den återstående effekten distribueras sedan över de övriga antennerna enligt ett ekvivalent men reducerat optimeringsproblem med färre kanalkoefficienter. För Gaussiska MIMO-kanaler visas att om en obegränsad optimal effektallokering för en antenn överskrider den individuella, per antenn angivna, begränsningen så är maximal effekt allokerad för just dessa antenner i den optimala strategin. Denna observation används för att beskriva en iterativ algoritm som beräknar den optimala transmissionsstrategin.

    I den andra delen av avhandlingen undersöker vi optimala transmissionsstrategier för Gaussiska MISO wiretap-kanaler. Motiverat av faktumet att den icke-säkrade kapaciteten över MISO wiretap-kanalen vanligtvis är större än den säkrade s.k. ’secrecy’-kapaciteten, studerar vi den optimala avvägningen mellan dessa två överföringshastigheter givet olika effektbegränsningar. Mer specifikt studeras total effektbegränsning enskilt, individuell effektbegränsning per antenn enskilt, samt sammanlänkade begränsningar på båda dessa. För att hitta regionsgränsen för optimala hastigheter, vilken beskriver den optimala avvägningen mellan icke-säkrad sändning och ’secrecy’-hastighet, härleds lösningar till relaterade problem där vi söker optimala transmissionsstrategier som maximerar den viktade summan av hastigheter med olika effektbegränsningar. Ekvivalenta formuleringar av optimeringsproblemen används för att härleda optimala transmissionsstrategier eftersom ursprungsproblemen ej är konvexa. En optimal lösning för problemet med total effektbegränsning ges i sluten form. För individuell effektbegränsning per antenn tillhandahåller vi nödvändiga villkor för att finna en optimal effektallokering. Tillräckliga villkor är endast tillgängliga i fallet av två sändarantenner. För specialfallet av parallella kanaler kan transmissionsstrategier härledas från ett ekvivalent problem för en punkt-till-punkt kanal. I detta fall existerar ingen avvägning mellan icke-säkrade och ’secrecy’ kapaciteten, endast en optimal strategi som maximerar båda kapaciteter.

    Avslutningsvis studeras optimala strategier för storskaliga MISO samt massiva MIMO system med sammankopplad hybrid analog-digital ’beamforming’-arkitektur,  radiofrekvens-kedja samt individuella effektbegränsningar per antenn. Studerat system är konfigurerat så att varje radiofrekvens-kedja matar en grupp av antenner. För det storskaliga MISO systemet tillhandahålls nödvändiga och tillräckliga villkor för att design av optimala analoga och digitala kodningsstrategier ska vara möjligt. Optimal strategi uppnås då fasförskjutningen i varje antenn är matchad till motsvarande kanal, varvid konstruktiv samverkan uppstår. För massiv MIMO ges dessvärre endast nödvändiga villkor. De nödvändiga villkoren för att designa digitala kodningsstrategier etableras baserat på en generaliserad s.k. ’water-filling’ effektallokeringsmetod med sammanlänkade begränsningar på total effekt och effekt per antenn, medan villkoren för de analoga kodningsstrategierna endast är baserade på effektbegränsningar per antenn. Vidare beskriver vi optimal effektallokering för sammankopplade system baserat på två egenskaper: (i) Varje radiokedja utnyttjas till full effekt, samt (ii) i fallet då optimala effektallokeringen i det obegränsade problemet överskrider specifika antenners begränsningar fås den optimala lösningen genom att allokera maximal effekt till motsvarande antenner.Resultaten i denna avhandling visar att framtida trådlösa nätverk kan uppnå högre datahastigheter med lägre effektförbrukning. Den design av optimala transmissionsstrategier som beskrivs i denna avhandling är därför värdefulla i den pågående implementeringen av framtida trådlösa nätverk. De insikter som ges genom analys och design av optimala transmissionsstrategier i avhandlingen ger också förståelse inom optimal effektallokering i praktiska implementeringar av multi-antennsystem.

