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  • 1. Ahlberg, M.
    et al.
    Lindmark, B.
    Simons, J.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Downlink propagation measurements in the GSM 900 and 1800 MHz bands1999In: IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.99CH37010), 1999, Vol. 3, p. 1506-1509 vol.3Conference paper (Refereed)
    Abstract [en]

    The authors investigate radio propagation in the GSM 900 and 1800 MHz bands in a typical Swedish suburban environment to determine whether or not it is practically feasible to co-site GSM 900 with GSM 1800 systems. They show that propagation in the GSM 1800 band is considerable higher (about 12 dB) than in the old GSM 900. In many cases this difference can be reduced by using dual band sector antennas with 3 dB higher gain at 1800 MHz. However, they also show that in small cells (radius <1000 m) this difference is of little concern and therefore it is possible to co-locate GSM 1800 sites within existing 900 MHz sites as a cost-effective way to increase the system capacity.

  • 2.
    Alasali, Mohammad
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    LTE MIMO Performance Measurements on Board Passenger Trains2013Conference paper (Other academic)
    Abstract [en]

    Providing passenger internet on board trains with continuous connectivity at high speeds and over large rural distances is a challenging issue. A frequently used solution to the problem is to use an on board WiFi network connected to the 3G or 4G networks deployed outside the train. In order to be able to provide the capacity and the data rates that tomorrow's business travelers are expecting it has been suggested to use a combination of MIMO and carrier aggregation in the LTE-Advance standard. In this study, we practically investigate the plausibility of using MIMO functionality in an 900 LTE system when the receive antennas are mounted at a train roof about 4m above ground and the base stations antennas are on average placed 2.3km away from the track in towers with an average height of 45m and, hence, most of the time in line of site. It is found that along our test route MIMO is in practice supported by the radio channel at around 70% of the time when the train is travelling with an average speed of 185km/h and the MIMO antennas are mounted 10.5m apart.

  • 3.
    Alasali, Mohammad
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    LTE MIMO performance measurements on trains2013In: 2013 7th European Conference on Antennas and Propagation (EuCAP), New York: IEEE , 2013, p. 2327-2330Conference paper (Refereed)
    Abstract [en]

    Providing passenger internet on board trains with continuous connectivity at high speeds and over large rural distances is a challenging issue. A frequently used solution to the problem is to use an on board WiFi network connected to the 3G or 4G networks deployed outside the train. In order to be able to provide the capacity and the data rates that tomorrow's business travelers are expecting it has been suggested to use a combination of MIMO and carrier aggregation in the LTE-Advance standard. In this study, we practically investigate the plausibility of using MIMO functionality in an 900 LTE system when the receive antennas are mounted at a train roof about 4m above ground and the base stations antennas are on average placed 2.3km away from the track in towers with an average height of 45m and, hence, most of the time in line of site. It is found that along our test route MIMO is in practice supported by the radio channel at around 70% of the time when the train is travelling with an average speed of 185km/h and the MIMO antennas are mounted 10.5m apart.

  • 4.
    Alasali, Mohammad
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Karlsson, M.
    Providing internet to trains using MIMO in LTE networks2014In: 2014 International Conference on Connected Vehicles and Expo, ICCVE 2014 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2014, p. 810-814Conference paper (Refereed)
    Abstract [en]

    Providing broadband passenger internet on board trains with continuous connectivity at high speeds and over large rural distances is a challenging issue. One solution to the problem is to use an onboard WiFi network connected to multiple 3G and 4G networks deployed outside the train and aggregate their combined capacity at the IP protocol level. In order to be able to provide the capacity and the data rates that tomorrow’s travelers are expecting, the future 4G standard (LTE-Advance) uses a combination of high order MIMO and carrier aggregation. In this study we use the Swedish company Icomera’s passenger internet system for our investigation. The system provides aggregation of multiple carrier and handover on an IP level. For about 10 years the system has in Sweden primarily been using multiple 3G communication links. However, here we present analysis and onboard measurements of a 2×2 MIMO channel to fast moving train in a live LTE 900 network. The results indicate that MIMO works surprisingly well and it is discussed that by combining 8×8 MIMO with carrier aggregation in future releases of 4G, it may be possible to bring gigabit internet connections to trains.

  • 5.
    Andersson, Daniel
    et al.
    Radarbolaget, Gävle.
    Wallin, Kjell
    Radarbolaget, Gävle.
    Javashvili, Otar
    Högskolan i Gävle, Radio Center Gävle.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    M-Sequence UWB Radar for Industrial Applications2010In: Program of GigaHertz Symposium 2010, March 9-10, at Lund University, 2010Conference paper (Other academic)
    Abstract [en]

    Ultra Wideband Radar has the potential of dramatically improving the control and surveillance of industrial processes in confined areas. An example is the application of UWB radar for surveillance of furnaces for heath treatment of steel billets developed by Radarbolaget in Gävle.

    In our installation at AB Sandvik Materials Technology, we have shown that by using a non-destructive UWB Radar technique it is possible to visualize in real-time the ongoing process inside the furnace behind a 0.5 m thick ceramic wall. Since the operating temperature inside the furnace is 1200 °C, there is today no other known method capable of visualizing the process for the operator of the furnace. The system is therefore designed to sustain high temperatures and powerful electromagnetic disturbances while performing measurement with wide dynamics and high stability.

