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  • 451.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Massive MIMO Communications2017Ingår i: 5G Mobile Communications / [ed] Xiang Wei; Zheng Kan; Xuemin Sherman, Switzerland: Springer, 2017, s. 77-116Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Every new network generation needs to make a leap in area data throughput, to manage the growing wireless data traffic. The Massive MIMO technologycan bring at least ten-fold improvements in area throughput by increasing the spec-tral efficiency (bit/s/Hz/cell), while using the same bandwidth and density of basestations as in current networks. These extraordinary gains are achieved by equipping the base stations with arrays of a hundred antennas to enable spatial multiplexing of tens of user terminals. This chapter explains the basic motivations and communication theory behind the Massive MIMO technology, and provides implementation-related design guidelines.

  • 452.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Downlink Power Control for Massive MIMO Cellular Systems with Optimal User Association2016Ingår i: IEEE International Conference on Communications, Malaysia, May 23-27, 2016: proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper aims to minimize the total transmit power consumption for Massive MIMO (multiple-input multiple-output) downlink cellular systems when each user is served by the optimized subset of the base stations (BSs). We derive a lower bound on the ergodic spectral efficiency (SE) for Rayleigh fading channels and maximum ratio transmission (MRT) when the BSs cooperate using non-coherent joint transmission. We solve the joint user association and downlink transmit power minimization problem optimally under fixed SE constraints. Furthermore, we solve a max-min fairness problem with user specific weights that maximizes the worst SE among the users. The optimal BS-user association rule is derived, which is different from maximum signal-to-noise-ratio (max-SNR) association. Simulation results manifest that the proposed methods can provide good SE for the users using less transmit power than in small-scale systems and that the optimal user association can effectively balance the load between BSs when needed.

  • 453.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Joint Pilot Design and Uplink Power Allocation in Multi-Cell Massive MIMO Systems2018Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 3, s. 2000-2015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper considers pilot design to mitigate pilot contamination and provide good service for everyone in multi-cell Massive multiple input multiple output (MIMO) systems. Instead of modeling the pilot design as a combinatorial assignment problem, as in prior works, we express the pilot signals using a pilot basis and treat the associated power coefficients as continuous optimization variables. We compute a lower bound on the uplink capacity for Rayleigh fading channels with maximum ratio detection that applies with arbitrary pilot signals. We further formulate the max-min fairness problem under power budget constraints, with the pilot signals and data powers as optimization variables. Because this optimization problem is non-deterministic polynomial-time hard due to signomial constraints, we then propose an algorithm to obtain a local optimum with polynomial complexity. Our framework serves as a benchmark for pilot design in scenarios with either ideal or non-ideal hardware. Numerical results manifest that the proposed optimization algorithms are close to the optimal solution obtained by exhaustive search for different pilot assignments and the new pilot structure and optimization bring large gains over the state-of-the-art suboptimal pilot design.

  • 454.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Joint Pilot Sequence Design and Power Control for Max-Min Fairness in Uplink Massive MIMO2017Ingår i: IEEE International Conference on Communications (ICC), 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper optimizes the pilot assignment and pilottransmit powers to mitigate pilot contamination in MassiveMIMO (multiple-input multiple-output) systems. While priorworks have treated pilot assignment as a combinatorial problem,we achieve a more tractable problem formulation by directlyoptimizing the pilot sequences. To this end, we compute alower bound on the uplink (UL) spectral efficiency (SE), forRayleigh fading channels with maximum ratio (MR) detectionand arbitrary pilot sequences. We optimize the max-min SEwith respect to the pilot sequences and pilot powers, under powerbudget constraints. This becomes an NP-hard signomial problem,but we propose an efficient algorithm to obtain a local optimumwith polynomial complexity. Numerical results manifest the nearoptimality of the proposed algorithm and show significant gainsover existing suboptimal algorithms.

  • 455.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Joint Power Allocation and User Association Optimization for Massive MIMO Systems2016Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 15, nr 9, s. 6384-6399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the joint power allocationand user association problem in multi-cell Massive MIMO(multiple-input multiple-output) downlink (DL) systems. Thetarget is to minimize the total transmit power consumptionwhen each user is served by an optimized subset of the basestations (BSs), using non-coherent joint transmission. We firstderive a lower bound on the ergodic spectral efficiency (SE),which is applicable for any channel distribution and precodingscheme. Closed-form expressions are obtained for Rayleigh fadingchannels with either maximum ratio transmission (MRT) or zeroforcing (ZF) precoding. From these bounds, we further formulatethe DL power minimization problems with fixed SE constraintsfor the users. These problems are proved to be solvable aslinear programs, giving the optimal power allocation and BS-user association with low complexity. Furthermore, we formulatea max-min fairness problem which maximizes the worst SEamong the users, and we show that it can be solved as aquasi-linear program. Simulations manifest that the proposedmethods provide good SE for the users using less transmit powerthan in small-scale systems and the optimal user associationcan effectively balance the load between BSs when needed.Even though our framework allows the joint transmission frommultiple BSs, there is an overwhelming probability that only oneBS is associated with each user at the optimal solution.

  • 456.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Multi-Cell Massive MIMO Performance with Double Scattering Channels2016Ingår i: Proceedings of IEEE International Workshop on Computer Aided Modelling and Design of Communication Links and Networks (CAMAD) 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 243-248Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the spectral efficiency (SE)of multi-cell Massive Multi-Input Multi-Output (MIMO) usingdifferent channel models. Prior works have derived closed form SE bounds and approximations for Gaussian distributedchannels, while we consider the double scattering model—a primeexample of a non-Gaussian channel for which it is intractable toobtain closed form SE expressions. The channels are estimatedusing limited resources, which gives rise to pilot contamination,and the estimates are used for linear detection and to computethe SE numerically. Analytical and numerical examples are usedto describe the key behaviors of the double scattering models,which differ from conventional Massive MIMO models. Finally,we provide multi-cell simulation results that compare the doublescattering model with uncorrelated Rayleigh fading and explainunder what conditions we can expect to achieve similar SEs.

  • 457.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sum Spectral Efficiency Maximization in Massive MIMO Systems: Benefits from Deep Learning2019Ingår i: ICC 2019 - 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE Communications Society, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the joint data and pilot power optimization for maximum sum spectral efficiency (SE) in multi-cell Massive MIMO systems, which is a non-convex problem. We first propose a new optimization algorithm, inspired by the weighted minimum mean square error (MMSE) approach, to obtain a stationary point in polynomial time. We then use this algorithm together with deep learning to train a convolutional neural network to perform the joint data and pilot power control in sub-millisecond runtime, making it suitable for online optimization in real multi-cell Massive MIMO systems. The numerical result demonstrates that the solution obtained by the neural network is 1% less than the stationary point for four-cell systems, while the sum SE loss is 2% in a nine-cell system.

  • 458.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Le, Tuan Anh
    Department of Design Engineering & Maths, Middlesex University London, United Kingdom.
    Distributed Power Control in Downlink Cellular Massive MIMO Systems2018Ingår i: WSA 2018: 22nd International ITG Workshop on Smart Antennas, VDE Verlag GmbH, 2018, s. 1-7Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper compares centralized and distributed methods to solve the power minimization problem with quality-of-service (QoS) constraints in the downlink (DL) of multi-cell Massive multiple-input multiple-output (MIMO) systems. In particular, we study the computational complexity, number of parameters that need to be exchanged between base stations (BSs), and the convergence of iterative implementations. Although a distributed implementation based on dual decomposition (which only requires statistical channel knowledge at each BS) typically converges to the global optimum after a few iterations, many parameters need to be exchanged to reach convergence.

  • 459.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Mollén, Christopher
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Large-scale-fading decoding in cellular Massive MIMO systems with spatially correlated channels2019Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, nr 4, s. 2746-2762Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Massive multiple-input–multiple-output (MIMO) systems can suffer from coherent intercell interference due to the phenomenon of pilot contamination. This paper investigates a two-layer decoding method that mitigates both coherent and non-coherent interference in multi-cell Massive MIMO. To this end, each base station (BS) first estimates the channels to intra-cell users using either minimum mean-squared error (MMSE) or element-wise MMSE estimation based on uplink pilots. The estimates are used for local decoding on each BS followed by a second decoding layer where the BSs cooperate to mitigate inter-cell interference. An uplink achievable spectral efficiency (SE) expression is computed for arbitrary two-layer decoding schemes. A closed form expression is then obtained for correlated Rayleigh fading, maximum-ratio combining, and the proposed large-scale fading decoding (LSFD) in the second layer. We also formulate a sum SE maximization problem with both the data power and LSFD vectors as optimization variables. Since this is an NP-hard problem, we develop a low-complexity algorithm based on the weighted MMSE approach to obtain a local optimum. The numerical results show that both data power control and LSFD improve the sum SE performance over single-layer decoding multi-cell Massive MIMO systems.

