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  • 51.
    Akram, Nadeem
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Schatz, Richard
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Kjebon, Olle
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Influence of electrical parasitics and drive impedance on the laser modulation response2004Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, nr 1, s. 21-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this letter, we analyze the effects of electrical parasitics and drive impedance on the laser modulation response. It is found that for lasers with small active-region volume, e.g., vertical-cavity surface-emitting lasers, the finite drive impedance and/or the laser parasitic capacitance can significantly enhance the damping of the laser resonance peak at low bias. This is due to the voltage fluctuations across the laser diode active layer during modulation. It is also shown that the real pole of the small-signal response transfer function corresponding to the laser parasitic cutoff frequency is not fixed but decreases with the increased bias level.

  • 52.
    Akram, Nadeem
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Silfvenius, Christofer
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Berggren, Jesper
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Halvledarmaterial, HMA (Stängd 20120101).
    Kjebon, Olle
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Design optimization of InGaAsP-InGaAlAs 1.55 mu;m strain-compensated MQW lasers for direct modulation applications2004Ingår i: Indium Phosphide and Related Materials, 2004. 16th IPRM. 2004 International Conference on, IEEE , 2004, s. 418-421Konferensbidrag (Refereegranskat)
    Abstract [en]

    A comprehensive simulation study of InGaAsP (well)/InGaAlAs(barrier) 1.55 mu;m strain-compensated MQW lasers is presented. For MQWs, a uniform vertical distribution of holes is achieved due to a reduced effective hole confinement energy by optimizing the bandgap and strain of the barriers and p-doping in the active region. Some preliminary results are also presented for the manufactured lasers using these QWs indicating a good material platform.

  • 53.
    Akram, Nadeem
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Silfvenius, Christofer
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Kjebon, Olle
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Schatz, Richard
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Design optimization of InGaAsP-InGaAlAs 1.55 mu m strain-compensated MQW lasers for direct modulation applications2004Ingår i: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 19, nr 5, s. 615-625Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a simulation study of InGaAsP(well)/InGaAlAs(barrier) 1.55 mum strain-compensated multi-quantum well (MQW) lasers is presented. Due to a large conduction band discontinuity in this material system, a higher material gain and differential gain can be obtained from such a quantum well (QW) as compared to a traditional InGaAsP/InGaAsP quantum well. The deeper electron well should also improve elevated temperature operating characteristics and reduce the electron spillover from QWs. For MQWs, a uniform vertical distribution of holes is achieved due to a reduced effective hole confinement energy by optimizing the bandgap and the strain in the barriers. A large number of quantum wells can be uniformly pumped, reducing the carrier density in each individual well. A uniform and low carrier density in all the wells help reduce the total Auger recombination current. High p-doping in the active region is shown to enhance the carrier and gain non-uniformity in the MQWs. A simulated high modulation bandwidth has been demonstrated, promising directly modulated lasers as a low-cost source for short to medium distance (1-10 km) high speed optical links.

  • 54.
    Al-Askary, Omar
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Papr reduction of coded OFDM signals based on iterative codeword construction2004Ingår i: ISCCSP: 2004 FIRST INTERNATIONAL SYMPOSIUM ON CONTROL, COMMUNICATIONS AND SIGNAL PROCESSING, NEW YORK: IEEE , 2004, s. 763-766Konferensbidrag (Refereegranskat)
    Abstract [en]

    Orthogonal Frequency Division Multiplexing (OFDM) allows transmission of data with high data rates over broad-band radio channels without the need for powerful equalization. However, OFDM is sensitive to non-linearities in the system due to the high Peak to Average Power Ratio (PAPR) in the transmitted signal. In this paper, we propose a simple method for reducing the PAPR in the OFDM signals using the well known BCH codes. The method relies on an iterative procedure to select a codeword that has a low PAPR from a translation of the code to another partition in a larger BCH code. The information about the chosen partition is loaded in the redundancy of the sent codeword and, therefore, no subcarriers are reserved for transmitting this information. The cost payed for this PAPR reduction is reduced error correction capability. Using this method, a reduction of the PAPR of up to 6 dB can be achieved with moderate complexity.

  • 55.
    Al-Askary, Omar
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Rizvi, Umar H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Khormuji, Majid N.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Rate adaptive generalized concatenated codes for wireless communication2005Ingår i: Proceedings of the INMIC 2005: 9th International Multitopic Conference - Proceedings, 2005, s. 137-142Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the construction and performance of rate adaptive generalized concatenated codes (GCCs) (sic) on linear block codes over Rayleigh fading Multi Input (sic) Output (MIMO) communication channels with N transmit (sic) N receive antennas. The code design criteria is chosen (sic) that it tries to follow the Shannon capacity of the MIMO (sic). It is envisaged that such codes provide a superior performance over systems that use Maximum Ratio Combining (sic) while maintaining the encoder/decoder complexity within acceptable level of practical usage. Furthermore it is expected (sic) these codes will provide good performance without an interver/deinterleaver because of their good burst error correction (sic).

  • 56.
    Al-Askary, Omar
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Sidiropoulos, Lazaros
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Kunz, Lukas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Vouzas, Christos
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Nassif, Chafic
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Adaptive coding for OFDM based systems using generalized concatenated codes2005Ingår i: VTC2005-SPRING: 2005 IEEE 61ST VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, PROCEEDINGS, 2005, s. 649-653Konferensbidrag (Refereegranskat)
    Abstract [en]

    Orthogonal Frequency Division Multiplexing (OFDM) is considered to be a promising candidate for future high-speed wireless communication systems. In this paper we present an adaptive coding scheme for OFDM based systems using generalized concatenated codes. We study the performance of HIPERLAN/2 after encoding with the proposed coding scheme and compare it to the standard convolutional coding scheme currently used. The criteria of our study is the optimization of the throughput. Through the adaptive scheme, we propose a modulation selection based on the average quality of the channel, and a code assigning method for the different sub-channels, that adapts to the channel conditions. We argue that the proposed scheme protects the information better than the ones in the conventional systems, since the latter do not take advantage of the individual sub-channel condition. Our simulations show that lower packet error rate can be accomplished for even higher throughput.