    The design of this radar is based on the idea of transmitting a continuous m-sequence and then detecting the correlated impulse response (see figure below). The wide bandwidth is a requirement for obtaining high spatial accuracy and resolution but puts further requirements on the design of the antennas and the electronics. Our results show that with this technique it is possible to determine the deformation of the steel billets inside the furnace with an accuracy of less than 5 mm. The radar system is also able to detect deformations in the furnace wall

    The m-sequence radar has many advantages over other UWB radar technologies since it e.g. does not require many analogue components. Its performance is a result of the choice of code length, sampling rate and averaging. However, the resolution is still limited by the impulse response of the analogue antenna (ringing).

    In this paper system parameters that affect the overall performance of an m-sequence radar are reviewed and means of enhancing its performance are discussed.

  • 6.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A preliminary investigation into the direct measurement of intra-ocular light scatter after radial keratotomy1991In: Clinical and experimental optometry, ISSN 0816-4622, E-ISSN 1444-0938, Vol. 74, no 6, p. 204-209Article in journal (Refereed)
    Abstract [en]

    A glare score based on intra-ocular light scatter and a questionnaire-based subjective assessment of glare were determined for 18 patients who had undergone radial keratotomy (RK) two weeks to 27 months previously. Results were compared to those of 15 control subjects. T-tests showed no significant difference in glare experienced under photopic conditions by RK patients and control subjects. There was no systematic relationship between glare scores and the subjective assessment of glare, nor between glare scores or subjective assessment of glare and the time which had elapsed since surgery. However, a weak relationship (r2=0.36) was found between glare scores and absolute refractive error. It was concluded that RK did not produce significant levels of intra-ocular light scatter under photopic conditions (155 lux).

  • 7.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Antenna systems for polarization diversity1997In: Microwave JournalArticle in journal (Refereed)
  • 8.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Comparison of three methods of evaluating glare.1992In: Acta ophthalmologica, ISSN 0001-639X, Vol. 70, no 1, p. 53-9Article in journal (Refereed)
    Abstract [en]

    A Humphrey Automatic Refractor Model 570 was used to measure the impairment of visual acuity for low contrast optotypes as a result of glare for normal subjects and for subjects with cataracts. This was compared with a direct measure of intraocular light scatter as measured by a compensating technique and with a subjective assessment of glare determined by a questionnaire. Only a weak correlation (r = 0.28) was found between the decrease in low contrast letter acuity and intraocular light scatter. The subjective assessment of glare sensitivity was not correlated with the decrease in low contrast letter acuity, but correlated to some extent (r = 0.55) with the measurement of intraocular light scatter.

  • 9.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Comparison of two glare measurement methods through light scattering modeling.1992In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 69, no 7, p. 532-7Article in journal (Refereed)
    Abstract [en]

    Two methods used for evaluation of glare in patients with opacities of the ocular media are compared. One is a low contrast letter test and the other is a direct light scattering meter. Theoretical expressions for the measures obtained from the two different glare tests are derived in terms of the point spread function. Measurements on healthy test persons wearing diffusive glasses with known light scattering properties were in good agreement with the theory. Data from 26 cataractous eyes are presented and discussed in light of the theory.

  • 10.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Dielectric-loaded circular ridge waveguide applicator for hyperthermia1988In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 1, no 6, p. 221-223Article in journal (Refereed)
    Abstract [en]

    An applicator for intracavitary hyperthermia treatment of cancer has been designed and tested. The applicator is a section of a dielectric-loaded circular ridge waveguide closed at both ends to form a transmission cavity. An aperture in the cavity wall can produce a directed heating of a tumor growing in the wall of a body cavity such as the vagina.

  • 11.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Disputing Viking navigation by polarized skylight.1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 21, p. 4754-5Article in journal (Refereed)
    Abstract [en]

    The widely held notion that the Vikings utilized polarization of skylight on overcast days for navigational purposes is demonstrated to have no scientific basis. The use of polarized skylight for navigation under partly cloudfree skies should be treated with caution and skepticism.

  • 12.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Dual polarised multibeam antenna1999In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 35, no 25, p. 2158-2160Article in journal (Refereed)
    Abstract [en]

    A dual polarised four-beam antenna array for the 1850-1990 MHz frequency band is presented. The polarisations are &plusmn;45&deg; to vertical. The antenna has eight inputs corresponding to two orthogonal polarisations and four beams. The return loss and cross-polar isolation for a single Butler beam exceeds 15 and 22 dB, respectively. The radiation pattern is similar to an ideal Butler pattern and the cross-polarisation level is &lt;-21 dB in the beams

  • 13.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Evaluation of a clinical glare test based on estimation of intraocular light scatter.1991In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 68, no 11, p. 881-7Article in journal (Refereed)
    Abstract [en]

    A glare test based on psychophysical estimation of intraocular light scatter and using a flickering, annular glare source was evaluated. The parameters determining the accuracy of the test were studied. In particular the influence of background light and flicker frequency were investigated and optimum values for best accuracy were found. Based on these findings a versatile and simple apparatus was constructed. Forty patients with various degrees of cataract were investigated in a clinical study. Patients, who subjectively experience severe glare problems, indeed show high glare values as measured with the apparatus. No obvious relation between visual acuity and glare score was found. In comparison with glare tests using a stationary glare source the use of a flickering glare source is advantageous in terms of sensitivity and accuracy.