  • 460.
    Van Chien, Trinh
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Mollén, Christopher
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Two-Layer Decoding in Cellular Massive MIMO Systems with Spatial Channel Correlation2019Ingår i: Proceedings of 2019 IEEE International Conference on Communications, ICC 2019, 2019, artikel-id 8761502Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies a two-layer decoding method that mitigates inter-cell interference in multi-cell Massive MIMO systems. In layer one, each base station (BS) estimates the channels to intra-cell users and uses the estimates for local decoding on each BS, followed by a second decoding layer where the BSs cooperate to mitigate inter-cell interference. An uplink achievable spectral efficiency (SE) expression is computed for arbitrary two-layer decoding schemes, while a closed-form expression is obtained for correlated Rayleigh fading channels, maximum-ratio combining (MRC), and large-scale fading decoding (LSFD) in the second layer. We formulate a non-convex sum SE maximization problem with both the data power and LSFD vectors as optimization variables and develop an algorithm based on the weighted MMSE (minimum mean square error) approach to obtain a stationary point with low computational complexity.

  • 461.
    Van der Perre, Liesbet
    et al.
    Katholieke Univ Leuven, Belgium; Lund Univ, Sweden; Lund Univ, Sweden.
    Liu, Liang
    Lund Univ, Sweden.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Efficient DSP and Circuit Architectures for Massive MIMO: State of the Art and Future Directions2018Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, nr 18, s. 4717-4736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Massive MIMO is a compelling wireless access concept that relies on the use of an excess number of base-station antennas, relative to the number of active terminals. This technology is a main component of 5G New Radio and addresses all important requirements of future wireless standards: a great capacity increase, the support of many simultaneous users, and improvement in energy efficiency. Massive MIMO requires the simultaneous processing of signals from many antenna chains, and computational operations on large matrices. The complexity of the digital processing has been viewed as a fundamental obstacle to the feasibility of Massive MIMO in the past. Recent advances on system-algorithm-hardware co-design have led to extremely energy-efficient implementations. These exploit opportunities in deeply-scaled silicon technologies and perform partly distributed processing to cope with the bottlenecks encountered in the interconnection of many signals. For example, prototype ASIC implementations have demonstrated zero-forcing precoding in real time at a 55 mW power consumption (20 MHz bandwidth, 128 antennas, and multiplexing of 8 terminals). Coarse and even errorprone digital processing in the antenna paths permits a reduction of consumption with a factor of 2 to 5. This article summarizes the fundamental technical contributions to efficient digital signal processing for Massive MIMO. The opportunities and constraints on operating on low-complexity RF and analog hardware chains are clarified. It illustrates how terminals can benefit from improved energy efficiency. The status of technology and real-life prototypes discussed. Open challenges and directions for future research are suggested.

  • 462.
    Vehkapera, Mikko
    et al.
    Aalto University, Finland.
    Riihonen, Taneli
    Aalto University, Finland.
    Girnyk, Maksym A.
    KTH Royal Institute Technology, Sweden; KTH Royal Institute Technology, Sweden.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Debbah, Merouane
    Huawei France RandD Centre, France; Supelec, France.
    Kildehoj Rasmussen, Lars
    KTH Royal Institute Technology, Sweden; KTH Royal Institute Technology, Sweden.
    Wichman, Risto
    Aalto University, Finland.
    Asymptotic Analysis of SU-MIMO Channels With Transmitter Noise and Mismatched Joint Decoding2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 3, s. 749-765Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hardware impairments in radio-frequency components of a wireless system cause unavoidable distortions to transmission that are not captured by the conventional linear channel model. In this paper, a "binoisy" single-user multiple-input multiple-output (SU-MIMO) relation is considered where the additional distortions are modeled via an additive noise term at the transmit side. Through this extended SU-MIMO channel model, the effects of transceiver hardware impairments on the achievable rate of multi-antenna point-to-point systems are studied. Channel input distributions encompassing practical discrete modulation schemes, such as, QAM and PSK, as well as Gaussian signaling are covered. In addition, the impact of mismatched detection and decoding when the receiver has insufficient information about the non-idealities is investigated. The numerical results show that for realistic system parameters, the effects of transmit-side noise and mismatched decoding become significant only at high modulation orders.

  • 463.
    Verenzuela, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Matthaiou, Michail
    Institute of Electronics, Communications and Information Technology (ECIT), Queen’s University Belfast, Northern Ireland .
    Hardware Design and Optimal ADC Resolution for Uplink Massive MIMO Systems2016Ingår i: IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM), Rio de Janeiro, Brazil, July 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work focuses on the hardware design for the efficient operation of Massive multiple-input multiple-output (MIMO) systems. A closed-form uplink achievable data rate expression is derived considering imperfect channel state information (CSI) and hardware impairments. We formulate an optimization problem to maximize the sum data rate subject to a constraint on the total power consumption. A general power consumption model accounting for the level of hardware impairments is utilized. The optimization variables are the number of base station (BS) antennas and the level of impairments per BS antenna. The resolution of the analog-to-digital converter (ADC) is a primary source of such impairments. The results show the trade-off between the number of BS antennas and the level of hardware impairments, which is important for practical hardware design. Moreover, the maximum power consumption can be tuned to achieve maximum energy efficiency (EE). Numerical results suggest that the optimal level of hardware impairments yields ADCs of 4 to 5 quantization bits.

  • 464.
    Verenzuela, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Matthaiou, Michail
    Institute of Electronics, Communications and Information Technology (ECIT), Queen’s University Belfast, .
    Per-antenna hardware optimization and mixed resolution ADCs in uplink massive MIMO2017Ingår i: Conference Record of The Fifty-FirstAsilomar Conference on Signals, Systems & Computers / [ed] Michael B. Matthews, IEEE conference proceedings, 2017, s. 27-31Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive multiple-input multiple-output (MIMO) is a key technology for next generation wireless networks that deploys many antennas at the base stations (BSs). This requires low-complexity hardware at each antenna branch that, in turn, increases distortions. This work studies the selection of per-antenna hardware quality in terms of analog-to-digital converters (ADCs) resolution. A new achievable spectral efficiency (SE) expression is derived and majorization theory is used to analyze the order preserving properties of the SE and the power consumption with respect to the per-antenna ADC resolutions. That is, given a fixed sum of ADC resolutions across the antenna array, is it preferable to use an equal-ADC over a mixed-ADC approach? The results show that having equal-resolution ADCs across the antenna array maximizes the SE and minimizes the power consumption.

  • 465.
    Verenzuela, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Pisa, Italy.
    Optimal Design of Wireless Networks for Broadband Access with Minimum Power Consumption2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE Communications Society, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    The continuous rise in wireless data traffic brings forth an increase in power consumption and static users constitute a large fraction of these traffic demands. This work focuses on designing cellular networks to deliver a given data rate per area and user, while minimizing the power consumption. In particular we are interested in optimizing the transmission power, density of access points (APs), number of AP antennas and number of users served in each cell. To this end, we consider a network model based on stochastic geometry and a detailed power consumption model to derive closed form expressions and obtain insights on the interplay of the aforementioned design parameters. The results show that, in contrast with previous works on optimal network design for energy efficiency, having exceedingly high AP density does not bring the most benefits in terms of power savings. Instead the AP density should be chosen according to the area data rate that we want to deliver. In addition numerical results show that the minimum power consumption is obtained in the Massive MIMO regime with many antennas and users per AP.

  • 466.
    Verenzuela, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Miao, Guowang
    KTH Royal Institute Technology, Sweden; Freelinguist Com, Sweden.
    Scalable D2D Communications for Frequency Reuse 1 in 5G2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 6, s. 3435-3447Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Proximity-based applications are becoming fast growing markets suggesting that device-to-device (D2D) communications is becoming an essential part of the future mobile data networks. We propose scalable admission and power control methods for D2D communications underlay cellular networks to increase the reuse of frequency resources and thus network capacity while maintaining QoS to all users. In practice, as D2D communications will generate a new layer of interference, it is essential to take D2D interference into account in inter-cell interference coordination for multi-cell communications. The aim of the proposed methods is to maximize the number of D2D links under QoS constraints, therefore maximizing network frequency reuse in a practical 5G multi-cell environment. Different schemes are designed for applications that have different levels of complexity and availability of channel state information. Numerical results show that by using D2D and the proposed multi-cell interference coordination and low power transmission method, the network spectral efficiency can be increased by as much as ten times, while low outage probability can be assured to provide QoS for all users.