  • 22.
    Cao, Le Phuong
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Transmit Beamforming for Single-User Large-Scale MISO Systems With Sub-Connected Architecture and Power Constraints2018Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 10, s. 2096-2099Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This letter considers optimal transmit beamforming for a sub-connected large-scale MISO system with RF chain and per-antenna power constraints. The system is configured such that each RF chain serves a group of antennas. For the hybrid scheme, necessary and sufficient conditions to design the optimal digital and analog precoders are provided. It is shown that, in the optimum, the optimal phase shift at each antenna has to match the channel coefficient and the phase of the digital precoder. In addition, an iterative algorithm is provided to find the optimal power allocation. We study the case where the power constraint on each RF chain is smaller than the sum of the corresponding per-antenna power constraints. Then, the optimal power is allocated based on two properties: each RF chain uses full power and if the optimal power allocation of the unconstraint problem violates a per-antenna power constraint then it is optimal to allocate the maximal power for that antenna.

  • 23.
    Cao, Phuong
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Optimal Transmit Strategies for Gaussian MISO Wiretap Channels2018Ingår i: IEEE Transactions on Information Forensics and Security, ISSN 1556-6013, E-ISSN 1556-6021Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This paper studies the optimal tradeoff between secrecy and non-secrecy rates of the MISO wiretap channels for different power constraint settings:sum power constraint only, per-antenna power constraints only and joint sum and per-antenna power constraints. The problem is motivated by the fact thatchannel capacity and secrecy capacity are generally achieved by different transmit strategies. First, a necessary and sufficient condition to ensure a positive secrecy capacity is shown. The optimal tradeoff between secrecy rate and transmission rate is characterized by a weighted rate sum maximization problem. Since this problem is not necessarily convex, equivalent problem formulations are introduced to derive the optimal transmit strategies. Under sum power constraint only, a closed-form solution is provided. Under per-antenna power constraints, necessary conditions to find the optimal power allocation are provided. Sufficient conditions are provided for the special case of two transmit antennas. For the special case of parallel channels, the optimal transmit strategies can deduced from an equivalent point-to-point channel problem. Lastly, the theoretical results are illustrated by numerical simulations.

  • 24.
    Cavarec, Baptiste
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Bengtsson, Mats
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    CHANNEL DEPENDENT CODEBOOK DESIGN IN SPATIAL MODULATION2018Ingår i: 2018 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE, 2018, s. 6413-6417Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a modulation design based on Spatial Modulation for the uplink in IoT applications. The proposed modulation design uses a Tabu search based deterministic heuristic to adapt the modulation link based on channel information fed back by the receiver. Our approach allows adaptivity to rate and energy constraints. We numerically validate the proposed method on a scenario with full channel state information available at the transceiver, showing clear performance gains compared to simpler heuristics and channel independent codebook designs.

  • 25.
    Celebi, Hasan Basri
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Pitarokoilis, Antonios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Training-assisted channel estimation for low-complexity squared-envelope receivers2018Ingår i: 2018 IEEE 19TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2018, s. 196-200Konferensbidrag (Refereegranskat)
    Abstract [en]

    Squared-envelope receivers, also known as energy detectors, are, due to their simplified circuitry, low-cost and low-complexity receivers. Hence they are attractive implementation structures for future Internet-of-Things (IoT) applications. Even though there is considerable work on the wider research area of squared-envelope receivers, a comprehensive comparison and statistical characterization of training-assisted channel estimators for squared-envelope receivers appear to be absent from the literature. A detailed description of practical channel estimation schemes is necessary for the optimal training design of latency-constrained IoT applications. In this paper, various channel estimators are derived, their bias and variance are studied, and their performance is numerically compared against the Cramer-Rao lower bound.

  • 26.
    Celebi, Hasan Basri
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Pitarokoilis, Antonios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Training-Assisted Channel Estimation for Low-Complexity Squared-Envelope Receivers2018Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC, Institute of Electrical and Electronics Engineers Inc. , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Squared-envelope receivers, also known as energy detectors, are, due to their simplified circuitry, low-cost and low-complexity receivers. Hence they are attractive implementation structures for future Internet-of-Things (IoT) applications. Even though there is considerable work on the wider research area of squared-envelope receivers, a comprehensive comparison and statistical characterization of training-assisted channel estimators for squared-envelope receivers appear to be absent from the literature. A detailed description of practical channel estimation schemes is necessary for the optimal training design of latency-constrained IoT applications. In this paper, various channel estimators are derived, their bias and variance are studied, and their performance is numerically compared against the Cramer-Rao lower bound.