  • 14.
    Beckman, Claes
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Center for Wireless Systems, Wireless@kth.
    Examining the performance of dul band base station antennas: What progress is being made?1996In: Integrating GSM & DCS 1800: Exploiting the business potential of, London: IIR , 1996Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    The recent growth in cellular communications has rapidly created a need for more radio channels. In order to make better use of the available frequency bands new access techniques such as TDMA (Time Division Multiple Access), FDMA (Frequency DMA) and CDMA (Code DMA) have been introduced. Still, the need for new channels is strong and new frequency bands have therefore been allocated for future wireless communication systems. These new communication systems, e.g. the European Personal Communication Network (PCN: 1710-1880MHz) and the North American Personal Communication System (PCS: 1850-1990MHz), use frequencies about twice as high as their predecessors (e.g. AMPS: 824-894MHz and GSM: 880-960MHz). However, at a time when our downtown areas already are littered with basestation antennas, operators are not keen to install more. Therefore, dual-band antennas have gained an increased interest. They would allow the operators to replace two antennas for separate frequency bands with one only, thus, reducing the windload of the towers and perhaps most importantly reducing the cost of installation.

  • 15.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Glare and contrast sensitivity before and after Nd: YAG laser capsulotomy.1994In: Acta ophthalmologica, ISSN 0001-639X, Vol. 72, no 1, p. 27-32Article in journal (Refereed)
    Abstract [en]

    The benefits of Nd:YAG laser capsulotomy on visual performance were evaluated in 13 patients with after-cataract following extracapsular cataract extraction. Besides clinical evaluation we measured: visual acuity, letter contrast sensitivity with and without the presence of a circular glare source (glare angle: 8 degrees). Finally, the patients were asked to evaluate their subjective glare problems. In all patients, visual acuity had decreased markedly compared to measurements 2 months after cataract surgery. Before capsulotomy we observed impaired letter contrast sensitivity and increased intraocular light scatter compared to normals. Following capsulotomy, VA and contrast sensitivity both improved by a factor of 2. The subjective glare problems diminished, although most patients showed minor decreases in intraocular light scatter. The limited glare induced loss of letter contrast sensitivity, present before capsulotomy, remained after treatment. Our study indicates that after-cataract impairs resolution and contrast sensitivity without necessarily causing a marked increase in light scatter as measured at a large angle.

  • 16.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Glare measurements before and after cataract surgery.1993In: Acta ophthalmologica, ISSN 0001-639X, Vol. 71, no 4, p. 471-6Article in journal (Refereed)
    Abstract [en]

    The efficacy of cataract surgery in improving visual performance was evaluated in 10 patients by measuring changes in intraocular light scatter, contrast sensitivity and glare induced visual loss. Two different methods were used to estimate these functions before and after cataract extraction with implantation of a monofocal posterior intraocular lens. By one method intraocular light scattering was assessed. By the other, letter contrast sensitivity and glare induced visual loss were determined. Preoperatively most patients had various glare problems, glare induced visual loss and increased intraocular light scatter. Following surgery the letter contrast sensitivity increased by a factor of 3 or more (mean 4.3). The glare problems diminished or disappeared after surgery, although several patients still had increased intraocular light scattering and glare induced visual loss compared to normals. Postoperatively the contrast sensitivity both with and without glare had increased to a level where the glare induced visual loss did not create any visual problems.

  • 17.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Imaging through light scattering eye media: letter identification1994In: Proc.SPIE, Vol. 2079, p. 2079-2079Article in journal (Refereed)
    Abstract [en]

    The influence of intraocular light scatter on letter identification in the absence and presence of glaring light is studied through computer simulations and simple experiments on healthy test subjects wearing diffusive glasses with known light scattering properties. An explicit expression for the point-spread function of a cataractous eye is used to calculate retinal images. For estimating resolution in the calculated images an assumed neural contrast sensitivity function is needed. The function used is derived from measurements by Campbell and Green. Experimental results are in agreement with theory. The analysis shows that visual acuity is quite insensitive even to substantial diffusive scattering provided that glare sources are not present in the field of view. Comparing measurements of ‘letter size’ with measurements of ‘letter contrast’ the latter method is found to measure intraocular light scattering more sensitively.

  • 18.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Intraocular light scattering in vision, artistic painting, and photography.1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 21, p. 4749-53Article in journal (Refereed)
    Abstract [en]

    Light scattering in the eye is reviewed, and its influence on vision is discussed in some detail. Isotropic scattering and formation of halos around point sources are described with reference to theory and experiments. Artists usually take intraocularly scattered light into account when painting natural scenes. A method to achieve similar effects in photography by the use of diffraction filters in front of the camera lens is demonstrated. A number of photos that illustrate the effects of such filters are shown.

  • 19.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Optical properties of diffractive, bifocal, intraocular lenses.1992In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 31, no 13, p. 2377-84Article in journal (Refereed)
    Abstract [en]

    The resolution of diffractive, bifocal, intraocular lenses was studied with regard to pupil displacement and diameter size through computer simulations, bench measurements, and patient vision-acuity measurements. Good agreement was obtained between these three methods of investigation. In particular, we find that pupil displacements of the order of 1 mm reduce the resolution considerably for these lenses.