  • 467.
    Vergara Alonso, Ekhiotz Jon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Energy Modelling and Fairness for Efficient Mobile Communication2016Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Energy consumption and its management have been clearly identified as a challenge in computing and communication system design, where energy economy is obviously of paramount importance for battery powered devices. This thesis addresses the energy efficiency of mobile communication at the user end in the context of cellular networks.

    We argue that energy efficiency starts by energy awareness and propose EnergyBox, a parametrised tool that enables accurate and repeatable energy quantification at the user end using real data traffic traces as input. EnergyBox offers an abstraction of the underlying states for operation of the wireless interfaces and allows to estimate the energy consumption for different operator settings and device characteristics. The tool is used throughout the thesis to quantify and reveal inefficient data communication patterns of widely used mobile applications.

    We consider two different perspectives in the search of energy-efficient solutions. From the application perspective, we show that systematically quantifying the energy consumption of design choices (e.g., communication patterns, protocols, and data formats) contributes to a significantly smaller energy footprint. From the system perspective, we devise a cross-layer solution that schedules packet transmissions based on the knowledge of the network parameters that impact the energy consumption of the handset. These attempts show that application level decisions require a better understanding of possible energy apportionment policies at system level.

    Finally, we study the generic problem of determining the contribution of an entity (e.g., application) to the total energy consumption of a given system (e.g., mobile device). We compare the state-of-the-art policies in terms of fairness leveraging cooperative game theory and analyse their required information and computational complexity. We show that providing incentives to reduce the total energy consumption of the system (as part of fairness) is tightly coupled to the policy selection. Our study provides guidelines to select an appropriate policy depending on the characteristics of the system. 

  • 468.
    Vergara Alonso, Ekhiotz Jon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Exploiting Energy Awareness in Mobile Communication2013Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Although evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions hamper the quality of experience to a great extent. The massive explosion of mobile applications with the ensuing data exchange over the cellular infrastructure is not only a blessing to the mobile user, but also has a price in terms of rapid discharge of the device battery. Wireless communication is a large contributor to the energy consumption. Thus, the current call for energy economy in mobile devices poses the challenge of reducing the energy consumption of wireless data transmissions at the user end by developing energy-efficient communication.

    This thesis addresses the energy efficiency of data transmission at the user end in the context of cellular networks. We argue that the design of energy-efficient solutions starts by energy awareness and propose EnergyBox, a parametrised tool that enables accurate and repeatable energy quantification at the user end using real data traffic traces as input. EnergyBox abstracts the underlying states for operation of the wireless interfaces and allows to estimate the energy consumption for different operator settings and device characteristics.

    Next, we devise an energy-efficient algorithm that schedules the packet transmissions at the user end based on the knowledge of the network parameters that impact the handset energy consumption. The solution focuses on the characteristics of a given traffic class with the lowest quality of service requirements. The cost of running the solution itself is studied showing that the proposed cross-layer scheduler uses a small amount of energy to significantly extend the battery lifetime at the cost of some added latency. 

    Finally, the benefit of employing EnergyBox to systematically study the different design choices that developers face with respect to data transmissions of applications is shown in the context of location sharing services and instant messaging applications. The results show that quantifying energy consumption of communication patterns, protocols, and data formats can aid the design of tailor-made solutions with a significantly smaller energy footprint. 

  • 469.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    EnergyBox: A Trace-driven Tool for Data Transmission Energy Consumption Studies2013Ingår i: EE-LSDS 2013, Energy Efficiency in Large Scale Distributed Systems, Springer, 2013, s. 19-34Konferensbidrag (Refereegranskat)
    Abstract [en]

    Although evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions hamper the quality of experience to a great extent. We argue that the design of energy-efficient solutions starts by energy-awareness and propose EnergyBox, a tool that provides accurate and repeatable energy consumption studies for 3G and WiFi transmissions at the user end. We recognize that the energy consumption of data transmission is highly dependable on the traffic pattern, and provide the means for trace-based iterative packet-driven simulation to derive the operation states of wireless interfaces. The strength of EnergyBox is that it allows to modularly set the 3G network parameters specified at operator level, the adaptive power save mode mechanism for a WiFi device, and the different power levels of the operation states for different handheld devices. EnergyBox enables efficient energy consumption studies using real data, which complements the device-dependent laborious physical power measurements. Using real application transmission traces, we have validated EnergyBox showing an accuracy range of 94-99% for 3G and 93-99% for WiFi compared to the real measured energy consumption by a 3G modem and a smartphone with WiFi.

  • 470.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Watts2Share: Energy-Aware Traffic Consolidation2013Ingår i: Green Computing and Communications (GreenCom), 2013 IEEE and Internet of Things (iThings/CPSCom), IEEE International Conference on and IEEE Cyber, Physical and Social Computing, IEEE Computer Society, 2013, s. 14-22Konferensbidrag (Refereegranskat)
    Abstract [en]

    Energy consumption is becoming the Achilles' heel of the mobile user quality of experience partly due to undisciplined use of the cellular (3G) transmissions by applications. The operator infrastructure is typically configured for peak performance, whereas during periods of underutilisation the handsets pay the price by staying in high energy states even if each application only uses a fraction of the maximum available bandwidth. In this paper we promote a bi-radio scenario where instead of independently using own cellular connections, several users share a single cellular link offered by one member of a coalition (a rotating aggregator). We present Watts2Share, an architecture for energy-aware traffic consolidation whereby group members' data flows transmitted through a second radio (e.g., WiFi) are aggregated by the aggregator and retransmitted through the cellular link. Through careful and repeatable studies we demonstrate that this scheme saves up to 68% of the total transmission energy in handsets compared to a pure 3G scenario. The studies are based on a wide range of real traffic traces and real cellular operator settings, and further illustrate that this scheme reduces the overall energy by reducing the signalling overhead, as well as extending the lifetime of all handsets.

  • 471.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Prihodko, Mihails
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Mobile Location Sharing: An Energy Consumption Study2013Ingår i: e-Energy '13 Proceedings of the 4th International Conference on Future Energy Systems: Where Energy, Computing and Communication Meet, New York, NY, USA: ACM Press, 2013, s. 289-290Konferensbidrag (Refereegranskat)
    Abstract [en]

    The use of a mobile device's battery for frequent transmissions of position data in a location sharing application can be more expensive than the location retrieval itself. This is in part due to energy-agnostic application development and in part dependent on choice of protocols. This paper studies the lightweight Message Queuing Telemetry Transport protocol (MQTT) as an application layer protocol on top of the third generation cellular communication. The energy efficiency and amount of data generated by the publish/subscribe MQTT protocol is experimentally compared against the Hypertext Transfer Protocol (HTTP), which is currently used in typical location sharing applications.

    The evaluation results indicate that MQTT is a good candidate as a protocol for location sharing. At comparable bandwidth and energy expenses MQTT offers better quality of user experience, since the subscribers are notified at once when the location of some interesting client has changed. Our measurements show that MQTT is more energy-efficient than HTTP in the idle state and when the number of other users with whom the client shares location is low. When the number of users increases beyond 3, HTTP becomes the preferred option in terms of energy efficiency at the cost of a higher notification delay.

  • 472.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Sanjuan, Joseba
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Kernel Level Energy-Efficient 3G Background Traffic Shaper for Android Smartphones2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Reducing the energy consumption of wireless devices is paramount to a wide spread adoption of mobile applications. Cellular communication imposes high energy consumption on the mobile devices due to the radio resource allocation, which differs from other networks such as WiFi. Most applications are unaware of the energy consumption characteristics of third generation cellular communication (3G). This makes the background small data transfers of undisciplined applications an energy burden due to inefficient utilisation of resources.

    While several approaches exist to reduce the energy consumption of this best-effort background traffic by means of traffic shaping, we find that they are mostly evaluated with simulations and the actual energy overhead for the traffic shaper itself has not been studied. In order to cover this gap, our work realises an existing energy saving algorithm as a Kernel Level Shaper (KLS) within the Android platform, and measures its energy footprint. The total energy savings of our implementation range from 8% to 58% for emulated real background traffic, that is categorised as best-effort traffic. We further show the implications of running the KLS during live operation of applications as an exploratory study.

  • 473.
    Vinogradova, Julia
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    On the separability of signal and interference-plus-noise subspaces in blind pilot decontamination2016Ingår i: 41st IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 3421-3425Konferensbidrag (Refereegranskat)
    Abstract [en]

    Consider a multicell multiuser MIMO (multiple-input multiple-output) system with a very large number of antennas at each base station (BS). The number of users in each cell is assumed to be fixed as the number of BS antennas grows large. Under certain conditions on the powers of the transmitting users, the signal eigenvalue spectrum is asymptotically separated from the interference-plus-noise spectrum as the number of BS antennas grows large. As it was observed in [1], this phenomenon allows to mitigate the pilot contamination problem. We provide the power limits for each user in the cell of interest above which such a separation occurs asymptotically. Unlike the approximative methods used in [1], we obtain these power limits by making use of the exact asymptotic characterizations of the interference-plus-noise spectrum. The results are based on the theory of small rank perturbations of large dimensional random matrices.