  • 27.
    Champati, Jaya
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Al-Zubaidy, Hussein
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Statistical Guarantee Optimization for Age of Information for the D/G/1 Queue2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Age of Information (AoI) has proven to be a useful metric in networked systems where timely information updates are of importance. Recently, minimizing the “average age” has received considerable attention. However, various applications pose stricter age requirements on the updates which demand knowledge of the AoI distribution. In this work, we study the distribution of the AoI and devise a problem of minimizing the tail of the AoI distribution function with respect to the frequency of generating information updates, i.e., the sampling rate of monitoring a process, for the D/G/1 queue model under FCFS queuing discipline. We argue that computing an exact expression for the AoI distribution may not always be feasible. Therefore, we opt for computing a bound on the tail of the AoI distribution and use it to formulate a tractable α-relaxed Upper Bound Minimization Problem (α-UBMP), where α > 1 is an approximation factor. This approximation can be used to obtain “good” heuristic solutions. We demonstrate the efficacy of our approach by solving α-UBMP for the D/M/1 queue. We show, using simulation, that the rate solutions obtained are near optimal for minimizing the tail of the AoI distribution.

  • 28.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Al-Zubaidy, H.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Statistical guarantee optimization for age of information for the D/G/1 queue2018Ingår i: INFOCOM 2018 - IEEE Conference on Computer Communications Workshops, Institute of Electrical and Electronics Engineers Inc. , 2018, s. 130-135Konferensbidrag (Refereegranskat)
    Abstract [en]

    Age of Information (AoI) has proven to be a useful metric in networked systems where timely information updates are of importance. Recently, minimizing the 'average age' has received considerable attention. However, various applications pose stricter age requirements on the updates which demand knowledge of the AoI distribution. In this work, we study the distribution of the AoI and devise a problem of minimizing the tail of the AoI distribution function with respect to the frequency of generating information updates, i.e., the sampling rate of monitoring a process, for the D/G/1 queue model under FCFS queuing discipline. We argue that computing an exact expression for the AoI distribution may not always be feasible. Therefore, we opt for computing a bound on the tail of the AoI distribution and use it to formulate a tractable a-relaxed Upper Bound Minimization Problem (a-UBMP), where a > 1 is an approximation factor. This approximation can be used to obtain 'good' heuristic solutions. We demonstrate the efficacy of our approach by solving a-UBMP for the D/M/1 queue. We show, using simulation, that the rate solutions obtained are near optimal for minimizing the tail of the AoI distribution. © 2018 IEEE.

  • 29.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Al-Zubaidy, Hussein
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    On the Distribution of AoI for the GI/GI/1/1 and GI/GI/1/2*Systems: Exact Expressions and Bounds2019Ingår i: IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (IEEE INFOCOM 2019), IEEE , 2019, s. 37-45Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since Age of Information (AoI) has been proposed as a metric that quantifies the freshness of information updates in a communication system, there has been a constant effort in understanding and optimizing different statistics of the AoI process for classical queueing systems. In addition to classical queuing systems, more recently, systems with no queue or a unit capacity queue storing the latest packet have been gaining importance as storing and transmitting older packets do not reduce AoI at the receiver. Following this line of research, we study the distribution of AoI for the GI/GI/1/1 and GI/GI/1/2* systems, under non-preemptive scheduling. For any single-source-single-server queueing system, we derive, using sample path analysis, a fundamental result that characterizes the AoI violation probability, and use it to obtain closed-form expressions for D/GI/1/1, M/GI/1/1 as well as systems that use zero-wait policy. Further, when exact results are not tractable, we present a simple methodology for obtaining upper bounds for the violation probability for both GI/GI/1/1 and GI/GI/1/2* systems. An interesting feature of the proposed upper bounds is that, if the departure rate is given, they overestimate the violation probability by at most a value that decreases with the arrival rate. Thus, given the departure rate and for a fixed average service, the bounds are tighter at higher utilization.