  • 20.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Performance analysis of applying up-link estimates in the down-link beamforming using a dual polarized array2000In: VTC2000-Spring. 2000 IEEE 51st Vehicular Technology Conference Proceedings (Cat. No.00CH37026), 2000, Vol. 2, p. 690-694 vol.2Conference paper (Refereed)
    Abstract [en]

    Most of the current and future mobile communications systems are frequency duplex systems, i.e. the up- and down-link are separated in frequency. Since the effect of the radio channel is not constant with frequency, this potentially limits the capacity gain using adaptive antennas. We use 150 MHz measurement data to simulate adaptive beamforming in a suburban environment. The information from the up-link at 1741 MHz is used for beamforming at this frequency as well as on the down-link at 1839 MHz. Our results show a reduction in C/I improvement of up to 10 dB between the up- and down-link

  • 21.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Plausibility of assuming ideal arrays for direction of arrival estimation1996In: IEEE Antennas and Propagation Society International Symposium. 1996 Digest, 1996, Vol. 2, p. 1364-1367 vol.2Conference paper (Refereed)
    Abstract [en]

    In order to fulfil the increasing demands on capacity and coverage of mobile communication systems smart or intelligent antennas have been suggested. These antennas increase the spectral efficiency of a wireless system by using arrays of antenna elements to shape RF signals in particular directions. Generally, smart antennas can be divided into two approaches: switched multi-beam and adaptive. Adaptive antennas utilize sophisticated signal processing algorithms to continuously distinguish between the desired signal, multipath and interfering signal as well as to calculate their direction of arrival (DOA). This makes it possible to smoothly track users with main lobes and interferers with nulls and thereby constantly maximizing the SINR (signal-to-interference and noise ratio). The DOA is one of the most important parameter for an adaptive antenna system to estimate. It is also the main subject of this paper. We establish whether or not it is plausible to assume the array to be ideal (which is often assumed in array signal processing theory) when the received signals are actually collected with a physical array consisting of standard folded dipoles. In doing so we first measured the element patterns (or steering vectors) of a twelve element antenna array. The results were then used in array signal processing simulations. The performance of two DOA estimation algorithms, MUSIC and ESPRIT, are studied and compared.

  • 22.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Polarization diversity in CDMA1998In: IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.98CH36, 1998, Vol. 4, p. 2236-2239 vol.4Conference paper (Refereed)
    Abstract [en]

    Since down-town areas are rapidly becoming littered with antennas, it is of great interest for operators to keep their contribution of antennas to a minimum. Dual polarized antennas may be a solution to reduce the number of antennas, and still obtain a satisfactory antenna diversity gain. However, in order for them to be competitive with space diversity configurations, the diversity gain obtained using dual polarized antennas must be comparable to the that obtained from space diversity. The purpose of this study is to analyse the diversity performance of a DS-CDMA system employing /spl plusmn/45 /spl deg/ dual polarized antennas, for different environments. A system model is presented and analysed.

  • 23.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    The 'light scattering factor'. Importance of stimulus geometry, contrast definition, and adaptation.1995In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 36, no 11, p. 2313-7Article in journal (Refereed)
    Abstract [en]

    PURPOSE: Paulsson and Sjöstrand have suggested that the light scattering factor (LSF) can be estimated by using the equation: LSF = L/E (M2/M1-1). Here L is the space average luminance of the target, E is the illuminance of the glare source, and M2 and M1 are modulation contrast thresholds in the presence and absence of the glare source. To compensate for change of adaptation. Abrahamsson and Sjöstrand later modified the above equation by introducing a correction factor (CF): LSF = L/E ((CF) (M2/M1-1). The purpose of this study is to analyze the validity of the above equations.

    METHODS: The importance of stimulus geometry, contrast definition, background luminance, and glare illumination is studied through theoretical analysis and comparison with earlier studies. Stimulus geometry and contrast definition are studied through optical modeling. Adaptation is modeled according to the laws of Weber and DeVries-Rose.

    RESULTS: The choice of contrast definition may corrupt the result by a factor of 2. At background luminance levels above approximately 10 cd/m2, the Paulsson-Sjöstrand equation agrees well with theory. At lower background levels, the Abrahamsson-Sjöstrand equation is used with correction factors derived from adaptation measurements. Using this equation and earlier published data from glare testing performed at 2 cd/m2, the results are found to be in fair agreement with the light scattering theory.

    CONCLUSIONS: Glare testing using the Paulsson-Sjöstrand equation is found to be valid as long as the measurements are performed at high luminance levels (above 10 cd/m2), with targets of low spatiotemporal frequencies (e.g., 2 cpd and 1 Hz) and with the use of a properly chosen definition of contrast. At lower luminance levels, the Abrahamsson-Sjöstrand equation may be used with well-derived correction factors.

  • 24.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    The performance of polarization diversity antennas at 1800 MHz1997In: IEEE Antennas and Propagation Society International Symposium 1997. Digest, 1997, Vol. 2, p. 1368-1371 vol.2Conference paper (Refereed)
    Abstract [en]

    Cellular radio systems have been in operation since the early 1970s and are experiencing tremendous growth. However, a major problem for cellular systems is the multipath, or short-term fading. One way to combat multipath fading on the uplink is to implement a diversity scheme at the base station. Until recently this was done by using two separate antennas positioned some distance apart from each other. The disadvantage with this method, however, is that the antennas have to be separated by several wavelengths to receive "independently fading" signals. Thus the antenna systems become large. With polarization diversity two antennas are also used but there is no need for any physical separation between them. Instead the two antennas are polarized in two orthogonal polarizations, e.g., horizontal/vertical or /spl plusmn/45 degrees slanted. In a study by Lotse et al. (see IEEE VTS 46th Vehicular Technology Conference Proceedings, vol.3, p.1643-46, 1996) it was found that space diversity yields typically about 1 dB better "diversity gain" than polarization diversity. However, how different antenna parameters affect the results has to our knowledge never been studied. The authors aim to fill this void.

