Digitala Vetenskapliga Arkivet

Ändra sökning
Avgränsa sökresultatet
123456 1 - 50 av 284
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    A. Mouris, Boules
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap. KTH Royal Institute of Technology.
    Ghauch, Hadi
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Nätverk och systemteknik.
    Thobaben, Ragnar
    Jonsson, B. Lars G.
    KTH, Tidigare Institutioner (före 2005), Teoretisk elektroteknik. KTH, Tidigare Institutioner (före 2005), Elektrotekniska system. KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Multi-tone Signal Optimization for Wireless Power Transfer in the Presence of Wireless Communication Links2020Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we study optimization of multi-tone signals for wireless power transfer (WPT) systems. We investigate different non-linear energy harvesting models. Two of them are adopted to optimize the multi-tone signal according to the channel state information available at the transmitter. We show that a second-order polynomial curve-fitting model can be utilized to optimize the multi-tone signal for any RF energy harvester design. We consider both single-antenna and multi-antenna WPT systems. In-band co-existing communication links are also considered in this work by imposing a constraint on the received power at the nearby information receiver to prevent its RF front end from saturation. We emphasize the importance of imposing such constraint by explaining how inter-modulation products, due to saturation, can cause high interference at the information receiver in the case of multi-tone signals. The multi-tone optimization problem is formulated as a non-convex linearly constrained quadratic program. Two globally optimal solution approaches using mixed-integer linear programming and finite branch-and-bound techniques are proposed to solve the problem. The achieved improvement resulting from applying both solution methods to the multi-tone optimization problem is highlighted through simulations and comparisons with other solutions existing in the literature.

  • 2.
    A. Mouris, Boules
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap. KTH Royal Institute of Technology.
    Kolitsidas, Christos
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Thobaben, Ragnar
    A Dual-Polarized Multi-Antenna Structure for Simultaneous Transmission of Wireless Information and Power2019Ingår i: A Dual-Polarized Multi-Antenna Structure for Simultaneous Transmission of Wireless Information and Power, IEEE, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a dual-polarized multi-antenna structure is designed at 2.45 GHz with the goal of allowing simultaneous transmission of wireless information and power. Differential feeding was used to minimize the mutual coupling due to radiation leakage in addition to a mushroom-type EBG structure for suppressing the surface waves. Simulation results for the proposed structure show a mutual coupling level lower than -40 dB between the information transmitting antenna and the power transmitting antennas for both polarizations. The isolation level between the antennas is improved by at least 22 dB and 14 dB for the E-plane and H-plane coupling, respectively.

  • 3. 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)
    Abstract [en]

    The recent commercial trends towards using smaller dish antennas for satellite receivers and the growing density of broadcasting satellites necessitate the application of robust adjacent satellite interference cancellation schemes. This orbital density growth along with the wider beamwidth of a smaller dish have imposed an overloaded scenario at the satellite receiver, where the number of transmitting satellites exceeds the number of receiving elements at the dish antenna. To ensure successful operation in this practical scenario, we propose a satellite receiver that enhances signal detection from the desired satellite by mitigating the interference from neighboring satellites. Towards this objective, we propose an enhanced list-based group-wise search detection (E-LGSD) receiver under the assumption of spatially correlated additive noise. To further enhance detection performance, the proposed satellite receiver utilizes a newly designed whitening filter to remove the spatial correlation among the noise parameters, while also applying a preprocessor that maximizes the signal-to-interference-plus-noise ratio. We exploit the structure of this filter and propose a reduced complexity LGSD (RC-LGSD) receiver. Extensive simulations under practical scenarios show that the proposed receiver enhances the performance of satellite broadcast systems in the presence of adjacent satellite interference compared with existing methods. Also, under pointing error, RC-LGSD exhibits similar behavior to that of the optimum receiver

  • 4. Afzal, Hassan
    et al.
    Aouada, Djamila
    Mirbach, Bruno
    Ottersten, Björn
    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)
    Abstract [en]

