| 1. |
- Harrysson, Fredrik, et al.
(author)
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The composite channel method : Efficient experimental evaluation of a realistic MIMO terminal in the presence of a human body
- 2008
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In: 2008 IEEE 67th Vehicular Technology Conference-Spring, VTC. - 1550-2252. - 9781424416455 ; , s. 473-477
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Conference paper (peer-reviewed)abstract
- The immediate environment of the transmit (TX) and receive (RX) antennas, including the antenna casings and the users holding the antennas, has a strong impact on the propagation channel and thus on wireless systems. In this paper we experimentally evaluate a method that synthetically combines double-directional measurements of the propagation channel (without the user influence) with measured antenna patterns of antennas-plus-users, by comparing obtained sample results with direct measurements in the same environment. The measurements are done for a static microcell 8×4 MIMO scenario at 2.6 GHz. A realistic user phantom was used together with a test terminal prototype with four antenna elements, and a number of different configurations and orientations of the phantom were tested. In average over all test cases, the mean signal power deviation between composite channel method and measurements was well within 1 dB. The composite method shows 6% higher terminal antenna correlation but similar statistical distributions as the measured. The differences between the model and measurements for the strongest eigenvalue (relevant for MRC combining) was found to be within 1 dB above 10% outage level. Relative deviations in the ergodic MIMO capacity were smaller than 10%.
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| 2. |
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| 3. |
- Harrysson, Fredrik, et al.
(author)
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Dual antenna terminals in an indoor scenario
- 2006
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In: [Host publication title missing]. - 1550-2252. ; 6, s. 2737-2741
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Conference paper (peer-reviewed)abstract
- The performance of two different dual antenna hand-held test mobile terminals has been investigated in a realistic indoor office environment and scenario, with respect to antenna performance, diversity combining and Shannon MIMO channel capacity. Measurements of a 2times2 MIMO channel at 1877.5 MHz (narrowband) were performed using a dual-polarized base station antenna. Analyses show that diversity gains, using ideal selection combining and maximum ratio combining, between 0.7 and 4.6 dB was achieved at the 10% outage probability level. Ideal dual-side beamforming (single branch) gives up to 3.3 dB capacity gain compared to single antenna systems at SNR less than 10 dB, however, decreases with rising SNR. Dual branch MIMO capacity gain is only significant at higher SNR above 10 dB. In addition, horizontal polarization at the base station was found to outperform vertical polarization in this scenario
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| 4. |
- Harrysson, Fredrik
(author)
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Modeling multiple antenna systems in realistic environments - a composite channel approach
- 2009
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Licentiate thesis (other academic/artistic)abstract
- For evaluation of specific antenna arrangements in wireless communication systems we need physical channel models that take into account the directional domain. Here we propose a practical approach to wireless channel modeling in, particularly, mobile communication systems, by using an assumption that the channel can be divided into separate parts or regions that can be treated and modeled individually. The idea is that the antenna part of the channel is the part considered in the design of the user equipment and can be characterized by a single measurement of each design, while the propagation part of the channel can be characterized separately, independent of the user equipment, based on generic channel sounder measurements with, as far as possible, open areas around the transmitter and the receiver antennas. For more complex antenna environments we may imagine intermediate scattering regions of the channel model between the antenna parts and the propagation part, that perhaps can or cannot be handled separately, e.g., a mobile phone user body, an office desk, a vehicle etc. A first step in evaluating such a composite model approach is to verify the validity of link simulations were the mobile phone antennas together with the user can be handled as a super-antenna with its aggregate far-field pattern to be combined with a directional channel model in a classical way. This is presented in Paper IV and the method is in its extensible form referred to as the Composite Channel Method. It is found that this method, as we expected, work well for statistical performance evaluation of diversity or spatial multiplexing. An extension of the composite approach is outlined with an attempt to find a simple yet accurate directional scattering model for the user hand and body that still catch the proper influence of antenna efficiencies, fading statistics and correlation. Such an approach is tested and presented for a single antenna inside a car in Paper II. A full ray-tracing model as the one presented in Paper I and also used in Paper II can capture all important eects of a propagation environment also for multiple antennas systems to the price of high complexity of the geometrical model. In Paper III a first investigation of user influence on an indoor 2x2 MIMO link is performed based on a simple measurement setup and the diversity performance is evaluated. In Paper IV the first step of the composite channel approach is evaluated with respect to MIMO by channel measurements including user influence in static outdoor-to-indoor and indoor scenarios. The approach is verified for statistical properties such as antenna correlation and MIMO eigenvalue distributions. It is found that the presence of the user, apart from introducing hand and body absorption and mismatch that increases the path loss, also increases the correlation between the antenna elements and, thus, slightly decreases potential MIMO capacity.
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| 5. |
- Riback, Mathias, et al.
(author)
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Carrier frequency effects on path loss
- 2006
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In: [Host publication title missing]. - 1550-2252. ; 6, s. 2717-2721
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Conference paper (peer-reviewed)abstract
- To study the carrier frequency effects on path loss, measurements have been conducted at four discrete frequencies in the range 460-5100 MHz. The transmitter was placed on the roof of a 36 meters tall building and the receive antennas were placed on the roof of a van. Both urban and suburban areas were included in the measurement campaign. The results show that there is a frequency dependency, in addition to the well known free-space dependency 20 log10(f), in most of the areas included in the measurements. In non line of sight conditions, the excess path loss is clearly larger at the higher frequencies than at the lower. A model capturing these effects is presented
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