  • 57.
    Alayon Glazunov, Andres
    Ericsson research.
    Considerations regarding the number of RAKE fingers required in CDMA RAKE receivers1998Konferensbidrag (Övrigt vetenskapligt)
  • 58. Alayon Glazunov, Andres
    ITU-R, WP-3K/36, 3M/117, Average building attenuation for indoor to satellite interferencepropagation at 5 GHz1999Rapport (Övrigt vetenskapligt)
  • 59.
    Alayon Glazunov, Andres
    Ericsson Research.
    ITU-R, WP-3K/69, 3M/153, Building attenuation loss measurements at the 5GHz in an officebuilding area2000Rapport (Övrigt vetenskapligt)
  • 60.
    Alayon Glazunov, Andres
    TeliaSonera.
    Joint impact of the mean effective gain and base station smart antennas on WCDMA-FDD systems performance2004Konferensbidrag (Refereegranskat)
  • 61.
    Alayon Glazunov, Andres
    Telia Research.
    Mean effective gain of user equipment antennas in double directional channels2004Ingår i: Proc. 15th IEEE Int. Symp. Personal, Indoor and Mobile Radio Communications PIMRC 2004, 2004, Vol. 1, s. 432-436Konferensbidrag (Refereegranskat)
    Abstract [en]

     This paper presents a revised definition of the Mean Effective Gain (MEG) of terminal antennas. It now includes the gain pattern of both the transmitting (BS) and receiving (MS) antennas, the path gain matrix as well as the joint angular power distributions of the two orthogonal polarizations at both ends. A closed form equation is provided followed by the analysis of some special cases and their practical implications.

  • 62.
    Alayon Glazunov, Andres
    Telia Sonera.
    Measurements of Radio Performances of UMTS Terminals in Speech Mode, (R4-040612), 3GPPTSG-RAN Working Group 4 (Radio) meeting #33, Yokohama, 15 - 19 Nov 20042004Rapport (Övrigt vetenskapligt)
  • 63.
    Alayon Glazunov, Andres
    Ericsson research.
    On the distribution of relevant radio channel figures in different propagationenvironments for performance evaluation of WCDMA systems2001Konferensbidrag (Refereegranskat)
  • 64.
    Alayon Glazunov, Andres
    Telia Research.
    Theoretical analysis of mean effective gain of mobile terminal antennasin Ricean channels2002Konferensbidrag (Refereegranskat)
  • 65.
    Alayon Glazunov, Andres
    Telia Sonera.
    UE antenna efficiency- a comparison of different figures of merit, (R4-030994), TSG-RANWorkingGroup 4 (Radio) meeting #29, San Diego, US, 17th-21st Nov 20032003Rapport (Övrigt vetenskapligt)
  • 66.
    Alayon Glazunov, Andres
    TeliaSonera.
    UE antenna efficiency impact on UMTS system/coverage capacity, (R4-030546), 3GPP, TSGRANWorking Group 4 (Radio) meeting #27, Paris, France 19th-23rd May 20032003Rapport (Övrigt vetenskapligt)
  • 67.
    Alayon Glazunov, Andres
    et al.
    Ericsson Research.
    Asplund, Henrik
    Ericsson Research.
    Berg, Jan-Erik
    Ericsson Research.
    Statistical analysis of measured shorttermimpulse response functions of 1.88 GHz radio channels in Stockholm with correspondingchannel model1999Konferensbidrag (Refereegranskat)
  • 68.
    Alayon Glazunov, Andres
    et al.
    KTH, Skolan för elektro- och systemteknik (EES). Lund University, Sweden.
    Gustafsson, Mats
    Molisch, Andreas F.
    On the Physical Limitations of the Interaction of a Spherical Aperture and a Random Field2011Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 59, nr 1, s. 119-128, artikel-id 5618544Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper derives physical limitations on the interactions of antennas exciting TM or TE modes (but not both) and wireless propagation channels. The derivation is based on the spherical vector wave expansion of the electromagnetic field outside a sphere circumscribing the antennas. The result is an extension of the seminal work of Chu on the classical limitations on maximum antenna gain and radiation Q. Rather than maximizing antenna gain in a single direction we obtain physical limitations on the antenna gain pattern, which is directly translated to more condensed parameters, i.e., the instantaneous effective gain G(i) and the mean effective gain G(e) if instantaneous realizations or correlation statistics of the expansion coefficients of the electromagnetic field are known, spectively. The obtained limitations are on the maximum of G(i)/Q and G(e)/Q, which establish a trade-off between link gain and Q.

  • 69.
    Alayon Glazunov, Andres
    et al.
    Lund University.
    Molisch, Andreas F.
    Lund University.
    Tufvesson, Fredrik
    Lund University.
    Fading characterization in a semi-anechoic chamber with artificial scatterers for Mean Effective Gain measurements of wireless handheld terminals2008Ingår i: 2008 IEEE Radio and Wireless Symposium, RWS, 2008, s. 611-614Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the methodology and corresponding analysis of the scattered field measurements in a semi-anechoic ferrite-lined chamber. The focus is on recreating a Rayleigh fading environment with realistic cross-polarization ratio (XPR) with the purpose of measuring the Mean Effective Gain (MEG) of mobile handheld terminal operating in the 900 MHz GSM band. The emulated XPR was similar in each of the studied scenarios and approximately equal to 12 dB. The Rayleigh fading hypothesis for the statistics of the envelope of the measured signals could not be rejected in most cases at the 95 % level with the Kolmogorov goodness-of-fit test.

