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  • 201.
    Hailong, Liang
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Evaluation of two Doppler radar systems for proximity sensing2014Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    Most of Doppler Radar systems are expensive to build and hard to take out for the testing.Therefore a portable and easy building Doppler Radar system has been implemented in recent years.For this thesis two Doppler radar systems which working in different frequency ranges (24 GHz and 2.4 GHz) shall be implemented with evaluating the possibilities regarding proximity sensing based on radar technology. There are two designs including. One is based on an ‘all-in-one’ chip from RF-beam Microwave and the other is based on components from Mini-Circuits.Those Radar kit were developed by using a frequency modulated continuous wave(FMCW) architecture.

    The radar works in three different modes:Doppler Time Intensity testing,Range Time Intensity and Synthetic Aperture Radar imaging.The whole system work with Matlab by recording the data.Doppler time intensity (DTI) plots with Doppler spectrum of passing vehicles and range-time intensity(RTI) plots with measuring the moving target versus time will be discussed.Synthetic Aperture Radar(SAR) image of urban terrain is acquired. 

  • 202.
    Hailong, Liang
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Min, Li
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Analysis software for the preparationof the antenna characteristics in the wireless system2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    With the development of the wireless communication system, the antenna has been

    widely used as an important tool in data transmission. However, there are many

    characteristic parameters for antenna need to be calculated by complex calculation.

    For example the mutual input impedance of dipole antenna, the Directivity coefficient

    and the Gain coefficient. Therefore, it is quite practically hard to implement by hand,

    especially for student who was studying on it. In order to solve this problem, this

    thesis has establishes the calculation procedure for the complex parameters of antenna

    by using MATLAB software.

  • 203.
    Hamberg, Dennis
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Design av PID-regulator baserad på kommersiell processormodul2013Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    The idea to develop  a platform for a PID-controller came from the need to control the temperature in  an espresso machine in a more exact way than a thermostat could perform. In discussions with Syntronic AB the idea developed into PID-control for industrial use. Syntronic AB suggested that the platform should be based on a commercially available processor module to shorten the development time. The suggestion included the use of the microcomputer Raspberry Pi, which supports USB, HDMI, memory card and Ethernet.

    The work began with establishing a schedule for the 10 weeks of the projects duration, and after that a system specification listing all functions, implementation and limitations was made. When the foundation of the system specification was done, a preliminary system design took shape.

    Because of the Raspberry Pi´s lack of Analog-to-Digital converter, a circuit board containing Wheatstone bridges, differential amplifiers and a two channel Analog-to-Digital converter was fabricated. The choice of Operative System fell on Linux Raspbian Wheezy, a popular Linux distribution with good documentation. Embedded programming was made solely in C language, Nginx was used as server application making it possible to show real-time graph and receive parameter input from a webpage. The webpage was written in PHP and JavaScript for server and client side respectively.

    To evaluate the PID-controller it was mounted inside an espresso machine where it controlled the temperature of the boiler. Aiming for a short settling time, parameters for the PID-controller was produced by testing.

  • 204.
    Hamid, Mohamed
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    On Finding Spectrum Opportunities in Cognitive Radios: Spectrum Sensing and Geo-locations Database2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The spectacular growth in wireless services imposes scarcity in term of the available radio spectrum. A solution to overcome this scarcity is to adopt what so called cognitive radio based on dynamic spectrum access. With dynamic spectrum access, secondary (unlicensed) users can access spectrum owned by primary (licensed) users when it is temporally and/or geographically unused. This unused spectrum is termed as spectrum opportunity. Finding these spectrum opportunities related aspects are studied in this thesis where two approaches of finding spectrum opportunities, namely spectrum sensing and geo-locations databases are considered.

    In spectrum sensing arena, two topics are covered, blind spectrum sensing and sensing time and periodic sensing interval optimization. For blind spectrum sensing, a spectrum scanner based on maximum minimum eigenvalues detector and frequency domain rectangular filtering is developed. The measurements show that the proposed scanner outperforms the energy detector scanner in terms of the probability of detection. Continuing in blind spectrum sensing, a novel blind spectrum sensing technique based on discriminant analysis called spectrum discriminator has been developed in this thesis. Spectrum discriminator has been further developed to peel off multiple primary users with different transmission power from a wideband sensed spectrum. The spectrum discriminator performance is measured and compared with the maximum minimum eigenvalues detector in terms of the probability of false alarm, the probability of detection and the sensing time.

    For sensing time and periodic sensing interval optimization, a new approach that aims at maximizing the probability of right detection, the transmission efficiency and the captured opportunities is proposed and simulated. The proposed approach optimizes the sensing time and the periodic sensing interval iteratively. Additionally, the periodic sensing intervals for multiple channels are optimized to achieve as low sensing overhead and unexplored opportunities as possible for a multi channels system.

    The thesis considers radar bands and TV broadcasting bands to adopt geo-locations databases for spectrum opportunities. For radar bands, the possibility of spectrum sharing with secondary users in L, S and C bands is investigated. The simulation results show that band sharing is possible with more spectrum opportunities offered by C band than S and L band which comes as the least one. For the TV broadcasting bands, the thesis treats the power assignment for secondary users operate in Gävle area, Sweden. Furthermore, the interference that the TV transmitter would cause to the secondary users is measured in different locations in the same area.

  • 205.
    Hamid, Mohamed
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS and Center for Wireless Systems, Wireless@kth .
    On Spectrum Sensing for Secondary Operation in Licensed Spectrum: Blind Sensing, Sensing Optimization and Traffic Modeling2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There has been a recent explosive growth in mobile data consumption. This, in turn, imposes many challenges for mobile services providers and regulators in many aspects. One of these primary challenges is maintaining the radio spectrum to handle the current and upcoming expansion in mobile data traffic. In this regard, a radio spectrum regulatory framework based on secondary spectrum access is proposed as one of the solutions for the next generation wireless networks. In secondary spectrum access framework, secondary (unlicensed) systems coexist with primary (licensed) systems and access the spectrum on an opportunistic base.

    In this thesis, aspects related to finding the free of use spectrum portions - called spectrum opportunities - are treated. One way to find these opportunities is spectrum sensing which is considered as an enabler of opportunistic spectrum access. In particular, this thesis investigates some topics in blind spectrum sensing where no priori knowledge about the possible co-existing systems is available.