  • 474.
    Vinogradova, Julia
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    DETECTION AND MITIGATION OF JAMMING ATTACKS IN MASSIVE MIMO SYSTEMS USING RANDOM MATRIX THEORY2016Ingår i: 2016 IEEE 17TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Consider the uplink of a single-cell multiuser MIMO system with a very large number of antennas, M, at the base station (BS) and K single-antenna users. A jamming device equipped with K-J antennas transmitting signals attempts to degrade the transmission between the users and the BS. In this paper, we propose a detection algorithm of the jamming attack as well as a method for its rejection. The proposed results are based on the application of results from random matrix theory. We assume that K and K-J are fixed as M converges to infinity while the coherence interval tau is assumed to be of the same order of magnitude as M

  • 475.
    von Heideken, Oskar
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Wennerfeldt, Max
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Serial Video Links in Automotive Applications2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis investigates the available and upcoming serializer and deserializer solutions for MIPI-CSI 2 camera interface, in order to reduce cable cost and lower installation complexity for mounting satellite cameras in automotive applications. A market survey was conducted resulting in several available and coming solutions. One solution found in the survey was selected together with Autoliv Sverige AB for further investigation and implementation in the form of a demonstration platform. The assembled serializer and deserializer units were tested together with a selection of automotive graded cables in order to test the system and establish the best suited cable with regards to cost, weight and performance. The results show that five serializer and deserializer solutions were found and the choice of cables is a trade-off between performance and external factors such as noise and required cable length.

  • 476.
    Wang, Jin
    et al.
    Northwestern Polytech Univ, Peoples R China; Xian Aeronaut Univ, Peoples R China.
    Zhang, Yingfeng
    Northwestern Polytech Univ, Peoples R China.
    Liu, Yang
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Tekniska fakulteten.
    Wu, Naiqi
    Macau Univ Sci and Technol, Peoples R China; Guangdong Univ Technol, Peoples R China.
    Multiagent and Bargaining-Game-Based Real-Time Scheduling for Internet of Things-Enabled Flexible Job Shop2019Ingår i: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 6, nr 2, s. 2518-2531Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the rapid advancement and widespread applications of information technology in the manufacturing shop floor, a huge amount of real-time data is generated, providing a good opportunity to effectively respond to unpredictable exceptions so that the productivity can be improved. Thus, how to schedule the manufacturing shop floor for achieving such a goal is very challenging. This paper addresses this issue and a new multiagent-based real-time scheduling architecture is proposed for an Internet of Things-enabled flexible job shop. Differing from traditional dynamic scheduling strategies, the proposed strategy optimally assigns tasks to machines according to their real-time status. A bargaining-game-based negotiation mechanism is developed to coordinate the agents so that the problem can be efficiently solved. To demonstrate the feasibility and effectiveness of the proposed architecture and scheduling method, a proof-of-concept prototype system is implemented with Java agent development framework platform. A case study is used to test the performance and effectiveness of the proposed method. Through simulation and comparison, it is shown that the proposed method outperforms the traditional dynamic scheduling strategies in terms of makespan, critical machine workload, and total energy consumption.

  • 477.
    Wang, Shuai
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem.
    Embedding data in an audio signal, using acoustic OFDM2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The OFDM technology has been extensively used in many radio communicationtechnologies. For example, OFDM is the core technology applied in WiFi, WiMAXand LTE. Its main advantages include high bandwidth utilization, strong noise im-munity and the capability to resist frequency selective fading. However, OFDMtechnology is not only applied in the field of radio communication, but has alsobeen developed greatly in acoustic communication, namely the so called acousticOFDM. Thanks to the acoustic OFDM technology, the information can be em-bedded in audio and then transmitted so that the receiver can obtain the requiredinformation through certain demodulation mechanisms without severely affectingthe audio quality.This thesis mainly discusses how to embed and transmit information in audioby making use of acoustic OFDM. Based on the theoretical systematic structure, italso designs a simulation system and a measurement system respectively. In thesetwo systems, channel coding, manners of modulation and demodulation, timingsynchronization and parameters of the functional components are configured in themost reasonable way in order to achieve relatively strong stability and robustnessof the system. Moreover, power control and the compatibility between audio andOFDM signals are also explained and analyzed in this thesis.Based on the experimental results, the author analyzes the performance of thesystem and the factors that affect the performance of the system, such as the typeof audio, distance between transmitter and receiver, audio output level and so on.According to this analysis, it is proved that the simulation system can work steadilyin any audio of wav format and transmit information correctly. However, dueto the hardware limitations of the receiver and sender devices, the measurementsystem is unstable to a certain degree. Finally, this thesis draws conclusions of theresearch results and points out unsolved problems in the experiments. Eventually,some expectations for this research orientation are stated and relevant suggestionsare proposed.

  • 478.
    Wannas, Hussain
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Full Duplex Multiuser MIMO with Massive Arrays2014Självständigt arbete på avancerad nivå (masterexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Half-Duplex Multiuser Multiple-Input Multiple-Output (HD MU-MIMO) systemscurrently employed in communication systems are not experiencing the selfinterference(SI) problem but they are not optimal in terms of efficiency and interms of resources used (time and frequency resources). Ignoring the effect of largescalefading, we start by explaining the uplink (UL) and downlink (DL) parts ofthe MU-MIMO system and how the sum-rate is calculated. We also introduce thethree linear receivers/precoders, Maximum-Ratio Combining (MRC)/Maximum-Ratio Transmission (MRT), Zero-Forcing (ZF), and Minimum Mean-Square Error(MMSE) and which of the three types is going to be used in the study of Full-Duplex Multiuser Multiple-input Multiple-output (FD MU-MIMO) system. Thenwe introduce FD MU-MIMO system, and how the equation used to calculate thesum-rate of the UL part changes when the SI occurs, and why SI problem is notpresent in the DL part. Next, we introduce the spectral efficiency (SE), and howto calculate it and why it is taken as a parameter to compare HD and FD systems.Also the effect of SI on FD MU-MIMO system is presented through simulationgraphs, then we move to show how to reduce SI effect by increasing the number ofantennas in the base-station (BS). Lastly, we take the effect of large scale fading inorder to reach a simple statistical model in the form cumulative distribution function(CDF) graph for different values of SI and compare those of FD MU-MIMOsystem to HD MU-MIMO. The results show that FD MU-MIMO together withmassive MIMO technology is very promising and would save time and frequencyresources which means an increase in the SE but SI must be below a certain level.

  • 479.
    Wiren, Jakob
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Data Storage Cost Optimization Based on Electricity Price Forecasting with Machine Learning in a Multi-Geographical Cloud Environment2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As increased demand of cloud computing leads to increased electricity costs for cloud providers, there is an incentive to investigate in new methods to lower electricity costs in data centers. Electricity price markets suffer from sudden price spikes as well as irregularities between different geographical electricity markets.

    This thesis investigates in whether it is possible to leverage these volatilities and irregularities between different electricity price markets, to offload or move storage in order to reduce electricity price costs for data storage.

    By forecasting four different electricity price markets it was possible to predict sudden price spikes and leverage these forecasts in a simple optimization model to offload storage of data in data centers and successfully reduce electricity costs for data storage.

  • 480.
    Wymeersch, Henk
    et al.
    Chalmers University of Technology, Sweden.
    Penna, Federico
    Politecnico di Torino, Italy.
    Savic, Vladimir
    Technical University of Madrid, Spain.
    Uniformly reweighted belief propagation: A factor graph approach2011Ingår i: Proc. of IEEE Intl. Symp. on Information Theory Proceedings (ISIT), 2011, s. 2000-2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    Tree-reweighted belief propagation is a message passing method that has certain advantages compared to traditional belief propagation (BP). However, it fails to outperform BP in a consistent manner, does not lend itself well to distributed implementation, and has not been applied to distributions with higher-order interactions. We propose a method called uniformly-reweighted belief propagation that mitigates these drawbacks. After having shown in previous works that this method can substantially outperform BP in distributed inference with pairwise interaction models, in this paper we extend it to higher-order interactions and apply it to LDPC decoding, leading performance gains over BP.

