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  • 101.
    Cheng, Hei Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Uplink pilot and data power control for single cell massive MIMO systems with MRC2015In: International Symposium on Wireless Communication Systems (ISWCS), 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 396-400Conference paper (Refereed)
    Abstract [en]

    This paper considers the jointly optimal pilot and data power allocation in single cell uplink massive MIMO systems. A closed form solution for the optimal length of the training interval is derived. Using the spectral efficiency (SE) as performance metric and setting a total energy budget per coherence interval the power control is formulated as optimization problems for two different objective functions: the minimum SE among the users and the sum SE. The optimal power control policy is found for the case of maximizing the minimum SE by converting it to a geometric program (GP). Since maximizing the sum SE is an NP-hard problem, an efficient algorithm is developed for finding KKT (local maximum) points. Simulation results show the advantage of optimizing the power control over both pilot and data power, as compared to heuristic power control policies.

  • 102.
    Cheng, Hei Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Some Fundamental Limits on Frequency Synchronization in Massive MIMO2013In: 2013 ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS, IEEE , 2013, p. 1213-1217Conference paper (Refereed)
    Abstract [en]

    The effect of frequency offsets on the uplink sumrate performance of massive MIMO systems is studied in the case of flat fading with pilot assisted estimation. Both collocated and distributed antenna architectures are studied to determine if there is a fundamental preference for collocated or distributed architectures from the perspective of frequency synchronization and its effect on the rate performance in a high mobility environment.

  • 103.
    Cheng, Hei Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Persson, Daniel
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios2015In: 2015 IEEE International Conference on Communications (ICC), IEEE , 2015, p. 1697-1702Conference paper (Refereed)
    Abstract [en]

    For both maximum ratio transmission (MRT) and zero forcing (ZF) precoding schemes and given any specific rate requirement the optimal transmit power, number of antennas to be used, number of users to be served and number of pilots spent on channel training are found with the objective to minimize the total consumed power at the base station. The optimization problem is solved by finding closed form expressions of the optimal transmit power and then search over the remaining discrete variables. The analysis consists of two parts, the first part investigates the situation when only power consumed in the RF amplifiers is considered. The second part includes both the power consumed in the RF amplifiers and in other transceiver circuits. In the former case having all antennas active while reducing the transmit power is optimal. Adaptive scheme to switch off some of the antennas at the base stations is found to be optimal in the latter case.

  • 104.
    Cheng, Hei Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Persson, Daniel
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    MIMO Capacity under Power Amplifiers Consumed Power and Per-Antenna Radiated Power Constraints2014In: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Institute of Electrical and Electronics Engineers (IEEE), 2014, p. 179-183Conference paper (Refereed)
    Abstract [en]

    We investigate the capacity of the multiple-input-multiple-output channel taking into account the consumed power in the power amplifiers. The mutual information is optimized with a limitation of total consumed power and per-antenna radiated power for a fixed channel with full channel state information at both the transmitter and receiver. The capacity is thus obtained by optimizing the input distribution to maximize the mutual information. Since the optimization problem is non-convex, direct computation of the capacity suffers from high computational complexity. Hence upper and lower bounds on the capacity are given as benchmarks for different ad-hoc schemes. An efficient suboptimal algorithm is also presented. Numerical results show that the suboptimal algorithm performs close to the capacity.

  • 105.
    Cheng, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    NOMA in Multiuser MIMO Systems with Imperfect CSI2017In: 2017 IEEE 18TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    This paper considers the use of NOMA in multiuser MIMO systems in practical scenarios where CSI is acquired through pilot signaling. A new NOMA scheme that uses shared pilots is proposed. Achievable rate analysis is carried out for a pilot signaling scheme including both uplink and downlink pilots. The achievable rate of the proposed NOMA scheme with shared pilots in each NOMA group is compared with the traditional orthogonal access scheme with orthogonal pilots. Numerical results show that when estimated downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. With increasing number of antennas at the base station, the gain from our proposed NOMA scheme is also increasing. This shows that there is a benefit of applying the proposed NOMA scheme in massive MIMO systems.

  • 106.
    Cheng, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Optimal Pilot and Payload Power Control in Single-Cell Massive MIMO Systems2017In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 65, no 9, p. 2363-2378Article in journal (Refereed)
    Abstract [en]

    This paper considers the jointly optimal pilot and data power allocation in single-cell uplink massive multiple-input-multiple- output systems. Using the spectral efficiency (SE) as performance metric and setting a total energy budget per coherence interval, the power control is formulated as optimization problems for two different objective functions: the weighted minimum SE among the users and the weighted sum SE. A closed form solution for the optimal length of the pilot sequence is derived. The optimal power control policy for the former problem is found by solving a simple equation with a single variable. Utilizing the special structure arising from imperfect channel estimation, a convex reformulation is found to solve the latter problem to global optimality in polynomial time. The gain of the optimal joint power control is theoretically justified, and is proved to be large in the low-SNR regime. Simulation results also show the advantage of optimizing the power control over both pilot and data power, as compared to the cases of using full power and of only optimizing the data powers as done in previous work.

  • 107.
    Cheng, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Performance Analysis of NOMA in Training-Based Multiuser MIMO Systems2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 1, p. 372-385Article in journal (Refereed)
    Abstract [en]

    This paper considers the use of non-orthogonal-multiple-access (NOMA) in multiuser MIMO systems in practical scenarios where channel state information (CSI) is acquired through pilot signaling. A new NOMA scheme that uses shared pilots is proposed. Achievable rate analysis is carried out for different pilot signaling schemes, including both uplink and downlink pilots. The achievable rate performance of the proposed NOMA scheme with shared pilot within each group is compared with the traditional orthogonal access scheme with orthogonal pilots. Our proposed scheme is a generalization of the orthogonal scheme, and can be reduced to the orthogonal scheme when appropriate power allocation parameters are chosen. Numerical results show that when downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. However with more groups of users present in the cell, it is preferable to use multi-user beamforming instead of NOMA.