  • 25.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Verifying 3G License Coverage Requirements2011In: Advances in Vehicular Networking Technologies / [ed] Miguel Almeida, InTech , 2011, p. 339-356Chapter in book (Other academic)
    Abstract [en]

    In the beginning of the 21’st century, the 3rd generation mobile phone systems, 3G, were introduced all around the world. In most countries, spectrum for this technology was allocated through some kind of licensing procedure. In Europe, the prevailing approach was to allocatespectrum through auctions, a process which led to a situation where the European operators found themselves committed to pay a staggering 130Bilion Euros for their 3G licenses.However, in most European countries, the fee was not the only obligation put on thelicensee: A coverage, “roll-out” requirement was in many cases also connected to the license(Northstream, 2002). Typically, these coverage requirements required that the licenseescover a certain area at a certain point in time after that the licenses had been awarded.In order for the regulators to verify that the licensees had met the coverage requirement and,hence, complied with the regulation, a method for coverage verification was needed. Suchmethods have therefore since then been developed by several European regulators (e.g. PTS2004; ECC 2007). In this book chapter we describe some general underlying consideration for the verification of radio coverage in UMTS systems and in particular we describe the Swedishmethodology developed by the Swedish Telecom regulator Post & Telestyrelsen (PTS).

  • 26.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wave propagation in curved road tunnels1998In: IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.98CH36, 1998, Vol. 4, p. 1876-1879 vol.4Conference paper (Refereed)
    Abstract [en]

    In the early seventies much work was done in order to understand the propagation loss of UHF waves in rectangular mine tunnels, using either waveguide methods or image techniques based on geometrical optics (GO). A simple and accurate model is needed for planning the deployment of mobile phone networks. The method presented a simple GO extension to the standard hybrid waveguide solution.

  • 27.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Bergek, Martin
    Wireless communication system for moving vehicles2013Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A wireless communication system for a moving vehicle, such as trains, is disclosed. The system includes at least one router in the moving vehicle for receiving and transmitting wireless voice communication and data communication to and from a stationary communication server outside the moving vehicle through an exterior mobile network. Further, the system includes at least one femtocell provided within the moving vehicle, and being connected to the router for wireless transferring of wireless voice communication and data communication between mobile terminals within the moving vehicle and the router. The at least one femtocell is controlled by a femtocell controller directly or indirectly connected to the communication server outside the moving vehicle.

  • 28.
    Beckman, Claes
    et al.
    Center for RF-Measurement Technology, University of Gävle.
    Belkow, Elena
    Post och Telestyrelsen.
    Eklund, Lars
    Post och Telestyrelsen.
    Landmark, Urban
    Post och Telestyrelsen.
    Wirdemark, Per
    Canaima International.
    Verifying 3G License Requirements: some Preliminary Swedish Results2008In: The 68th IEEE Vehicular Technology Conference: VTC2008-Fall, IEEE , 2008, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In the year 2000, the Swedish Telecom regulator “Post&Telestyrelsen” (PTS) granted in a “beauty contest” four licenses for operation of 3G mobile networks. Through this process, the licensees committed themselves to cover 8.860.000 inhabitants of the Swedish population. In order to verify the coverage and confirm compliance with the license requirements, PTS, developed a test procedure in close collaboration with the licensees.

    The present paper gives an overview of the considerations behind the design of the test method and presents some preliminary results. Today all Swedish 3G operators comply with the licence requirement and it is concluded that a method for verifying the requirement accepted by the licensees is an important tool for successful licensing of spectrum and fulfilment of licensing obligations.

  • 29.
    Beckman, Claes
    et al.
    University of Gävle.
    Eklund, Lars
    Karlsson, Bo
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wirdemark, Per
    Verifying 3G licence requirements when every dB is worth a billion2006In: First European Conference on Antennas & Propagation: EuCAP 2006 / [ed] H. Lacoste & L. Ouwehand, 2006, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In the year 2000, the Swedish Telecom regulator: “Post&Telestyrelsen”, PTS, granted in a “beauty contest” four licenses for operations of 3G systems. To verify the coverage and the license requirements, PTS, has developed a test procedure where the field strength of the primary Common Pilot Channel, CPICH, is measured in a drive test. Designing such a test constitutes a number of challenges mainly due to the fact that in 3G the accuracy in the measurement needs to be extremely high since even a small systematic error of ~1dB could in Sweden have the consequence that each operator would have to build an extra +1000 sites at a staggering cost of ~1billion SEK!

    The present paper gives an overview of the considerations behind the design of the test method used for verification of the 3G licence requirements in Sweden.

  • 30.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Garcia, J.
    Alfredsson, S.
    Brunström, A.
    On the impact of velocity on the train-to-earth MIMO propagation channel: Statistical observations and qualitative analysis2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, IEEE conference proceedings, 2017, p. 1865-1866Conference paper (Refereed)
    Abstract [en]

    We provide measured data collected from 97 trains completing over 7000 journeys in Sweden showing that the throughput over LTE is impacted by train velocity. In order to explain these observations we assume that the underlying causes can be found in the implementation of the MIMO system into LTE Rel. 8 and the diffuse scattering of signals from ground reflections.

  • 31.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Karlsson, B.
    The story of Allgon: HF, VHF, cellular and microwave antennas during allmost 60 years2013In: 2013 7th European Conference on Antennas and Propagation (EuCAP), IEEE , 2013, p. 3171-3173Conference paper (Refereed)
    Abstract [en]

    Allgon, 'The Antenna Specialist', was a leading international design house and manufacturer of antennas for almost 60 years. The company was started in Stockholm in 1947 under the name of 'Antennspecialisten', by the Swedish engineer Torbjörn Cramner and his wife Veronica. In 1951 the company moved to Åkersberga north of Stockholm where its main facilities where located until the late 90's. During its life time the company designed and produced antennas for HF, VHF, Cellular and Microwave frequency bands, and for military, emergency, private and cellular radio systems. The company was in 2004 acquired by the US based company Powerwave but still today many of its original antenna designs are in production and many thousands of its base station antennas for mobile networks are still deployed all around the World.