  • 481.
    Wymeersch, Henk
    et al.
    Chalmers University of Technology, Sweden.
    Penna, Federico
    Politecnico di Torino, Italy.
    Savic, Vladimir
    Technical University of Madrid, Spain.
    Uniformly Reweighted Belief Propagation for Estimation and Detection in Wireless Networks2012Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 11, nr 4, s. 1587-1595Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we propose a new inference algorithm, suitable for distributed processing over wireless networks. The algorithm, called uniformly reweighted belief propagation (URW-BP), combines the local nature of belief propagation with the improved performance of tree-reweighted belief propagation (TRW-BP) in graphs with cycles. It reduces the degrees of freedom in the latter algorithm to a single scalar variable, the uniform edge appearance probability ρ. We provide a variational interpretation of URW-BP, give insights into good choices of ρ, develop an extension to higher-order potentials, and complement our work with numerical performance results on three inference problems in wireless communication systems: spectrum sensing in cognitive radio, cooperative positioning, and decoding of a low-density parity-check (LDPC) code.

  • 482.
    Wymeersch, Henk
    et al.
    Chalmers University of Technology, Sweden.
    Penna, Federico
    Fraunhofer Heinrich Hertz Institute, Berlin, Germany.
    Savic, Vladimir
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Zhao, Jun
    Chalmers University of Technology, Sweden.
    Comparison of reweighted message passing algorithms for LDPC decoding2013Ingår i: IEEE International Conference on Communications (ICC), 2013, IEEE , 2013, s. 3264-3269Konferensbidrag (Refereegranskat)
    Abstract [en]

    Low density parity check (LDPC) codes can be decoded with a variety of decoding algorithms, offering a trade-off in terms of complexity, latency, and performance. We describe seven distinct LDPC decoders and provide a performance comparison for a practical regular LDPC code. Our simulations indicate that the best performance/latency trade-off is achieved by one version ofthe reweighted max-product decoder. When latency is not an issue, the traditional sum-product decoder yields the best performance.

  • 483.
    Xiao, Ming
    et al.
    KTH Royal Institute Technology, Sweden.
    Mumtaz, Shahid
    Institute Telecomunicacoes, Portugal.
    Huang, Yongming
    Southeast University, Peoples R China.
    Dai, Linglong
    Tsinghua University, Peoples R China.
    Li, Yonghui
    University of Sydney, Australia; University of Sydney, Australia.
    Matthaiou, Michail
    Queens University of Belfast, North Ireland.
    Karagiannidis, George K.
    Aristotle University of Thessaloniki, Greece; Aristotle University of Thessaloniki, Greece.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Yang, Kai
    Tongji University, Peoples R China.
    Chih-Lin, I
    China Mobile, Peoples R China.
    Ghosh, Amitabha
    Nokia Bell Labs, NJ USA.
    Millimeter Wave Communications for Future Mobile Networks2017Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 35, nr 9, s. 1909-1935Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Millimeter wave (mmWave) communications have recently attracted large research interest, since the huge available bandwidth can potentially lead to the rates of multiple gigabit per second per user. Though mmWave can be readily used in stationary scenarios, such as indoor hotspots or backhaul, it is challenging to use mmWave in mobile networks, where the transmitting/receiving nodes may be moving, channels may have a complicated structure, and the coordination among multiple nodes is difficult. To fully exploit the high potential rates of mmWave in mobile networks, lots of technical problems must be addressed. This paper presents a comprehensive survey of mmWave communications for future mobile networks (5G and beyond). We first summarize the recent channel measurement campaigns and modeling results. Then, we discuss in detail recent progresses in multiple input multiple output transceiver design for mmWave communications. After that, we provide an overview of the solution for multiple access and backhauling, followed by the analysis of coverage and connectivity. Finally, the progresses in the standardization and deployment of mmWave for mobile networks are discussed.

  • 484.
    Yang, Ching-Hsiang
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem.
    Screen Content Coding in HEVC: Mixed Raster Content with Matching Pursuit2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Screen content coding is used to improve coding efficiency of synthetic contents in videos, such as text and UI elements, as opposed to contents captured using photo-graphic equipment, which most video codecs are optimized for. One way of improving screen content coding efficiency is to utilize mixed block coding with matching pursuit. By separating the prediction and transformation steps for overlay and background elements, better contrast and signal-to-noise ratio can be achieved. The paper describes the implementation of such algorithm within the HEVC reference encoder, and discusses the experimental results on several test images.

  • 485.
    You, Lei
    et al.
    Qingdao University, Peoples R China.
    Lei, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. University of Maryland, MD USA.
    A Performance Study of Energy Minimization for Interleaved and Localized FDMA2014Ingår i: 2014 IEEE 19TH INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD), IEEE , 2014, s. 16-20Konferensbidrag (Refereegranskat)
    Abstract [en]

    Optimal channel allocation is a key performance engineering aspect in single-carrier frequency-division multiple access (SC-FDMA). It is of significance to consider minimum sum power (Min-Power), subject to meeting specified users demand, since mobile users typically employ battery-powered handsets. In this paper, we prove that Min-Power is polynomial-time solvable for interleaved SC-FDMA (IFDMA). Then we propose a channel allocation algorithm for IFDMA, which is guaranteed to achieve global optimum in polynomial time. We numerically compare the proposed algorithm with optimal localized SC-FDMA (LFDMA) for Min-Power. The results show that LFDMA outperforms IFDMA in the maximal supported user demand. When the user demand can be satisfied in both LFDMA and IFDMA, LFDMA performs slightly better than IFDMA. However MinPower is polynomial-time solvable for IFDMA whereas it is not for LFDMA.

  • 486.
    You, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Lei, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. University of Maryland, MD 20740 USA.
    Optimizing Power and User Association for Energy Saving in Load-Coupled Cooperative LTE2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider an energy minimization problem for cooperative LTE networks. To reduce energy consumption, we investigate how to jointly optimize the transmit power and the association between cells and user equipments (UEs), by taking into consideration joint transmission (JT), one of the coordinated multipoint (CoMP) techniques. We formulate the optimization problem mathematically. For solving the problem, a dynamic power allocation algorithm that adjusts the transmit power of all cells, and an algorithm for optimizing the cell-UE association, are proposed. The two algorithms are iteratively used in an algorithmic framework to enhance the energy performance. Numerically, the proposed algorithms can lead to lower energy consumption than the optimal energy setting in the non-JT case. In comparison to fixed power allocation in JT, the proposed dynamic power allocation algorithm is able to significantly reduce the energy consumption.

  • 487.
    You, Lei
    et al.
    Uppsala University, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. Uppsala University, Sweden.
    Joint CoMP-Cell Selection and Resource Allocation in Fronthaul-Constrained C-RAN2017Ingår i: 2017 15TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cloud-based Radio Access Network (C-RAN) is a promising architecture for future cellular networks, in which Baseband Units (BBUs) are placed at a centralized location, with capacity-constrained fronthaul connected to multiple distributed Remote Radio Heads (RRHs) that are far away from the BBUs. The centralization of signal processing enables the flexibility for coordinated multi-point transmission (CoMP) to meet high traffic demand of users. We investigate how to jointly optimize CoMP-cell selection and base station resource allocation so as to enhance the quality of service (QoS), subject to the fronthaul capacity constraint in orthogonal frequency-division multiple access (OFDMA) based C-RAN. The problem is proved to be NP-hard in this paper. To deal with the computational complexity, we derive a partial optimality condition as the foundation for designing a cell-selection algorithm. Besides, we provide a solution method of the optimum of the time-frequency resource allocation problem without loss of fairness on the QoS enhancement of all users. The simulations show good performance of the proposed algorithms for jointly optimizing the cell selection and resource allocation in a C-RAN, with respect to QoS.

  • 488.
    Yuan, Di
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Karipidis, Eleftherios
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    On Optimal Link Activation with Interference Cancelation in Wireless Networking2013Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, nr 2, s. 939-945Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fundamental aspect in performance engineering of wireless networks is optimizing the set of links that can be concurrently activated to meet given signal-to-interference-and-noise ratio (SINR) thresholds. The solution of this combinatorial problem is the key element in scheduling and cross-layer resource management. In this paper, we assume multiuser decoding receivers, which can cancel strongly interfering signals. As a result, in contrast to classical spatial reuse, links being close to each other are more likely to be active concurrently. Our focus is to gauge the gain of successive interference cancellation (SIC), as well as the simpler, yet instructive, case of parallel interference cancellation (PIC), in the context of optimal link activation. We show that both problems are NP-hard and develop compact integer linear programming formulations that enable to approach global optimality. We provide an extensive numerical performance evaluation, indicating that for low to medium SINR thresholds the improvement is quite substantial, especially with SIC, whereas for high SINR thresholds the improvement diminishes and both schemes perform equally well.