  • 70.
    Alayon Glazunov, Andres
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Prasad, Sathyaveer
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bolin, Thomas
    Prytz, Kjell
    Impact of Scattering Within a Multipath Simulator Antenna Array on the Ricean Fading Distribution Parameters in OTA Testing2014Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 62, nr 6, s. 3257-3269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the unwanted scattering that exists within the multipath simulator (MPS) array antennas employed in over the air (OTA) testing of mobile terminals. The impact of scattering is evaluated in terms of the measurement uncertainty of the average received power and the Ricean K-factor. The maximum ratio combining diversity is investigated for a generic device under test comprising two half-wavelength dipole antennas. We provide closed-form expressions for the uncertainties of the average received power and the Ricean K-factor for a uniform circular array of MPS antennas and a 2-D uniformly distributed angle-of-arrival spectrum. We also derive the maximum number of MPS antennas and the minimum ring radius of the MPS system as a function of the separation between the most distant antenna elements if the device under test employs a uniform linear array. As a result, we provide design guidelines for MPS array in terms of the number antennas, the radius of the MPS array and the wavelength of the carrier frequency.

  • 71.
    Alayon Glazunov, Andres
    et al.
    Lund University.
    Tufvesson, Fredrik
    Lund University.
    Gustafsson, Mats
    Lund University.
    Molisch, Andreas F.
    Lund University.
    Kristensson, Gerhard
    Lund University.
    Branch cross-correlation in presence of spatially selective interference expressed in terms of the spherical vector wave expansion of the electromagnetic field2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we present an analysis of the cross-correlation coe±cient between signals at two antennabranches (ports) in the presence of spatially selective interference and additive white gaussian noise. Morespeci¯cally, we look at a §45± slanted polarization diversity arrangement, which is rotated around the axisperpendicular to the plane containing the antennas. Results are provided as a function of the rotation angle.The analysis is based on the spherical vector wave multi-pole expansion of both the ¯eld impinging on theantennas and the antenna radiation properties.

  • 72.
    Alayon Glazunov, Andres
    et al.
    Lund University.
    Tufvesson, Fredrik
    Lund University.
    Gustafsson, Mats
    Lund University.
    Molisch, Andreas F.
    Lund University.
    Kristensson, Gerhard
    Lund University.
    On the mean effective gain expressed in terms of the spherical vector wave expansion of the electromagnetic field2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    The mode expansion o®ers a general framework for the analysis of the interaction between antennas andpropagation channels. In this paper, the Mean E®ective Gain (MEG) of an antenna is expressed in termsof the spherical vector wave expansion of the electromagnetic ¯eld. An explicit expression of the MEG isprovided as a function of the normalized average power of modes excited in the propagation channel andthe correlation between the channel modes due to the polarization and spatial selectivity of plane wavesimpinging at the antenna.

  • 73.
    Alayon Glazunov, Andres
    et al.
    TeliaSonera.
    Wang, Ying
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Experimental Evaluation of CW MIMO Channel Capacity in Urban Multicell Environment2006Konferensbidrag (Refereegranskat)
  • 74.
    Alexander, Paul D.
    et al.
    University of South Australia.
    Grant, Alex J.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Filter structure for iterative signal processing2002Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The invention is an iterative signal processing arrangement having one or more pairs of first and second signal processing components. These pairs are in iterative configuration with each of the first signal processing components having as its input one or more received signals dependent upon one or more transmitted signals. For each said signal processing component pair the output of said first signal processing component is an estimate of a characteristic of a selected transmitted signal based on the current and one or more previous input signals received by said first signal processing component. This estimate is input to said corresponding second signal processing component which provides a further estimate of said selected transmitted signal. The outputs of all said second components of respective pairs are input to their corresponding first components in a succeeding iteration cycle.

  • 75.
    Alexander, Paul D.
    et al.
    Cohda Wireless Pty Ltd, Australia.
    Grant, Alex J.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Jakas, Steven Peter
    Cohda Wireless Pty Ltd, Australia.
    Filter structure for iterative signal processing2002Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The present invention relates to improved multiple access communications. In one form, the invention relates to an improved signal processing method and apparatus for an iterative method of determining the reception of a signal in a multi user packet based wireless OFDM (Orthogonal Frequency Division Multiplexing) communication system. In other forms the present invention provides recursive filtering for joint iterative decoding in a variety of systems and functions such as linear multiple access channel decoders, iterative equalisation, iterative joint channel estimation and detection/decoding, iterative space-time processing, iterative multi user interference cancellation and iterative demodulation.; In one particular form the present invention provides an iterative decoding circuit for a wireless multiuser communications receiver comprising a first signal processing means for receiving at least one received signal, said first signal processing means comprising at least two linear iterative filters such that the first linear iterative filter provides an estimate of a selected received signal to an estimated signal output and a second linear iterative filter provides estimates of at least one other received signal, delayed by one iteration cycle, to an input of said first linear iterative filter, a second signal processing means for receiving the estimated signal output of the first linear iterative filter and providing a further received signal estimate to the input of the first signal processing means in a succeeding iteration cycle of the decoding circuit.