    As a standalone contribution in blind spectrum sensing arena, a new blind sensing technique is developed in this thesis. The technique is based on discriminant analysis statistical framework and called spectrum discriminator (SD). A comparative study between the SD and some existing blind sensing techniques was carried out and showed a reliable performance of the SD.

    The thesis also contributes by exploring sensing parameters optimization for two existing techniques, namely, energy detector (ED) and maximum-minimum eigenvalue detector (MME). For ED, the sensing time and periodic sensing interval are optimized to achieve as high detection accuracy as possible. Moreover, a study of sensing parameters optimization in a real-life coexisting scenario, that is, LTE cognitive femto-cells, is carried out with an objective of maximizing cognitive femto-cells throughput. In association with this work, an empirical statistical model for LTE channel occupancy is accomplished. The empirical model fits the channels' active and idle periods distributions to a linear combination of multiple exponential distributions. For the MME, a novel solution for the filtering problem is introduced. This solution is based on frequency domain rectangular filtering. Furthermore, an optimization of the observation bandwidth for MME with respect to the signal bandwidth is analytically performed and verified by simulations.

    After optimizing the parameters for both ED and MME, a two-stage fully-blind self-adapted sensing algorithm composed of ED and MME is introduced. The combined detector is found to outperform both detectors individually in terms of detection accuracy with an average complexity lies in between the complexities of the two detectors. The combined detector is tested with measured TV and wireless microphone signals.

    The performance evaluation in the different parts of the thesis is done through measurements and/or simulations. Active measurements were performed for sensing performance evaluation. Passive measurements on the other hand were used for LTE downlink channels occupancy modeling and to capture TV and wireless microphone signals.

  • 206.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Communications Systems Lab (CoS), Royal Institute of Technology (KTH), Stockholm, Sweden .
    Barbe, Kurt
    Vrije Universiteit Brussel, ELEC.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Communications Systems Lab (CoS), Royal Institute of Technology (KTH), Stockholm, Sweden .
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Spectrum sensing through spectrum discriminator and maximum minimum eigenvalue detector: a comparative study2012Inngår i: 2012 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), New York: IEEE conference proceedings, 2012, s. 2252-2256Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a new spectrum sensing technique for cognitive radios based on discriminant analysis called spectrum discriminator and compare it with the maximum minimum eigenvalue detector. The common feature between those two techniques is that neither prior knowledge about the system noise level nor the primary user signal, that might occupy the band under sensing, is required. Instead the system noise level will be derived from the received signal. The main difference between both techniques is that the spectrum discriminator is a non-parametric technique while the maximum minimum eigenvalue detector is a parametric technique. The comparative study between both has been done based on two performance metrics: the probability of false alarm and the probability of detection. For the spectrum discriminator an accuracy factor called noise uncertainty is defined as the level over which the noise energy may vary. Simulations are performed for different values of noise uncertainty for the spectrum discriminator and different values for the number of received samples and smoothing factor for the maximum minimum eigenvalue detector.

  • 207.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    A Novel Approach for Energy Detector Sensing Time and Periodic Sensing Interval Optimization in Cognitive Radios2011Inngår i: Proceedings of the 4th International Conference on Cognitive Radio and Advanced Spectrum Management, New York: ACM Press, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a new approach of optimizing the sensing time and periodic sensing interval for energy detectors has been explored. This new approach is built upon maximizing the probability of right detection, captured opportunities and transmission efficiency. The probability of right detection is defined as the probability of having no false alarm and correct detection. Optimization of the sensing time relies on maximizing the summation of the probability of right detection and the transmission efficiency while optimization of periodic sensing interval subjects to maximizing the summation of transmission efficiency and the captured opportunities. The optimum sensing time and periodic sensing interval are dependent on each other, hence, iterative approach to optimize them is applied and convergence criterion is defined. The simulations show that both converged sensing time and periodic sensing interval increase with the increase of the channel utilization factor, moreover, the probability of false alarm, the probability of detection, the probability of right detection, the transmission efficiency and the captured opportunities have been taken as the detector performance metrics and evaluated for different values of channel utilization factor and signal-to-noise ratio.

  • 208.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Frequency Hopping for Fair Radio Resources Allocation in TVWS2015Inngår i: ICWMC 2015: The Eleventh International Conference onWireless and Mobile Communications / [ed] Carlos Becker Westphall, Iwona Pozniak-Koszalka, Eugen Borcoci & Dragana Krstic, 2015, s. 71-76Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Using frequency hopping for fair resources allocation in TV white spaces is proposed and evaluated in this paper. The degree of fairness is judged by the achieved throughput by different secondary users. The throughput of the secondary users is determined by their permissible transmission power and the interference from the TV and other secondary users. The permissible transmission power for secondary users in TV white spaces in different channels is investigated. The main concern of calculating the permissible secondary user transmission power is protecting the primary TV receivers from harmful interference. With the aid of SPLAT (RF Signal Propagation, Loss, And Terrain analysis tool), the received TV signal power in a study case of the surroundings of the city of Gävle is fetched. The interference from the TV transmission into the free channels is measured in six different locations. The simulated system is a deployed Wi-Fi access points in a building representing an office environment in an urban area. Moreover, the size of the hopping set and the number of APs influences are investigated.

  • 209.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Geo-location Spectrum Opportunities Database in Downlink Radar Bands for OFDM Based Cognitive Radios2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a model to investigate the spectrum opportunities for cognitive radio networks in three radar frequency bands L, S and C at a specific location is introduced. We consider underlay unaware spectrum sharing model. The Secondary System we assume is an OFDM based system. The followed strategy is built upon defining a specific co or adjacent channel as a spectrum opportunity if -and only if- the interference generated by the secondary system occupying that channel  into the radar system is less than the permissible interference defined by the value of Interference to Noise ratio (INR) and the radar receiver inherited noise level. The simulation results show that for the same transmission parameters C band offer more spectrum opportunities than S band which is itself offers more spectrum opportunities than L band.

  • 210.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Maximum Minimum Eigen Values Based Spectrum Scanner in GNU Radio2011Inngår i: RFMTC11, Gävle, 2011Konferansepaper (Annet vitenskapelig)
  • 211.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Maximum Minimum Eigenvalues Based Spectrum Scanner for Cognitive Radios2012Inngår i: 2012 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), New York: IEEE conference proceedings, 2012, s. 2248-2251Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we introduce a technique for spectrum scanning with the maximum minimum eigenvalue detection based spectrum sensing. The fundamental problem we address in this paper is the inability of using maximum minimum eigenvalue detection with filtering in time domain where the white noise becomes coloured. The solution we propose here is based on frequency domain rectangular filtering. By frequency domain rectangular filtering we take the spectral lines inside each sub-band and throw out the rest. After doing the frequency domain rectangular filtering, we generate the corresponding time domain signal and inject it to the maximum minimum eigenvalue detector. An experimental verification has been performed and the obtained results show that the technique is implementable with a performance better than the energy detector as a reference technique in terms of the probability of detection when both technique have the same probability of false alarm.

