| 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. |
- Florén, Fredrik, et al.
(författare)
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Throughput analysis of three multiuser diversity schemes
- 2003
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Ingår i: 57th IEEE Semiannual Vehicular Technology Conference. VTC 2003 (Cat. No.03CH37431). - 0780377575 ; , s. 2686-2690
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Konferensbidrag (refereegranskat)abstract
- The throughput of three slot allocation schemes for the downlink of a wireless TDMA system are investigated under the assumption of block-Rayleigh fading. The schemes use the instantaneous SNR at the users in order to take advantage of the independent fading of the channels. In the first scheme, which has been proposed earlier (R. Knopp et al., 1995), the base station transmits to the user that experiences the largest SNR in every slot. In the second scheme, which is a variant of an existing scheme (P. Viswanath et al., June 2002), the user with highest ratio between instantaneous SNR and mean SNR is transmitted to. Lastly, we propose a scheme that compares the SNR at a user to a threshold in order determine if transmission to that user shall occur. If the SNR is below the threshold, transmission to another user is attempted. The results indicate that considerable throughput gains can be achieved even with limited SNR feedback, although there exists a trade-off between throughput and delay
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| 3. |
- Geijer Lundin, Erik, et al.
(författare)
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Adaptive Filtering Applied to an Uplink Load Estimate in WCDMA
- 2003
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Ingår i: Proceedings of the 57th IEEE Semiannual Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780377575 ; , s. 452-456
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Konferensbidrag (refereegranskat)abstract
- In the uplink of a WCDMA system, a natural choice of resource quantity is the uplink noise rise, i.e., total received power over noise power. Unfortunately this quantity is hard to measure and estimates are often noisy. This paper focuses on relative load which is closely related to the noise rise. Model-based signal processing with change detection techniques is herein used to suppress noise and minor oscillations while being alert on fast load changes. The time varying model identified in the process can also be used for prediction of future values, something which resource management algorithms can benefit from.
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| 4. |
- Geijer Lundin, Erik, et al.
(författare)
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Uplink Load Estimates in WCDMA with Different Availability of Measurements
- 2003
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Ingår i: Proceedings of the 57th IEEE Semiannual Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780377575 ; , s. 1198-1202 vol.2
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Konferensbidrag (refereegranskat)abstract
- In the uplink of a WCDMA system, a natural choice of resource management control quantity is the uplink noise rise, i.e., total received power over noise power. Unfortunately this quantity is hard to measure. In this paper, we propose and evaluate a number of noise rise estimates which all rely on path gain measurements. These measurements can be made available either periodically or event-driven as described in 3GPP (Release 99). Simulations show that event-driven measurements yield comparable performance to periodic measurements, but with much fewer measurement reports. Despite severely limited path gain knowledge due to that some users report to another RNC, we still manage to estimate the uplink noise rise reasonably well.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Oechtering, Tobias J., et al.
(författare)
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On the capacity of a distributed multiantenna system using cooperative transmitters
- 2003
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Ingår i: 57TH IEEE VEHICULAR TECHNOLOGY CONFERENCE, VTC 2003-SPRING, VOLS 1-4, PROCEEDINGS. - 0780377575 ; , s. 75-79
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Konferensbidrag (refereegranskat)abstract
- Future radio systems will make use of cooperative concepts between independent transmitters and receivers to increase the coverage area and the data rate, and/or to decrease the power consumption of the wireless communication network. Therefore, a station wishing to transmit cooperates with reachable stations in its vicinity to achieve a performance gain from the resulting distributed multiple antenna link. The resulting communication situation is related to the common multiple access channel. We consider the simple cooperative concept of amplify and forward, where the cooperating stations retransmit the amplified, received signal. In order to gain knowledge about the properties of the cooperative transmitter system, it is sensible to analyze its capacity. Furthermore, the amplification factors which maximize the system capacity with respect to the total transmission power of all transmit stations will lead to important system design information.
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| 8. |
- Queseth, Olav
(författare)
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A Multidisciplinary study of Competition in unlicensed networks
- 2003
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Ingår i: 57TH IEEE VEHICULAR TECHNOLOGY CONFERENCE, VTC 2003-SPRING, VOLS 1-4, PROCEEDINGS. - New York : IEEE. - 0780377575 ; , s. 699-703
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Konferensbidrag (refereegranskat)abstract
- At the same time as 3G networks are deployed low-cost WLAN technology is used to create high data rate coverage in hotspots. Should this be viewed as a complement to 3G systems or is it a competitor? To understand, these technical properties of short range systems are mapped on the influence on the microeconomic firm behaviour. The influence on competition and the possibility to gain benefits from cheating are studied. The results indicate competition can be ensured.
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