  • 76.
    Alexander, Paul D.
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    On the windowed Cholesky factorization of the time-varying asynchronous CDMA channel1998Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 46, nr 6, s. 735-737Artikel i tidskrift (Refereegranskat)
  • 77.
    Alexander, Paul D.
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Schlegel, Christian B.
    University of Texas, San Antonio, USA.
    A linear receiver for coded multiuser CDMA1997Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 45, nr 5, s. 605-610Artikel i tidskrift (Refereegranskat)
  • 78.
    Alexiou, Nikolaos
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Basagiannis, S.
    Petridou, S.
    Formal security analysis of near field communication using model checking2016Ingår i: Computers & security (Print), ISSN 0167-4048, E-ISSN 1872-6208, Vol. 60, s. 1-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Near field communication (NFC) is a short-range wireless communication technology envisioned to support a large gamut of smart-device applications, such as payment and ticketing. Although two NFC devices need to be in close proximity to communicate (up to 10 cm), adversaries can use a fast and transparent communication channel to relay data and, thus, force an NFC link between two distant victims. Since relay attacks can bypass the NFC requirement for short-range communication cheaply and easily, it is important to evaluate the security of NFC applications. In this work, we present a general framework that exploits formal analysis and especially model checking as a means of verifying the resiliency of NFC protocol against relay attacks. Toward this goal, we built a continuous-time Markov chain (CTMC) model using the PRISM model checker. Firstly, we took into account NFC protocol parameters and, then, we enhanced our model with networking parameters, which include both mobile environment and security-aware characteristics. Combining NFC specifications with an adversary's characteristics, we produced the relay attack model, which is used for extracting our security analysis results. Through these results, we can explain how a relay attack could be prevented and discuss potential countermeasures.

  • 79. Ali, Amjad
    et al.
    Jafri, Syeda I.
    Habib, Ayesha
    Amin, Yasar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. University of Engineering and Technology (UET), Pakistan.
    Tenhunen, Hannu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    RFID Humidity Sensor Tag for Low-cost Applications2017Ingår i: APPLIED COMPUTATIONAL ELECTROMAGNETICS SOCIETY JOURNAL, ISSN 1054-4887, Vol. 32, nr 12, s. 1083-1088Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article presents a low-cost, flexible, chipless Radio Frequency Identification (RFID) tag for humidity monitoring applications. The tag exhibits moisture sensing feature within a compact geometrical dimension of 20mm x 17.6mm. The design is loaded with 12 resonators, where each resonator represents 1 bit in the frequency domain. For the designed 12-bit tag, 11 inverted C-shaped resonators are dedicated for encoding 11-bit information in their spectral signature. An integrated meandered-shaped resonator, covered with moisture sensitive Kapton (R) HN film, functions as a 1-bit moisture sensor. It is deployed for monitoring relative humidity (RH) levels, simultaneously. The passive RFID tag is realized on Taconic TLX-0 and has an operational bandwidth of 2.62 GHz. Furthermore, the design is modeled and analyzed for multiple substrates. The performance of the sensor tag for various humidity levels indicates that it is a potential solution for inexpensive sensing applications.

  • 80.
    Alija Fuertes, Miguel Jesús
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.), Industriell ekonomi och organisation (Avd.).
    Mobile Devices: Dominant Design as a Goal2013Självständigt arbete på grundnivå (kandidatexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Since the beginning of the smartphones in the 80s, the mobile device market has grown and evolved towards devices connected everywhere, with hardware more and more close to computers and laptops than a classic mobile telephone. Nowadays, this market seems to be crowded and some companies seem not to know exactly which step is next. In this manner, a concept appears in the market as a solution or a difficulty to overcome: the dominant design. The thesis aims to establish an analysis and definition of what a dominant design is and how we should understand this concept: which are the costumers’ demands and needs? How can we relate this information with the dominant design? What is the strategy of the firm before designing a device? Do they use a concept similar to a dominant design?. The research base its analysis in a theoretical framework based in innovation and marketing literature, to then compare the model studied with data collected from surveys made to customers, interviews made to workers of the mobile device market, and different new projects on the market. The research finishes with a discussion about the theoretical and the empirical frameworks, and concludes replying the research questions, and defining a dominant design and its current situation in the market.

  • 81.
    Alizadeh, Mahmoud
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Characterisation, Modelling and Digital Pre-DistortionTechniques for RF Transmitters in Wireless Systems2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wireless systems have become an inevitable part of modern technologies serving humankind. The rapid growth towards large dimensional systems, e.g. 5th generation (5G) technologies, incurs needs for improving the performance of the systems and considering aspects to make them as far as possible environmentally friendly in terms of power efficiency, cost, and so on. One of the key parts of every wireless communication system is the radio frequency (RF) power amplifier (PA), which consumes the largest percentage of the total energy. Hence, accurate models of RF PAs can be used to optimize their design and to compensate for signal distortions. This thesis starts with two methods for frequency-domain characterisation to analyse the dynamic behaviour of PAs in 3rd-order non-linear systems. Firstly, two-tone signals superimposed on large-signals are used to analyse the frequency-domain symmetry properties of inter-modulation (IM) distortions and Volterra kernels in different dynamic regions of RF PAs in a single-input single-output (SISO) system. Secondly, three-tone signals are used to characterise the 3rd-order self- and cross-Volterra kernels of RF PAs in a 3 × 3 multiple-input multiple-output (MIMO) system. The main block structures of the models are determined by analysing the frequency-domain symmetry properties of the Volterra kernels in different three-dimensional (3D) frequency spaces. This approach significantly simplifies the structure of the 3rd-order non-linear MIMO model.

    The following parts of the thesis investigate techniques for behavioural modelling and linearising RF PAs. A piece-wise modelling technique is proposed to characterise the dynamic behaviour and to mitigate the impairments of non-linear RF PAs at different operating points (regions). A set of thresholds decompose the input signal into several sub-signals that drive the RF PAs at different operating points. At each operating point, the PAs are modelled by one sub-model, and hence, the complete model consists of several sub-models. The proposed technique reduces the model errors compared to conventional piece-wise modelling techniques.