  • 108.
    Cheng, Victor
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Persson, Daniel
    Qamcom Res and Technol AB, Sweden.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Optimal MIMO Precoding Under a Constraint on the Amplifier Power Consumption2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 1, p. 218-229Article in journal (Refereed)
    Abstract [en]

    The capacity of the MIMO channel taking into account both a limitation on total consumed power, and per-antenna radiated power constraints is considered. The total consumed power takes into account the traditionally used sum radiated power, and also the power dissipation in the amplifiers. For a fixed channel with full CSI at both the transmitter and the receiver, maximization of the mutual information is formulated as an optimization problem. Lower and upper bounds on the capacity are provided by numerical algorithms based on partitioning of the feasible region. Both bounds are shown to converge and give the exact capacity when number of regions increases. The bounds are also used to construct a monotonic optimization algorithm based on the branch-and-bound approach. An efficient suboptimal algorithm based on successive convex approximation performing close to the capacity is also presented. Numerical results show that the performance of the solution obtained from the suboptimal algorithm is close to that of the global optimal solution. Simulation results also show that in the low SNR regime, antenna selection provides performance that is close to the optimal scheme while at high SNR, uniform power allocation performs close to the optimal scheme.

  • 109.
    ChengWen, Xing
    et al.
    Beijing Institute of Technology, China .
    ZeSong, Fei
    Beijing Institute of Technology, China .
    Na, Li
    Beijing Institute of Technology, China .
    YanTao, Han
    Beijing Institute of Technology, China .
    Danev, Danyo
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    JingMing, Kuang
    Beijing Institute of Technology, China .
    Statistically robust resource allocation for distributed multi-carrier cooperative networks2013In: Science China Information Sciences, ISSN 1674-733X, Vol. 56, no 2, p. 109-121Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate joint subcarrier and power allocation scheme for distributed multi-carrier cooperative networks with imperfect channel state information. Using practical channel estimation algorithms, the statistic model of the channel estimation error is first derived. Then based on the channel error model, the resource allocation scheme aims at maximizing the sum rate of the overall network. Specifically, both subcarrier allocation and power allocation are taken into account. In the subcarrier allocation, a realistic problem of the power leakage between neighboring subcarriers is also addressed. Furthermore, based on Lagrange dual-decomposition algorithm, a practical power allocation algorithm is proposed. Finally, the simulation results demonstrate the performance advantages of the proposed robust design.

  • 110.
    Chien, Trinh Van
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering. Sungkyunkwan University, South Korea.
    Dinh, Khanh Quoc
    ungkyunkwan Univ, Sch Elect & Comp Engn, Seoul, South Korea.
    Jeon, Byeungwoo
    Sungkyunkwan Univ, Sch Elect & Comp Engn, Seoul, South Korea.
    Burger, Martin
    University of Munster, Germany.
    Block compressive sensing of image and video with nonlocal Lagrangian multiplier and patch-based sparse representation2017In: Signal processing. Image communication, ISSN 0923-5965, E-ISSN 1879-2677, Vol. 54, p. 93-106Article in journal (Refereed)
    Abstract [en]

    Although block compressive sensing (BCS) makes it tractable to sense large-sized images and video, its recovery performance has yet to be significantly improved because its recovered images or video usually suffer from blurred edges, loss of details, and high-frequency oscillatory artifacts, especially at a low subrate. This paper addresses these problems by designing a modified total variation technique that employs multi-block gradient processing, a denoised Lagrangian multiplier, and patch-based sparse representation. In the case of video, the proposed recovery method is able to exploit both spatial and temporal similarities. Simulation results confirm the improved performance of the proposed method for compressive sensing of images and video in terms of both objective and subjective qualities.

  • 111.
    Chopra, Ribhu
    et al.
    IIT Guwahati, India.
    Murthy, Chandra R.
    IISc Bangalore, India.
    Suraweera, Himal A.
    Univ Peradeniya, Sri Lanka.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Analysis of Nonorthogonal Training in Massive MIMO Under Channel Aging With SIC Receivers2019In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 26, no 2, p. 282-286Article in journal (Refereed)
    Abstract [en]

    We analyze the effect of channel aging on the achievable rate of time division duplexed massive multiple input multiple output systems serving a number of users under aging channels, using nonorthogonal multiple access (NOMA) and orthogonal multiple access (OMA). Using the recently proposed shared uplink pilot based channel estimation for NOMA, we derive bounds on the channel estimation error variance for the two schemes. We then derive the achievable spectral efficiencies of the two schemes. Using numerical results, we show that, in slowly varying channels, using NOMA with shared pilots is preferable over OMA, while the reverse is true under fast varying channels.

  • 112.
    Chopra, Ribhu
    et al.
    IIT Guwahati, India.
    Murthy, Chandra R.
    Indian Inst Sci, India.
    Suraweera, Himal A.
    Univ Peradeniya, Sri Lanka.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Performance Analysis of FDD Massive MIMO Systems Under Channel Aging2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 2, p. 1094-1108Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the effect of channel aging on the uplink and downlink performance of an FDD massive MIMO system, as the system dimension increases. Since the training duration scales linearly with the number of transmit dimensions, channel estimates become increasingly outdated in the communication phase, leading to performance degradation. To quantify this degradation, we first derive bounds on the mean squared channel estimation error. We use the bounds to derive deterministic equivalents of the receive SINRs, which yields a lower bound on the achievable uplink and downlink spectral efficiencies. For the uplink, we consider maximal ratio combining and MMSE detectors, while for the downlink, we consider matched filter and regularized zero forcing precoders. We show that the effect of channel aging can be mitigated by optimally choosing the frame duration. It is found that using all the base station antennas can lead to negligibly small achievable rates in high user mobility scenarios. Finally, numerical results are presented to validate the accuracy of our expressions and illustrate the dependence of the performance on the system dimension and channel aging parameters.

  • 113.
    Chuasomboon, Sasit
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    A comparison of ranging and localization techniques in indoor, urban, and tunnel environments2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Localization in wireless network sensors is an attractive research area nowadays. It is widely used in many applications e.g., indoor/outdoor asset tracking, intrusion detection, search-and-rescue, road traffic monitoring, and water quality monitoring. An accuracy and robustness to noise are important issues for localization which is needed to study and research to find the best solution. This thesis compares a ranging and localization techniques in indoor, urban and tunnel through a high performance ray-tracing simulator, Wireless InSiteR . Ranging techniques are based on two standard distance related measurement schemes e.g., RSS and TOA. A linearized least squares technique with reference node selection approach is chosen to estimate unknown nodes positions. Indoor and urban area are built-in floor plan and terrain available in simulator program, while tunnel is designed. In general, localization accuracy suffers from multipath and NLOS condition. This thesis also observes characteristic of them from ray-tracing method perspective. Firstly, important simulation parameters such as number ofreflections/diffractions, types of waveform, and types of antenna are analyzed oneach environments. Then, the models for distance estimation based on RSS and TOA measurements are created using measurements in simulated environments. The thesis proposes four scenarios for distance estimation model. They are line-of-sight (LOS), non-line-of-sight (NLOS), combination of LOS and NLOS, and NLOS with obstacle. All four scenarios models are derived along with model error distribution to observe characteristic of noise due to multipath and NLOS condition. Finally, the localization using only LOS condition measurements, is tested on each environment and compared results in term of accuracy.