  • 30. Chang, Z.
    et al.
    Lei, L.
    Zhang, H.
    Ristaniemi, T.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Han, Z.
    Energy-Efficient and Secure Resource Allocation for Multiple-Antenna NOMA With Wireless Power Transfer2018Ingår i: IEEE Transactions on Green Communications and Networking, ISSN 2473-2400, Vol. 2, nr 4, s. 1059-1071Artikel i tidskrift (Refereegranskat)
  • 31. Charalambous, C. D.
    et al.
    Stavrou, Photios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Kourtellaris, C. K.
    Tzortzis, I.
    Directed Information Subject to a Fidelity. Applications to Conditionally Gaussian Processes2018Ingår i: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 3071-3076, artikel-id 8550054Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper is concerned with the minimization of directed information over conditional distributions that satisfy a fidelity of reconstructing a conditionally Gaussian random process by another process, causally. This information theoretic extremum problem is directly linked, via bounds to the optimal performance theoretically attainable by non-causal, causal and zero-delay codes of data compression. The application example includes the characterization of causal rate distortion function for conditionally Gaussian random processes subject to a meansquare error fidelity.

  • 32.
    Charalambous, Themistoklis
    et al.
    Aalto Univ, Dept Elect Engn & Automat, Espoo, Finland..
    Kim, Su Min
    Korea Polytech Univ, Dept Elect Engn, Shihung, South Korea..
    Nomikos, Nikolaos
    Univ Aegean, Dept Informat & Commun Syst Engn, Samos, Greece..
    Bengtsson, Mats
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Johansson, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Relay-pair selection in buffer-aided successive opportunistic relaying using a multi-antenna source2019Ingår i: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 84, s. 29-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study a cooperative network with a buffer-aided multi-antenna source, multiple half-duplex (HD) buffer-aided relays and a single destination. Such a setup could represent a cellular downlink scenario, in which the source can be a more powerful wireless device with a buffer and multiple antennas, while a set of intermediate less powerful devices are used as relays to reach the destination. The main target is to recover the multiplexing loss of the network by having the source and a relay to simultaneously transmit their information to another relay and the destination, respectively. Successive transmissions in such a cooperative network, however, cause inter-relay interference (IRI). First, by assuming global channel state information (CSI), we show that the detrimental effect of IRI can be alleviated by precoding at the source, mitigating or even fully cancelling the interference. A cooperative relaying policy is proposed that employs a joint precoding design and relay-pair selection. Note that both fixed rate and adaptive rate transmissions can be considered. For the case when channel state information is only available at the receiver side (CSIR), we propose a relay selection policy that employs a phase alignment technique to reduce the IRI. The performance of the two proposed relay pair selection policies are evaluated and compared with other state-of-the-art relaying schemes in terms of outage and throughput. The results show that the use of a powerful source can provide considerable performance improvements.

  • 33.
    Chen, Xianhao
    et al.
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China.;Xidian Univ, State Key Lab Integrated Serv Networks, Xian 710126, Shaanxi, Peoples R China..
    Liu, Gang
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Ma, Zheng
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Zhang, Xi
    Texas A&M Univ, Dept Elect & Comp Engn, Networking & Informat Syst Lab, College Stn, TX 77843 USA..
    Xu, Weiqiang
    Zhejiang Sci Tech Univ, Sch Informat Sci & Technol, Hangzhou 310018, Zhejiang, Peoples R China..
    Fan, Pingzhi
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Optimal Power Allocations for Non-Orthogonal Multiple Access Over 5G Full/Half-Duplex Relaying Mobile Wireless Networks2019Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 18, nr 1, s. 77-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the power allocation problems for non-orthogonal multiple access with coordinated direct and relay transmission (CDRT-NOMA), where a base station (BS) communicates with its nearby user directly, while communicating with its far user only through a dedicated relay node (RN). The RN is assumed to operate in either half-duplex relaying (HDR) mode or full-duplex relaying (FDR) mode. Based on instantaneous channel state information (CSI), the dynamic power allocation problems under HDR and FDR schemes are formulated respectively, with the objective of maximizing the minimum user achievable rate. After demonstrating the quasi-concavity of the considered problems, we derive the optimal closed-form power allocation policies under the HDR scheme and the FDR scheme. Then, a hybrid relaying scheme dynamically switching between HDR and FDR schemes is further designed. Moreover, we also study the fixed power allocation problems for the considered CDRT-NOMA systems based on statistical CSI so as to optimize the long-term system performance. The simulations show that our proposed power allocation policies can significantly enhance the performance of CDRT-NOMA systems.