    A block structure modelling technique is proposed for RF PAs in a MIMO system based on the results of the three-tone characterisation technique. The main structures of the 3rd- and higher-order systems are formulated based on the frequency dependence of each block. Hence, the model can describe more relevant interconnections between the inputs and outputs than conventional polynomial-type models.

    This thesis studies the behavioural modelling and compensation techniques in both the time and the frequency domains for RF PAs in a 3 × 3MIMO system. The 3D time-domain technique is an extension of conventional 2D generalised memory polynomial (GMP) techniques. To reduce the computational complexity, a frequency-domain technique is proposed that is efficient and feasible for systems with long memory effects. In this technique, the parameters of the model are estimated within narrow sub-bands. Each sub-band requires only a few parameters, and hence the size of the model for each sub-band is reduced.

  • 82. Alizai, Muhammad Hamad
    et al.
    Landsiedel, Olaf
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Wehrle, Klaus
    Exploiting the Burstiness of Intermediate-Quality Wireless Links2012Ingår i: International Journal of Distributed Sensor Networks, ISSN 1550-1329, s. 826702-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We address the challenge of link estimation and routing over highly dynamic links, thats is, bursty links that rapidly shift between reliable and unreliable periods of transmissions. Based on significant empirical evidence of over 100,000 transmissions over each link in 802.15.4 and 802.11 testbeds, we propose two metrics, expected future transmissions (EFT) and MAC(3), for runtime estimation of bursty wireless links. We introduce a bursty link estimator (BLE) that based on these two metrics, accurately estimates bursty links in the network rendering them available for data transmissions. Finally, we present bursty routing extensions (BRE): an adaptive routing strategy that uses BLE for forwarding packets over bursty links if they offer better routing progress than long-term stable links. Our evaluation, comprising experimental data from widely used IEEE 802.15.4-based testbeds, reveals an average of 19% and a maximum of 42% reduction in the number of transmissions when routing over long-range bursty links typically ignored by routing protocols. Additionally, we show that both BLE and BRE are not tied to any specific routing protocol and integrate seamlessly with existing routing protocols and link estimators.

  • 83.
    Al-Saadeh, Osama
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Performance of In-Band Full-Duplex for 5G Wireless Networks2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Inomband hel duplex är en ny typ av duplexmetod som tillåter radionoder att sända och ta emot i samma frekvensoch tidsresurs. Att implementera inomband hel duplex har fram tills nu inte ansetts praktiskt genomförbart till följd av självstörningar. Framsteg inom signalbehandling har dock gjort det möjligt att begränsa denna självstörningseffekt. Emellertid har systemprestanda av inomband hel duplex inte undersökts tillräckligt noga i tidigare verk.Inomband hel duplex och dess prestanda för trådlösa 5G småcellsnätverk inomhus har studerats med hjälp av datasimuleringar och jämförts med dynamisk och statisk tidsdelning. Utöver detta har prestanda för de olika duplexmetoderna med avseende på två tekniker för störningsundertryckning, lobformning och störningseliminering, också undersökts.Våra resultat indikerar att för trådlösa nätverk med högt radioresursutnyttjande bör inomband hel duplex kombineras med lobformning och störningseliminering för att uppnå en prestandavinst jämfört med traditionella duplexmetoder. Bara då kan inomband hel duplex anses vara fördelaktig oberoende av radioresursutnyttjande och andelen upp- och nedlänkstrafik.Resultaten tyder också på att sändareffekten för radioaccesspunkterna bör vara jamförbar med den för mobilenheterna för att en prestandavinst med inomband hel duplex ska kunna uppnås.

  • 84. Al-Saadeh, Osama
    et al.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    A performance comparison of in-band full duplex and dynamic TDD for 5G indoor wireless networks2017Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, artikel-id 50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In-band full duplex has emerged as a solution for high data rate and low access delay for 5G wireless networks after its feasibility has been demonstrated. However, the impact of the in-band full duplex on the system-level performance of multi-cell wireless networks has not been investigated thoroughly. In this paper, we conduct an extensive simulation study to investigate the performance of in-band full duplex for indoor 5G small cell wireless networks. Particularly, we compare the in-band full duplex with static and dynamic time division duplexing schemes which require much less hardware complexity. We examine the effects of beamforming and interference cancellation under various traffic demands and asymmetry situations in the performance comparison. Our objective is to identify under which condition and with which technology support the in-band full duplex becomes advantageous over the simpler duplexing schemes. Numerical results indicate that for highly utilized wireless networks, in-band full duplex should be combined with interference cancellation and beamforming in order to achieve a performance gain over traditional duplexing schemes. Only then in-band full duplex is considered to be advantageous at any number of active mobile stations in the network and any downlink to uplink traffic proportion. Our results also suggest that in order to achieve a performance gain with the in-band full duplex in both links, the transmit power of the access points and the mobile stations should be comparable.

  • 85.
    Al-Zubaidy, Hussein
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fodor, Viktoria
    KTH, Skolan för elektro- och systemteknik (EES), Nätverk och systemteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Nätverk och systemteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Flierl, Markus
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Reliable Video Streaming With Strict Playout Deadline in Multihop Wireless Networks2017Ingår i: IEEE transactions on multimedia, ISSN 1520-9210, E-ISSN 1941-0077, Vol. 19, nr 10, s. 2238-2251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Motivated by emerging vision-based intelligent services, we consider the problem of rate adaptation for high-quality and low-delay visual information delivery over wireless networks using scalable video coding. Rate adaptation in this setting is inherently challenging due to the interplay between the variability of the wireless channels, the queuing at the network nodes, and the frame-based decoding and playback of the video content at the receiver at very short time scales. To address the problem, we propose a low-complexity model-based rate adaptation algorithm for scalable video streaming systems, building on a novel performance model based on stochastic network calculus. We validate the analytic model using extensive simulations. We show that it allows fast near-optimal rate adaptation for fixed transmission paths, as well as cross-layer optimized routing and video rate adaptation in mesh networks, with less than 10% quality degradation compared to the best achievable performance.