  • 489.
    Zahidi, Salman
    Linköpings universitet, Institutionen för systemteknik, Informationskodning.
    Biometrics - Evaluation of Current Situation2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Information security has always been a topic of concern in the world as an emphasis on new techniques to secure the identity of a legitimate user is regarded as top priority. To counter such an issue, we have a traditional way of authentication factors “what you have” and “what you know” in the form of smart cards or passwords respectively. But biometrics is based on the factor “who are you” by analyzing human physical or behavioral characteristics. Biometrics has always been an efficient way of authorization and is now considered as a $1500 million industry where fingerprints dominate the biometrics while iris is quickly emerging as the most desirable form of biometric technique.The main goal of this thesis is to compare and evaluate different biometrics techniques in terms of their purpose, recognition mechanism, market value and their application areas. Since there are no defined evaluating criteria, my method of evaluation was based on a literature survey from internet, books, IEEE papers and technical surveys. Chapter 3 is focused on different biometrics techniques where I discuss them briefly but in chapter 4, I go deeper into Iris, fingerprints, facial techniques which are prominent in biometrics world. Lastly, I had a general assessment of the biometrics, their future growth and suggested specific techniques for different environment like access controls, e-commerce, national ids, and surveillance.

  • 490.
    Zappone, Alessio
    et al.
    TU Dresden, Dresden, Germany.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Jorswieck, Eduard
    TU Dresden, Dresden, Germany.
    A Framework for Globally Optimal Energy-Efficient Resource Allocation in Wireless Networks2016Konferensbidrag (Refereegranskat)
  • 491.
    Zhao, Yuxin
    et al.
    Ericsson Research, Linköping, Sweden.
    Yin, Feng
    Ericsson Research, Linköping, Sweden.
    Gunnarsson, Fredrik
    Ericsson Research, Linköping, Sweden.
    Amirijoo, Mehdi
    Ericsson Research, Linköping, Sweden.
    Hendeby, Gustaf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gaussian Process for Propagation modeling and Proximity Reports Based Indoor Positioning2016Ingår i: 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring), IEEE , 2016, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    The commercial interest in proximity services is increasing. Application examples include location-based information and advertisements, logistics, social networking, file sharing, etc. In this paper, we consider network-based positioning based on times series of proximity reports from a mobile device, either only a proximity indicator, or a vector of RSS from observed nodes. Such positioning corresponds to a latent and nonlinear observation model. To address these problems, we combine two powerful tools, namely particle filtering and Gaussian process regression (GPR) for radio signal propagation modeling. The latter also provides some insights into the spatial correlation of the radio propagation in the considered area. Radio propagation modeling and positioning performance are evaluated in a typical office area with Bluetooth-Low-Energy (BLE) beacons deployed for proximity detection and reports. Results show that the positioning accuracy can be improved by using GPR.

  • 492.
    Zhao, Yuxin
    et al.
    Ericsson Research, Linköping, Sweden.
    Yin, Feng
    Ericsson Research, Linköping, Sweden.
    Gunnarsson, Fredrik
    Ericsson Research, Linköping, Sweden.
    Amirijoo, Mehdi
    Ericsson Research, Linköping, Sweden.
    Özkan, Emre
    ISY, Linköping University.
    Gustafsson, Fredrik
    ISY, Linköping University.
    Particle Filtering for Positioning Based on Proximity Reports2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The commercial interest in proximity services is increasing. Application examples include location-based information and advertisements, logistics, social networking, file sharing, etc. In this paper, we consider positioning of devices based on time series proximity reports from a mobile device to a network node. This corresponds to nonlinear measurements with respect to the device position in relation to the network nodes. Therefore, particle filtering is applicable for positioning. Positioning performance is evaluated in a typical office area with Bluetooth-low-energy beacons deployed for proximity detection and report. Accuracy is concluded to vary spatially over the office floor, and in relation to the beacon deployment density.

  • 493.
    Örn, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Szilassy, Martin
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Dil, Bram
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    A Novel Multi-Step Algorithm for Low-Energy Positioning Using GPS2016Ingår i: Fusion 2016, 19th International Conference on Information Fusion: Proceedings, 2016, s. 1469-1476Konferensbidrag (Refereegranskat)
    Abstract [en]

    GPS is widely used for localization and tracking, however traditional GPS receivers consume too much energy for many applications. This paper implements and evaluates the performance of a low-energy GPS prototype. The main difference is that a traditional GPS needs to sample signals transmitted by satellites for 30 seconds to estimate its position. Our prototype reduces this time by three orders of magnitude and it can compute positions from only 2 milliseconds of data. We present a new algorithm that increases robustness by filtering on estimated residuals instead of using an altitude database. In addition, we show that our new algorithm works with both fixed and moving targets. The solution consists of (1) a portable device that samples the GPS signal and (2) a server that utilizes Doppler navigation and Coarse Time Navigation to estimate positions. We performed tests in a wide variety of environments and situations. These tests show that our prototype provides a median positioning error of roughly 40 meters even when the GPS receiver is moving at 80 kilometres per hour.

  • 494.
    Örn, Sara
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Realistic Multi-Cell Interference Coordination in 4G/LTE2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the LTE mobile system, all cells use the same set of frequencies. This means that a user could experience interference from other cells. A method that has been studied in order to reduce this interference and thereby increase data rate or system throughput is to coordinate scheduling between cells. Good results of this have been found in different studies. However, the interference is generally assumed to be known. Studies using estimated interference and simulating more than one cluster of cells have found almost no gain.

    This thesis will focus on how to use information from coordinated scheduling and other traffic estimates to do better interference estimation and link adaption. The suggested method is to coordinate larger clusters and use the coordination information, as well as estimates of which cells will be transmitting, to make estimates of interference from other cells. The additional information from interference estimation is used in the link adaptation. Limitations in bandwidth of the backhaul needed to send data between cells are considered, as well as the delay it may introduce. A limitation of the scope is that MIMO or HetNet scenarios have not been simulated.

    The suggested method for interference estimation and link adaptation have been implemented and simulated in a system simulator. The method gives a less biased estimate of SINR, but there are no gains in user bit rate. The lesser bias is since the method is better at predicting high SINR than the base estimate is. The lack of gains regarding user bit rate may result from the fact that in the studied scenarios, users where not able to make use of the higher estimated SINR since the base estimate is already high.

    The conclusion is that the method might be useful in scenarios where there are not full load, but the users either have bad channel quality or are able to make use of very high SINR. Such scenarios could be HetNet or MIMO scenarios, respectively.

  • 495.
    Östh, Joakim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Study of Six-Port Modulators and Demodulators for High-Speed Data Communications2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    There is an increasing demand for high-speed wireless data communications to support consumers’ need for, among other things, real time streaming of high definition video and fast file transfers. One radio architecture that has a potential to meet the increasing demand for high-speed data communications is a radio technique based on the six-port architecture. In addition to high-speed, the six-port radio also allows low power consumption and low cost. In this thesis, a comprehensive study of the six-port radio technique for high data rate (> 1 Gbit/s) and low complexity are presented.

    Firstly, a technique to suppress the carrier leakage was proposed, analyzed and verified by measurements. The proposed technique uses only a phase shifting network between the six-port correlator and its variable impedance loads, hence it is easy to implement. When the proposed carrier leakage suppression technique is used together with differential control signals, it also has the benefit of both improving the linearity and increasing the output power of the modulator. The same carrier leakage suppression technique can also be used in a six-port demodulator (receiver) to improve its performance.

    Secondly, Schottky diodes were proposed to be used as high-speed variable impedance loads. A six-port modulator operating at 7.5 GHz, using the carrier leakage suppression technique together with Schottky diodes as variable impedance loads, was manufactured. Measurements on a 16 quadrature amplitude modulated (QAM) signal with a symbol rate of 300 Msymbol/s, i.e., a data rate of 1.2 Gbit/s, have proved high-speed operation, good modulation properties as well as carrier leakage suppression.

    Thirdly, a six-port demodulator was built for high data rate applications and measurements were conducted to characterize its performance. Demodulation of a 16-QAM signal at a data rate of 1.67 Gbit/s results in an acceptable bit error rate and error vector magnitude (EVM) performance.

    Last but not least, new diode configurations were proposed, analyzed and verified for use in six-port demodulators. Using the proposed diode configurations, the use of differential amplifiers, as commonly used in a six-port demodulator, can be avoided. Avoiding the use of differential amplifiers allows high-speed processing and at the same time reduces the power consumption and implementation complexity. In the context of the new diode configurations, it was shown that a six-port receiver has better EVM vs frequency performance and lower implementation complexity, compared to a five-port or four-port receiver.