  • 34. Christopoulos, D.
    et al.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Multicast Multigroup Precoding and User Scheduling for Frame-Based Satellite Communications2015Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, nr 9, s. 4695-4707Artikel i tidskrift (Refereegranskat)
  • 35.
    Ciftci, Baris
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Norrga, Staffan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Kildehöj, Lars
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    A Proposal for Wireless Control of Submodules in Modular Multilevel Converters2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The modular multilevel converter is one of the most preferred converters for high-power conversion applications. Wireless control of the submodules can contribute to its evolution by lowering the material and labor costs of cabling and by increasing the availability of the converter. However, wireless control leads to many challenges for the control and modulation of the converter as well as for proper low-latency high-reliability communication. This paper investigates the tolerable asynchronism between phase-shifted carriers used in modulation from a wireless control point of view and proposes a control method along with communication protocol for wireless control. The functionality of the proposed method is validated by computer simulations in steady state.

  • 36.
    Ciftci, Baris
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Norrga, Staffan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Simple Distributed Control for Modular Multilevel Converters2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The central control of MMC becomes demanding in computation power and communication bandwidth as the number of submodules increase. Distributed control methods can overcome these bottlenecks. In this paper, a simple distributed control method together with synchronization of modulation carriers in the submodules is presented. The proposal is implemented on a lab-scale MMC with asynchronous-serial communication on a star network between the central and local controllers. It is shown that the proposed control method works satisfactorily in the steady state. The method can be applied as is to MMCs with any number of submodules per arm.

  • 37. Danilo, Spano
    et al.
    Symeon, Chatzinotas
    Stefano, Andrenacci
    Jens, Krause
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Per-antenna power minimization in symbol-level precoding for the multibeam satellite downlink2018Ingår i: International Journal of Satellite Communications and Networking, Vol. 37, nr 1, s. 15-30Artikel i tidskrift (Refereegranskat)
  • 38.
    del Aguila Pla, Pol
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Inverse problems in signal processing: Functional optimization, parameter estimation and machine learning2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Inversa problem uppstår vid alla vetenskapliga undersökningar. Våra sinnen och mätinstrument -rådata -ger faktiskt sällan svaren vi letar efter. Vi behöver då utveckla vår förståelse av hur data genererats, d.v.s., använda en modell, för att kunna dra korrekta slutsatser. Att lösa inversa problem är,enkelt uttryckt, att använda modeller för att få fram den information man vill ha från tillgängliga data.

    Signalbehandling handlar om utveckling av system som skapar, behandlar eller överför signaler (d.v.s., indexerade data) för att nå ett visst mål. Ett exempel på mål för en sådant system är att lösa ett inverst problem utifrån den analyserade signalen med hjälp av en modell. Signalbehandling kan dock även handla om att skapa en signal, så att denna avslöjar en parameter för utredning genom ett inverst problem. Inversa problem och signalbehandling är två fält som överlappar i stor utsträckning, och som använder sig av samma koncept och verktyg. Denna avhandling utforskar gränslandet mellan dessa två fält, och presenterar resultat inom modellering, optimering, statistik, maskininlärning, biomedicinsk avbildning och automatisk kontroll.

    Det nya vetenskapliga innehållet i den här avhandlingen är baserat på de sju artiklar som återges här i Del II. I fem av dessa artiklar beskrivs ett antal relaterade metoder för optimering och maskininlärning för källokalisering medhjälp av diffusions- och konvolutionsmodellering, med tillämpningar framförallt inom biomedicinsk bildbehandling. Dessa inkluderas i Publikationer A, B,E, F och G, och behandlar också modellering och simulering av en familj av bildbaserade immunkemiska detektionsmetoder. Publikation C presenterar analys av ett system för klocksynkronisering mellan två noder förbundna med en kanal, vilket är ett problem med särskild relevans för automatisk kontroll. Systemet använder en specifik noddesign för att generera en signal som möjliggör skattning av synkroniseringsparametrarna. Analysen bidrar avsevärt till metodiken för att identifiera sågtandsmönstrande signalmodeller under olika förhållanden. Avslutningsvis presenteras i Publikation D resultat som tidigare i stora drag förbisetts inom signalbehandlingsfältet. Här karaktäriseras även den information som kvantiserade linjära modeller innehåller om deras läges- och skalparametrar.