  • 32.
    Beckman, Claes
    et al.
    Högskolan i Gävle.
    Klahr, Stefan
    Ett ödesval för regionen2009In: Gefle Dagblad, ISSN 1103-9302, no 6 februariArticle in journal (Other (popular science, discussion, etc.))
  • 33.
    Beckman, Claes
    et al.
    University of Gävle.
    Lindmark, Björn
    Base station antennas for mobile communications2007In: 2007 IEEE International Symposium on Antennas and Propagation, 2007Conference paper (Other academic)
    Abstract [en]

    This course gives the participants a general overview of the application, implementation and design of current and future base station antennas for mobile communications. It is aimed at microwave, RF- and antenna engineers in the wireless area, but also useful for researchers looking for relevant research topics and system engineers needing a deeper understanding of the antenna component of their system. The course explains underlying theoretical and practical implementation aspects of base station antennas in mobile communication networks of today and the future.

    The course is divided into three main parts:

    (i) System Aspects,

    (ii) BTS Antenna Design,

    (iii) Diversity and MIMO

    In the first part the fundamental parameters of a base station antenna are discussed in the context of radio network design. In particular we discuss parameters such as gain, radiation patterns, frequency bands and power handling and put them in the context of cell planning, propagation and capacity.

    In the second part a general overview of base station antenna design is given. In particular the design aspects of radiators, feed networks and reflectors are discussed. Furthermore, a general discussion of array synthesis for base station antennas is given.

    In the final part of the course we give an overview of the underlying theory of diversity and MIMO systems. In particular we discuss the requirements that these systems put on the base station antennas in order to be able to deliver the data rates expected from WiMAX and the long term evolution of 3G systems.

  • 34.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Lindmark, Björn
    The evolution of base station antennas for mobile communications2007In: International Conference on Electromagnetics in Advanced Applications: ICEAA 07, IEEE conference proceedings, 2007, p. 85-92Conference paper (Refereed)
    Abstract [en]

    This paper gives a general overview of the design of base station antennas for mobile communications. It explains underlying theoretical and practical implementation aspects in mobile communication networks of today and the future. In the first part the fundamental parameters of a base station antenna are discussed in the context of radio network design. In particular we discuss parameters such as gain, radiation patterns, frequency bands and power handling and put them in the context of cell planning, propagation and capacity. In the final parts of the paper we give an overview of the underlying theory of diversity and MIMO systems.

  • 35.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lindmark, Björn
    Ahl´berg, Mikael
    Dual Band Base Station Antenna Systems1998In: Broad Band Radio Access, Linköping, 1998, p. 69-74, article id 9Conference paper (Other academic)
    Abstract [en]

    An analysis of the possibilities of using dualband antennas in cellular radio is presented. Results from simultaneous measurements at 900 MHz and 1800 MHz are presented and analyzed. Based on the measured results, a dual polarized, dual band base station antenna has been designed. Such an antenna proveides the opportunity to replace a 4 antenna space diversity installation with a single antenna, thereby reducing costs and tower space.

  • 36.
    Beckman, Claes
    et al.
    Chalmers University of Technology, Sweden.
    Lundgren, L.
    Roos, D.
    Dielectric-loaded circular ridge waveguide applicator for hyperthermia1988In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 1, no 6, p. 221-223Article in journal (Refereed)
    Abstract [en]

    An applicator for intracavitary hyperthermia treatment of cancer has been designed and tested. The applicator is a section of a dielectric-loaded circular ridge waveguide closed at both ends to form a transmission cavity. An aperture in the cavity wall can produce a directed heating of a tumor growing in the wall of a body cavity such as the vagina.

  • 37.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Nilsson, Kristoffer
    The Technical and Economic Consequences of Protecting GSM-R in Sweden2016In: 2016 IEEE 83RD VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    A number of protection criteria were implemented by the Swedish regulator PTS in order to protect the GSM-R operations in Sweden. In order to protect the GSM-R receivers from interference and blocking, two different constraints were implemented: First, a limitation of the "out-of-band" emissions from the mobile operators' existing base stations operating in the 900MHz band was implemented. Secondly, a limitation of the aggregated power received over the railroad within the operator's spectrum allocation in the 900 band was added. In this study, the background of these protection criteria is presented and their technical and economic consequences estimated. Regarding "out-of-band" emissions from base stations, four alternative protection levels have been investigated: -92, -95, -98 and -107 dBm. It is found that in order to meet these requirements, safety distances of between 280 and 1200m need to be introduced, which means that between 1500 and 2700 base stations would be needed to be taken out of service. In order to avoid blocking, the received power over the embankment from each base station within the public GSM band would also be needed to be limited. The consequences of limiting the received power levels to either -10, -23 or -40 dBm were here investigated. Given the level of blocking protection, it is found that between 1085 and 2330 base stations within the vicinity of the railway track would be affected and possibly needed to be shut down To avoid causing interference, all operators - with the exception of Hi3G - may limit their "out-of-band" emissions by installing filters on the base stations. The cost of such installations is estimated at 50 000 SEK per base station. Depending on the protection level that is applied, the estimated total cost for the mobile operators is between 67 and 113 million SEK (about 12 million Euros). In order to protect the GSM-R receivers from blocking, some 3500 locomotives would need to be equipped with additional filters at a total cost of around 130 million SEK (about 14 million Euros).