    Delarbeten
    1. Direct Carrier Six-Port Modulator Using a Technique to Suppress Carrier Leakage
    Öppna denna publikation i ny flik eller fönster >>Direct Carrier Six-Port Modulator Using a Technique to Suppress Carrier Leakage
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    2011 (Engelska)Ingår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, nr 3, s. 741-747Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents a direct carrier six-port modulator. To allow arbitrary load impedances to be used and for suppression of carrier leakage, a new circuit architecture with a technique to suppress carrier leakage is proposed and implemented. A theoretical model of the proposed modulator is derived. A prototype modulator utilizing diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz for verification of the proposed technique. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 100 Msymbol/s is generated, as well as good carrier leakage suppression.

    Ort, förlag, år, upplaga, sidor
    IEEE Institute of Electrical and Electronics, 2011
    Nyckelord
    Carrier leakage suppression, direct carrier modulator, six-port correlator
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-67308 (URN)10.1109/TMTT.2011.2104972 (DOI)000288460500026 ()
    Tillgänglig från: 2011-04-08 Skapad: 2011-04-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    2. Carrier Leakage Suppression and EVM Dependence on Phase Shifting Network in Six-Port Modulator
    Öppna denna publikation i ny flik eller fönster >>Carrier Leakage Suppression and EVM Dependence on Phase Shifting Network in Six-Port Modulator
    2012 (Engelska)Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
    Abstract [en]

    In six-port modulators a phase shifting network on specific ports can be used to suppress the carrier leakage that may be present if this network is not present. A model is derived to predict the carrier leakage suppression and error vector magnitude (EVM) as a function of the phase shifting network Sparameters. Both carrier leakage suppression and EVM can be expressed by the same error function. The error function can be used to find the allowed amplitude and phase mismatch in the phase shifting network, or to optimize the performance of a phase shifting network over a given frequency range. A broadband phase shifting network, based on a loaded transmission line, is designed and optimized to operate at a relative bandwidth of 60% for an EVM < 10%. This should be compared to a phase shifting network based on a single transmission line with a corresponding bandwidth of only 12%. The broadband phase shifting network is useful for six-port modulators with carrier leakage suppression, targeting UWB applications.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2012
    Nyckelord
    Six-Port Modulator, Carrier Leakage, EVM, Broadband
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77194 (URN)10.1109/ICMMT.2012.6230247 (DOI)978-1-4673-2184-6 (ISBN)
    Konferens
    International Conference on Microwave and Millimeter Wave Technology ICMMT, May 5-8, Shenzhen, China
    Tillgänglig från: 2012-05-08 Skapad: 2012-05-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    3. Schottky diode as high-speed variable impedance load in six-port modulators
    Öppna denna publikation i ny flik eller fönster >>Schottky diode as high-speed variable impedance load in six-port modulators
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    2011 (Engelska)Ingår i: ICUWB 2011: 2011 IEEE International Conference on Ultra-Wideband (ICUWB), 2011, s. 68-71Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
    Abstract [en]

    The use of Schottky diodes as high-speed variable impedance loads in six-port modulators are proposed and analyzed in this paper. The impedance dependency of diode parameters and local oscillator power are investigated by theoretical analysis and simulations. A prototype for a direct carrier six-port modulator using Schottky diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 300 Msymbol/s is generated, i.e., at a data rate of 1.2 Gbit/s, validating the use of Schottky diodes as high-speed variable impedance loads in six-port modulators.

    Serie
    IEEE International Conference on Ultra- Wideband (ICUWB), ISSN 2162-6588 ; 2011
    Nyckelord
    Schottky diodes, electric impedance measurement, modulators, oscillators, quadrature amplitude modulation
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77196 (URN)10.1109/ICUWB.2011.6058924 (DOI)978-1-4577-1762-8 (ISBN)978-1-4577-1763-5 (ISBN)
    Konferens
    IEEE International Conference on Ultra-Wideband (ICUWB),14-16 September, 2011, Bologna, Spain
    Tillgänglig från: 2012-05-08 Skapad: 2012-05-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    4. Six-Port Gigabit Demodulator
    Öppna denna publikation i ny flik eller fönster >>Six-Port Gigabit Demodulator
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    2011 (Engelska)Ingår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, nr 1, s. 125-131Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents measurement results for a six-port-based demodulator designed for a center frequency of 7.5 GHz and with a bandwidth of 1 GHz for operation in the ultra-wideband band. The demodulator includes the six-port correlator, diodes, and amplifiers needed to recover the baseband data. Measurement results show that the prototype supports data rates at 1.7 Gbit/s with bit-error rate 5 . 10(-5) if a two-tap linear equalizer is used and bit-error rate 4 . 10(-3) if only threshold detection is used. The measured performance of the used six-port correlator including the amplifiers is presented and their influence on the overall system performance is discussed. Limitations in the present system and possible improvements are also considered.

    Ort, förlag, år, upplaga, sidor
    IEEE Institute of Electrical and Electronics, 2011
    Nyckelord
    Demodulator, six-port correlator
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-66297 (URN)10.1109/TMTT.2010.2091198 (DOI)000286109400015 ()
    Tillgänglig från: 2011-03-11 Skapad: 2011-03-11 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    5. Diode Configurations in Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Öppna denna publikation i ny flik eller fönster >>Diode Configurations in Six-Port Receivers with Simplified Interface to Amplifier and Filter
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    2010 (Engelska)Ingår i: 2010 IEEE International Conferenceon Ultra-Wideband (ICUWB2010): Proceedings – Volume 1, Piscataway, NJ, USA: IEEE , 2010, s. 1-4Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper presents two new diode configurations for use with six-port based demodulators. The first proposed diode configuration allows a simplified diode to filter/amplifier interface. The second configuration allows for full-wave rectification and suppression of odd-order harmonics. A demodulator prototype utilizing the new diode concept is designed for a center frequency of 7.5 GHz and with a bandwidth of 1 GHz for verification. The demodulator includes the six-port correlator, diodes and amplifiers needed to recover the baseband data.

    Ort, förlag, år, upplaga, sidor
    Piscataway, NJ, USA: IEEE, 2010
    Nyckelord
    amplifiers, demodulators, diodes, radio receivers
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77198 (URN)10.1109/ICUWB.2010.5615597 (DOI)978-1-4244-5306-1 (ISBN)978-1-4244-5305-4 (ISBN)
    Konferens
    IEEE International Conference on Ultra-Wideband (ICUWB),20-23 September, 2010, Nanjing, China
    Tillgänglig från: 2012-05-08 Skapad: 2012-05-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    6. Performance Evaluation of Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Öppna denna publikation i ny flik eller fönster >>Performance Evaluation of Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Visa övriga...
    2011 (Engelska)Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
    Abstract [en]

    In six-port modulators a phase shifting network on specific ports can be used to suppress the carrier leakage that may be present if this network is not present. A model is derived to predict the carrier leakage suppression and error vector magnitude (EVM) as a function of the phase shifting network Sparameters. Both carrier leakage suppression and EVM can be expressed by the same error function. The error function can be used to find the allowed amplitude and phase mismatch in the phase shifting network, or to optimize the performance of a phase shifting network over a given frequency range. A broadband phase shifting network, based on a loaded transmission line, is designed and optimized to operate at a relative bandwidth of 60% for an EVM < 10%. This should be compared to a phase shifting network based on a single transmission line with a corresponding bandwidth of only 12%. The broadband phase shifting network is useful for six-port modulators with carrier leakage suppression, targeting UWB applications.

    Nyckelord
    Six-Port Modulator, Carrier Leakage, EVM, Broadband
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77200 (URN)10.1109/ICUWB.2011.6058824 (DOI)978-1-4577-1762-8 (ISBN)978-1-4577-1763-5 (ISBN)
    Konferens
    IEEE International Conference on Ultra-Wideband (ICUWB), 14-16 September 2011, Bologna, Spain
    Tillgänglig från: 2012-05-08 Skapad: 2012-05-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    7. Data and Carrier Interleaving in Six-Port Receivers for Increased Data Rate
    Öppna denna publikation i ny flik eller fönster >>Data and Carrier Interleaving in Six-Port Receivers for Increased Data Rate
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    2010 (Engelska)Ingår i: 2010 IEEE International Conferenceon Ultra-Wideband (ICUWB2010: Proceedings - Volume 1, 2010, s. 1-4Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
    Abstract [en]

    This paper proposes how antenna polarization can be utilized to increase the maximum data rate in a multiple six-port receiver system. By utilizing data and carrier interleaving, the total information bandwidth increases and therefore the maximum data rate. Prototype antennas were manufactured and the measured results were later used in a simulation model with three channels for verification of the concept.