  • 114.
    Cipriano, Antonio
    et al.
    Thales Communications and Security, Colombes, France.
    Agostini, Philippe
    Thales Communications and Security, Colombes, France.
    Blad, Anton
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Knopp, Raymond
    Institut Eurecom, Sophia Antipolis, France.
    Cooperative Communications with HARQ in a Wireless Mesh Network Based on 3GPP LTE2012In: Signal Processing Conference (EUSIPCO), 2012, IEEE , 2012, p. 1004-1008Conference paper (Refereed)
    Abstract [en]

    This paper presents some results from of the FP7 ICT-LOLA (achieving LOw LAtency in wireless communications) project on the design of clusterized wireless mesh network based on 3GPP LTE. First, we focus on the general MAC/PHY structure of the clusterized mesh network based on 3GPP LTE. Then, the concept of virtual link is presented for inter-cluster communications combining MAC layer forwarding, hybrid automatic repeat request (HARQ) and cooperative communications with Decode and Forward (DF). The goal of a virtual link is to enable low latency data transfer in inter-cluster communications. The virtual link solution is studied by simulations thanks to OpenAirInterface which integrates LTE MAC and PHY layer procedures, as well as adaptations needed for the LOLA wireless mesh network. Simulation results show that the proposed distributed solution smoothly adapts to the link conditions. A loss in throughput efficiency is the price to be paid in certain configurations for the distributed operation of the virtual link. Nevertheless, the technique helps in reducing the average number of transmissions thus contributing to improve the latency of the system.

  • 115.
    Cirkic, Mirsad
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Persson, Daniel
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 12, p. 6421-6434Article in journal (Refereed)
    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.

  • 116.
    Cooke, Henrik
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Implementation and evaluation of packet loss concealment schemes with the JM reference software2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Communication over today’s IP-based networks are to some extent subject to packet loss. Most real-time applications, such as video streaming, need methods to hide this effect, since resending lost packets may introduce unacceptable delays. For IP-based video streaming applications such a method is referred to as a packet loss concealment scheme.

    In this thesis a recently proposed mixture model and least squares-based packet loss concealment scheme is implemented and evaluated together with three more well known concealment methods. The JM reference software is used as basis for the implementation, which is a public available software codec for the H.264 video coding standard. The evaluation is carried out by comparing the schemes in terms of objective measurements, subjective observations and a study with human observers.

    The recently proposed packet loss concealment scheme shows good performance with respect to the objective measures, and careful observations indicate better concealment of scenes with fast motion and rapidly changing video content. The study with human observers verifies the results for the case when a more sophisticated packetization technique is used.

    A new packet loss concealment scheme, based on joint modeling of motion vectors and pixels, is also investigated in the last chapter as an additional contribution of the thesis.

  • 117.
    Cottatellucci, Laura
    et al.
    Eurecom, France.
    Mestre, Xavier
    CTTC, Spain.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Ribeiro, Alejandro
    University of Minnesota, USA.
    Cooperative Communications in Wireless Networks: Editorial Material in EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING2009In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, article id 768314Article in journal (Other academic)
  • 118.
    Dabrowski, Jerzy
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Qazi, Fahad
    Catena Wireless Elect AB, Sweden.
    Spectrum Sensing for Cognitive Radio Based on Flexible RF Filtering2016In: 2016 INTERNATIONAL CONFERENCE ON SIGNALS AND ELECTRONIC SYSTEMS (ICSES) PROCEEDINGS, IEEE , 2016, p. 270-275Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate a spectrum sensing technique suitable for cognitive radio (CR) considered a means to mitigate congestion in the future multiple access communication systems. The ultimate objective is opportunistic use of unoccupied frequency bands called spectrum holes or white spaces, which belong to another system. For this purpose, first, we identify the spectrum sensor (SS) nonlinearities and scan the available spectrum in wideband mode where the primary task is to identify strong interference. :Next, by a complementary analysis we pick up channels which are likely to be spectrum holes. In the second stage the SS is tuned to a selected sub-band by making use of a built-in flexible RF filter which largely attenuates interference and the related intermodulation distortions (IMD). The scan process carried out in this stage is aimed at detection of a vacant channel, i.e. containing only noise that must he distinguished from a possible weak signal that usually requires a significant computation overhead, but as the scan is narrowband and the S/N ratio can he high, the related overhead is largely reduced compared to the wideband sensing approach. The strength of this technique is in the flexible RF filter eliminating IMll which typically tend to obscure the spectrum holes.

  • 119.
    Dackenberg, Jens
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Software Communication Architecture - Waveform Distribution with MHAL2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For a long time radio devices have been constructed in hardware with a fixed functionality. This way of constructing radio devices is starting to change with the concept of Software Defined Radio (SDR) evolving. The SDR concept leads to more flexible and long lasting radio devices. In order to make the radio software more standardized and portable, the U.S. military has defined the Software Communication Architecture (SCA). Internal communication within the SCA is done by CORBA, which limit waveforms to be only distributed over CORBA-capable hardware. The U.S. military has defined the Modem Hardware Abstraction Layer(MHAL) to enable distribution over devices not supporting CORBA. This thesis presents an implementation of MHAL and an underlying transport mechanism based on Ethernet. The implementation is done for the OSSIE package. The implementation is evaluated both in terms of real-time and throughput performance. The results show that MHAL achieves good performance, in comparison to CORBA, and can greatly be used to distribute waveforms over both CORBA and non-CORBA capable devices.

  • 120.
    Danev, Danyo
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    On Signal Detection Techniques for the DVB-T Standard2010In: Proceedings of the International Symposium on Communications, Control and Signal Processing (ISCCSP), 2010, p. 1-5Conference paper (Other academic)
    Abstract [en]

    In this paper we discuss some spectrum sensing techniques for detection of DVB-T signals. Their performance is compared in terms of probability of detection and ROC curves. Some simulation results are presented for various scenarios.