  • 212.
    Hamid, Mohamed
    et al.
    University of Agder, Kristiansand, Norway.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Radio Resource Allocation for Indoor Secondary Access in TV White Space2016Inngår i: International Journal On Advances in Telecommunications, ISSN 1942-2601, E-ISSN 1942-2601, Vol. 19, nr 1-2, s. 25-34Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers fair radio resource assignment for secondary users operating in TV white space by means of frequency hopping. The achieved throughput for different secondary users is used to measure the degree of fairness. The permissible transmission power for secondary users is set to protect the TV transmission from excessive interference. Hence, there are different limits on the secondary transmission power when operating in different idle TV channels because different adjacent channels generates different amounts of interference based on the TV receiver transfer function in the frequency domain. Moreover, different free TV channels experience different amounts of interference due to the non-linearities in the TV transmission. A model for power assignment in each of the free TV channels is developed based on the received TV signal, TV receiver characteristics and secondary user location. For the sake of fair resource allocation, frequency hopping is proposed herein, and its performance is evaluated. In this study, three different TV transmitters located in three different cities in Sweden, namely, Gavle, Stockholm and Link ¨ oping, are ¨ exploited where the interference from the TV transmission into the free channels is measured. For the secondary system, the deployment of indoor WiFi access points in an office environment is considered and simulated. The main finding is that frequency hopping can provide fair radio resource distribution in terms of the obtainable throughput. Moreover, it is shown that the denser the area is, the higher the achievable secondary throughput due to the higher attenuation of the interfering signals.

  • 213.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Communication Systems Department, KTH Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Ben Slimane, Slimane
    Communication Systems Department, KTH Royal Institute of Technology, Stockholm, Sweden.
    Signal Bandwidth Impact on Maximum-Minimum Eigenvalue Detection2015Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 3, s. 395-398, artikkel-id 7001062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of the signal bandwidth and observation bandwidth on the detection performance of the maximumminimum eigenvalue detector is studied in this letter. The considered signals are the Gaussian signals. The optimum ratio between the signal and the observation bandwidth is analytically proven to be 0.5 when reasonable values of the system dimensionality are used. The analytical proof is verified by simulations.

  • 214.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Royal Institute of Technology (KTH), Stockholm, Sweden .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Vrije Universiteit Brussel, Belgium .
    Mohammed, Abbas
    Blekinge Institute of Technology.
    Iterative Optimization of Energy Detector Sensing Time and Periodic Sensing Interval in Cognitive Radio Networks2013Inngår i: Self-Organization and Green Applications in Cognitive Radio Networks / [ed] Anwer Al-Dulaimi, John Cosmas, Abbas Mohammed, IGI Global, 2013, 1, s. 53-69Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In this chapter the authors propose a new approach for optimizing the sensing time and periodic sensing interval for energy detectors in cognitive radio networks. The optimization of the sensing time depends on maximizing the summation of the probability of right detection and transmission efficiency, while the optimization of periodic sensing interval is subject to maximizing the summation of transmission efficiency and captured opportunities. Since the optimum sensing time and periodic sensing interval are dependent on each other, an iterative approach to optimize them simultaneously is proposed and a convergence criterion is devised. In addition, the probability of detection, probability of false alarm, probability of right detection, transmission efficiency, and captured opportunities are taken as performance metrics for the detector and evaluated for various values of channel utilization factors and signal-to-noise ratios.

  • 215.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Department of Communication System and wireless@ kth, KTH Royal Institute of Technology, Stockholm.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Slimane, Ben
    Department of Communication System and wireless@ kth, KTH Royal Institute of Technology, Stockholm.
    Energy and Eigenvalue-Based Combined Fully-Blind Self-Adapted Spectrum Sensing Algorithm2016Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 65, nr 2, s. 630-642Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, a comparison between energy and maximum-minimum eigenvalue detectors is performed. The comparison has been made concerning the sensing complexity and the sensing accuracy in terms of the receiver operating characteristics curves. The impact of the signal bandwidth compared to the observation bandwidth is studied for each detector. For the energy detector, the probability of detection increases monotonically with the increase of the signal bandwidth. For the maximum-minimum eigenvalue detector, an optimal value of the ratio between the signal bandwidth and the observation bandwidth is found to be 0.5 when reasonable values of the system dimensionality are used. Based on the comparison findings, a combined two-stage detector is proposed. The combined detector performance is evaluated based on simulations and measurements. The combined detector achieves better sensing accuracy than the two individual detectors with a complexity lies in between the two individual complexities. The combined detector is fully-blind and self-adapted as the maximum-minimum eigenvalue detector estimates the noise and feeds it back to the energy detector. The performance of the noise estimation process is evaluated in terms of the normalized mean square error.

  • 216.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap. Department of Communication Systems and wireless@ kth, KTH Royal Institute of Technology, Stockholm.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Slimane, Ben Slimane
    Department of Communication Systems and wireless@ kth, KTH Royal Institute of Technology, Stockholm.
    Downlink Throughput Driven Channel Access Framework for Cognitive LTE Femto-CellsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    This paper proposes an optimized sensing based channel access framework for the LTE cognitive femto cells with an objective of maximizing femto-cells downlink throughput. Energy detection is used by the LTE cognitive femto cells to locate and thereafter utilize the free channels. Moreover, periodic sensing is adopted to detect any changes of the sensing outcomes. The developed channel access framework is based on an objective of maximization the femto-cell downlink throughput which varies with the macro-cell channel occupancy. Therefore, the LTE macro-cell occupancy statistics are empirically modelled using exponential distributions mixture. The LTE cognitive femto-cell downlink throughput is maximized by compromising the transmission efficiency, the explored spectrum opportunities and the interference from the macro-cell. An analytical solution for the optimal periodic sensing interval that maximizes the throughput is found and verified by simulations. The obtained results show that there is indeed a single periodic sensing interval value that maximizes the LTE cognitive femto-cell downlink throughput which changes with the change of the macro-cell channel occupancy. Yet, at a specific channel occupancy statistical parameters, our framework provides the optimal throughput. At the peak of the macro-cell traffic, our framework increased the femto-cell throughput by $\simeq 15\%$ compared to the senseless case. The impact of the available channels for opportunistic access is studied. The simulation results show that increasing the number of the available channels becomes less significant for more than three channels.

