| 1. |
- Almers, Peter, et al.
(författare)
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The effect of receiver antenna array horizontal orientation on MIMO channel capacity
- 2003
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Ingår i: [Host publication title missing]. - 1090-3038. - 0780377575 ; 1, s. 34-38
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Konferensbidrag (refereegranskat)abstract
- In multiple-input multiple-output (MIMO) systems the horizontal orientation of a linear array has, in some situations a large influence on the available channel capacity. In this paper, we investigate the effect of horizontal array orientation on channel capacity, eigenvalue distribution and antenna complex correlation coefficient in such systems. We present channel measurements in an office corridor environment for a 6/spl times/6 MIMO system and compare the capacity results to those of a physical and non-physical model based on the measurements. The results show that under LOS conditions the channel capacity can vary significantly depending on the receiver array orientation in the horizontal plane.
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| 2. |
- Bizjajeva, Svetlana, et al.
(författare)
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Mobile positioning in MIMO system using particle filtering
- 2007
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Ingår i: 2007 IEEE 66TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5. - 1090-3038. - 9781424402632 ; , s. 792-798
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Konferensbidrag (refereegranskat)abstract
- his paper represents the results of a simulation study on positioning of a mobile unit in MIMO settings. We used two different approaches for modeling the mobile movement, combined with a simple geometrical model for the MIMO channel. Three different particle filters were implemented for the position estimation. The results show that all three filters are able to achieve estimation accuracy required by Federal Communication Commission. The dimensionality of the particle filter state space is independent of the number of antenna elements, and it is possible to increase the number of antennas and use more sophisticated channel models without changing the filtering algorithms.
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| 3. |
- Choi, Y S, et al.
(författare)
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Fast antenna selection algorithms for MIMO systems
- 2003
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Ingår i: IEEE 58th Vehicular Technology Conference, 2003. VTC 2003-Fall.. - 1090-3038. - 0780379543 ; 3, s. 1733-1737
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Konferensbidrag (refereegranskat)abstract
- We consider the capacity of multiple-input-multiple-output (MIMO) systems with reduced complexity. One link end uses all available antennas, while the other chooses the "best" L out of N antennas. The selection of the optimum antenna subset requires an exhaustive search of all possible combinations, involving (/sub L//sup N/) computations of determinants of size L /spl times/ L, which can become prohibitively complex. In this paper, we suggest a class of fast antenna selection algorithm that are based on the correlation or mutual information between the signals at the different antenna elements. It requires less than N/sup 2/ vector multiplications and thus leads to dramatic savings on the computation time. Its performance is very close to the optimum selection procedure: the capacity penalty is less than l bit/s/Hz for the analyzed examples. The algorithm thus offers the possibility of almost-optimum selection even in fast-changing environments.
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| 4. |
- Foroughi, Farzad, et al.
(författare)
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Low complexity channel estimation for LTE in fast fading environments for implementation on multi-standard platforms
- 2010
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Ingår i: IEEE 72ND VEHICULAR TECHNOLOGY CONFERENCE FALL 2010. - 1090-3038.
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Konferensbidrag (refereegranskat)abstract
- In this paper a number of low-complexity channel estimator structures tailored to the needs of LTE terminals have been investigated. The focus has been on the algorithms exhibiting reduced complexity while providing an acceptable level of performance. To design these estimators other factors such as interoperability with another OFDM-based standard, DVB-H, in a multi-standard environment have been taken into account. The key underlying parameter has been exploiting the pilot pattern in LTE providing the possibility of minimal filtering in time domain while exhibiting an acceptable level of performance in fast fading environments.
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| 5. |
- Hult, Tommy, et al.
(författare)
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MIMO applications for interference mitigation in multiple high altitude platform WCDMA systems
- 2009
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Ingår i: 2009 IEEE 70Th Vehicular Technology Conference Fall, Vols 1-4. - Anchorage : IEEE. - 1090-3038. ; , s. 1172-1176
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the possibility of multiple HAP coverage of a common cell area. In particular we study the uplink system performance since it is considered as a worst case scenario. In order to obtain further enhancement (interference mitigation) we also apply space-time diversity techniques, such as Single-Input Multiple-Output (SIMO) receive diversity or Multiple-Input Multiple-Output (MIMO) diversity, to improve the spectrum reuse in the multiple HAP scenario. We will show the level of improvement using SIMO and MIMO algorithms, the practical limits on the number of HAPs and SIMO/MIMO system dimension in response to traffic demands and the type of service used.
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| 6. |
- Kapetanovic, Dzevdan, et al.