  • 121.
    Danev, Danyo
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Axell, Erik
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Spectrum Sensing Methods for Detection of DVB-T Signals in AWGN and Fading Channels2010In: Proceedings of the 21st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2010, p. 2721-2726Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider spectrum sensing of DVB-T signals in differentfading environments. We compare state-of-the-art detectorsincluding detectors based on pilot subcarriers, as well as detectors for general OFDM signals that exploit the correlation structure incurred by the cyclicprefix. Energy detection is also included for comparison. We shownumerically that the choice of detector depends on the scenario, the detectorrequirements, and on the available prior knowledge. We also show that it ispossible to obtain good detection performance by exploiting the correlation,even in a frequency selective channel.

  • 122.
    Danev, Danyo
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Dodunekov, Stefan
    Bulgarian Academy of Sciences.
    A Family of Ternary Quasi-Perfect BCH Codes2008In: Designs, Codes and Cryptography, ISSN 0925-1022, E-ISSN 1573-7586, Vol. 49, p. 265-271Article in journal (Refereed)
    Abstract [en]

    In this paper we present a family of ternary quasi-perfect BCH codes. These codes are of minimum distance 5 and covering radius 3. The first member of this family is the ternary quadratic-residue code of length 13.

  • 123.
    Danev, Danyo
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Dodunekov, Stefan
    Bulgarian Academy of Science.
    Radkova, Diana
    Sofia University.
    A family of constacyclic ternary quasi-perfect codes with covering radius 32011In: DESIGNS CODES AND CRYPTOGRAPHY, ISSN 0925-1022, Vol. 59, no 1-3, p. 111-118Article in journal (Refereed)
    Abstract [en]

    In this paper a family of constacyclic ternary quasi-perfect linear block codes is presented. This family extends the result presented in a previous work by the first two authors, where the existence of codes with the presented parameters was stated as an open question. The codes have a minimum distance 5 and covering radius 3.

  • 124.
    Danev, Danyo
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Dodunekov, Stefan
    Bulgarian Academy of Sciences, Bulgaria.
    Radkova, Diana
    Sofia University, Bulgaria.
    A Family of Constacyclic Ternary Quasi-Perfect Codes with  Covering Radius 32009In: Proceedings of the International Workshop on Coding and Cryptography (WCC'09), 2009, p. 111-118Conference paper (Refereed)
    Abstract [en]

    In this paper a family of constacyclic ternary quasi-perfect linearblock codes is presented. This family extends the result presented ina previous work by the first two authors, where the existence of codeswith the presented parameters was stated as an open question. The codes have a minimum distance 5 and covering radius 3.

  • 125.
    de Carvalho, Elisabeth
    et al.
    Aalborg University, Denmark.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Popovski, Petar
    Aalborg University, Denmark.
    RANDOM ACCESS FOR MASSIVE MIMO SYSTEMS WITH INTRA-CELL PILOT CONTAMINATION2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING PROCEEDINGS, IEEE , 2016, p. 3361-3365Conference paper (Refereed)
    Abstract [en]

    Massive MIMO systems, where the base stations are equipped with hundreds of antenna elements, are an attractive way to attain unprecedented spectral efficiency in future wireless networks. In the "classical" massive MIMO setting, the terminals are assumed fully loaded and a main impairment to the performance comes from the inter-cell pilot contamination, i.e., interference from terminals in neighboring cells using the same pilots as in the home cell. However, when the terminals are active intermittently, it is viable to avoid inter-cell contamination by pre-allocation of pilots, while same-cell terminals use random access to select the allocated pilot sequences. This leads to the problem of intra-cell pilot contamination. We propose a framework for random access in massive MIMO networks and derive new uplink sum rate expressions that take intra-cell pilot collisions, intermittent terminal activity, and interference into account. We use these expressions to optimize the terminal activation probability and pilot length.

  • 126.
    de Carvalho, Elisabeth
    et al.
    Aalborg University, Denmark.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Popovski, Petar
    Aalborg University, Denmark.
    Random Pilot and Data Access in Massive MIMO for Machine-Type Communications2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 12, p. 7703-7717Article in journal (Refereed)
    Abstract [en]

    A massive MIMO system, represented by a base station with hundreds of antennas, is capable of spatially multiplexing many devices and thus naturally suited to serve dense crowds of wireless devices in emerging applications, such as machine-type communications. Crowd scenarios pose new challenges in the pilot-based acquisition of channel state information and call for pilot access protocols that match the intermittent pattern of device activity. A joint pilot assignment and data transmission protocol based on random access is proposed in this paper for the uplink of a massive MIMO system. The protocol relies on the averaging across multiple transmission slots of the pilot collision events that result from the random access process. We derive new uplink sum rate expressions that take pilot collisions, intermittent device activity, and interference into account. Simplified bounds are obtained and used to optimize the device activation probability and pilot length. A performance analysis indicates how performance scales as a function of the number of antennas and the transmission slot duration.

  • 127.
    de Carvalho, Elisabeth
    et al.
    Aalborg University, Denmark.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Popovski, Petar
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Random Access Protocols for Massive MIMO2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 5, p. 216-222Article in journal (Refereed)
    Abstract [en]

    5G wireless networks are expected to support new services with stringent requirements on data rates, latency and reliability. One novel feature is the ability to serve a dense crowd of devices, calling for radically new ways of accessing the network. This is the case in machine-type communications, but also in urban environments and hotspots. In those use cases, the high number of devices and the relatively short channel coherence interval do not allow per-device allocation of orthogonal pilot sequences. This article addresses the need for random access by the devices to pilot sequences used for channel estimation, and shows that Massive MIMO is a main enabler to achieve fast access with high data rates, and delay-tolerant access with different data rate levels. Three pilot access protocols along with data transmission protocols are described, fulfilling different requirements of 5G services.