  • 217.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Slimane, Ben Slimane
    KTH.
    Empirical Statistical Model for LTE Downlink Channel Occupancy2017Inngår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 96, nr 1, s. 855-866Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper develops an empirical statistical channel occupancy model for downlink long-term evolution (LTE) cellular systems. The model is based on statistical distributions mixtures for the holding times of the channels. Moreover, statistical distribution of the time when the channels are free is also considered. The data is obtained through an extensive measurement campaign performed in Stockholm, Sweden. Two types of mixtures are considered, namely, exponential and log-normal distributions to fit the measurement findings. The log-likelihood of both mixtures is used as a quantitative measure of the goodness of fit. Moreover, finding the optimal number of linearly combined distributions using the Akaike information criterion (AIC) is investigated. The results show that good fitting can be obtained by using either exponential or log-normal distributions mixture. Even though, the fitting is done for a representative case with a tempo-spatial consideration, the model is yet applicable in general for LTE and other cellular systems in a wider sense.

  • 218.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Slimane, Ben Slimane
    Royal Institute of Technology (KTH), Communication Systems.
    Sample covariance matrix eigenvalues based blind SNR estimation2014Inngår i: 2014 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Proceedings, 2014, s. 718-722Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a newly developed SNR estimation algorithm is presented. The new algorithm is based on the eigenvalues of the samples covariance matrix of the recieved signal. The presented algorithm is blind in the sense that both the noise and the signal power are unknown and estimated from the received samples. The Minimum Descriptive Length (MDL) criterion is used to split the signal and noise corresponding eigenvalues. The experimental results are judged using the Normalized Mean Square Error (NMSE) between the estimated and the actual SNRs. The results show that depending on the value of received vectors size, N, and the number of received vectors, L, the NMSE is changed and down to −55 dB NMSE can be achieved for the highest used values of N and L.

  • 219.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Barbé, Kurt
    Vrije Universiteit Brussel.
    Slimane, Ben
    KTH.
    Blind Spectrum Sensing for Cognitive Radios Using Discriminant Analysis: A Novel Approach2013Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, nr 11, s. 2912-2921Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we present a new spectrum sensing technique for cognitive radios based on discriminant analysis called spectrum discriminator. The presented technique uses the knowledge of the noise uncertainty and a probabilistic validation to overcome the limitations of the discriminant analysis. A comparative study between the proposed technique and the maximum-minimum eigenvalue detection has been performed based on two performance metrics: the probability of false alarm and the probability of detection. The spectrum discriminator has been further developed to a peel-off technique where all primary users can be detected. The performance of the spectrum discriminator and the peel-off technique has been tested on simulations and experimentally verified. The comparative study is based on simulations as well as measurements.

  • 220.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Ferrer Coll, Javier
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Chilo, José
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel, Brussels, Belgium .
    Multi-Interference Detection Algorithm using Discriminant Analysis in Industrial Environments2013Inngår i: 39th Annual Conference of the IEEE Industrial Electronics Society (IECON 2013), New York: IEEE conference proceedings, 2013, s. 5600-5604Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a technique to detect multiple impulsive interference in an industrial environment is proposed and evaluated. The technique is based on discriminant analysis which iteratively peels-off the impulsive interferences. The probability of detection of the technique is tested with and without the iterative peeling-off part. The simulations show that the SIR can be improved by applying the detection technique and then blank or clip the impulsive interference components. The improvement in the SIR depends on the impulsive interference parameters and it can reach up to 17 dB.

  • 221.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Mohammed, Abbas
    Blekinge Institute of Technology.
    MAC Layer Spectrum Sensing in Cognitive Radio Networks2013Inngår i: Self-Organization and Green Applications in Cognitive Radio Networks / [ed] Anwer Al-Dulaimi, John Cosmas, Abbas Mohammed, IGI Global, 2013, 1, s. 210-230Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Efficient use of the available licensed radio spectrum is becoming increasingly difficult as the demand and usage of the radio spectrum increases. This usage of the spectrum is not uniform within the licensed band but concentrated in certain frequencies of the spectrum while other parts of the spectrum are inefficiently utilized. In cognitive radio environments, the primary users are allocated licensed frequency bands while secondary cognitive users can dynamically allocate the empty frequencies within the licensed frequency band, according to their requested quality of service specifications. In this chapter, the authors investigate and assess the performance of MAC layer sensing schemes in cognitive radio networks. Two performance metrics are used to assess the performance of the sensing schemes: the available spectrum utilization and the idle channel search delay for reactive and proactive sensing schemes. In proactive sensing, the adapted and non-adapted sensing period schemes are also assessed. Simulation results show that proactive sensing with adapted periods provides superior performance at the expense of higher computational cost performed by network nodes.

  • 222.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Mohammed, Abbas
    BTH.
    Yang, Zhe
    On Spectrum Sharing and Dynamic Spectrum Allocation: MAC Layer Spectrum Sensing in Cognitive Radio Networks2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    One of the most critical issues regarding wireless networksregulation agencies is how to manage the available electromagneticradio spectrum in a way that satisfies the needs of the huge growingin wireless systems both economically and technically, especiallywith the recent crowding in the available spectrum. Hence, buildingcognitive radio systems supporting dynamic access to the availablespectrum has appeared recently as a novel solution for the wirelesssystem huge expansion. In this paper we investigate the MAC layersensing schemes in cognitive radio networks, where both reactiveand proactive sensing are considered. In proactive sensing theadapted and non-adapted sensing periods schemes are also assessed.The assessment of these sensing schemes has been held via twoperformance metrics: available spectrum utilization and idlechannel search delay. Simulation results show that with proactivesensing adapted periods we achieve the best performance but withan observable overhead computational tasks to be done by thenetwork nodes

  • 223.
    Hamid, Mohamed
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH, Stockholm, Sweden; University of Agder, Kristiansand, Norway.
    Slimane, Ben
    KTH, Stockholm, Sweden.
    Van Moer, Wendy
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Spectrum Sensing Challenges: Blind Sensing and Sensing Optimization2016Inngår i: IEEE Instrumentation & Measurement Magazine, ISSN 1094-6969, E-ISSN 1941-0123, Vol. 19, nr 2, s. 44-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By any measure, wireless communications is one of the most evolving fields in engineering. This, in return, has imposed many challenges, especially in handling the hunger for higher data rates in the next generation wireless networks. Among these challenges is how to provide the needed resources in terms of the electromagnetic radio spectrum for these networks. In this regard, cognitive radio (CR) based on dynamic spectrum access (DSA) has been attracting huge attention as a promising solution for more efficient utilization of the available radio spectrum. DSA is based on finding and opportunistically accessing the free-of-use portions of spectrum. To facilitate DSA, spectrum sensing can be used. However, spectrum sensing faces many challenges in different aspects. Such aspects include blind sensing and sensing optimization, which are both to a great extent measurement challenges. We discuss different contributions in addressing these two challenges in this article.