    In this article, we discuss enhanced full 360 degrees 3D reconstruction of dynamic scenes containing non-rigidly deforming objects using data acquired from commodity depth or 3D cameras. Several approaches for enhanced and full 3D reconstruction of non-rigid objects have been proposed in the literature. These approaches suffer from several limitations due to requirement of a template, inability to tackle large local deformations and topology changes, inability to tackle highly noisy and low-resolution data, and inability to produce online results. We target online and template-free enhancement of the quality of noisy and low-resolution full 3D reconstructions of dynamic non-rigid objects. For this purpose, we propose a view-independent recursive and dynamic multi-frame 3D super-resolution scheme for noise removal and resolution enhancement of 3D measurements. The proposed scheme tracks the position and motion of each 3D point at every timestep by making use of the current acquisition and the result of the previous iteration. The effects of system blur due to per-point tracking are subsequently tackled by introducing a novel and efficient multi-level 3D bilateral total variation regularization. These characteristics enable the proposed scheme to handle large deformations and topology changes accurately. A thorough evaluation of the proposed scheme on both real and simulated data is carried out. The results show that the proposed scheme improves upon the performance of the state-of-the-art methods and is able to accurately enhance the quality of low-resolution and highly noisy 3D reconstructions while being robust to large local deformations.

  • 5.
    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.

  • 6.
    Ali, Sadiq
    et al.
    Electrical Engineering, University of Engineering and Technology of Peshawar, Pakistan.
    Jansson, Magnus
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Seco-Granados, Gonzalo
    Telecommunications and Systems Engineering, Universitat Autònoma de Barcelona, Spain.
    Lopez-Salcedo, Jose A.
    Universitat Autònoma de Barcelona, Spain.
    Kronecker-Based Fusion Rule for Cooperative Spectrum Sensing with Multi-Antenna Receivers2014Ingår i: Electronics, ISSN 2079-9292, Vol. 3, nr 4, s. 675-688Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper considers a novel fusion rule for spectrum sensing scheme for a cognitive radio network with multi-antenna receivers. The proposed scheme exploits the fact that when any primary signal is present, measurements are spatially correlated due to presence of inter-antenna and inter-receiver spatial correlation. In order to exploit this spatial structure, the generalized likelihood ratio test (GLRT) operates with the determinant of the sample covariance matrix. Therefore, it depends on the sample size N and the dimensionality of the received data (i.e., the number of receivers K and antennas L). However, when the dimensionality fK; Lg is on the order, or larger than the sample size N, the GLRT degenerates due to the ill-conditioning of the sample covariance matrix. In order to circumvent this issue, we propose two techniques that exploit the inner spatial structure of the received observations by using single pair and multi-pairs Kronecker products. The performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages with respect to the traditional (i.e., unstructured) GLRT approach.

  • 7.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 8.
    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.

  • 9.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap. Department of Electrical Engineering, Mathematics and Science, University of Gävle, Gävle, Sweden.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Rönnow, Daniel
    Univ Gavle, Dept Elect Engn Math & Sci, Gavle, Sweden..
    Behavioral modeling and digital pre-distortion techniques for RF PAs in a 3 x 3 MIMO system2019Ingår i: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 11, nr 10, s. 989-999Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern telecommunications are moving towards (massive) multi-input multi-output (MIMO) systems in 5th generation (5G) technology, increasing the dimensionality of the systems dramatically. In this paper, the impairments of radio frequency (RF) power amplifiers (PAs) in a 3 x 3 MIMO system are compensated in both the time and the 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 the system is split into several narrow sub-bands, and the parameters of the model are estimated for each sub-band. 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 consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioral modeling and digital pre-distortion (DPD) perspectives. The experimental results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects in the both time and frequency domains.

  • 10.
    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.

  • 11.
    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.

  • 12.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap. University of Gävle.
    Rönnow, Daniel
    University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, 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.

  • 13. 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)
    Abstract [en]

    This paper addresses the problem of exploiting interference among simultaneous multiuser transmissions in the downlink of multiple-antenna systems. Using symbol-level precoding, a new approach toward addressing the multiuser interference is discussed through jointly utilizing the channel state information (CSI) and data information (DI). The interference among the data streams is transformed under certain conditions to a useful signal that can improve the signal-to-interference noise ratio (SINR) of the downlink transmissions and as a result the system's energy efficiency. In this context, new constructive interference precoding techniques that tackle the transmit power minimization (min power) with individual SINR constraints at each user's receiver have been proposed. In this paper, we generalize the constructive interference (CI) precoding design under the assumption that the received MPSK symbol can reside in a relaxed region in order to be correctly detected. Moreover, a weighted maximization of the minimum SNR among all users is studied taking into account the relaxed detection region. Symbol error rate analysis (SER) for the proposed precoding is discussed to characterize the tradeoff between transmit power reduction and SER increase due to the relaxation. Based on this tradeoff, the energy efficiency performance of the proposed technique is analyzed. Finally, extensive numerical results show that the proposed schemes outperform other state-of-the-art techniques. © 2002-2012 IEEE