  • 128.
    De, Swades
    et al.
    Department of Electrical Engineering and Bharti School of Telecom, Indian Institute of Technology Delhi, India.
    Kaushik, K.
    Department of Electrical Engineering and Bharti School of Telecom, Indian Institute of Technology Delhi, India.
    Mishra, Deepak
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Stochastic Solar Harvesting Characterization for Sustainable Sensor Node Operation2019In: IET Wireless Sensor Systems, ISSN 2043-6386, p. 1-11Article in journal (Refereed)
    Abstract [en]

    Self-sustainability of low power wireless sensor nodes is the need of the hour to realize ubiquitous wireless networks. To address this requirement we investigate the practical feasibility of sustainable green sensor network with solar-powered nodes. We propose simple yet efficient (i) analytical circuit model for solar panel assisted supercapacitor charging and (ii) statistical model for characterizing the solar intensity distribution. Combining these circuit and statistical models, we derive a novel solar charging rate distribution for the solar-powered supercapacitor. To gain analytical insights, we also propose an ideal diode based tight approximation for the practical supercapacitor charging circuit model. The accuracy of these proposed analytical models have been validated by extensive numerical simulations based on the real-world data, i.e., solar intensity profile and solar panel characteristics. The derived solar charging rate distribution is used to investigate the supported sampling rate of the node with different varying number of on-board sensors for a given energy outage probability. Results suggest that for an energy outage probability of 0.1, at New Delhi, a 40 F supercapacitor and a 3 W solar panel can support the operation of Waspmote with 6 on-board toxic gas sensors with a sampling rate of 65 samples per day. Further, we use the proposed models to estimate the practical supercapacitor and solar panel sizes required to ensure sustainability of sensor node operation at different geographical locations with varying sensing rate.

  • 129.
    Do, Tan Tai
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    JAMMING RESISTANT RECEIVERS FOR MASSIVE MIMO2017In: 2017 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 3619-3623Conference paper (Refereed)
    Abstract [en]

    We design jamming resistant receivers to enhance the robustness of a massive MIMO uplink channel against jamming. In the pilot phase, we estimate not only the desired channel, but also the jamming channel by exploiting purposely unused pilot sequences. The jamming channel estimate is used to construct the linear receive filter to reduce impact that jamming has on the achievable rates. The performance of the proposed scheme is analytically and numerically evaluated. These results show that the proposed scheme greatly improves the rates, as compared to conventional receivers. Moreover, the proposed schemes still work well with stronger jamming power.

  • 130.
    Do, Tan Tai
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Mohammad Razavizadeh, S.
    Iran University of Science and Technology, Iran.
    Jamming-Resistant Receivers for the Massive MIMO Uplink2018In: IEEE Transactions on Information Forensics and Security, ISSN 1556-6013, E-ISSN 1556-6021, Vol. 13, no 1, p. 210-223Article in journal (Refereed)
    Abstract [en]

    We design a jamming-resistant receiver scheme to enhance the robustness of a massive MIMO uplink system against jamming. We assume that a jammer attacks the system both in the pilot and data transmission phases. The key feature of the proposed scheme is that, in the pilot phase, the base station estimates not only the legitimate channel, but also the jamming channel by exploiting a purposely unused pilot sequence. The jamming channel estimate is used to construct linear receiver filters that reject the impact of the jamming signal. The performance of the proposed scheme is analytically evaluated using the asymptotic properties of massive MIMO. The best regularized zero-forcing receiver and the optimal power allocations for the legitimate system and the jammer are also studied. Numerical results are provided to verify our analysis and show that the proposed scheme greatly improves the achievable rates, as compared with conventional receivers. Interestingly, the proposed scheme works particularly well under strong jamming attacks, since the improved estimate of the jamming channel outweighs the extra jamming power.

  • 131.
    Do, Tan Tai
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Ngo, Hien
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Duong, Trung Q.
    Queens University of Belfast, North Ireland.
    Oechtering, Tobias J.
    KTH Royal Institute Technology, Sweden.
    Skoglund, Mikael
    KTH Royal Institute Technology, Sweden.
    Massive MIMO Pilot Retransmission Strategies for Robustification Against Jamming2017In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 6, no 1, p. 58-61Article in journal (Refereed)
    Abstract [en]

    This letter proposes anti-jamming strategies based on pilot retransmission for a single user uplink massive MIMO under jamming attack. A jammer is assumed to attack the system both in the training and data transmission phases. We first derive an achievable rate which enables us to analyze the effect of jamming attacks on the system performance. Counter-attack strategies are then proposed to mitigate this effect under two different scenarios: random and deterministic jamming attacks. Numerical results illustrate our analysis and benefit of the proposed schemes.

  • 132.
    Du, Jinfeng
    et al.
    KTH.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Xiao, Ming
    KTH.
    Skoglund, Mikael
    KTH.
    Optimal Symbol-by-Symbol Costa Precoding for a Relay-aided Downlink Channel2011In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, no 8, p. 2274-2284Article in journal (Refereed)
    Abstract [en]

    In this article, we consider practical approaches to Costa precoding (also known as dirty paper coding). Specifically, we propose a symbol-by-symbol scheme for cancellation of interference known at the transmitter in a relay-aided downlink channel. For finite-alphabet signaling and interference, we derive the optimal (in terms of maximum mutual information) modulator under a given power constraint. A sub-optimal modulator is also proposed by formulating an optimization problem that maximizes the minimum distance of the signal constellation, and this non-convex optimization problem is approximately solved by semi-definite relaxation. For the case of binary signaling with binary interference, we obtain a closed-form solution for the sub-optimal modulator, which only suffers little performance degradation compared to the optimal modulator in the region of interest. For more general signal constellations and more general interference distributions, we propose an optimized Tomlinson-Harashima precoder (THP), which uniformly outperforms conventional THP with heuristic parameters. Bit-level simulation shows that the optimal and sub-optimal modulators can achieve significant gains over the THP benchmark as well as over non-Costa reference schemes, especially when the power of the interference is larger than the power of the noise.

  • 133.
    Duc Ho, Chung
    et al.
    Queens Univ Belfast, North Ireland.
    Ngo, Hien
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering. Queens Univ Belfast, North Ireland.
    Matthaiou, Michail
    Queens Univ Belfast, North Ireland.
    Three-Way Massive MIMO Relaying with Successive Cancelation Decoding2018In: INDUSTRIAL NETWORKS AND INTELLIGENT SYSTEMS, INISCOM 2017, Springer, 2018, Vol. 221, p. 79-90Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a novel transmission scheme for a three-way massive multiple-input multiple-output (MIMO) relay network where three users exchange their data with the help of a decode-and-forward relay station equipped with a very large antenna array. Our proposed scheme needs only two time-slots for the information exchange. More precisely, the three users first send their symbols to the relay. Then, the relay uses the maximum-ratio combining technique to decode all transmitted symbols and simultaneously transmits these symbols to all three users. Each user applies successive cancelation decoding to decode symbols transmitted from other users. We study the sum spectral efficiency of our proposed transmission protocol. We show that the sum spectral efficiency of our proposed scheme increases noticeably compared to the one of the conventional scheme where three time-slots are required to exchange data among the three users, without increasing the system complexity.