  • 224.
    HASSAN, HAMID ALI
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Design & Size Reduction analysis of Microstrip Hairpin Bandpass Filters2015Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
    Abstract [en]

    This thesis presents Design, Measurement and analysis for size reduction of the Coupled line micro strip Hairpin band pass filters (MHBPF’s). Hairpin filters are an interesting topic for microwave designers. These planar circuits are widely used in wireless transceivers and other microwave projects due to an easy design process. The filter design and analysis described in this paper can be used for wireless transceivers as well as for microwave links.

    Two techniques have been employed for the size reduction and four different filters have been designed. 1st Technique, Conventional Hairpin configuration uses folding of the normal λ/2 resonators into U shape. 2nd technique exploits the cross coupling of the resonators for further size reduction of the filters.  From 1st to last design, different properties of micro strip and couple lines have been analyzed, observed, and finally exploited to reach to a more compact solution.

    Agilent ADS have been used for the simulation process of the initial filters. Further on, AWR Microwave office has been used for the EM simulation part of the project and a detailed analysis for the size reduction with respect to the different properties of the materials used.

    Since insertion loss method is going to be used for the designs, low pass filter prototypes parameters are used for further conversion to band pass. The loaded Q factor and the mix coupling coefficients between resonators have been calculated from standard empirical equations.

    FR4 substrate is used for manufacturing process. RogersRO3210 has also been used as a substrate for 3-section design in AWR Microwave Office for the illustration of size reduction with respect to substrate properties.

    The design with FR4 substrate has been manufactured and tested. The results have been analyzed on Vector Network Analyzer and displayed in results sections.

  • 225.
    He, Shabai
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Simulation of wireless communications in underground tunnels2012Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
    Abstract [en]

    The new released 4G standard wireless communication reminds us that higher transmission data rate and more reliable service are required urgently. However, to fulfill the demand can face problems in a complex environment like mines. In this thesis, characterization of underground tunnel mines with the idea of combating intersymbol interference effect is presented.

               Ray tracing simulation method is applied to characterize channel impulse response in different positions of an underground tunnel. From this channel impulse response, we can obtain how intersymbol interference affects different wireless systems. Intersymbol interference occurs due to multipath propagation of time dispersion channel.

              Adaptive Equalization is the most effective way to compensate intersymbol interference. Adaptive filter adapts filter coefficients to compensate the channel so that the combination of the filter and channel offers a flat frequency response and linear phase. The bit error rate performance without using adaptive equalization is compared with using equalizer. Moreover, adaptive equalization approaches using RLS and LMS algorithms are compared with each other. The tradeoff between convergence rate, computation cost instability and ensemble averaged minimum squared errors are analyzed to determine how to select the optimum adaptive equalizer.

  • 226.
    Hedström, Gustav
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Larsson, Simon
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    AGV-system för transport av långa borrstänger: En förstudie2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Materialtransporterna på Sandvik Mining AB i Sandviken ska optimeras för att undvika stillestånd i produktionsceller på grund av för många parallella arbetsuppgifter. För att göra detta ska ett AGV-system implementeras i en produktionscell för att hantera materialtransporterna där. Målet med detta arbete är att öka kunskaperna kring AGV-system och hur ett system skulle kunna implementeras i cellen. För att implementera detta AGV-system skrevs en litteraturstudie och fallstudier av existerande AGV-system på fyra olika avdelningar inom Sandvik Group genomfördes. Resultatet av litteraturstudien och fallstudierna är ett förslag på en färdig lösning för en pilotanläggning. Pilotanläggningen är komplett med lösningar för truckar, materialställage, teknisk utrustning samt en kravspecifikation med krav som bör ställas på ett AGV-system. Pilotanläggningen som presenteras är anpassad till de produkter som transporteras i anläggningen och tar hänsyn till framtida vidareutvecklingar av systemet. Slutsatsen av detta arbete är att den lösning som presenteras uppfyller de krav som ställs på ett AGV-system för den miljö det ska implementeras i.

  • 227.
    Helgesson, Christian
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Minska risken för överbelastning av kallsaxen: En fallstudie i Ovakos finvalsverk i Boxholm2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    En kallsax på Ovakos finvalsverk i Boxholm ska bytas ut. Efter bytet av kallsaxen vill man undvika att kallsaxens kapacitet överstigs, då det annars finns en risk att den nya kallsaxen går sönder. För att undvika detta utvärderades om inställningarna för stångordnaren, som förser kallsaxen med stänger, kunde automatiseras. Vid automatiseringen programmerades controller och HMI system som redan finns på Ovakos finvalsverk i Boxholm med de extra funktioner som krävdes för automatiseringen. Att använda den befintliga utrustningen för att göra automatiseringen var ett av målen vid automatiseringen. Det finns begränsningar för automationssystemet på grund av att den tekniska utrustningen i finvalsverket inte var tillräcklig. Eftersom den tekniska utrustningen inte var tillräcklig för att använda fullständig automation måste en operatör bestämma när automationen ska användas. I och med att operatören bestämmer när automationen ska användas var det av intresse att veta vilka faktorer som påverkar operatören att använda sig av eller att välja bort automationen. Faktorer som kan påverka operatörers användning av automationssystem är till exempel tilltro till automationssystemet, övertro till automationssystemet, operatörens arbetsbelastning och användarvänligheten hos automationssystemet. Genom en frågeenkät till berörda operatörer, mätdata från controller och MES-systemet har en utvärdering av hur automationssystemet fungerar med den tekniska utrustningen gjorts. Resultatet av utvärderingen pekar ut faktorer som förhindrar att automationen fungerar på ett tillfredställande sätt. Det största problemet med automationssystemet är att det felberäknar antalet stålstänger som får klippas. Andra felkällor vid användning av automationen är att automationssystemet ger en felaktig bild att det fungerar när det inte ger korrekta värden, vilket kan leda till övertro på automationssystemet. Det borde kunna motverkas genom utbildning om automationssystemet, samt att automationssystemet måste tydligare indikera när det inte fungerar, till exempel med larm och meddelanden i HMI-systemet. Resultatet av studien är att en utökning av stångordnarens automation är möjlig, men utifrån studien kan man inte dra slutsatsen om en utökad automation minskar risken för överbelastning av kallsaxen.

