| 1. |
|
|
| 2. |
|
|
| 3. |
- Almers, Peter, et al.
(författare)
-
Keyhole effects in MIMO wireless channels - measurements and theory
- 2003
-
Ingår i: GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489). - 0780379748 ; , s. 1781-1785
-
Konferensbidrag (refereegranskat)abstract
- It has been predicted theoretically that for some environments, the capacity of wireless MIMO systems can become very low, even for uncorrelated signals; this effect has been termed "keyhole" or "pinhole". We present the first unique measurements of this effect. The measurements were performed in a controlled indoor environment that was designed to obtain a keyhole. We analyze the limitations for measurement-based capacity calculations and keyhole investigations. We further present error bounds for the capacity and eigenvalue distributions due to measurement imperfections, such as finite signal-to-noise ratio and multipath leakage. The bounds are compared to the measurement results and show excellent agreement. Finally, we analyze the envelope distribution and find that, as expected from theory, it follows a double Rayleigh
|
|
| 4. |
- Almers, Peter, et al.
(författare)
-
Measured capacity gain using waterfilling in frequency selective MIMO channels
- 2002
-
Ingår i: The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2002 , vol 1-5, Proceedings. - 0780375890 ; , s. 1347-1351
-
Konferensbidrag (refereegranskat)abstract
- We analyze the channel capacity of multiple-input multiple-output (MIMO) systems in frequcncy selective channels, with channel knowledge at the transmitter side. An optimum transmission scheme uses Shannon's principle of waterfilling jointly in the frequency and the spatial domain. However, we show in this paper that the largest gain by using waterfilling resides in the spatial domain, and that the capacity gain from the frequency domain is very small for MIMO systems. We quantify the gain for a theoretical Rayleigh fading channel model and for microcellular channels as measured in an enclosed court-yard.
|
|
| 5. |
- Almers, Peter, et al.
(författare)
-
Measurement of keyhole effect in a wireless multiple-input multiple-output (MIMO) channel
- 2003
-
Ingår i: IEEE Communications Letters. - 1089-7798. ; 7:8, s. 373-375
-
Tidskriftsartikel (refereegranskat)abstract
- It has been predicted theoretically that for some environments, the capacity of wireless multiple-input multiple-output systems can become very low even for uncorrelated signals; this effect has been termed "keyhole" or "pinhole." In this letter, We present the (to our knowledge) first measurement of this effect. The measurements are done in a controlled indoor environment, with transmitter and receiver in two adjacent rooms. One of the rooms is shielded, and propagation to, the other room can occur only through a hole or a waveguide in the wall. We find that only the waveguide leads to an unambiguous keyhole, while a hole of the same size still allows multimodal propagation. Measurement of amplitude statistics also confirm theoretical predictions.
|
|
| 6. |
- Almers, Peter, et al.
(författare)
-
The effect of receiver antenna array horizontal orientation on MIMO channel capacity
- 2003
-
Ingår i: [Host publication title missing]. - 1090-3038. - 0780377575 ; 1, s. 34-38
-
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.
|
|
| 7. |
- Kåredal, Johan, et al.
(författare)
-
Statistical analysis of the UWB channel in an industrial environment
- 2004
-
Ingår i: [Host publication title missing]. - 0780385217 ; , s. 81-85
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present a statistical model for the ultra-wideband (UWB) channel in an industrial environment. Based on a set of measurements in a factory hall, we find that the abundance of metallic scatterers causes dense multipath scattering. This can be seen to produce mostly a Rayleigh distributed small-scale fading signal, with only a few paths exhibiting Nakagami distributions. For the power delay profile, we suggest a generalization of the Saleh-Valenzuela model where clusters with different excess delays have different ray power decay constants; the decay constants follow a linear dependence on the delay. This model provides an excellent fit to the measured data. We also note that for non-line-of-sight scenarios at larger distances, several hundred multipath components need to be collected to capture 50% of the available energy
|
|
| 8. |
- Kåredal, Johan, et al.
(författare)
-
UWB channel measurements in an industrial environment
- 2004
-
Ingår i: [Host publication title missing]. - 0780387945 ; , s. 3511-3516
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present the (to our knowledge) first measurement results for ultra-wideband channels in industrial environments, i.e., a factory hall. The measurements are done with virtual arrays, which allows analysis of the small-scale fading statistics, as well as a directional analysis. We find that there is dense multipath scattering due to the abundance of metallic scatterers in the considered environment. Multiple scatterer clusters can be identified both in the delay and the angular domain. Typical rms delay spreads lie between 30 ns for LOS scenarios and 40 ns for NLOS scenarios. For non-LOS scenarios at large distances, the maximum of the power delay profile is observed some 40 ns after the arrival of the first multipath components. We also draw conclusions about the behavior of typical UWB system designs in the measured channels
|
|
| 9. |
- Molisch, Andreas, et al.
(författare)
-
Statistical MIMO Propagation Channel Models - An overview
- 2004
-
Ingår i: Proc. IEEE European Microwave Conference (EuMC), Amsterdam, Netherlands, October 2004, invited paper.
-
Konferensbidrag (refereegranskat)abstract
- Statistical propagation channel models for MIMO systems can be grouped into two classes: physical and analytical. Physical models describe the statistics of the multipath components and are in widespread use for implementation and testing of systems (e.g. 3GPP, IEEE 802.11n). Analytical (or nonphysical) models describe the statistics of the transfer functions between the antenna elements at the transmit and receive side; they are popular for theoretical analysis of MIMO systems. This paper provides a taxonomy of the different modeling approaches, and describes their strengths and weaknesses.
|
|
| 10. |
- Wyne, Shurjeel, et al.
(författare)
-
Outdoor to indoor office MIMO measurements at 5.2 GHz
- 2004
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 0780385217 ; 1, s. 101-105
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the results of one of the first measurement campaigns for the double-directional characterization of outdoor to indoor wireless propagation channels. Such channels play a vital role for cellular systems with multiple antenna elements at transmitter and receiver, i.e. multiple-input multiple-output (MIMO) systems. Measurements were performed at 5.2 GHz between 53 different receiver locations in an office building, and three "base station" positions on a nearby rooftop. In the paper we present results for angular-delay profiles, RMS angular spread, and other statistical parameters characterizing delay and angular dispersion.
|
|
| 11. |
- Wyne, Shurjeel, et al.
(författare)
-
Why the channel matrix in a LOS scenario has zero mean entries
- 2004
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During a recent measurement campaign, we encountered some problems in extracting the rice factor from measurements. There were different answers to the question of what constitutes the correct line-of-sight component. This document highlights those issues and is meant to be a basis of discussion. Any feedback on the raised issues is welcome.
|
|
