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  • 1.
    Ahmed Mohamed Ahmed, Mazz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Traffic Model Based Energy Efficient Radio Access Network2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As the concerns about global energy consumption increased the matter of energy consumption in Radio Access Networks (RANs) became an important issue especially with the exponential growth in demanded traffic. This interest of developing innovative technologies to reduce the expected energy consumption by the mobile communication sector was driven by environmental concerns and cost reduction.

    The aim of this thesis is to introduce a new methodology to make the Radio Access Network (RAN) more energy efficient based on jointly the demanded throughput and a realistic traffic profile. Furthermore, to find a metric that quantifies the relation between the Energy Efficiency (EE), Spectrum Efficiency (SE) and demanded throughput.

    The proposed methodology for reducing the energy consumption in the RAN characterizes the offered throughput in order to determine the sufficient energy needed. The manner for reducing the energy consumed by the RAN is simply by switching (OFF/ON) Base Stations (BSs) based on the demanded throughput which introduces an energy efficient RAN.

    The results show a significant reduction in the energy consumption with regard to the demanded traffic. Moreover, it gives a measure of the EE with consideration to the SE which enhances the performance evaluation from an EE point of view during the RAN planning phase.

  • 2.
    Cheng, Yuelong
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Ma, Xiaoying
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Cyclic Redundancy Check for Zigbee-Based Meeting Attendance Registration System2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The research accomplished in this dissertation is focused on the design of effective solutions to the problem that error codes occur in the ZigBee-based meeting attendance registration system. In this work, several different check algorithms are compared, and the powerful error-detecting Cyclic Redundancy Check (CRC) algorithm is studied. In view of the features of the meeting attendance registration system, we implement the check module of CRC-8. This work also considers the data reliability. We assume use retransmission mechanism to ensure the validity and completeness of transmission data. Finally, the potential technical improvement and future work are presented.

  • 3.
    Gonzales-Fuentes, Lee
    et al.
    Vrije Universiteit Brussel.
    Barbe, Kurt
    Vrije Universiteit Brussel.
    Van Moer, Wendy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Vrije Universiteit Brussel.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Cognitive Radios: Discriminant Analysis for Automatic Signal Detection in Measured Power Spectra2013In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, no 12, p. 3351-3360Article in journal (Refereed)
    Abstract [en]

    Signal detection of primary users for cognitive radios enables spectrum use agility. In normal operation conditions, the sensed spectrum is nonflat, i.e., the power spectrum is not constant. A novel method proposes the segmentation of the measured spectra into regions where the flatness condition is approximately valid. As a result, an automatic detection of the significant spectral components together with an estimate of the magnitude of the spectral component and a measure of the quality of classification becomes available. In this paper, we optimize the methodology for signal detection in cognitive radios such that the probability that a spectral component was incorrectly classified is iteratively reduced. Simulation and measurement results show the advantages of the presented technique in different types of spectra.

  • 4.
    Hamid, Mohamed
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    On Finding Spectrum Opportunities in Cognitive Radios: Spectrum Sensing and Geo-locations Database2013Licentiate thesis, comprehensive summary (Other academic)
    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.

  • 5.
    Hamid, Mohamed
    et al.
    University of Agder, Kristiansand, Norway.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Radio Resource Allocation for Indoor Secondary Access in TV White Space2016In: International Journal On Advances in Telecommunications, ISSN 1942-2601, E-ISSN 1942-2601, Vol. 19, no 1-2, p. 25-34Article in journal (Refereed)
    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.

  • 6.
    Hamid, Mohamed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Institute of Technology (KTH), Stockholm, Sweden .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Vrije Universiteit Brussel, Belgium .
    Mohammed, Abbas
    Blekinge Institute of Technology.
    Iterative Optimization of Energy Detector Sensing Time and Periodic Sensing Interval in Cognitive Radio Networks2013In: Self-Organization and Green Applications in Cognitive Radio Networks / [ed] Anwer Al-Dulaimi, John Cosmas, Abbas Mohammed, IGI Global, 2013, 1, p. 53-69Chapter in book (Refereed)
    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.

  • 7.
    Hamid, Mohamed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    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 Approach2013In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, no 11, p. 2912-2921Article in journal (Refereed)
    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.

  • 8.
    Hamid, Mohamed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Mohammed, Abbas
    Blekinge Institute of Technology.
    MAC Layer Spectrum Sensing in Cognitive Radio Networks2013In: Self-Organization and Green Applications in Cognitive Radio Networks / [ed] Anwer Al-Dulaimi, John Cosmas, Abbas Mohammed, IGI Global, 2013, 1, p. 210-230Chapter in book (Refereed)
    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.