  • 228.
    Hernández, Héctor
    Högskolan i Gävle, Institutionen för teknik och byggd miljö.
    Automatic Balance Coin Roll Dispenser2008Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [en]

    The product I am to improve is the coin roll dispenser (CRD). This kind of machine delivers automatically coin rolls to the customer when he introduces either notes or a bank card. The aim is to introduce a new functionality call “automatic balance”. The machine must be able to know the amount of coin rolls it has inside at any moment and without receiving any external information.

    For this purpose a prototype must be designed, assembled and tested. Therefore the project will combine sensing technologies, electronic processing, and hardware and software development.

    The results must proof that the system is completely reliable.

  • 229.
    Horvath, György
    et al.
    Institutionen för kliniska vetenskaper, sektionen för onkologi, radiofysik, radiologi och urologi, Avdelningen för onkologi.
    Chilo, José
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Lindblad, Thomas
    Royal Institute of Technology, Stockholm, Sweden.
    Different volatile signals emitted by human ovarian carcinoma and healthy tissue2010Inngår i: Future Oncology, ISSN 1479-6694, E-ISSN 1744-8301, Vol. 6, nr 6, s. 1043-1049Artikkel, forskningsoversikt (Fagfellevurdert)
  • 230.
    Horvath, György
    et al.
    Sahlgrenska Universitetssjukhuset i Göteborg.
    Chilo, José
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Lindblad, Thomas
    KTH.
    Elektronisk näsa hittar cancer i äggstockarna2010Inngår i: Dagens medicin, ISSN 1104-7488, s. 13-13Artikkel i tidsskrift (Annet vitenskapelig)
  • 231.
    Hossain, Md.Maruf
    Högskolan i Gävle, Institutionen för teknik och byggd miljö.
    ''Design of RF Front End for Multi-Band Multi-System GNSS Receiver''2008Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [en]

    The up growing wireless communication field always need such a system which is simple but more reliable for multiple applications. To fulfill these demands the modern receiver RF frontend can play an important role. A successful design could be a better solution, not only simple but also modern receiver architecture topology is necessary.The main objective of this dissertation is to design a simple RF-Front end for both multi-band multi-systems Global Navigation Satellite System (GNSS i.e. GPS and Galileo) receiver which

    will provide civil signals on multiple frequencies, similar to those currently available for only military purpose and finally implement and test the receiver front end. Different topologies have been investigated and finally the direct digitization RF front end receiver topology is chosen for simplicity, cost and performance. The entire RF front receiver consists of a broad band LNA, a broad band pass filter and a band stop filter. This kind of receiver needs a minimum feasible sampling frequency which is 434 MHz for designed methodology.A simple receiver RF front end for GNSS application is designed to demonstrate and it has been implemented and tested. The receiver is yield the minimum power consumption which is 26mA

    current from 3V power supply.Although, there are no such a specifications for combined future GPS/Galileo receiver, the

    simple design performance is satisfactory and it will be an interesting future work from commercial point of view.

  • 232.
    Hossain, Zakir
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Planar Antennas for Terahertz Detectors2012Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
    Abstract [en]

    The use of the millimeter-wave and terahertz (THz) systems are becoming very important in various scientific and military applications. In many applications i.e. radio-astronomy, THz imaging, remote sensing, secure communication links, THz radars, plasma diagnostics etc. the use millimeter-wave and THz technologies are increasing rapidly and in these applications, integreted lens antennas are porividing attractive solutions. But perfect modeling  and simulation of the lens antenna and beam pattern calculation is still a challenge for the antenna engineers.

     

                In this thesis project thorough investigation has been done to optimize the simulation technique in the EM simulator CST MWS to get reliable and accurate simulation results which may replace the time consuming, complex and expensive measurements in sub-millimeter/THz frequency range. Different experiments are done by retriving from the publications related to this project for the result comparison.

     

                Later on with this optimized simulation process an extended hemispherical lens antenna integrated with log-spiral feed is designed for THz frequency range. Most of the desired goals are achieved during the design process as the design goal is to produce a constant radiation beam and polarization over the a broad bandwidth (500GHz-750GHz)

  • 233.
    Hosseinzadeh Dadash, Amirhossein
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap.
    A Cyber-Physical Testbed for Wireless Networked Control Systems2020Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The cyber-physical system is the keyword of the fourth industrial revolution. The internet changed the way that humans interact with each other, and cyber-physical systems will change the way that we interact with the physical world around us. There are five levels for designing cyber-physical systems, the most important level among these five levels in which the physical world gets connected to the cyber world is the cyber level in which a cyber model of the system is built, following levels and any further decision will heavily depend on the cyber model that is derived in this level. In this project, the network of wireless control cars will be used as a simulation of Wireless Networked Control system for testing and implementation of the cyber-physical algorithms, this network of cars is composed of three parts: cars, controllers and communication link. The cyber model of the cars will be derived in the first part and will be validated through simulation. In the second part, three controllers will be designed for the cyber model and physical model, these controllers are: the controller for closed-loop control of one car, controller for distance and speed control of two cars and controller for distance and speed control of platoon of cars, all of these controllers will be designed according to PID, Linear Quadraticand Model Predictive Control. Finally, the communication link between the cyber controller and physical device will be implemented and a cyber controller will be used for controlling the physical system.

  • 234.
    Händel, Peter
    Signal Processing Lab, School of Electrical Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Power Spectral Density Error Analysis of Spectral Subtraction Type of Speech Enhancement Methods2007Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, nr 96384Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theoretical framework for analysis of speech enhancement algorithms is introduced for performance assessment of spectral subtraction type of methods. The quality of the enhanced speech is related to physical quantities of the speech and noise (such as stationarity time and spectral flatness), as well as to design variables of the noise suppressor. The derived theoretical results are compared with the outcome of subjective listening tests as well as successful design strategies, performed by independent research groups.