  • 134.
    Duc Ho, Chung
    et al.
    Queens University of Belfast, North Ireland.
    Ngo, Hien
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Matthaiou, Michail
    Queens University of Belfast, North Ireland.
    Duong, Trung Q.
    Queens University of Belfast, North Ireland.
    On the Performance of Zero-Forcing Processing in Multi-Way Massive MIMO Relay Networks2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 4, p. 849-852Article in journal (Refereed)
    Abstract [en]

    We consider a multi-way massive multiple-input multiple-output relay network with zero-forcing processing at the relay. By considering the time-division duplex protocol with channel estimation, we derive an analytical approximation of the spectral efficiency. This approximation is very tight and simple, which enables us to analyze the system performance, as well as to compare the spectral efficiency with zero-forcing and maximum-ratio processing. Our results show that by using a very large number of relay antennas and with the zero-forcing technique, we can simultaneously serve many active users in the same time-frequency resource, each with high spectral efficiency.

  • 135.
    Duc Ho, Chung
    et al.
    Queens University of Belfast, North Ireland.
    Ngo, Hien Quoc
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering. Queens University of Belfast, North Ireland.
    Matthaiou, Michail
    Queens University of Belfast, North Ireland.
    Duong, Trung Q.
    Queens University of Belfast, North Ireland.
    Multi-way Massive MIMO Relay Networks with Maximum-Ratio Processing2017In: 2017 INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SIGNAL PROCESSING, TELECOMMUNICATIONS and COMPUTING (SIGTELCOM), IEEE , 2017, p. 124-128Conference paper (Refereed)
    Abstract [en]

    This paper considers a multi-way massive multiple-input multiple-output (MIMO) relaying system. The bearing-information is exchanged among multiple users with the help of a multiple-antenna relay (the base station). The maximum-ratio (MR) processing is applied at the relay under the assumption of perfect channel state information. The spectral efficiency and the asymptotic results for the signal-to-interference-plus-noise ratio (when the number of relay antennas becomes large) are derived. By using a massive number of antennas, the transmit power at both user side and/or relay can be made inversely proportional to the number of relay antennas without degradation in the system performance.

  • 136.
    Duong, Quoc-Tai
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, Faculty of Science & Engineering.
    Dabrowski, Jerzy
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, Faculty of Science & Engineering.
    Highly linear open-loop output driver design for high speed capacitive DACs2013In: 2013 NORCHIP, 11–12 November, 2013, Vilnius, LITHUANIA, 2013, p. 1-4Conference paper (Refereed)
    Abstract [en]

    Design of a high speed output driver for capacitive digital-to-analog converters (SC DACs) is presented. As the output voltage swing of those DACs is usually greater than 300 mVpp the driver is designed for large signal operation that is a challenge in terms of the DAC linearity. Two non-linearity cancellation techniques are applied to the driver circuit, the derivative superposition (DS) and the resistive source degeneration resulting in HD3 <; -70 dB and HD2 <; -90 dB over the band of 0.5-4 GHz in 65-nm CMOS. For the output swing of 300 mVpp and 1.2 V supply its power consumption is 40 mW. For verification the driver is implemented in a 12-bit pipeline SC DAC. In simulations the complete Nyquist-rate DAC achieves SFDR of 64 dB for signal bandwidth up to 2.2 GHz showing a negligible non-linearity contribution by the designed driver for signal frequencies up to 1.3 GHz and a degradation by 3 dB at 2.2 GHz.

  • 137.
    Duong, Quoc-Tai
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, Faculty of Science & Engineering.
    Dabrowski, Jerzy J.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Focused Calibration for Advanced RF Test with Embedded RF Detectors2013In: European Conference on Circuit Theory and Design (ECCTD), 2013, IEEE , 2013, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In this paper a technique suitable for on-chip IP3/IP2 RF test by embedded RF detectors is presented. A lack of spectral selectivity of the detectors and diverse nonlinearity of the circuit under test (CUT) impose stiff constraints on the respective test measurements for which focused calibration approach and a support by customized models of CUT is necessary. Also cancellation of second-order intermodulation effects produced by the detectors under the two-tone test is required. The test technique is introduced using a polynomial model of the CUT. Simulation example of a practical CMOS LNA under IP3/IP2 RF test with embedded RF detectors is presented showing a good measurement accuracy.

  • 138.
    Duong, Trung Q.
    et al.
    Blekinge Institute of Technology, Karlskrona, Sweden..
    Ngo, Hien Quoc
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Zepernick, Hans-Jurgen
    Blekinge Institute of Technology, Karlskrona, Sweden..
    Nallanathan, Arumugam
    King’s College London, London, United Kingdom..
    Distributed Space-Time Coding in Two-Way Fixed Gain Relay Networks over Nakagami-m Fading2012In: Proceedings of the IEEE International Conference on Communicatons (ICC), IEEE , 2012, p. 3521-3525Conference paper (Refereed)
    Abstract [en]

    The distributed Alamouti space-time code in two-way fixed gain amplify-and-forward (AF) relay is proposed in this paper. In particular, closed-form expressions for approximated ergodic sum-rate and exact pairwise error probability (PWEP) are derived for Nakagami-m fading channels. To reveal further insights into array and diversity gains, an asymptotic PWEPis also obtained. Finally, numerical results are provided to corroborate the proposed theoretical analysis.

  • 139.
    Eamrurksiri, Techin
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Implementation and Analysis of Spectrum Sensing Algorithms for SIMO Links2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cognitive radio is an autonomous transceiver that is continuously sensing theongoing communication in its environment, it then starts the communication whenever it is appropriate. Therefore, cognitive radio helps improving the spectrum utilization of the overall communication system. However, without suitable spectrum sensing techniques, cognitive radio would fail. Hence, in this thesis we investigate and implement various spectrum sensing algorithms via software defined radio for both single antenna and multiple antenna cases. The main communi-cation scheme that we are using is OFDM. Moreover, both computer simulations and real-world measurements, have also been done for comparison and analysis ofthe detector’s performance. The detectors we are using are based on correlationfunction of the received signal and generalized likelihood ratio test with its eigen-value. The results from the simulations and measurements are then representedas probability of missed detection curves for different signal to noise ratios. Ourresults show that the performance of the generalized likelihood ratio test baseddetectors are at least 2 dB better than the correlation based detector in our mea-surement. Moreover, our simulations show that they are able to outperform thecorrelation function detector by more than 6 dB. Although, generalized likelihoodratio test based detectors seem to be better than the correlation function baseddetector, it requires more computational power which may limit its practical use.

