References of "Ottersten, Björn 50002797"
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See detailSpectrum Allocation for Decentralized Transmission Strategies: Properties of Nash Equilibria
von Wrycza, Peter; Shankar, Bhavani UL; Bengtsson, Mats et al

in EURASIP Journal on Advances in Signal Processing (2009)

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See detailRobust and Distributed Beamforming
Gan, Zheng; Kai-Kit, Wong; Arogyaswami, Paulraj et al

in Wireless Communications & Signal Processing, 2009. WCSP 2009. International Conference on (2009)

This paper studies the use of amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst ... [more ▼]

This paper studies the use of amplify-and-forward (AF) relays for robust beamforming, with the aid of imperfect channel state information (CSI) at the sender. In particular, the maximization of the worst-case signal-to-noise ratio (SNR) at the destination terminal is studied under a bounded spherical region for the norm of CSI error vector. We show that under a condition on the estimated CSI quality, the robust-optimal collaborative-relay beamforming (CRBF) can be obtained by S-Procedure and rank relaxation techniques. In addition, a distributed algorithm is proposed by examining the structure of the optimal CRBF. [less ▲]

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See detailDetection Based on Relaxation in MIMO Systems
Jalden, Joakim; Ottersten, Björn UL

in Handbook on Advancements in Smart Antenna Technologies for Wireless Networks (2009)

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See detailTraining-Based Bayesian MIMO Channel and Channel Norm Estimation
Björnson, Emil; Ottersten, Björn UL

in Acoustics, Speech and Signal Processing, 2009. ICASSP 2009. IEEE International Conference on (2009)

Training-based estimation of channel state information in multi-antenna systems is analyzed herein. Closed-form expressions for the general Bayesian minimum mean square error (MMSE) estimators of the ... [more ▼]

Training-based estimation of channel state information in multi-antenna systems is analyzed herein. Closed-form expressions for the general Bayesian minimum mean square error (MMSE) estimators of the channel matrix and the squared channel norm are derived in a Rayleigh fading environment with known statistics at the receiver side. When the second-order channel statistics are available also at the transmitter, this information can be exploited in the training sequence design to improve the performance. Herein, mean square error (MSE) minimizing training sequences are considered. The structure of the general solution is developed, with explicit expressions at high and low SNRs and in the special case of uncorrelated receive antennas. The optimal length of the training sequence is equal or smaller than the number of transmit antennas. [less ▲]

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See detailAcquiring Partial CSI for Spatially Selective Transmission by Instantaneous Channel Norm Feedback
Hammarwall, David; Bengtsson, Mats; Ottersten, Björn UL

in IEEE Transactions on Signal Processing (2008), 56(3), 11881204

In the design of next-generation multiuser communication systems, multiple-antenna transmission is an essential part providing additional spatial degrees of freedom and allowing efficient use of resources ... [more ▼]

In the design of next-generation multiuser communication systems, multiple-antenna transmission is an essential part providing additional spatial degrees of freedom and allowing efficient use of resources. A major limiting factor in the resource allocation is the amount of channel state information (CSI) available at the transmitter, particularly in multiuser systems where the feedback from each user terminal must be limited. Herein, we show that the Euclidean norm of the instantaneous channel, when combined with long-term channel statistics provides sufficient information for the transmitter to efficiently utilize multiuser diversity in time, frequency, and space. We consider the downlink of a communication system where the base station has multiple transmit antennas whereas each user terminal has a single receive antenna. The CSI provided by channel statistics and feedback of the norm of the instantaneous channel vector is studied in depth for correlated Rayleigh and Ricean fading channels, within a minimum mean-square error (MMSE) estimation framework. An asymptotic analysis (high instantaneous SNR) is presented which shows that channel realizations with large channel norm provide additional spatial CSI at the transmitter. This makes the proposed scheme ideal for multiuser diversity transmission schemes, where resources are only allocated to users experiencing favorable channel conditions. [less ▲]

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See detailFeedback Reduction in Uplink MIMO OFDM Systems by Chunk Optimization
Jorswieck, Eduard; Sezgin, Aydin; Ottersten, Björn UL et al

in IEEE International Conference on Communications (ICC) (2008)

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See detailExploiting Long-term Statistics in Spatially Correlated Multi-user MIMO Systems with Quantized Channel Norm Feedback
Björnson, Emil; Ottersten, Björn UL

in Proceedings IEEE International Conference on Acoustics, Speech, and Signal (ICASSP) (2008)

In wireless multiple antenna and multi-user systems, the spatial dimensions may be exploited to increase the performance by means of antenna gain, spatial diversity, and multi-user diversity. A limiting ... [more ▼]