  • 235.
    Händel, Peter
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Royal Institute of Technology, Signal Processing Lab, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Royal Institute of Technology, Signal Processing Lab, Stockholm, Sweden.
    Jansson, Magnus
    Royal Institute of Technology, Signal Processing Lab, Stockholm, Sweden.
    Model based dynamic characterization of analog-digital converters at radio frequency2007Inngår i: ISSPA 2007 9th International symposium on signal processing and its applications. Vols 1-3, 2007, s. 1403-1408Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A dynamic characterization of analog-digital converter in-tegral nonlinearity (INL) is considered. When using a plu-rality of test frequencies in the measurement set-up, thedynamic errors of the converter are characterized. TheINL is modeled by low and high code components - LCFand HCF, respectively. The LCF and HCF are parameter-ized and a least squares method is derived for the estima-tion of the parameter values from obtained measurements.A closed form solution to the estimation problem is de-rived and its performance is illustrated by a numerical ex-ample. The proposed method is believed to be fruitful inwide-band characterization of analog-digital converters atradio frequency, and thus of importance for the evaluationof modern and future wireless communication systems.

  • 236.
    Händel, Peter
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Jansson, Magnus
    Medawar, Samer
    Modeling the dynamics of analog-digital-converters at radio frequency2007Inngår i: RF Measurement Technology Conference, Gävle 11-12 September 2007, 2007Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 237.
    Händel, Peter
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle. Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Centre, Stockholm, Sweden.
    Prasad, Sathyaveer
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle. Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Centre, Stockholm, Sweden.
    Beckman, Claes
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle.
    Maximum likelihood estimation of reverberation chamber direct-to-scattered ratio2009Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, nr 25, s. 1285-1286Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The exact maximum likelihood estimator of the direct-to-scattered ratio of the Rician channel in a reverberation chamber is derived and its performance analysed. It is shown that the estimator obeys a non-central F-distribution, the mean value and variance of which are derived. For well stirred chambers, it is shown that the systematic error in the estimated ratio may be significant.

  • 238.
    Händel, Peter
    et al.
    Department of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Dirty MIMO Transmitters: Does It Matter?2018Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 8, s. 5425-5436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The radio frequency transmitter is a key component in contemporary MIMO OFDM systems. A detailed study of a 2×2 MIMO transmitter subjected to correlated input data streams, nonlinear distortion, thermal noise, and crosstalk is provided by stochastic modeling. The effects of correlated input streams, crosstalk and nonlinearities are studied in detail, and exemplified both by approximate expressions and numerical simulations. Key results include exact and approximate expressions for the normalized mean-squared error (NMSE) for systems with or without digital predistortion, the relationship between NMSE and the signal-to-noise-and-distortion ratio, the properties of the distortion noise, and a novel design for power amplifier back-off for MIMO-transmitters subject to crosstalk. The theoretical derivations are illustrated by numerical examples and simulation results, and their relationship to state-of-the-art research are discussed. OAPA

  • 239.
    Händel, Peter
    et al.
    KTH.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    MIMO and Massive MIMO Transmitter Crosstalk2019Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of hardware-induced crosstalk in MIMO transmitters, subject to nonlinear power amplifier distortion, are considered in this paper. A methodology that provides tractable results and a clear understanding of the effects of crosstalk on transmitter performance is introduced and applied to different transmitter models. In particular, a physically motivated 2×2 MIMO transmitter model, which is subjected to input and output crosstalk, is studied in detail, as well as a behavior motivated transmitter model, which is subjected to linear crosstalk. For the latter structure, asymptotic results, when the number of transmitters tends to infinity, are derived. These results provide insight into different 1D and 2D transmitter structures in the massive MIMO scenario. The methodology provides tractable analytical results of the performance of the transmitter. It is shown that the transmitter crosstalk degrades the performance in terms of normalized mean squared error with 3 dB going from a 2×2 set-up to a 1D array of a massive amount of transmitters, and an additional 3 dB loss going from a 1D to 2D transmitter structure. Transmitter input power back-off optimization is further studied, with back-off determination that takes the effects of MIMO crosstalk into account in order to increase the energy efficiency of the transmitter.

  • 240.
    Händel, Peter
    et al.
    Department of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Modeling Mixer and Power Amplifier Impairments2019Inngår i: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 29, nr 7, s. 441-443, artikkel-id 8733818Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combating the effects of mixer and power amplifier (PA) imperfections on transmitter performance is crucial for the design of wireless systems. PA compression and in-phase/quadrature imbalance are analyzed for a single-input-single-output transmitter model. The influence of the imperfection on the normalized mean squared error (NMSE) of the transmitter is studied using an analytical framework that relies on the classic Bussgang theory. The study concludes with a closed-form expression for the NMSE that provides insights into the behavior of the transmitter. © 2019 IEEE.

  • 241.
    Härjebäck, Mattias
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik.
    Analys av systemegenskaper på ett regionnät hos Härjeåns Nät AB2015Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Det ställs höga krav på att elleveransen i Sverige skall vara kontinuerlig och av hög kvalité. Asymmetri i elnät på grund av elektriska och magnetiska fält mellan faserna kan leda till att nollpunktspänningen i nätet blir hög. Detta examensarbete undersöker huruvida otransponerade ledningar påverkar asymmetrin, och därmed nollpunktspänningen i nätet. Transponering innebär att faserna i en kraftledning byter plats med varandra så att de ligger lika lång sträcka i varje position. En fallstudie på Härjeåns Nät har utförts med fokus på detta. Härjeåns Nät har problem med hög nollpunktspänning i delar av sitt regionnät. Med hjälp av ett modelleringsprogram som tillhandahålls av Sweco utförs beräkningar av vad den teoretiska nollpunktspänningen i ett otransponerat nät bör bli. En litteraturstudie har även gjorts för att ta reda på om andra författare anser att transponering är nödvändigt eller inte. Både resultaten av litteraturstudien och de beräknade resultaten pekar åt samma håll. Resultaten visar att den höga nollpunktspänningen mest troligt inte beror på otransponerade elledningar men en slutsats är trots detta att transponeringar bör utföras vid ny- eller ombyggnad av större ledningar.    