  • 86.
    Amin, Yasar
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Tenhunen, Hannu A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Zheng, Lirong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Blueprint and integration of vastly efficient 802.11A WLAN front-end2006Ingår i: WSEAS Transactions on Electronics, ISSN 1109-9445, Vol. 3, nr 4, s. 258-261Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Next generation wireless communications terminals will demand the use of advanced component integration processes and high density packaging technologies in order to reduce size and to increase performance. This paper presents high density multilayer interconnects and integrated passives used to design high performance prototype filter for 5GHz wireless LAN receiver realized on MCM-D substrate. The thin film implementation of Multichip Module technology is identified as a useful platform for the integration of GaAs MMIC and silicon device technologies for microwave applications where performance, size and weight are critical factors. The ability of the MCM-D technology to provide controlled impedance, microstrip structures and integrated thin film passive components with useful performance in the microwave frequency regime has now been demonstrated.

  • 87.
    Amin, Yasar
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Tenhunen, Hannu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Jamal, Habibullah
    Zheng, Li-Rong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Duo, Xinzhong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Chip-package codesign of receiver front end modules for RF/wireless applications2005Ingår i: 2005 IEEE/ACES International Conference on Wireless Communications and Applied Computational Electromagnetics, New York: IEEE , 2005, s. 767-770Konferensbidrag (Refereegranskat)
  • 88.
    Andersson, Fredrik
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Grafisk utvecklingsplattform för signalbehandling - Design och implementation2013Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    We have different kinds of signal processing everywhere around us in our everyday life, in our cellphones, when we are listening to music, watching TV etc. This makes signal processing a very interesting and important technical area, where the demand of skilled engineers sets the limit of what is possible.

    Working with signal processing requires in-depth knowledge in areas such as mathematics, physics, electronics, and other related areas. For this, it has traditionally been demanded by a talented developer to also master the advanced programming languages such as C / C + + and Assembler.

    This has begun to change; today there are several companies that offer graphical development environments for signal processing, environments where programming skills are not needed anymore, and the focus can be on signal processing instead.

    The goal with this project is to build a corresponding graphical development environment to reach an understanding of what is required of these systems, and also to grasp what opportunities that are available within graphic programming. Inspiration for the work has partly arise from some of the tools available on the market, and partly from previous theses that have been written about graphic programming.

    The challenge lies in creating a program that can execute signal diagrams in real time from given signal blocks, and be able to handle feedback loops in an efficient way and to do so at the lowest "cost" in terms of clock cycles as possible. This should also be compared against to code, compile and run a complete signal diagram directly.

    To increase the usability it should also be possibility to externally manage in real time the parameters of the signal diagram during execution.

    The interface is a separate program, which is to some extent similar to Matlab Simulink, where a signal diagram is drawn up graphically by connecting wires between different signal blocks. This signal scheme is then executed in an additional program that serves as a runtime environment. In this report, the term "signal engine" is used for this program.

    Signal engine is equivalent to the program that should have been run directly into a standalone DSP (Digital Signal Processor) if a more classic design had been selected, but now runs as a separate process in Windows.

  • 89.
    Andersson, Göran
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Västberg, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Devlic, Alisa
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Cavdar, Cicek
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Energy efficient heterogeneous network deployment with cell DTX2016Ingår i: 2016 IEEE International Conference on Communications (ICC),, IEEE, 2016, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper evaluates different means of reducing power consumption of macro base stations (BS) and heterogeneous mobile network deployments (HetNet) considering the time dimension. These approaches are based on the same idea of reducing the load of heavily loaded macro cells and putting them to discontinuous transmission (DTX) mode during the time of inactivity by either (1) macro cell densification or (2) offloading traffic to small cells. Activity factor of a BS is defined as the fraction of time the BS is transmitting over a fixed time period. It is shown that by macro cell layer network densification, the average daily area power consumption can be reduced by up to 73 % with the use of cell DTX. However, reducing the activity factor by macro layer densification is not cost effective, as already demonstrated in previous studies. Alternatively, by adding small cells and enabling their DTX capability, power consumption can be reduced by up to 29 %. Adding small cells is especially effective in terms of energy savings, when users are distributed around hot spots, where additional coverage and capacity is required.

  • 90.
    Andersson, Mattias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Coding and Transmission Strategies for Secrecy2014Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [sv]

    I den här avhandlingen behandlar vi flera problem relaterade till informationsteoretisk säkerhet. Wiretap-kanalen är den enklaste informationsteoretiska modellen som behandlar säkerhet och i de första kapitlen av avhandlingen designar vi praktiska koder för wiretap-kanalen.

    Först designar vi glesa paritetskontrollkoder (LDPC) med två kanttyper för den binära erasure-wiretap-kanalen (BEC-WT). För scenariot där huvudkanalen är felfri och avlyssnarens kanal är en binär erasure-kanal (BEC) konstruerar vi en följd av koder som uppnår säkerhetkapaciteten. Dessa koder är baserade på vanliga LDPC-koder för BEC. Vår konstruktion fungerar dock inte när huvudkanalen inte är felfri. Om så inte är fallet använder vi en metod baserad på linjär programmering för att optimera gradfördelningen hos våra koder, vilket låter oss designa kodensembler som har prestanda nära säkerhetskapaciteten hos BEC-WT. Vi generaliserar sedan en av Méassons, Montanaris och Urbankes metoder för att räkna ut den betingade entropin av meddelandet hos avlyssnaren.