In wireless multiple antenna and multi-user systems, the spatial dimensions may be exploited to increase the performance by means of antenna gain, spatial diversity, and multi-user diversity. A limiting factor in such systems is the channel information required by the transmitter to control the intra-cell interference. Herein, the properties of spatially correlated channels with longterm statistical information at the transmitter and fixed-rate feedback of the quantized Euclidean channel norm are analyzed using a spectral subspace decomposition framework. A spatial division multiple access scheme is proposed with interference suppression at the receiver and joint scheduling and zero-forcing beamforming at the transmitter. Closed-form expressions for first and second moments of the feedback conditional channel statistics are derived. It is shown that only a few bits of feedback are required to achieve reliable rate estimation and weighted sum-rate maximization. [less ▲]

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See detailFeedback design in multiuser MIMO systems using quantization splitting and hybrid instantaneous/statistical channel information
Björnson, Emil; Hammarwall, David; Zakhour, Randa et al

in Proceedings ICT Mobile and Wireless Communications Summit (2008)

In the design of next generation multiuser communication systems, multiple antenna transmission is an essential part providing spatial multiplexing gain and allowing efficient use of resources. A major ... [more ▼]

In the design of next generation multiuser communication systems, multiple antenna transmission is an essential part providing spatial multiplexing gain and allowing efficient use of resources. A major limiting factor in the resource allocation is the amount of channel state information (CSI) available at the transmitter, particularly in multiuser systems where the feedback from each user terminal must be limited. To this effect we propose two independent approaches for an efficient representation of the channel in multiuser MIMO systems. In the first approach, channel quantization is considered where the total number of feedback bits is limited. A resource allocation scheme is proposed where the available rate is split between the scheduling phase, where all users feed back a coarse CSI quantization, and the precoding phase where the selected receivers refine their CSI. The optimum splitting of the available feedback rate provides a large increase in performance and even simple heuristic splitting gives a noticeable advantage. In the second approach, we exploit a combination of instantaneous and statistical channel information. For spatially correlated Rayleigh and Ricean channels, it is shown that the CSI to large extent can be represented by the channel norm when the long-term channel statistics are known. Within a minimum mean square error (MMSE) estimation framework, feedback of a few bits of the quantized channel norm is sufficient to perform efficient resource allocation and achieve performance close to that of full CSI. [less ▲]

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See detailFeedback Reduction in Uplink MIMO OFDM Systems by Chunk Optimization
Jorswieck, Eduard; Sezgin, Aydin; Ottersten, Björn UL et al

in EURASIP Journal on Applied Signal Processing (2008)

Detailed reference viewed: 60 (0 UL)
See detailCapacity and Gain Analysis of a Reconfigurable MEMS Antenna
Mowlér, Marc; Khalid, Bilal; Lindmark, Björn et al

in Nordic Conference on Radio Science and Communications (RVK) (2008)

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See detailDirectional Dependence of Large Scale Parameters in Wireless Channel Models
Jalden, Niklas; Zetterberg, Per; Ottersten, Björn UL

in IEEE Wireless Communications (2008)

In this paper the autocorrelation properties of shadow fading and angle spread at both the base station (BS) and at the mobile station (MS) are analyzed using urban macro cellular measurement data. The ... [more ▼]

In this paper the autocorrelation properties of shadow fading and angle spread at both the base station (BS) and at the mobile station (MS) are analyzed using urban macro cellular measurement data. The shadow fading parameter is shown to have a longer decorrelation distance than the angle spread at both the BS and at the MS. Furthermore, we observe variations in the shadow fading that depend on the direction of the MS movement. The same dependence is not observed in the angle spreads. These results indicate that the origin of the angle spread is local to the transmitter and receiver, while the shadow fading depends on the intermediate environment. [less ▲]

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See detailGuaranteed Performance Region in Fading Orthogonal Space-Time Coded Broadcast Channels
Jorswieck, Eduard; Ottersten, Björn UL; Sezgin, Aydin et al

in EURASIP Journal on Wireless Communications & Networking (2008)

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See detailSystem Evaluation of Optimal Downlink Beamforming in Wireless Communication
Stridh, Rickard; Bengtsson, Mats; Ottersten, Björn UL

in Vehicular Technology Conference, 2001. VTC 2001 Fall. IEEE VTS 54th (2001)

We investigate the use of joint optimal downlink beamforming, power control and access point allocation, in a multicell SDMA system. Smart antennas are used at the access points and single antennas are ... [more ▼]

We investigate the use of joint optimal downlink beamforming, power control and access point allocation, in a multicell SDMA system. Smart antennas are used at the access points and single antennas are used at the terminals. The possibility to send messages to multiple terminals on the same frequency in the same time slot is exploited. An algorithm for removing users from a congested system, in order to avoid outage is proposed and evaluated Results show that the proposed algorithm gives substantial increase of the system performance compared to random removal of users. [less ▲]

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See detailESPRIT for Wideband Signals
Ottersten, Björn UL; Kailath, T.

in 21st Asilomar Conference on Signals, Systems, and Computers (1987)

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See detailARMA Spectral Estimation via Model Reduction
Wahlberg, Bo; Ottersten, Björn UL

in Proceedings of American Control Conference (1986)

Detailed reference viewed: 79 (0 UL)