  • 39.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Cell detection by functional inverse diffusion and non-negative group sparsity – Part I: Modeling and Inverse Problems2018Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, nr 20, s. 5407-5421Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this two-part paper, we present a novel framework and methodology to analyze data from certain image-based biochemical assays, e.g., ELISPOT and Fluorospot assays. In this first part, we start by presenting a physical partial differential equations (PDE) model up to image acquisition for these biochemical assays. Then, we use the PDEs' Green function to derive a novel parametrization of the acquired images. This parametrization allows us to propose a functional optimization problem to address inverse diffusion. In particular, we propose a non-negative group-sparsity regularized optimization problem with the goal of localizing and characterizing the biological cells involved in the said assays. We continue by proposing a suitable discretization scheme that enables both the generation of synthetic data and implementable algorithms to address inverse diffusion. We end Part I by providing a preliminary comparison between the results of our methodology and an expert human labeler on real data. Part II is devoted to providing an accelerated proximal gradient algorithm to solve the proposed problem and to the empirical validation of our methodology.

  • 40.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Cell detection by functional inverse diffusion and non-negative group sparsity – Part II: Proximal optimization and Performance evaluation2018Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, nr 20, s. 5422-5437Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this two-part paper, we present a novel framework and methodology to analyze data from certain image-based biochemical assays, e.g., ELISPOT and Fluorospot assays. In this second part, we focus on our algorithmic contributions. We provide an algorithm for functional inverse diffusion that solves the variational problem we posed in Part I. As part of the derivation of this algorithm, we present the proximal operator for the non-negative group-sparsity regularizer, which is a novel result that is of interest in itself, also in comparison to previous results on the proximal operator of a sum of functions. We then present a discretized approximated implementation of our algorithm and evaluate it both in terms of operational cell-detection metrics and in terms of distributional optimal-transport metrics.

  • 41.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Cell detection on image-based immunoassays2018Ingår i: 2018 IEEE 15th International Symposium on Biomedical Imaging (ISBI 2018), IEEE, 2018, s. 431-435Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cell detection and counting in the image-based ELISPOT and Fluorospot immunoassays is considered a bottleneck.The task has remained hard to automatize, and biomedical researchers often have to rely on results that are not accurate.Previously proposed solutions are heuristic, and data-based solutions are subject to a lack of objective ground truth data. In this paper, we analyze a partial differential equations model for ELISPOT, Fluorospot, and assays of similar design. This leads us to a mathematical observation model forthe images generated by these assays. We use this model to motivate a methodology for cell detection. Finally, we provide a real-data example that suggests that this cell detection methodology and a human expert perform comparably.

  • 42.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Convolutional group-sparse coding and source localization2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a new interpretation of non-negatively constrained convolutional coding problems as blind deconvolution problems with spatially variant point spread function. In this light, we propose an optimization framework that generalizes our previous work on non-negative group sparsity for convolutional models. We then link these concepts to source localization problems that arise in scientific imaging, and provide a visual example on an image derived from data captured by the Hubble telescope.

  • 43.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Inferences from quantized data - Likelihood logconcavityManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we present to the signal processing community the most general likelihood logconcavity statement for quantized data to date, together with its proof, which has never been published. In particular, we show how Prékopa’s theorem can be used to show that the likelihood for quantized linear models is jointly logconcave with respect to both its location and scale parameter in a broad range of cases. In order to show this result and explain the limitations of the proof technique, we study sets generated by combinations of points with positive semi-definite matrices whose sum is the identity.