  • 14. Alodeh, M.
    et al.
    Chatzinotas, S.
    Ottersten, Björn
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    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)
    Abstract [en]

    Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems aimed at creating constructive interference among transmitted data streams. This can be enabled by designing the precoded signal of the multiantenna transmitter on a symbol level, taking into account both channel state information and data symbols. Previous literature has studied this paradigm for Mary phase shift keying modulations by addressing various performance metrics, such as power minimization and maximization of the minimum rate. In this paper, we extend this to generic multi-level modulations, i.e., Mary quadrature amplitude modulation by establishing connection to PHY layer multicasting with phase constraints. Furthermore, we address the adaptive modulation schemes which are crucial in enabling the throughput scaling of symbol-level precoded systems. In this direction, we design the signal processing algorithms for minimizing the required power under per-user signal to interference noise ratio or goodput constraints. Extensive numerical results show that the proposed algorithm provides considerable power and energy efficiency gains, while adapting the employed modulation scheme to match the requested data rate.

  • 15.
    Asif, Rizwan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS.
    Löffel, Hendrik Jan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS.
    Assavasangthong, Vorapol
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS.
    Martinelli, Giulio
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS.
    Gajland, Phillip
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Datavetenskap, Teoretisk datalogi, TCS.
    Rodríguez Gálvez, Borja
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Aerial path planning for multi-vehicles2019Ingår i: Proceedings - IEEE 2nd International Conference on Artificial Intelligence and Knowledge Engineering, AIKE 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, s. 267-272, artikel-id 8791733Konferensbidrag (Refereegranskat)
    Abstract [en]

    Unmanned Aerial Vehicles (UAV) are a potential solution to fast and cost efficient package delivery services. There are two types of UAVs, namely fixed wing (UAV-FW) and rotor wing (UAV-RW), which have their own advantages and drawbacks. In this paper we aim at providing different solutions to a collaborating multi-agent scenario combining both UAVs types. We show the problem can be reduced to the facility location problem (FLP) and propose two local search algorithms to solve it: Tabu search and simulated annealing.

  • 16.
    Avula, Ramana R.
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    On design of optimal smart meter privacy control strategy against adversarial MAP detection2020Ingår i: Proceedings of the ICASSP 2020 - 2020 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Barcelona, Spain, 2020Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the optimal control problem of the maximum a posteriori (MAP) state sequence detection of an adversary using smart meter data. The privacy leakage is measured using the Bayesian risk and the privacy-enhancing control is achieved in real-time using an energy storage system. The control strategy is designed to minimize the expected performance of a non-causal adversary at each time instant. With a discrete-state Markov model, we study two detection problems: when the adversary is unaware or aware of the control. We show that the adversary in the former case can be controlled optimally. In the latter case, where the optimal control problem is shown to be non-convex, we propose an adaptive-grid approximation algorithm to obtain a sub-optimal strategy with reduced complexity. Although this work focuses on privacy in smart meters, it can be generalized to other sensor networks. 

    Ladda ner fulltext (pdf)
    fulltext
  • 17.
    Avula, Ramana R.
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Optimal privacy-by-design strategy for user demand shaping in smart grids2020Ingår i: Proceedings of the 2020 IEEE Power & Energy Society Innovative Smart Grid Technologies, Washington, DC, USA, USA, 2020Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we propose an optimal privacy-by-design strategy using an energy storage system (ESS) that is capable of shaping the user demand to follow a time-varying target profile. In addition, we consider the ESS usage cost due to its energy losses and capacity degradation. We measure the privacy leakage in terms of the Bayesian risk. The proposed strategy is computed by solving a multi-objective optimization problem using the Markov decision process framework. With numerical simulations using real household consumption data and a lithium-ion battery model, we study the trade-off between the achievable Bayesian risk, the variations in the user demand from the target profile and the energy storage cost. The results show that by trading-off some privacy, the variations in the user demand can be reduced while improving the battery lifetime.