    Vi visar sedan att Arikans polära koder kan användas för att uppnå hela kapacitets-ekvivokationsregionen för en degraderad symmetrisk wiretap-kanal med binärt inalfabet. Vi designar också polära koder för decode-and-forward-protokollet för den fysiskt degraderade reläkanalen och för den bidirektionella broadcastkanalen med gemensamma och konfidentiella meddelanden. Vi visar att koderna uppnår kapaciteten och kapacitets-ekvivokationsregionen för dessa kanalmodeller.

    I nästföljande kapitel behandlar vi en gaussisk kanalmodell. Vi visar att Josephs och Barrons glesa regressionskoder (SPARCs) kan användas för att uppnå säkerhetskapaciteten för wiretapkanaler med gaussiskt brus och för decode-and-forward-protokollet för reläkanalen. Vi behandlar också generering av hemliga nycklar från korrelerade gaussiska källor med hjälp av en publik kanal av begränsad kapacitet. Vi visar att SPARC-koder uppnår kapacitetsregionen för detta problem.

    I det sista kapitlet behandlar vi generering av hemliga nycklar över fädande kanaler. Vi behandlar först ett scenario med flera antenner och högt signal-till-brusförhållande (SNR) och föreslår ett protokoll baserat på träning och slumpdelning. Vi behandlar sedan ett scenario med en antenn hos varje terminal och lågt SNR, där vi begränsar den ena terminalen till att endast sända pilotsignaler. Vi föreslår ett protokoll baserat på sporadisk träning och opportunistisk sändning med en wiretap-kod och visar att det är optimalt.

  • 91.
    Andersson, Mattias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Coding for the Wiretap Channel2011Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    We consider code design for Wyner’s wiretap channel. Optimal coding schemes for this channel require an overall code that is capacity achieving for the main channel, partitioned into smaller subcodes, all of which are capacity achieving for the wiretapper’s channel. To accomplish this we introduce two edge type low density parity check (LDPC) ensembles for the wiretap channel. For the scenario when the main channel is error free and the wiretapper’s channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the binary erasure wiretap channel (BEC- WT). We generalize a method of M ́easson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wire- tapper. This conditional entropy is a measure of how much information is leaked to the wiretapper. We apply this method to relatively simple ensembles and find that they show very good secrecy performance.

    Based on the work of Kudekar, Richardson, and Urbanke, which showed that regular spatially coupled codes are capacity achieving for the BEC, we construct a regular two edge type spatially coupled ensem- ble. We show that this ensemble achieves the whole capacity-equivocation region for the BEC-WT.

    We also find a coding scheme using Arıkans polar codes. These codes achieve the whole capacity-equivocation region for any symmetric binary input wiretap channel where the wiretapper’s channel is degraded with respect to the main channel.

     

  • 92.
    Andersson, Mattias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Khisti, Ashish
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Secret-key agreement over a non-coherent block-fading MIMO wiretap channel2012Ingår i: Information Theory Workshop (ITW), 2012 IEEE, IEEE , 2012, s. 153-157Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study secret-key agreement over a non-coherent block-fading multiple input multiple output (MIMO) wiretap channel. We give an achievable scheme based on training and source emulation and analyze the rate in the high SNR regime. Based on this analysis we find the optimal number of antennas to use for training. Our main result is that if the sum of the number of antennas at Alice and Bob is larger than the coherence time of the channel, the achievable rate does not depend on the number of antennas at Eve. In this case source emulation is not needed, and using only training is optimal. We also consider the case when there is no public channel available. In this case we show that secret-key agreement is still possible by using the wireless channel for discussion, giving the same number of secure degrees of freedom as in the case with a public channel.

  • 93.
    Andersson, Mattias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Kliewer, Joerg
    Klipsch School of Electrical and Computer Engineering New Mexico State University.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Equivocation of Eve using two edge type LDPC codes for the binary erasure wiretap channel2010Ingår i: 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), 2010, s. 2045-2049Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider transmission over a binary erasure wiretap channel using the code construction method introduced by Rathi et al. based on two edge type Low-Density Parity-Check (LDPC) codes and the coset encoding scheme. By generalizing the method of computing conditional entropy for standard LDPC ensembles introduced by Méasson, Montanari, and Urbanke to two edge type LDPC ensembles, we show how the equivocation for the wiretapper can be computed. We find that relatively simple constructions give very good secrecy performance and are close to the secrecy capacity.

  • 94.
    Andersson, Mattias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kliewer, Jorg
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Nested Polar Codes for Wiretap and Relay Channels2010Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 14, nr 8, s. 752-754Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that polar codes asymptotically achieve the whole capacity-equivocation region for the wiretap channel when the wiretapper's channel is degraded with respect to the main channel, and the weak secrecy notion is used. Our coding scheme also achieves the capacity of the physically degraded receiver-orthogonal relay channel. We show simulation results for moderate block length for the binary erasure wiretap channel, comparing polar codes and two edge type LDPC codes.

  • 95.
    Andersson, Mattias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Schaefer, Rafael F.
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Polar Coding for Bidirectional Broadcast Channels with Common and Confidential Messages2013Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 31, nr 9, s. 1901-1908Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The integration of multiple services such as the transmission of private, common, and confidential messages at the physical layer is becoming important for future wireless networks in order to increase spectral efficiency. In this paper, bidirectional relay networks are considered, in which a relay node establishes bidirectional communication between two other nodes using a decode-and-forward protocol. In the broadcast phase, the relay transmits additional common and confidential messages, which then requires the study of the bidirectional broadcast channel (BBC) with common and confidential messages. This channel generalizes the broadcast channel with receiver side information considered by Kramer and Shamai. Low complexity polar codes are constructed that achieve the capacity region of both the degraded symmetric BBC, and the BBC with common and confidential messages. The use of polar codes allows an intuitive interpretation of how to incorporate receiver side information and secrecy constraints as different sets of frozen bits at the different receivers for an optimal code design. In order to show that the constructed codes achieve capacity, a tighter bound on the cardinality of an auxiliary random variable used in the converse is found using a method by Salehi.