  • 242.
    Ikram, Amna
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Design and development of a multiband loop antenna for cellular mobile handsets2010Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
  • 243.
    Ikram, Amna
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Beckman, Claes
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Irmscher, Stefan
    Laird Technologies.
    Design and Development of a Multiband Loop Antenna for Cellular Mobile Handsets2011Inngår i: IEEE International Workshop on Antenna Technology, 2011, s. 251-254Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the results of the design and characterization of a loop antenna for mobile cellularh andsets. Based on a typical smart phone antenna geometry, a bottom mounted off-ground meanderline loop antennah as been designed, which has the potential to cover the required bands of Long Term Evolution (LTE) US 700MHz, Global System for Mobile communications (GSM) 824-960MHz, Digital Communication System (DCS) 1710-1880 MHz, Personal Communication Services PCS 1850-1990 MHz, Universal Mobile Telecommunications System (UMTS) 1920-2170MHz and LTE EU 2500. The carrier volume of 50*10*5mm3 and ground plane of length 100mm is used. The carrier permittivity εr is 2.66 and loss tangent tanδ is 0.00629 @2.44GHz. Copper is used as a metal part of the antenna having conductivity of 5.8e7 S/m and thickness of 0.1mm. The antenna supports balanced and unbalanced modes for certain frequencies. It is highly efficient in terms of small volumetric size for a given bandwidth of operations. The antenna generates weak near field electric and magnetic fields complying with the standards for the Specific Absorption Rate (SAR) and Hearing Aid Compability (HAC). The impact of body effects on the radiation efficiency has been quantified. The measured results of the prototype are in good agreement with the simulated results.

  • 244.
    Imtiaz, Muhammad
    Högskolan i Gävle, Akademin för teknik och miljö.
    NEW INTEGRATED SDARS ANTENNA ELEMENT FOR AUTOMOTIVE APPLICATIONS2011Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    In the past few years the demand for light weight compact automotive antennas in the customersdesired mounting position has brought a challenge for the automotive antenna developers. Due to thehigh demands for the accuracy and compactness it became very difficult to develop antenna elementswhich fulfil all the strict requirements. Integrated SDARS (Satellite Digital Audio Radio Service)antenna element is one of such tasks which require strong gain requirements at particular elevationangles for the best reception of the satellite signals along with the car manufacturer’s desired mountingpositions.To achieve the desired objectives for SDARS element, different antenna designs were proposed andtested during the project work. Finally a newly developed two port cylindrical dielectric resonatorantenna (DRA) with a parasitic element is presented due to its high performance, simplicity andcompactness. The newly developed DRA antenna fulfils the strict SiriusXm gain requirements for thechallenging mounting position in the car. The SDARS antenna element is simulated using CSTMicrowave Studio and verified by prototype measurements. The developed DRA antenna element hasa broad beam with a peak gain more than 6dBi at the null position. An axial ratio of less than 3dB isachieved at the peak gain position. Real time 3D far field measurements are taken by using the MiDAS4.1 system which verifies the simulated results of the developed integrated SDARS antenna. A goodagreement is achieved between the simulated and measured results.

  • 245.
    Indrawibawa, I. Nyoman
    et al.
    Department of Electrical Engineering, South Westphalia University of Applied Sciences, Soest, Germany.
    Virk, Gurvinder S.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Exoskeleton for assisting human walking2013Inngår i: Nature-Inspired Mobile Robotics: Proceedings of the 16th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2013, World Scientific Publishing Co. , 2013, s. 117-124Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As the ageing society's problems evolve, mobility aid requirements are beginning to gain impetus and detailed studies on humans performing their normal activities for daily living are becoming urgent. The paper presents the design of a lower-body exoskeleton, which can be easily put on and worn, and used for recording human motions. In this way, the mobility requirements for performing daily living tasks are determined. The research involves the design of a 4 degree of freedom (DOF) lower-body prototype system used in acquiring basic motion data from volunteers as they perform basic walking tasks using embedded sensors for recording the hip and knee angles and transmitting them wirelessly. Walking tests with 20 volunteers are carried out after ethical considerations have been addressed; these cover human safety, full informed consent and privacy ensured by presenting the results in an anonymous manner. 

  • 246.
    Isaksson, Magnus
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Behavioural Modelling of Radio Frequency Power Amplifiers: An Evaluation of Some Block Structure and Neural Network Models2005Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This work considers behavioral modelling of radio frequency power amplifiers. Due to the use of modern digital modulation methods power amplifiers are nowadays subjected to signals having a considerable bandwidth and a fast changing envelope. This means that traditional quasi-memoryless amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) characteristics are no longer enough to describe and model the behavior of power amplifiers, neither can they be successfully used for linearization.

    In this thesis, sampled input and output data are used for identification and validation of some block structure models with memory. The time-discrete Volterra model, the Wiener model, the Hammerstein model, and the radial-basis function neural network are all identified and compared with respect to in-band and out-of-band errors. Two different signal types, i.e. multi tones and noise, with different powers, peak-to-average ratios, and bandwidths have been used as input to the amplifier. Two different power amplifiers were investigated, one designed for the third generation mobile telecommunication systems and one for the second generation.

    A stepped three-tone measurement technique based on digitally modulated baseband signals is presented. The third-order Volterra kernel were determined from identified inter-modulation products. The properties of the Volterra kernel along certain parts in the three dimensional frequency space were analysed and compared to the Wiener and Hammerstein models.

  • 247.
    Isaksson, Magnus
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Parameter-reduction for Volterra models in radio frequency power amplifier applications2007Inngår i: RF Measurement Technology Conference, Gävle 11-12 September, 2007Konferansepaper (Annet vitenskapelig)
  • 248.
    Isaksson, Magnus
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Radio Frequency Power Amplifiers: Behavioral Modeling, Parameter-Reduction, and Digital Predistortion2009Bok (Annet vitenskapelig)
  • 249.
    Isaksson, Magnus
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Radio Frequency Power Amplifiers: Behavioral Modeling, Parameter-Reduction, and Digital Predistortion2007Doktoravhandling, med artikler (Annet vitenskapelig)
  • 250.
    Isaksson, Magnus
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Rönnow, Daniel
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    A Kautz-Volterra Behavioral Model for RF Power Amplifiers2006Inngår i: IEEE MTT-S International Microwave Symposium Digest, 2006, 2006, s. 485-488Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new type of behavioral power amplifier (PA) model, a discrete-time Kautz-Volterra (KV) model, is presented. In the model a priori knowledge of the system properties in terms of different poles for different nonlinear orders is used, which is needed for modeling nonlinear and linear memory effects in PAs. An accurate model can thus be achieved with a small number of parameters. Simulated results of parallel Hammerstein and Wiener structures and from modeling the behavior of a PA are presented

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