    Ladda ner fulltext (pdf)
    fulltext
  • 18.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 19.
    Avula, Ramana Reddy
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, 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.

    Ladda ner fulltext (pdf)
    fulltext
  • 20.
    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.

  • 21.
    Bahnsen, Alejandro Correa
    et al.
    Univ Luxembourg, Interdisciplinary Ctr Secur Reliabil & Trust.
    Aouada, Djamila
    Univ Luxembourg, Interdisciplinary Ctr Secur Reliabil & Trust.
    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. Univ Luxembourg, Interdisciplinary Ctr Secur Reliabil & Trust.
    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)
    Abstract [en]

    Several real-world classification problems are example-dependent cost-sensitive in nature, where the costs due to misclassification vary between examples. However, standard classification methods do not take these costs into account, and assume a constant cost of misclassification errors. State-of-the-art example-dependent cost-sensitive techniques only introduce the cost to the algorithm, either before or after training, therefore, leaving opportunities to investigate the potential impact of algorithms that take into account the real financial example-dependent costs during an algorithm training. In this paper, we propose an example-dependent cost-sensitive decision tree algorithm, by incorporating the different example-dependent costs into a new cost-based impurity measure and a new cost-based pruning criteria. Then, using three different databases, from three real-world applications: credit card fraud detection, credit scoring and direct marketing, we evaluate the proposed method. The results show that the proposed algorithm is the best performing method for all databases. Furthermore, when compared against a standard decision tree, our method builds significantly smaller trees in only a fifth of the time, while having a superior performance measured by cost savings, leading to a method that not only has more business-oriented results, but also a method that creates simpler models that are easier to analyze. (C) 2015 Elsevier Ltd. All rights reserved.

  • 22.
    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.

  • 23.
    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.

  • 24.
    Bassi, Germán
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Johansson, Karl H.
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Statistical Parameter Privacy2020Ingår i: Privacy in Dynamical Systems / [ed] Farhad Farokhi, Springer Nature, 2020, s. 65-82Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    We investigate the problem of sharing the outcomes of a parametric source with an untrusted party while ensuring the privacy of the parameters. We propose privacy mechanisms which guarantee parameter privacy under both Bayesian statistical as well as information-theoretic privacy measures. The properties of the proposed mechanisms are investigated and the utility-privacy trade-off is analyzed.

  • 25.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 26.
    Bassi, Germán
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Piantanida, Pablo
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    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.

  • 27.
    Bassi, Germán
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    On the Mutual Information of Two Boolean Functions, with Application to Privacy2019Ingår i: Proceedings 2019 IEEE International Symposium on Information Theory (ISIT), IEEE , 2019, s. 1197-1201Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate the behavior of the mutual information between two Boolean functions of correlated binary strings. The covariance of these functions is found to be a crucial parameter in the aforementioned mutual information. We then apply this result in the analysis of a specific privacy problem where a user observes a random binary string. Under particular conditions, we characterize the optimal strategy for communicating the outcomes of a function of said string while preventing to leak any information about a different function.

  • 28.
    Borpatra Gohain, Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Jansson, Magnus
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    RELATIVE COST BASED MODEL SELECTION FOR SPARSE HIGH-DIMENSIONAL LINEAR REGRESSION MODELS2020Konferensbidrag (Refereegranskat)
  • 29.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 30.
    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.

  • 31.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 32.
    Cao, Phuong
    et al.
    Ericsson AB, Kista, Sweden.
    Oechtering, Tobias J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Optimal Transmit Strategies for Gaussian MISO Wiretap Channels2020Ingår i: IEEE Transactions on Information Forensics and Security, ISSN 1556-6013, E-ISSN 1556-6021, Vol. 15, s. 829-838Artikel i tidskrift (Refereegranskat)
    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 that channel 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 derived. Sufficient conditions are provided for the special case of two transmit antennas. For the special case of aligned channels, the optimal transmit strategies can deduced from an equivalent point-to-point channel problem. Last, the theoretical results are illustrated by numerical simulations.

    Ladda ner fulltext (pdf)
    fulltext
  • 33.
    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.