  • 96.
    Andersson, Mattias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Zaidi, Syed Ali Abbas
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Wernersson, Niklas
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Nonlinear distributed sensing for closed-loop control over Gaussian channels2011Ingår i: Communication Technologies Workshop (Swe-CTW), 2011 IEEE Swedish, IEEE conference proceedings, 2011, s. 19-23Konferensbidrag (Refereegranskat)
    Abstract [en]

    A scenario of distributed sensing for networked control systems is considered and a new approach to distributed sensing and transmission is presented. The state process of a scalar first order linear time invariant dynamical system is sensed by a network of wireless sensors, which then instantaneously transmit their measurements to a remotely situated control unit over parallel Gaussian channels. The control unit aims to stabilize the system in mean square sense. The proposed non-linear delay-free sensing and transmission strategy is compared with the well-known amplify-and-forward strategy, using the LQG control cost as a figure of merit. It is demonstrated that the proposed nonlinear scheme outperforms the best linear scheme even when there are only two sensors in the network. The proposed sensing and transmission scheme can be implemented with a reasonable complexity and it is shown to be robust to the uncertainties in the knowledge of the sensors about the statistics of the measurement noise and the channel noise.

  • 97.
    Andersson, Per
    et al.
    Handelshögskolan, Stockholm School of Economics.
    Markendahl, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Value added services and new business roles for support of mobile professional users and project working processes2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we will discuss services that support the value creation process and the interaction between companies in the supply chain. The value added services for professional users hence should support both the internal working processes within a company and, maybe even more important, the interaction between different market actors.   We will discuss how communication systems and value added services can be designed in order to support professional users.

    We target business users using services supporting work in mobile environments with a temporary project organization. The discussion and some analysis will be based on findings from construction projects and from public safety services.  These “projects” are usually temporary with different duration, highly mobile and geographically distributed organizations with common work processes that require close interaction between multiple users and partners belonging to different organizations.

    The analysis starts with characterization of user behavior, user environments and project organizations.  Communication and mobility patterns are described and possible services and business roles are proposed.

    Analysis of empirical results in identification of different types of organization of the provider network. The position of actors within this network is important. Using these findings we discuss adaptive or adaptable business models that could be configured in different ways depending on the duration and the position of actors within the network. An important aspect is the ability for companies to change perspective and consider new ways to assess business opportunities and/or to organize the value creation activities. 

  • 98.
    Andersson, Per
    et al.
    Handelshögskolan, Stockholm School of Economics.
    Markendahl, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Mattsson, Lars-Gunnar
    Handelshögskolan, Stockholm School of Economics.
    Global policy networks’ involvement in service innovation. Turning the mobile phone into a wallet by applying NFC technology2011Ingår i: The IMP Journal, ISSN 2059-1403, E-ISSN 0809-7259, Vol. 5, nr 3, s. 193-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mobile phone attracts an increasing number of service applications enabled by technical developments. On-going efforts aim to widen the scope of mobile payments and “turning the mobile phone into a wallet” with the help of Near Field Technology (NFC). A number of industries are involved in this development. To enable large scale commercial application of the new technology for mobile payments, several global industry associations, what we label Global Policy Networks (GPNs), are involved in standard setting, certification, visions and promotion of business applications, etc. The purpose of the paper is to analyze the role of GPNs in establishing global policies to enable business actors to develop and implement local policies applying the new technology for business purposes. The paper focuses on how some yet to be settled global policy issues affect local policies.

  • 99.
    Andersson, Per
    et al.
    Handelshögskolan, Stockholm School of Economics.
    Markendahl, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Mattsson, Lars-Gunnar
    Handelshögskolan, Stockholm School of Economics.
    Technical development and the formation of new business ventures, The case of new mobile payment and ticketing services2011Ingår i: The IMP Journal, ISSN 2059-1403, E-ISSN 0809-7259, Vol. 5, nr 1, s. 23-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    How do new business ventures emerge, and how is their emergence linked to technical development? What are the challenges of forming new business ventures when the business involves the connection of previously unconnected or loosely connected networks? This paper analyses the connections between technical development and the formation of new business ventures.

    A set of case studies is presented that show how existing market structures, business development and associated wireless, technologies and systems are affected by the emergence of new mobile payment and ticketing services. This paper presents result from an on-going research project on near field communication based services in Sweden. In late 2008 the project “Foundation For NFC/Sensor Network B2B2C Services” (FORCE) was initiated by TeliaSonera Mobile Network, KTH Center for Wireless System, and Center for Information and Communication Research at the Stockholm School of Economics.

  • 100.
    Andersson, Per
    et al.
    Handelshögskolan, Stockholm School of Economics.
    Markendahl, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Mattsson, Lars-Gunnar
    Handelshögskolan, Stockholm School of Economics.
    The formation of new business ventures in networks: creating new intermediary roles and extracting value from the exploitation of technology2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper analyzes new business formation connected to the use of established mobile technologies and associated services. The purpose of the paper is to describe how a set of alternative business network situations can emerge when established wireless application technologies are exploited and new value is created and new business ventures are formed. A set of short cases describe how new business can be created based on established SMS applications and services. The paper discusses central aspects of the formation of new business ventures in networks. Here, focus is on opportunities to create value based on the exploitation of existing technology. The technology is used in a new way and is perceived by existing actors as an opportunity to exploit by creating a new intermediary performing a new role. In business practice, technology development is related to formation of new business ventures, they cannot be separated from each other.

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