  • 44.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Pellaco, Lissy
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Dwivedi, Satyam
    Ericsson Research.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Clock synchronization over networks - Identifiability of the sawtooth modelManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we analyze the two-node joint clocksynchronization and ranging problem. We focus on the case of nodes that employ time-to-digital converters to determine the range between them precisely. This specific design leads to a sawtooth model for the captured signal, which has not been studied in detail before from an estimation theory standpoint. In the study of this model, we recover the basic conclusion of a well-known article by Freris, Graham, and Kumar in clock synchronization. Additionally, we discover a surprising identifiability result on the sawtooth signal model: noise improves the theoretical condition of the estimation of the phase and offset parameters. To complete our study, we provide performance references for joint clock synchronization and ranging. In particular, we present the Cramér-Rao lower bounds that correspond to a linearization of our model, as well as a simulation study on the practical performance of basic estimation strategies under realistic parameters. With these performance references, we enable further research in estimation strategies using the sawtooth model and pave the path towards industrial use.

  • 45.
    del Aguila Pla, Pol
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Saxena, Vidit
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Jaldén, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    SpotNet – Learned iterations for cell detection in image-based immunoassays2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Accurate cell detection and counting in the image-based ELISpot and FluoroSpot immunoassays is a challenging task. Recently proposed methodology matches human accuracy by leveraging knowledge of the underlying physical process of these assays and using proximal optimization methods to solve an inverse problem. Nonetheless, thousands of computationally expensive iterations are often needed to reach a near-optimal solution. In this paper, we exploit the structure of the iterations to design a parameterized computation graph, SpotNet, that learns the patterns embedded within several training images and their respective cell information. Further, we compare SpotNet to a convolutional neural network layout customized for cell detection. We show empirical evidence that, while both designs obtain a detection performance on synthetic data far beyond that of a human expert, SpotNet is easier to train and obtains better estimates of particle secretion for each cell.

  • 46. Demisse, G. G.
    et al.
    Aouada, D.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Deformation Based Curved Shape Representation2018Ingår i: IEEE Transaction on Pattern Analysis and Machine Intelligence, ISSN 0162-8828, E-ISSN 1939-3539, Vol. 40, nr 6, s. 1338-1351Artikel i tidskrift (Refereegranskat)
  • 47. Demisse, Girum G.
    et al.
    Aouada, Djamila
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Deformation-Based 3D Facial Expression Representation2018Ingår i: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP), ISSN 1551-6857, E-ISSN 1551-6865, Vol. 14, nr 1s, s. 17-1Artikel i tidskrift (Refereegranskat)
  • 48. Dokhanchi, S. H.
    et al.
    Mysore, B. S.
    Mishra, K. V.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    A mmWave Automotive Joint Radar-Communications System2019Ingår i: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 55, nr 3, s. 1241-1260Artikel i tidskrift (Refereegranskat)
  • 49. Domouchtsidis, S.
    et al.
    Tsinos, C. G.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Symbol-Level Precoding for Low Complexity Transmitter Architectures in Large-Scale Antenna Array Systems2019Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 18, nr 2, s. 852-863Artikel i tidskrift (Refereegranskat)
  • 50.
    Du, Rong
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Gkatzikis, Lazaros
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    On Maximizing Sensor Network Lifetime by Energy Balancing2018Ingår i: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 5, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many physical systems, such as water/electricity distribution networks, are monitored by battery-powered wireless-sensor networks (WSNs). Since battery replacement of sensor nodes is generally difficult, long-term monitoring can be only achieved if the operation of the WSN nodes contributes to long WSN lifetime. Two prominent techniques to long WSN lifetime are 1) optimal sensor activation and 2) efficient data gathering and forwarding based on compressive sensing. These techniques are feasible only if the activated sensor nodes establish a connected communication network (connectivity constraint), and satisfy a compressive sensing decoding constraint (cardinality constraint). These two constraints make the problem of maximizing network lifetime via sensor node activation and compressive sensing NP-hard. To overcome this difficulty, an alternative approach that iteratively solves energy balancing problems is proposed. However, understanding whether maximizing network lifetime and energy balancing problems are aligned objectives is a fundamental open issue. The analysis reveals that the two optimization problems give different solutions, but the difference between the lifetime achieved by the energy balancing approach and the maximum lifetime is small when the initial energy at sensor nodes is significantly larger than the energy consumed for a single transmission. The lifetime achieved by energy balancing is asymptotically optimal, and that the achievable network lifetime is at least 50% of the optimum. Analysis and numerical simulations quantify the efficiency of the proposed energy balancing approach.

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