  • 9.
    Hamid, Mohamed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Mohammed, Abbas
    BTH.
    Yang, Zhe
    On Spectrum Sharing and Dynamic Spectrum Allocation: MAC Layer Spectrum Sensing in Cognitive Radio Networks2010Conference paper (Refereed)
    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

  • 10.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH.
    Density estimation models for strong nonlinearities in RF power amplifiers2014In: Proceedings of the Asia-Pacific Microwave Conference 2014, 2014, p. 116-118Conference paper (Refereed)
    Abstract [en]

    The paper presents a method for modeling strongnonlinear effects in power amplifiers based on the principlesof density estimation. The static nonlinear transfer function isobtained by averaging measured data. The performance obtainedwith density estimation is similar to the one using high ordernonlinear static polynomial models. The benefit of consideredmethod over the ones using polynomial models is that the formerestimates blindly the structure of the transfer function and doesnot suffer from numerical instabilities.

  • 11.
    Pallares, Joan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Study of industrial environment using Zigbee protocol and modeling industrial noise2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis is focused on the industrial environment. This study aims to understand the difficulties wireless communications have when performing in these types of environment with a specific standard (and protocol) Zigbee.

    These difficulties are due mainly to the physical effects and interferences as well the electromagnetic waves from these wireless transmission signals can suffer. The background of this project is to analyze how industries can implement wireless sensor networks (using Zigbee standard) for their factories in order for them to be beneficial i.e. reliable or if it is possible.

    Industries normally tend to keep in the path of the old fashioned way i.e. wired systems which are more robust and can cope with the hard system requirements.

    Some study on these environment effects (interference as well) is performed. The results show how this (Zigbee) sensor network could be or should be implemented in order to have the best performance (disposition of devices, type of environment considering only industrial environments, etc.).

    Specifically, these results show that Zigbe wireless sensor networks are limited to some conditions in order to obtain the desired reliability. These conditions are that these networks must be performed in absorbing environments, LoS disposition of devices, not too long diatance between devices and not other networks in the same area using the same frequency band.

    The limitation of absorbing environments is because the dispersion effects in the (highly) reflective environments are critically damageful for the link. The limitation of the other devices operating in the same frequency band in a close area is due to the fact that Zigbee has no frequency diversity. Last but not least, the limitations to LoS and not too long maximum range (approximately 50 meters) are related since the range would be (much) lower than 50 meters if the communication was in NLoS disposition of devices.

    The noise in this environment is also studied and modeled. The results show that as the impulsive index (which is ameasure of the number of impulses that reach the receiver in a certain unit of time) takes larger values, the distribution approximates that of a Gaussian and as A takes lower values the reults show an impulsive characteristic. The Probability of error is computed for values of A less than 1, where the impulsive characterstic is shown, and as A takes larger values the error is greater. 

  • 12.
    Ramamoorthy, Dhayalini
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Impact of Mutual Coupling among Antenna Arrays on the Performance of the Multipath Simulator System2014Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    This thesis work presents a study on the impact of mutual coupling among antenna arrays on the performance of the multipath simulator (MPS) system. In MIMO systems, it is a wellknown fact that the mutual coupling significantly affects their system performance. The impact of mutual coupling on MIMO system performance is an important consideration for compact antenna arrays. Hence, it is very important to investigate the impact of mutual coupling on the accuracy of measurements in a MPS system. In this project, the impact of coupling within the MPS array antennas is addressed by performing simulations based on the proposed MPS scattering model which fulfills the far-field (Fraunhoferdistance) boundary conditions. The coupling phenomenon within the MPS array antennas is studied by designing a uniform circular array (UCA) of radius,R consisting of NMPS antennas with single device under test (DUT) antenna at the center. The elements of the array are matched half-wave dipole antennas and the phase of the array elements is kept constant throughout. In this work it is assumed that all the elements in the array are identical and located in the far-field region. This study is carried out by performing MPS simulations in HFSS at the LTE-A band of 2.6GHz. The approach used to model the entire system is by comparing the S-parameters (S21: Forward transmission coefficient parameter) between various array configuration. The simulation results suggest that the impact of mutual coupling increases with the number of MPS antennas and decreases with the radius of the MPS ring. Theradiated power is also measured with and without mutual coupling. Finally, it is concluded that the impact of coupling within the MPS antennas is best countered by designing a large MPS system (preferably R = 10λ or greater), despite the higher incurred costs.

