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- Almers, Peter, et al.
(författare)
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Keyhole effects in MIMO wireless channels - measurements and theory
- 2003
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Ingår i: GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489). - 0780379748 ; , s. 1781-1785
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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
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- Almers, Peter, et al.
(författare)
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Measured capacity gain using waterfilling in frequency selective MIMO channels
- 2002
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Ingår i: The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2002 , vol 1-5, Proceedings. - 0780375890 ; , s. 1347-1351
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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.
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- Almers, Peter, et al.
(författare)
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Measurement of keyhole effect in a wireless multiple-input multiple-output (MIMO) channel
- 2003
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Ingår i: IEEE Communications Letters. - 1089-7798. ; 7:8, s. 373-375
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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.
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- 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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- Gezici, S, et al.
(författare)
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On the performance of transmitted-reference impulse radio
- 2004
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Ingår i: GLOBECOM '04. IEEE Global Telecommunications Conference.
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Konferensbidrag (refereegranskat)abstract
- We consider a time-hopping impulse-radio system that uses transmitted-reference pulses for implicit channel estimation and equalization. A hybrid receiver structure first performs a filtering matched to the hopping sequence, and a subsequent correlation of the data pulses with the reference pulses. We analyze the performance of such a system both in AWGN and in multipath. For the AWGN case, we give exact expressions for the bit error probability that take into account the non-Gaussian nature of the noise-noise crossterms arising in the correlators. For the multipath case, we analyze inter-frame interference, as well as multipath interference from the reference pulse to the data pulse, providing dosed-form equations in the limit of a large number of multipath components.
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- Kåredal, Johan, et al.
(författare)
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Statistical analysis of the UWB channel in an industrial environment
- 2004
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Ingår i: [Host publication title missing]. - 0780385217 ; , s. 81-85
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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
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- Kåredal, Johan, et al.
(författare)
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UWB channel measurements in an industrial environment
- 2004
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Ingår i: [Host publication title missing]. - 0780387945 ; , s. 3511-3516
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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
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