  • 38. Beckman, Claes
    et al.
    Sjöstrand, J
    Confocal fundus imaging with a scanning laser ophthalmoscope in eyes with cataract.1995In: British Journal of Ophthalmology, ISSN 0007-1161, E-ISSN 1468-2079, Vol. 79, no 10, p. 900-4Article in journal (Refereed)
    Abstract [en]

    AIMS/BACKGROUND: The study aimed to determine the influence of increased intraocular light scatter on the contrast in scanning laser ophthalmoscope (SLO) images and to examine to what extent SLO images can visualise the fundus through media opacities due to cataract.

    METHODS: Intraocular light scatter was estimated from measurements of letter contrast sensitivity before and after cataract surgery in five eyes. SLO images were obtained before and after surgery using confocal apertures of 1, 2, 4, and 10 mm, at laser wavelengths of 633 and 780 nm. Visibility of the fundus was determined by measurements of retinal contrast. SLO images were compared with standard fundus photographs.

    RESULTS: SLO images obtained before surgery revealed details of the retina that were unresolvable in the fundus photographs because of light scattering. By using one of the three smallest apertures, image contrast was further improved. However, no simple relations between aperture size, estimated light scatter, and image contrast could be found.

    CONCLUSION: SLO imaging was found to be superior to fundus photography for viewing the retina in eyes with cataract. Owing to the inhomogeneous nature of cataracts, the optimal choice of confocal aperture and laser wavelength is not simple and must be individualised.

  • 39.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Smith, Gregory
    Shared Networks: Making Wireless Communications Affordable2005In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 12, no 2, p. 78-85Article in journal (Refereed)
    Abstract [en]

    In the wake of the substantial financial commitments incurred by European and other UMTS network operators in the form of licence fees, licensees have turned to network sharing as a means of reducing the capital requirements needed to bring 3G services to market. The reception from European regulators has been mixed, due to concerns that this inhibits competition, slow buildout, or otherwise result in reduced consumer benefits. The authors believe that the generic product life cycle model provides insights that indicate that network sharing, within an appropriately constructed regulatory framework, is not a threat to vigorous competition in the 3G industry, and in fact is one of the keys to stimulating the development of advanced, ubiquitous, affordable services.

  • 40.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Smith, Gregory
    The Benefits of network Sharing2005In: Radiovetenskap och Kommunikation: RVK 2005, 2005, p. 147-151Conference paper (Refereed)
  • 41.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Thaung, Jörgen
    Sjöstrand, Johan
    In-vitro lens scatter measurements and glare testing1994Conference paper (Other academic)
  • 42.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Antenna Tilt Load Balancing in Self-Organizing Networks2013In: International Journal of Research in Wireless Systems, ISSN 2320-3617, Vol. 2, no 1, p. 21-26Article in journal (Other academic)
    Abstract [en]

    Base station antenna tilt is a powerful tuning parameter in traditional cellular network optimization. With theintroduction of Self-Organizing Networks (SON), this parameter may now be used also in the context of self-optimization.One envisioned scenario is load balancing (LB), where the coverage shaping properties of the antenna radiation pattern canbe used to control the cell borders. In this paper, a generalized framework for antenna tilt LB is presented and discussed. Inorder to assess the performance of antenna tilt as a tool for load balancing, simulations are performed to determine theeffect of tilt angle, vertical beamwidth and handover offset. The results show that there is a direct relation between theseparameters and the number of users that can be shifted towards neighboring cells. In conclusion, it is found that usingantennas with narrow vertical beamwidths together with small hand over offsets is an efficient way of performing loadbalancing but results also in high SIR variations.

  • 43.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Base station antenna tilt for load balancing2013In: 2013 7th European Conference on Antennas and Propagation (EUCAP), New York: IEEE , 2013, p. 2039-2043Conference paper (Refereed)
    Abstract [en]

    The coverage shaping and interference reduction ability of base station antenna tilt are important tools in cellular network optimization. Through tilt changes, the coverage area of a serving cell may also be either reduced or expanded. Therefore, antenna tilt has the potential to be used for load balancing purposes. This paper gives an overview of base station antennas performance and antenna tilt. Simulations are performed in order to determine the impact of tilt changes when used for load balancing. The results show that while antenna tilt load balancing can improve the Grade of Service (GoS) in a congested cell, it will also influence the user bit rates and total cell throughput for both the congested cell and the neighbors.

  • 44.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Base Station Antenna Tilt for Load Balancing and Potential use in Self-Optimizating Networks2013Conference paper (Other academic)
    Abstract [en]

    The coverage shaping and interference reduction ability of base station antenna tilt are important tools in cellular network optimization. Through tilt changes, the coverage area of a serving cell may also be either reduced or expanded. Therefore, antenna tilt has the potential to be used for load balancing purposes. With the introduction of Self-Organizing Networks (SON) in the mobile communications, this parameter may now be used also in the context of self-optimization, to address the common situation where traffic has an uneven spatial distribution between serving cells. This work gives an overview of base station antennas and antenna tilt. Simulations are performed in order to determine the impact of tilt changes when used for load balancing. The effect of tilt angle, vertical beam width and handover offset are analyzed also. The results show that there is a direct relation between these parameters and the number of users that can be shifted towards neighboring cells. In conclusion, it is found that using antennas with narrow vertical beam widths together with small hand over offsets is an efficient way of performing load balancing but results also in high SIR. Although antenna tilt load balancing can improve the Grade of Service (GoS) in a congested cell, it will also influence the user bit rates and total cell throughput for both the congested cell and the neighbors.