  • 13.
    Savic, Vladimir
    et al.
    Department of Electrical Engineering (ISY), Linköping University, Linköping, Sweden.
    Ferrer-Coll, Javier
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Ängskog, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Chilo, José
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Stenumgaard, Peter
    Department of Electrical Engineering (ISY), Linköping University, Linköping, Sweden; Swedish Defense Research Agency (FOI), Linköping, Sweden .
    Larsson, Erik G.
    Department of Electrical Engineering (ISY), Linköping University, Linköping, Sweden .
    Measurement analysis and channel modeling for TOA-based ranging in tunnels2015In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, no 1, p. 456-467Article in journal (Refereed)
    Abstract [en]

    A robust and accurate positioning solution is required to increase the safety in GPS-denied environments. Although there is a lot of available research in this area, little has been done for confined environments such as tunnels. Therefore, we organized a measurement campaign in a basement tunnel of Linköping university, in which we obtained ultra-wideband (UWB) complex impulse responses for line-of-sight (LOS), and three non-LOS (NLOS) scenarios. This paper is focused on time-of-arrival (TOA) ranging since this technique can provide the most accurate range estimates, which are required for range-based positioning. We describe the measurement setup and procedure, select the threshold for TOA estimation, analyze the channel propagation parameters obtained from the power delay profile (PDP), and provide statistical model for ranging. According to our results, the rise-time should be used for NLOS identification, and the maximum excess delay should be used for NLOS error mitigation. However, the NLOS condition cannot be perfectly determined, so the distance likelihood has to be represented in a Gaussian mixture form. We also compared these results with measurements from a mine tunnel, and found a similar behavior.

  • 14.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Digital Compensation Techniques for Transmitters in Wireless Communications Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since they appeared, wireless technologies have deeply transformed our society. Today, wireless internet access and other wireless applications demandincreasingly more traffic. However, the continuous traffic increase can be unbearableand requires rethinking and redesigning the wireless technologies inmany different aspects. Aiming to respond to the increasing needs of wirelesstraffic, we are witnessing a rapidly evolving wireless technology scenario.This thesis addresses various aspects of the transmitters used in wireless communications.Transmitters present several hardware (HW) impairments thatcreate distortions, polluting the radio spectrum and decreasing the achievabletraffic in the network. Digital platforms are now flexible, robust and cheapenough to enable compensation of HW impairments at the digital base-bandsignal. This has been coined as ’dirty radio’. Dirty radio is expected in future transmitters where HW impairments may arise to reduce transmitter cost or to enhance power efficiency. This thesis covers the software (SW) compensation schemes of dirty radio developed for wireless transmitters. As describedin the thesis, these schemes can be further enhanced with knowledge of thespecific signal transmission or scenarios, e.g., developing cognitive digital compensationschemes. This can be valuable in today’s rapidly evolving scenarioswhere multiple signals may co-exist, sharing the resources at the same radiofrequency (RF) front-end. In the first part, this thesis focuses on the instrumentation challenges andHWimpairments encountered at the transmitter. A synthetic instrument (SI)that performs network analysis is designed to suit the instrumentation needs.Furthermore, how to perform nonlinear network analysis using the developedinstrument is discussed. Two transmitter HW impairments are studied: themeasurement noise and the load impedance mismatch at the transmitter, asis their coupling with the state-of-the-art digital compensation techniques.These two studied impairments are inherent to measurement systems and areexpected in future wireless transmitters. In the second part, the thesis surveys the area of behavioral modeling and digital compensation techniques for wireless transmitters. Emphasis is placed on low computational complexity techniques. The low complexity is motivated by a predicted increase in the number of transmitters deployed in the network, from base stations (BS), access points and hand-held devices. A modeling methodology is developed that allows modeling transmitters to achieve both reduced computational complexity and low modeling error. Finally, the thesis discusses the emerging architectures of multi-channel transmittersand describes their digital compensation techniques. It revises the MIMOVolterra series formulation to address the general modeling problem anddrafts possible solutions to tackle its dimensionality. In the framework of multi-channel transmitters, a technique to compensate nonlinear multi-carrier satellite transponders is presented. This technique is cognitive because it uses the frequency link planning and the pulse-shaping filters of the individual carriers. This technique shows enhanced compensation ability at reduced computational complexity compared to the state-of-the-art techniques and enables the efficient operation of satellite transponders.

  • 15.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit2014In: Proceedings of the 44th European Microwave Conference, 2014, p. 833-836Conference paper (Refereed)
    Abstract [en]

    A general description of nonlinear dynamic MIMO systems, given by Volterra series, has significantly larger complexity than SISO systems. Modeling and predistortion of MIMO amplifiers consequently become unfeasible due to the large number of basis functions. We have designed digital predistorters for a MIMO amplifier using a basis pursuit method for reducing model complexity. This method reduces the numerical problems that appear in MIMO Volterra predistorters due to the large number of basis functions. The number of basis functions was reduced from 1402 to 220 in a 2x2 MIMO amplifier and from 127 to 13 in the corresponding SISO case. Reducing the number of basis functions caused an increase of approximately 1 dB of model error and adjacent channel power ratio.

  • 16.
    Ängskog, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Chilo, José
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Stenumgaard, Peter
    FOI.
    Limitations of WLAN IEEE 802.11 in Industrial Environments2012Conference paper (Refereed)
1 - 16 of 16
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