  • 34. Celebi, Hasan Basri
    et al.
    Pitarokoilis, Antonios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Low-latency communication with computational complexity constraints2019Ingår i: Proceedings of the International Symposium on Wireless Communication Systems, 2019, s. 384-388Konferensbidrag (Refereegranskat)
    Abstract [en]

    Low-latency communication is one of the most important application scenarios in next-generation wireless networks. Often in communication-theoretic studies latency is defined as the time required for the transmission of a packet over a channel. However, with very stringent latency requirements and complexity constrained receivers, the time required for the decoding of the packet cannot be ignored and must be included in the total latency analysis through accurate modeling. In this paper, we first present a way to calculate decoding time using per bit complexity metric and introduce an empirical model that accurately describes the trade-off between the decoding complexity versus the performance of state-of-the-art codes. By considering various communication parameters, we show that including the decoding time in latency analyses has a significant effect on the optimum selection of parameters.

  • 35.
    Celebi, Hasan Basri
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Pitarokoilis, Antonios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, 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. , 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.

  • 36.
    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.

  • 37.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Al-Zubaidy, Hussein
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Transient Analysis for Multihop Wireless Networks Under Static Routing2020Ingår i: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 28, nr 2, s. 722-735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, we investigate the transient behavior of a sequence of packets/bits traversing a multi-hop wireless network under static routing. Our work is motivated by novel applications from the domain of process automation, MachineType Communication (MTC) and cyber- physical systems, where short messages are communicated and statistical guarantees need to be provided on a per-message level. In order to optimize such a network, apart from understanding the stationary system dynamics, an understanding of the short-term dynamics (i.e. transient behavior) is also required. To this end, we derive novel Wireless Transient Bounds (WTB) for end-to-end delay and backlog in a multi-hop wireless network using stochastic network calculus approach. We start by analyzing a single end-toend path, i. e. a line topology, and then we show how the obtained results can be applied to a mesh network with static routing using a concept called 'leftover service'. WTB depends on the initial backlog at each node as well as the instantaneous channel states. We numerically compare WTB with Kernel-Based-Transient Bound ( KBTB), which can be obtained by adapting existing stationary bound, as well as simulated end-to- end delay of the investigated network. While KBTB and stationary bounds are not able to capture the short-term system dynamics well, WTB provides relatively tight upper bound and has a decay rate that closely matches the simulation. This is achieved by WTB only with a slight increase in the computational complexity, by a factor of O(T + N), where T is the duration of the arriving sequence and N is the number of hops in the network. We believe that the presented analysis and the bounds are necessary tools for future work on transient network optimization for many important emerging applications, e.g., massive MTC, critical MTC, edge computing and autonomous vehicle.

  • 38.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Liang, B.
    Single Restart with Time Stamps for Parallel Task Processing with Known and Unknown Processors2020Ingår i: IEEE Transactions on Parallel and Distributed Systems, ISSN 1045-9219, E-ISSN 1558-2183, Vol. 31, nr 1, s. 187-200, artikel-id 8765409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the problem of scheduling nn tasks on m+m^{\prime }m+m' parallel processors, where the processing times on mm processors are known while those on the remaining m^{\prime }m' processors are not known a priori. This semi-online model is an abstraction of certain heterogeneous computing systems, e.g., with the mm known processors representing local CPU cores and the unknown processors representing remote servers with uncertain availability of computing cycles. Our objective is to minimize the makespan of all tasks. We initially focus on the case m^{\prime }=1m'=1 and propose a semi-online algorithm termed Single Restart with Time Stamps (SRTS), which has time complexity O(n \log n)O(nlogn). We derive its competitive ratio in comparison with the optimal offline solution. If the unknown processing times are deterministic, the competitive ratio of SRTS is shown to be either always constant or asymptotically constant in practice, respectively in cases where the processing times are independent and dependent on mm. A similar result is obtained when the unknown processing times are random. Furthermore, extending the ideas of SRTS, we propose a heuristic algorithm termed SRTS-Multiple (SRTS-M) for the case m^{\prime }>1m'>1. Finally, where tasks arrive dynamically with unknown arrival times, we extend SRTS to Dynamic SRTS (DSRTS) and find its competitive ratio. Besides the proven competitive ratios, simulation results further suggest that SRTS and SRTS-M give superior performance on average over randomly generated task processing times, substantially reducing the makespan over the best known alternatives. Interestingly, the performance gain is more significant for task processing times sampled from heavy-tailed distributions.