  • 140.
    Eghbali, Amir
    et al.
    Thyselius AB, Huawei Technol. Sweden AB, Gothenburg, Sweden.
    Johansson, Håkan
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Design of Modulated Filter Banks and Transmultiplexers With Unified Initial Solutions and Very Few Unknown Parameters2015In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 62, no 4, p. 397-401Article in journal (Refereed)
    Abstract [en]

    This brief proposes a method for designing modulated filter banks (FBs) with a large number of channels. The impulse response of the long prototype filter is parameterized in terms of a few short impulse responses, thus significantly reducing the number of unknown parameters. The proposed method starts by first obtaining an FB with a few channels. The solution of this FB is then partly reused as an initial (very close to final) solution in the design of FBs with a large number of channels. The number of unknown parameters hence drastically reduces. For example, we can first design a cosine modulated FB (CMFB) with three channels whose prototype filter has a stopband attenuation of about 40 dB. We can then reuse the solution of this CMFB in the design of a CMFB with 16 384 channels whose prototype filter has a similar stopband attenuation. With our proposed method, we need to reoptimize only 14 parameters to design the CMFB with 16 384 channels.

  • 141.
    Ekman, Björn
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Machine Learning for Beam Based Mobility Optimization in NR2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One option for enabling mobility between 5G nodes is to use a set of area-fixed reference beams in the downlink direction from each node. To save power these reference beams should be turned on only on demand, i.e. only if a mobile needs it. An User Equipment (UE) moving out of a beam's coverage will require a switch from one beam to another, preferably without having to turn on all possible beams to find out which one is the best.

    This thesis investigates how to transform the beam selection problem into a format suitable for machine learning and how good such solutions are compared to baseline models. The baseline models considered were beam overlap and average Reference Signal Received Power (RSRP), both building beam-to-beam maps. Emphasis in the thesis was on handovers between nodes and finding the beam with the highest RSRP. Beam-hit-rate and RSRP-difference (selected minus best) were key performance indicators and were compared for different numbers of activated beams.

    The problem was modeled as a Multiple Output Regression (MOR) problem and as a Multi-Class Classification (MCC) problem. Both problems are possible to solve with the random forest model, which was the learning model of choice during this work. An Ericsson simulator was used to simulate and collect data from a seven-site scenario with 40 UEs. Primary features available were the current serving beam index and its RSRP. Additional features, like position and distance, were suggested, though many ended up being limited either by the simulated scenario or by the cost of acquiring the feature in a real-world scenario.

    Using primary features only, learned models' performance were equal to or worse than the baseline models' performance. Adding distance improved the performance considerably, beating the baseline models, but still leaving room for more improvements.

  • 142.
    Eliardsson, Patrik
    et al.
    Swedish Def Research Agency, Sweden.
    Axell, Erik
    Swedish Def Research Agency, Sweden.
    Wiklundh, Kia C.
    Swedish Def Research Agency, Sweden.
    Stenumgaard, Peter
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology. Swedish Def Research Agency, Sweden.
    Channel Selection that Considers the Impulse Characteristics of the Local Interference2014In: 2014 INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC COMPATIBILITY (EMC EUROPE), IEEE , 2014, p. 517-522Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose improved methods to select the most suitable frequency for transmission by also including information about the local interference environment. Knowledge of the local interference is included in the frequency selection through estimation of the interference power, and in addition through estimation of the impulsiveness of the interference. We evaluate the methods for both unicast and multicast scenarios using different performance measures, and show that the suggested methods can significantly reduce the bit error probability in relevant scenarios.

  • 143.
    Eliardsson, Patrik
    et al.
    FOI.
    Wiklundh, Kia
    FOI.
    Axell, Erik
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Johansson, Björn
    FOI.
    Stenumgaard, Peter
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Analysis of the local HF interference environment at a military platform2013In: Nordic HF Conference Proceedings 2013, 2013, p. 3.4-Conference paper (Refereed)
    Abstract [en]

    High frequency (HF) communications are of vital importance for modern military operations. However, HF channels are touchy and unpredictable, prone to noise, fading, jamming, and interference. Therefore, a number of prediction tools for channel selection have been developed. However, existing tools do not consider the local actual electromagnetic interference at receivers located on navy and army platforms. Measurements on military platforms show that also the local interference environment can be crucial and has large variations in frequency and time. In this paper we analyze the levels and dynamics of local interference from a typical military platform. We show that the variations regarding interference waveform can be very large between two consecutive seconds of measurement. This means that the interference impact in terms of bit error probability also will be very large between such consecutive seconds. The overall conclusion is that future methods for HF-frequency selection would be significantly improved by considering the characteristics of local interference from electrical equipment.

  • 144.
    Eriksson, Anton
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Robust Echo-Cancellation for Simple VoIP-Applications in Embedded Systems2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Voice over IP (VoIP) is the group of techniques for delivering voice communications over Internet Protocol (IP) networks. It has mainly served as the possible substitution for regular PSTN over the last decades, but has recently gained an increased interest in various areas such as alarm applications and customer service. Acoustic echo is the situation were a distorted version of the sent signal is transmitted back to the sender, due to acoustic feedback between loudspeaker and microphone. There already exists several algorithms to solve this problem, and this thesis provides a study of the performance in relation to the computational complexity of the algorithms. This is in order to indicate which approaches are better suited for implementation in an embedded system, where resources are limited. During the thesis a number of algorithms were tested, including variations of the LMS algorithm, some other approaches utilizing the correlation between echo and signal, and the RLS algorithm. They were first tested in MATLAB, on speech signals recorded at Syntronic and distorted by adding echo, then tested by implementation in C, and run on speech signals recorded in a simulated VoIP system at Syntronic. The results were then evaluated in terms of efficiency and computational complexity.