  • 45. Braun, Christian
    et al.
    Engblom, Gunnar
    Beckman, Claes
    Allgon System AB, Sweden.
    Evaluation of antenna diversity performance for mobile handsets using 3-D measurement data1999In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 47, no 11, p. 1736-1738Article in journal (Refereed)
    Abstract [en]

    An evaluation of two-branch antenna diversity on mobile telephones is performed in the presence of head and hand phantoms to model the influence of the user. Two mobile telephone prototypes for the 1800-MHz band are considered. The evaluation is done by measuring the three-dimensional (3-D) complex radiation patterns from each antenna with the prototypes positioned near the phantom head and hand (i.e., in talk position) and calculating the diversity performance for three different scenarios of the incoming field. The two-branch antenna setups on both prototypes produce a calculated diversity gain of about 9 dB for selection diversity at the 99% reliability level.

  • 46. Elofsson, C.
    et al.
    Karlsson, C.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    On the interference between digital terrestrial television and mobile broadband in the Swedish 800 MHz band2014In: IEEE International Symposium on Electromagnetic Compatibility, IEEE conference proceedings, 2014, p. 528-532Conference paper (Refereed)
    Abstract [en]

    In 2011, the Swedish regulator (PTS) invited all interested parties to apply for licenses to use radio transmitters in the 790-862 MHz frequency band. The licenses are service and technology neutral but all licensees are expected to provide Mobile Broadband (MBB) services using the LTE standard. In order to protect the Digital Terrestrial Television (DTT) services provided in the adjacent bands from interference, PTS imposed a number of technical conditions on the licensees. Here, a brief overview of these technical conditions is given, and a measurement campaign in order to investigate the interference between MBB and DTT services was conducted. The measurements show that the technical requirements indeed provide the additional protection for DTT reception from the MBB downlink as envisioned by PTS. However, the measurements also indicate that MBB services may be suffering from interference from TV Channel 60 within a radius of about 5km from the DTT transmitter. One year after the rollout of MBB services in the Swedish 800MHz band, very few complaints had been received by the regulator. This may be explained with that in cases where interference with the TV reception did occur, the licensees have provided additional filters for free. Another reason may be that to date only a low number of terminals including the 800 band have yet reached the Swedish market and worse interference problems from the MBB uplink may still appear.

  • 47. Garcia, J.
    et al.
    Alfredsson, S.
    Brunstrom, A.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Train Velocity and Data Throughput - A Large Scale LTE Cellular Measurements Study2017In: 2017 IEEE 86th Vehicular Technology Conference (VTC-Fall), IEEE conference proceedings, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Train-mounted aggregation routers that provide WiFi access to train passengers and bundle external communication over multiple cellular modems&#x002F;links is an efficient way of providing communication services on trains. However, the characteristics of such systems have received limited attention in the literature. In this paper we address this gap by examining the communication characteristics of such systems based on a large data set gathered over six months from an operational Swedish railway system. We focus our examination on the relationship between per link throughput and train velocity. Using Levenberg- Marquardt non-linear regression a noticeable critical point is observed for an RS-SINR of around 12 dB. At this point the impact of increased train velocity on per link throughput changes from being negative to becoming positive. Using a machine learning approach we also explore the relative importance of several observed metrics in relation to per link throughput.

  • 48. Halim, Humam
    et al.
    Prasad, Sathyaveer
    Högskolan i Gävle, Ämnesavdelningen för elektronik.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Evaluation of a Near Field Scanner for TRP and Radiation Pattern Measurements of GSM Mobile Phones2009In: 3rd European Conference on  Antennas and Propagation, 2009. EuCAP 2009., Berlin: EUCAP2009 , 2009, p. 2207-2211Conference paper (Other academic)
    Abstract [en]

    In this paper a new tool for estimation of the radio performance of terminal antennas in terms of Total Radiated Power, TRP is tested and evaluated. The tool is known as Lab Express and is developed by the Canadian company EMSCAN.  The results from measurements performed with the Lab Express are compared with of the radiation patterns and total radiated power (TRP) estimates, measured with a CTIA approved Satimo SG24 chamber.

        The TRP and radiation pattern measurements are performed on 10 commercially available mobile phones at GSM 900 and GSM 1800 frequency bands. The dependency of the measured TRP on the positioning of the mobile phone on EMSCAN is also tested. Our results indicate that the TRP measured with Lab Express is well correlated with the results obtained from the Satimo SG24 chamber even though the Lab Express equipment seem to over estimate the TRP with on average about 4dB at 900MHz and about 1.3dB at 1800MHz.

  • 49.
    Händel, Peter
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Prasad, Sathyaveer
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Beckman, Claes
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Maximum likelihood estimation of reverberation chamber direct-to-scattered ratio2009In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, no 25, p. 1285-U24Article in journal (Refereed)
    Abstract [en]

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

  • 50.
    Ikram, Amna
    et al.
    Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap.
    Beckman, Claes
    University of Gävle.
    Irmscher, Stefan
    Laird Technologies.
    Design and Development of a Multiband Loop Antenna for Cellular Mobile Handsets2011In: IEEE International Workshop on Antenna Technology, 2011, p. 251-254Conference paper (Refereed)
    Abstract [en]

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

12 1 - 50 of 65
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