  • 39.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Mamduhi, Mohammad H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Performance Characterization Using AoI in a Single-loop Networked Control System2019Ingår i: IEEE INFOCOM 2019 - IEEE Conference on Computer Communications Workshops, INFOCOM Workshops 2019, IEEE , 2019, s. 197-203Konferensbidrag (Refereegranskat)
    Abstract [en]

    The joint design of control and communication scheduling in a Networked Control System (NCS) is known to be a hard problem. Several research works have successfully designed optimal sampling and/or control strategies under simplified communication models, where transmission delays/times are negligible or fixed. However, considering sophisticated communication models, with random transmission times, result in highly coupled and difficult-to-solve optimal design problems due to the parameter inter-dependencies between estimation/control and communication layers. To tackle this problem, in this work, we investigate the applicability of Age-of-Information (AoI) for solving control/estimation problems in an NCS under i.i.d. transmission times. Our motivation for this investigation stems from the following facts: 1) recent results indicate that AoI can be tackled under relatively sophisticated communication models, and 2) a lower AoI in an NCS may result in a lower estimation/control cost. We study a joint optimization of sampling and scheduling for a single-loop stochastic LTI networked system with the objective of minimizing the time-average squared norm of the estimation error. We first show that, under mild assumptions on information structure the optimal control policy can be designed independently from the sampling and scheduling policies. We then derive a key result that minimizing the estimation error is equivalent to minimizing a non-negative and non-decreasing function of AoI. The parameters of this function include the LTI matrix and the covariance of exogenous noise in the LTI system. Noting that the formulated problem is a stochastic combinatorial optimization problem and is hard to solve, we resort to heuristic algorithms by extending existing algorithms in the AoI literature. We also identify a class of LTI system dynamics for which minimizing the estimation error is equivalent to minimizing the expected AoI.

  • 40. Chang, Z.
    et al.
    Lei, L.
    Zhang, H.
    Ristaniemi, T.
    Chatzinotas, S.
    Ottersten, Björn
    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)
  • 41. Charalambous, C. D.
    et al.
    Stavrou, Photios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, 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.

  • 42.
    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.

  • 43.
    Chen, Xianhao
    et al.
    Southwest Jiaotong Univ, Chengdu, Sichuan, Peoples R China..
    Liu, Gang
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, SWJTU, Chengdu, Sichuan, Peoples R China.;Southeast Univ, Nanjing, Jiangsu, Peoples R China..
    Ma, Zheng
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Southwest Jiaotong Univ, Chengdu, Sichuan, Peoples R China.;Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu, Sichuan, Peoples R China..
    Zhang, Xi
    Texas A&M Univ, Networking & Informat Syst Lab, Dept Elect & Comp Engn, College Stn, TX 77843 USA..
    Fan, Pingzhi
    Southwest Jiaotong Univ, Inst Mobile Commun, Chengdu, Sichuan, Peoples R China..
    Chen, Shanzhi
    China Acad Telecommun Technol, Beijing, Peoples R China.;Beijing Univ Posts & Telecommun, Beijing, Peoples R China..
    Yu, F. Richard
    Carleton Univ, Ottawa, ON, Canada..
    WHEN FULL DUPLEX WIRELESS MEETS NON-ORTHOGONAL MULTIPLE ACCESS: OPPORTUNITIES AND CHALLENGES2019Ingår i: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 26, nr 4, s. 148-155Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    NOMA is a promising radio access technology for 5G wireless systems. The core of NOMA is to support multiple users in the same resource block via power or code domain multiplexing, which provides great enhancement in spectrum efficiency and connectivity. Meanwhile, with the recent advance in self-interference (SI) cancelation techniques, FD wireless communication has become a feasible technology enabling radios to receive and transmit simultaneously. This article aims to investigate the combination of these two emerging technologies. At first, several typical scenarios and protocols are presented to illustrate the application of the FD technique in NOMA systems. Then, a novel NOMA system with FD base stations (BSs) based on C-RAN is proposed. Furthermore, power allocation policies are discussed for the proposed scheme, and simulation results are provided to demonstrate its superiority. Finally, challenges and research opportunities of FD NOMA systems are also identified to stimulate future research.

  • 44.
    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.

  • 45.
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 46.
    Ciftci, Baris
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elkraftteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Norrga, Staffan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elkraftteknik.
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elkraftteknik.
    Simple Distributed Control for Modular Multilevel Converters2019Ingår i: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe, Brussels: European Power Electronics and Drives Association, 2019, , s. 10artikel-id 8915488Konferensbidrag (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.