    Nyckelord
    Antennas, electromagnetic wave polarisation, radio receivers
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77201 (URN)10.1109/ICUWB.2010.5614449 (DOI)978-1-4244-5306-1 (ISBN)978-1-4244-5305-4 (ISBN)
    Konferens
    IEEE International Conference on Ultra-Wideband (ICUWB), 20-23 September, Nanjing, China
    Tillgänglig från: 2012-05-08 Skapad: 2012-05-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
    8. Baseband complexity comparison of six-, five-, and four-port receivers
    Öppna denna publikation i ny flik eller fönster >>Baseband complexity comparison of six-, five-, and four-port receivers
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    2012 (Engelska)Ingår i: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 54, nr 6, s. 1502-1506Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The use of six-port correlators to implement six-port receivers has been intensively studied. The six-port receiver can also be modified to a five-port or a four-port receiver. However, the six-, five-, or four-port receiver solution requires different baseband processing to recover the baseband In-phase (I) and Quadrature-phase (Q) data. A unified mathematical model for the six-, five- and four-port receivers is presented in this article. Possible solutions to recover the baseband data are discussed and compared. The investigation shows that the six-port receiver has advantages over the five- and four-port receivers in terms of complexity when analog baseband processing is used. Simulations are conducted to verify the model and to estimate the error vector magnitude versus frequency; the simulation also shows that the six-port receiver operates over a wider bandwidth than the five- or four-port receiver.

    Ort, förlag, år, upplaga, sidor
    Wiley-Blackwell, 2012
    Nyckelord
    six-port receiver, five-port receiver, four-port receiver, baseband complexity
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-76606 (URN)10.1002/mop.26833 (DOI)000301715800045 ()
    Tillgänglig från: 2012-04-13 Skapad: 2012-04-13 Senast uppdaterad: 2019-06-17
    9. LO Leakage in Six-Port Modulators and Demodulators and its Suppression Techniques
    Öppna denna publikation i ny flik eller fönster >>LO Leakage in Six-Port Modulators and Demodulators and its Suppression Techniques
    2012 (Engelska)Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
    Abstract [en]

    In a six-port demodulator utilizing diodes for power detection, impedance mismatch at the interface between the six-port correlator and diodes generates unwanted local oscillator (LO) leakage to the radio frequency (RF) port. A six-port modulator that uses variable reflection coefficients at specific ports to generate a modulated RF may also suffer from LO leakage if there is a static part in the reflection coefficient. It is known that LO leakage to the RF port not only generates unwanted emission of the LO signal, but also degrades the receiver system performance due to a dynamic dc offset and second-order non-linearity at the detected baseband signal. How this LO leakage appears to the RF port in six-port demodulators and modulators are analyzed. Two different approaches to suppress the LO leakage is then discussed: a) diode impedance matching and b) introduction of a λ/4 line on specific ports. The performance when λ/4 lines are used on specific ports is verified by measurement for both a demodulator and a modulator. The measurement shows high suppression of the LO leakage.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2012
    Nyckelord
    Six-Port Correlator, Six-Port Receiver, LO Leakage, LO Suppression
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77207 (URN)10.1109/MWSYM.2012.6258402 (DOI)978-1-4673-1086-4 (ISBN)978-1-4673-1085-7 (ISBN)
    Konferens
    International Microwave Symposium, June 17-22, Montréal, Canada
    Tillgänglig från: 2012-05-08 Skapad: 2012-05-08 Senast uppdaterad: 2019-06-17Bibliografiskt granskad
  • 496.
    Östlund, Pierre
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Design, implementation och simulering av ett MAC-protokoll för mobila trådlösa sensornätverk2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Trådlösa sensornätverk byggs upp av trådlösa sensorer, som gemensamt arbetar för att lösa en viss uppgift. Ett exempel på en sådan uppgift kan vara insamling av pollennivåer i luften över en stor yta. Sensornoderna vidarebefordrar datan sinsemellan tills den når en datainsamlingsnod någonstans i nätverket där den sedan lagras och efterbehandlas. Generellt gäller att sensornoder är små, billiga, kommunicerar trådlöst och har en väldigt lång livslängd. Traditionellt sett har sen- sornoder också antagits vara statiska (stillastående), vilket medför begränsningar om noderna bärs av exempelvis människor eller monteras på fordon.

    I detta examensarbete presenteras matmac , ett mac-protokoll som designats för att hantera mobila noder i trådlösa sensornätverk. En referensimplementa- tion av matmac har implementerats i operativsystemet Contiki och utvärderats med varierande konfigurationsparametrar, rörelsehastigheter och dataintensitet i simulatorn Cooja. Resultatet från utvärderingen visar att mekanismerna för mo- bilitetshantering i matmac främjar sensornodernas förmåga att pålitligt överföra data trots att de är mobila. 

  • 497.
    Čirkić, Mirsad
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Optimization of Computational Resources for MIMO Detection2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    For the past decades, the demand in transferring large amounts of data rapidly and reliably has been increasing drastically. One of the more promising techniques that can provide the desired performance is the multiple-input multiple-output (MIMO) technology where multiple antennas are placed at both the transmitting and receiving side of the communication link. One major implementation difficulty of the MIMO technology is the signal separation (detection) problem at the receiving side of the MIMO link. This is due to the fact that the transmitted signals interfere with each other and that separating them can be very difficult if the MIMO channel conditions are not beneficial, i.e., the channel is not well-conditioned.

    For well-conditioned channels, low-complexity detection methods are often sufficiently accurate. In such cases, performing computationally very expensive optimal detection would be a waste of computational power. This said, for MIMO detection in a coded system, there is always a trade-off between performance and complexity. The fundamental question is, can we save computational resources by performing optimal detection only when it is needed, and something simpler when it is not? This is the question that this thesis aims to answer. In doing so, we present a general framework for adaptively allocating computational resources to different (“simple” and“difficult”) detection problems. This general framework is applicable to any MIMO detector and scenario of choice, and it is exemplified using one particular detection method for which specific allocation techniques are developed and evaluated.

    Delarbeten
    1. Allocation of Computational Resources for Soft MIMO Detection
    Öppna denna publikation i ny flik eller fönster >>Allocation of Computational Resources for Soft MIMO Detection
    2011 (Engelska)Ingår i: IEEE Journal of Selected Topics in Signal Processing, ISSN 1932-4553, Vol. 5, nr 8, s. 1451-1461Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. Our main results are a formulation of the problem as a mathematical optimization problem with a well-defined objective function and constraints, and algorithms that solve this optimization problem efficiently computationally.

    Ort, förlag, år, upplaga, sidor
    IEEE conference proceedings, 2011
    Nationell ämneskategori
    Signalbehandling
    Identifikatorer
    urn:nbn:se:liu:diva-69612 (URN)10.1109/JSTSP.2011.2162719 (DOI)000297348500006 ()
    Anmärkning
    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Mirsad Čirkić, Daniel Persson and Erik G. Larsson, Allocation of Computational Resources for Soft MIMO Detection, 2011, accepted IEEE Journal of Selected Topics in Signal Processing Tillgänglig från: 2011-07-06 Skapad: 2011-07-06 Senast uppdaterad: 2016-08-31
    2. Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
    Öppna denna publikation i ny flik eller fönster >>Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
    2012 (Engelska)Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, nr 12, s. 6421-6434Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We present approximations of the LLR distribution for a class of fixed-complexity soft-output MIMO detectors, such as the optimal soft detector and the soft-output via partial marginalization detector. More specifically, in a MIMO AWGN setting, we approximate the LLR distribution conditioned on the transmitted signal and the channel matrix with a Gaussian mixture model (GMM). Our main results consist of an analytical expression of the GMM model (including the number of modes and their corresponding parameters) and a proof that, in the limit of high SNR, this LLR distribution converges in probability towards a unique Gaussian distribution.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2012
    Nyckelord
    Fixed-complexity sphere-decoder; Gaussian mixture model; LLR distribution; MIMO detection; partial marginalization
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-87205 (URN)10.1109/TSP.2012.2217336 (DOI)000311805000024 ()
    Anmärkning

    On the defence date of the Licentiate Thesis the status of this article was Manuscript and the title was Approximating the LLR Distribution for the Optimal and Partial Marginalization MIMO Detectors.

    Tillgänglig från: 2013-01-14 Skapad: 2013-01-14 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
  • 498.
    Čirkić, Mirsad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Near-Optimal Soft-Output Fixed-Complexity MIMO Detection via Subspace Marginalization and Interference Suppression2012Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE Signal Processing Society, 2012, , s. 4s. 2805-2808Konferensbidrag (Refereegranskat)
    Abstract [en]

    The fundamental problem of our interest here is soft MIMO detection. We propose a method that yields excellent performance, atlow and at fixed (deterministic) complexity. Our method provides a well-defined tradeoff between computational complexity and performance. Apart from an initial step consisting of selecting columns,the algorithm involves no searching nor algorithmic branching; hence the algorithm has a completely predictable run-time, and it is readily and massively parallelizable.

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