(författare)
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Linear Precoders for Parallell Gaussian Channels with Low Decoding Complexity
- 2011
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Ingår i: IEEE 74th Vehicular Technology Conference (VTC). - 1090-3038. ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Consider the transmission of complex-valued symbols over N parallell channels in additive white Gaussian noise. It is well known that linear precoding of the complex-valued data improves system performance (e. g. symbol error rate, information rate, MMSE, etc.) at a cost of increased decoding complexity at the receiver. This work constructs precoders that are constrained to have a decoding complexity which equals that of no precoding, while still improving the system performance significantly compared with the no precoding case. This is achieved by designing the precoder so that it precodes the complex data streams separately, by utilizing the latest result from optimal real-valued precoding, and transmitting the real and complex parts of one symbol over different antennas.
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| 7. |
- Medbo, Jonas, et al.
(författare)
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Temporal radio channel variations with stationary terminal
- 2004
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Ingår i: [Host publication title missing]. - 1090-3038. - 0780385217 ; 1, s. 91-95
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Konferensbidrag (refereegranskat)abstract
- In wireless communications, stationary terminal scenarios are becoming increasingly important as bitrates goes up. Consequently, the need to improve the knowledge about the channel behavior and to develop realistic channel models for these scenarios is also increasing. The present work comprises both measurements and modeling of the radio channel when the terminal is stationary. The measurements were performed at 5 GHz in indoor scenarios using a vector network analyzer. The measured channel was essentially static most of the time. Only about 1% of the time did it show substantial channel variations. An important finding is that the dominant cause for temporal channel variations in the measurements was the movement of persons in the vicinity of either antenna. This is also supported by a simple model, based on a single moving scatterer, which shows good agreement with measurements.
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| 8. |
- Mehta, N B, et al.
(författare)
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Rate of MIMO Systems with CSI at Transmitter and Receiver from Pilot-Aided Estimation
- 2004
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Ingår i: IEEE 60th Vehicular Technology Conference, VTC 2004-Fall.. - 1090-3038. - 0780385217 ; 3, s. 1575-1579
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Konferensbidrag (refereegranskat)abstract
- We consider realistic multiple input multiple output antenna systems operating over spatially colored channels with instantaneous, albeit imperfect, channel state information at the receiver and only covariance knowledge available at the transmitter. We focus on pilot-aided channel estimation in which the receiver uses minimum mean square error channel estimation. For such a setup, our goal is then to design both the pilot and data sequences optimally to maximize the information rates achievable over the channel. We first demonstrate that the estimation error cannot be modeled as additive white Gaussian noise. We adopt a lower bound on channel capacity with imperfect channel knowledge and show that an optimum design leads to a matching of the eigenspaces of the pilots and of the data to the eigenspace of the channel. Furthermore, the ranks of the pilot and data covariance matrices need to be equal, and the optimal training duration need only equal the above rank. The assignment of powers to the different modes of transmission can then be obtained numerically. The paper, in essence, extends the results in the literature that assume perfect channel knowledge at the receiver, and shows that fully exploiting covariance knowledge leads to a visible improvement in capacity when compared to schemes that assume no channel knowledge, whatsoever, at the transmitter.
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| 9. |
- Molisch, Andreas
(författare)
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Effect of far scatterer clusters in MIMO outdoor channel models
- 2003
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Ingår i: The 57th IEEE Semiannual Vehicular Technology Conference. VTC 2003-Spring.. - 1090-3038. - 0780377575 ; 1, s. 534-538
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Konferensbidrag (refereegranskat)abstract
- We consider the clustering structure of wireless MIMO channels, and the impact that multiple clusters have on the performance of MIMO systems. We show that multiple clusters frequently occur in urban environments. We then proceed to demonstrate that a channel with multiple scatterer clusters behaves differently than a channel with one cluster and the same rms angular spread. The differences are quantified in terms of correlation coefficients, information-theoretic capacity, and interference-suppression capabilities. This demonstrates the necessity of correctly taking into account the clustering structure.
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| 10. |
- Nakache, Y P, et al.
(författare)
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Spectral Shape of UWB Signals-Influence of Modulation Format, Multiple Access Scheme and Pulse Shape
- 2003
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Ingår i: The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.. - 1090-3038. - 0780377575 ; 4, s. 2510-2514
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Konferensbidrag (refereegranskat)abstract
- This paper studies how to design the spectrum of a UWB signal in accordance with the FCC regulations and IEEE 802.15.3a recommendations. We show that the "conventional" UWB system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that violate the regulations. The impact of different modulation and multiple access schemes on the spectrum shaping is derived from the power spectral density of a non-linear and memoryless modulation. Detailed theoretical and simulation results stress the difficulties raised by the use of dithered pulse trains. We thus propose several solutions to achieve compliance with the FCC spectral masks.
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