  • 145.
    Eriksson, Jonas
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Moosavi, Reza
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Complexity Reduction of Blind Decoding Schemes Using CRC Splitting2012In: 2012 IEEE Global Communications Conference (GLOBECOM), IEEE , 2012, p. 3731-3736Conference paper (Refereed)
    Abstract [en]

    Blind decoding, used on control channels of some multi-user wireless  access systems, is a technique for achieving adaptive modulation and  coding. The idea is to adapt the modulation and coding scheme to the  channel quality but instead of signaling the parameters used  explicitly, the receiver blindly tries a number of fixed parameter  combinations until a successful decoding attempt is detected, with  the help of a cyclic redundancy check. In this paper we suggest a  new method for reducing the complexity and energy consumption  associated with such blind decoding schemes. Our idea is to use a  mini-CRC injected early in the data stream to determine if the  current decoding attempt is using the correct modulation and coding  parameters. We analyze and exemplify the complexity gain of this  approach and also investigate the impact of the rearrangement of the  CRC scheme in terms of the probability of undetected error. The  presented results for the complexity gain are promising and the  impact on the error detection capability turns out to be small if  any.

  • 146.
    Eriksson, Jonas
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Moosavi, Reza
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Wiberg, Niclas
    Ericsson AB, Sweden.
    Frenger, Pål
    Ericsson AB, Sweden.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Coding of Scheduling Information in OFDM2009In: Proceedings of the 69th IEEE Vehicular Technology Conference, 2009Conference paper (Refereed)
    Abstract [en]

    Control signaling strategies for scheduling information in cellular OFDM systems are studied. A single-cell multiuser system model is formulated that provides system capacity estimates accounting for the signaling overhead. Different scheduling granularities are considered, including the one used in the specifications for the 3G Long Term Evolution (LTE). A greedy scheduling method is assumed, where each resource is assigned to the user for which it can support the highest number of bits. The simulation results indicate that the cost of control signaling does not outweigh the scheduling gain, when compared with a simple round-robin scheme that does not need signaling of scheduling information. Furthermore, in the studied scenario, joint coding and signaling of scheduling information over all selected users is found to be superior to separate coding and signaling for each user. The results also indicate that the scheduling granularity used for LTE provides better performance than the full granularity.

  • 147.
    Eriksson, Kristoffer
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Dynamic Resource Allocation in Wireless Networks2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis we investigate different algorithms for dynamic resource allocation in wireless networks. We introduce a general framework for modeling systems whichis applicable to many scenarios. We also analyze a specific scenario with adaptivebeamforming and show how it fits into the proposed framework. We then studytwo different resource allocation problems: Quality-of-Service (QoS) constraineduser scheduling and sum-rate maximization. For user scheduling, we select some“good” set of users that is allowed to use a specific resource. We investigatedifferent algorithms with varying complexities. For the sum-rate maximizationwe find the global optimum through an algorithm that takes advantage of thestructure of the problem by reformulating it as a D.C. program, i.e., a minimizationover a difference of convex functions. We validate this approach by showing that itis more efficient than an exhaustive search at exploring the space of solutions. Thealgorithm provides a good benchmark for more suboptimal algorithms to comparewith. The framework in which we construct the algorithm, apart from being verygeneral, is also very flexible and can be used to implement other low complexitybut suboptimal algorithms.

  • 148.
    Eriksson, Kristoffer
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Shi, Shuying
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Vucic, Nikola
    Fraunhofer German-Sino Lab for Mobile Communications MCI.
    Schubert, Martin
    Fraunhofer German-Sino Lab for Mobile Communications MCI.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Globally Optimal Resource Allocation for Achieving Maximum Weighted Sum Rate2010In: Proceedings of the IEEE Global Communications Conference (GLOBECOM), 2010, p. 1-6Conference paper (Refereed)
    Abstract [en]

    We establish a general optimization framework for joint resource allocation and interference mitigation. By utilizing axiomatic interference functions, our problem formulation is very general and includes many problems as special cases. We consider the sum rate maximization problem, which is known to be NP hard. It is shown that due to the structural model of the interference function, the joint optimization of powers and adaptive receive strategies ends up with the optimization solely with respect to powers. This facilitates our formulation of the problem under consideration as a problem of difference of convex functions (DC). Based on this DC representation, we employ a prismatic branch and bound algorithm to find a global optimum.

  • 149.
    Eriksson, Marcus
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Analysis of Digital Predistortion in a Wideband Arbitrary Waveform Generator2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Digital predistortion is a signal processing technique used to remove undesired distortions caused by nonlinear system effects. This method is predominately used to linearize power amplifiers in communication systems in order to achieve efficient transmitter circuits. However, the technique can readily be applied to cancel undesired nonlinear behavior in other types of systems.

    This thesis investigates the effectiveness of digital predistortion in the context of a wideband arbitrary waveform generator. A theoretical foundation discussing nonlinear system models, predistortion architectures and system identification methods is complemented with a simulation study and followed by verification on a real system.

    The best predistorter is able to fully suppress the undesired distortions for any fixed two-tone sinusoidal signal. Furthermore, the results indicate the existence of a wideband predistorter which yield acceptable suppression over a frequency range of several hundred MHz.

  • 150.
    Eriksson, Viktor
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Extraction of radio frequency quality metric from digital video broadcast streams by cable using software defined radio2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this master thesis was to investigate how effiecient the extractionof radiofrequency quality metrics from digital video broadcast (DVB) streamscan become using software defined radio. Software defined radio (SDR) is a fairlynew technology that offers you the possibility of very flexible receivers and transmitters where it is possible to upgrade the modulation and demodulation overtime.

    Agama is interested in SDR for use in the Agama Analyzer, a widely deployedmonitoring probe running on top of standard services. Using SDR, Agama coulduse that in all deployments, such as DVB by cable/terrestrial/satellite (DVBC/T/S), which would simplify logistics.

    This thesis is an implementation of a SDR to be able to receive DVB-C. TheSDR must perform a number of adaptive algorithms in order to prevent the received symbols from being significantly different from the transmitted ones. Themain parts of the SDR include timing recovery, carrier recovery and equalization.Timing recovery performs synchronization between the transmitted and receivedsymbols and the carrier recovery performs synchronization between the carrierwave of the transmitter and the local oscillator in the receiver. The thesis discusses various methods to perform the different types of synchronizations andequalizations in order to find the most suitable methods.

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