    Ladda ner fulltext (pdf)
    fulltext
  • 47.
    Costamagna, Paola
    et al.
    Univ Genoa, Dept Chem & Ind Chem DCCI, Via Dodecaneso 31, I-16146 Genoa, Italy..
    De Giorgi, Andrea
    Univ Genoa, Dept Elect Elect & Telecommun Engn DITEN, Via Opera Pia 11A, I-16145 Genoa, Italy..
    Moser, Gabriele
    Univ Genoa, Dept Elect Elect & Telecommun Engn DITEN, Via Opera Pia 11A, I-16145 Genoa, Italy..
    Pellaco, Lissy
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Trucco, Andrea
    Univ Genoa, Dept Elect Elect & Telecommun Engn DITEN, Via Opera Pia 11A, I-16145 Genoa, Italy..
    Data-driven fault diagnosis in SOFC-based power plants under off-design operating conditions2019Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 44, nr 54, s. 29002-29006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Data-driven fault diagnosis is a promising approach for the early detection and isolation of malfunctions in power generation plants deploying solid oxide fuel cells (SOFCs). Despite the supervised classifier used in a data-driven system is trained by samples gathered under one specific design-point operating condition, during real operation the plant can move to a new, unexpected off-design operating condition, reducing the performance of the diagnosis system. This Short Communication demonstrates that this reduction is heavily mitigated if the supervised classifier is adapted to the new condition through the domain adaptation statistical technique. The present study shows that a probability of correct classification between 85% and 94% can be achieved in off-design, when a probability of 95% is obtained at the design-point.

  • 48. Dai, B.
    et al.
    Ma, Zheng
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Luo, Y.
    Liu, X.
    Zhuang, Z.
    Xiao, Ming
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Enhancing Physical Layer Security in Internet of Things via Feedback: A General Framework2020Ingår i: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 7, nr 1, s. 99-115, artikel-id 8856252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a general framework for enhancing the physical layer security (PLS) in the Internet of Things (IoT) systems via channel feedback is established. To be specific, first, we study the compound wiretap channel (WTC) with feedback, which can be viewed as an ideal model for enhancing the PLS in the downlink transmission of IoT systems via feedback. A novel feedback strategy is proposed and a corresponding lower bound on the secrecy capacity is constructed for this ideal model. Next, we generalize the ideal model (i.e., the compound WTC with feedback) by considering channel states and feedback delay, and this generalized model is called the finite state compound WTC with delayed feedback. The lower bounds on the secrecy capacities of this generalized model with or without delayed channel output feedback are provided, and they are constructed according to variations of the previously proposed feedback scheme for the ideal model. Finally, from a Gaussian fading example, we show that the delayed channel output feedback enhances the achievable secrecy rate of the finite state compound WTC with only delayed state feedback, which implies that feedback helps to enhance the PLS in the downlink transmission of the IoT systems.

  • 49.
    Dai, Bin
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Yu, Liman
    Chengdu Text Coll, Sch Econ & Management, Chengdu 611731, Sichuan, Peoples R China..
    Liu, Xuxun
    South China Univ Technol, Sch Elect & Informat Engn, Guangzhou 510641, Guangdong, Peoples R China..
    Ma, Zheng
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Feedback Coding Schemes for the Broadcast Channel With Mutual Secrecy Requirement at the Receivers2019Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, nr 9, s. 6039-6052Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The broadcast channel with mutual secrecy requirement at the receivers (BC-MSR-R) is a basic model characterizing the physical layer security (PLS) in the down-link of the wireless communication systems, where one transmitter sends two independent messages to two receivers via a broadcast channel, and each receiver can successfully decode his/her intended message and wishes to overhear the other one's message. This paper studies how to enhance the already existing secrecy rate region of the BC-MSR-R via receivers' feedback. Specifically, we propose two feedback strategies for the BC-MSR-R, where one uses the feedback to generate pure secret keys protecting the transmitted messages, and the other uses the feedback to generate not only keys but also cooperative messages helping the receivers to improve their decoding performance. Different inner bounds on the secrecy capacity region of the BC-MSR-R with noiseless feedback are constructed according to different feedback strategies, and these bounds are further illustrated by a Dueck-type example.

  • 50.
    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.

    Ladda ner fulltext (pdf)
    delAguilaPla_PhDthesis.pdf
123456 1 - 50 av 284
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf