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Čirkić, Mirsad
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Jiang, X., Cirkic, M., Kaltenberger, F., Larsson, E. G., Deneire, L. & Knopp, R. (2015). MIMO-TDD Reciprocity under Hardware Imbalances: Experimental Results. In: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC): . Paper presented at IEEE International Conference on Communications (ICC) (pp. 4949-4953). IEEE
Öppna denna publikation i ny flik eller fönster >>MIMO-TDD Reciprocity under Hardware Imbalances: Experimental Results
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2015 (Engelska)Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2015, s. 4949-4953Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

For time division duplexing (TDD) systems, the physical channel in the air is reciprocal for uplink (UL) and downlink (DL) within the channel coherence time. However when the transceivers radio frequency (RF) hardware is taken into consideration, TDD channel reciprocity no longer holds because of the non-symmetric characteristics of RF transmit and receive chains. Relative calibration has been proposed to compensate this hardware impairment with a multiplicative matrix. In this paper we perform hardware measurements on this calibration matrix which gives a direct insight on the physical phenomenon of TDD transceivers. Especially, we inspect the assumption that this calibration matrix is diagonal, which is widely adopted in literature but has never been verified by experiments. This work can be regarded as an experimental base for TDD calibration or for theoretical analysis of non-perfect channel reciprocity of TDD systems.

Ort, förlag, år, upplaga, sidor
IEEE, 2015
Serie
IEEE International Conference on Communications, ISSN 1550-3607
Nyckelord
MIMO; TDD; channel reciprocity; relative calibration; hardware impairment
Nationell ämneskategori
Elektroteknik och elektronik
Identifikatorer
urn:nbn:se:liu:diva-127294 (URN)10.1109/ICC.2015.7249107 (DOI)000371708105029 ()978-1-4673-6432-4 (ISBN)
Konferens
IEEE International Conference on Communications (ICC)
Tillgänglig från: 2016-04-20 Skapad: 2016-04-19 Senast uppdaterad: 2016-08-31
Čirkić, M. (2014). Efficient MIMO Detection Methods. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Öppna denna publikation i ny flik eller fönster >>Efficient MIMO Detection Methods
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

For the past decades, the demand in transferring large amounts of data rapidly and reliably has been increasing drastically. One of the more promising techniques that can provide the desired performance is multiple-input multiple-output (MIMO) technology where multiple antennas are placed at both the transmitting and receiving side of the communication link. This performance potential is extremely high when the dimensions of the MIMO system are increased to an extreme (in the number of hundreds or thousands of antennas). One major implementation difficulty of the MIMO technology is the signal separation (detection) problem at the receiving side of the MIMO link, which holds for medium-size MIMO systems and even more so for large-size systems. This is due to the fact that the transmitted signals interfere with each other and that separating them can be very difficult if the MIMO channel conditions are not beneficial, i.e., the channel is not well-conditioned.

The main problem of interest is to develop algorithms for practically feasible MIMO implementations without sacrificing the promising performance potential that such systems bring. These methods involve inevitably different levels of approximation. There are computationally cheap methods that come with low accuracy and there are computationally expensive methods that come with high accuracy. Some methods are more applicable in medium-size MIMO than in large-size MIMO and vice versa. Some simple methods for instance, which are typically inaccurate for medium-sized settings, can achieve optimal accuracy for certain large-sized settings that offer close-to-orthogonal spatial signatures. However, when the dimensions are overly increased, then even these (previously) simple methods become computationally burdensome. In different MIMO setups, the difficulty in detection shifts since methods with optimal accuracy are not the same. Therefore, devising one single algorithm which is well-suited for feasible MIMO implementations in all settings is not easy.

This thesis addresses the general MIMO detection problem in two ways. One part treats a development of new and more efficient detection techniques for the different MIMO settings. The techniques that are proposed in this thesis demonstrate unprecedented performance in many relevant cases. The other part revolves around utilizing already proposed detection algorithms and their advantages versus disadvantages in an adaptive manner. For well-conditioned channels, low-complexity detection methods are often sufficiently accurate. In such cases, performing computationally very expensive optimal detection would be a waste of computational power. This said, for MIMO detection in a coded system, there is always a trade-off between performance and complexity. Intuitively, computational resources should be utilized more efficiently by performing optimal detection only when it is needed, and something simpler when it is not. However, it is not clear whether this is true or not. In trying to answer this, a general framework for adaptive computational-resource allocation to different (“simple” and “difficult”) detection problems is proposed. This general framework is applicable to any MIMO detector and scenario of choice, and it is exemplified using one particular detection method for which specific allocation techniques are developed and evaluated.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2014. s. 43
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1570
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:liu:diva-103675 (URN)10.3384/diss.diva-103675 (DOI)978-91-7519-413-4 (ISBN)
Disputation
2014-02-21, Visionen, Hus B (ing°ang 27), Campus Valla, Linköpings universitet, Linköping, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2014-01-22 Skapad: 2014-01-22 Senast uppdaterad: 2019-11-19Bibliografiskt granskad
Čirkić, M. & Larsson, E. G. (2014). On the Complexity of Very Large Multi-User MIMO Detection. In: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE: . Paper presented at IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (pp. 55-59). IEEE Press
Öppna denna publikation i ny flik eller fönster >>On the Complexity of Very Large Multi-User MIMO Detection
2014 (Engelska)Ingår i: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE, IEEE Press, 2014, s. 55-59Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

This work discusses efficient techniques for detection in large-size multi-user multiple-input multiple-output (MIMO) systems that are highly overdetermined. We exemplify the application of conjugate gradient methods in the setup of our interest and compare its performance with respect to methods based on the Neumann series expansion. We bring to light some important insights on the performance versus complexity tradeoffs that have not been uplifted before.

Ort, förlag, år, upplaga, sidor
IEEE Press, 2014
Serie
IEEE International Workshop on Signal Processing Advances in Wireless Communications, ISSN 2325-3789
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:liu:diva-103672 (URN)10.1109/SPAWC.2014.6941316 (DOI)000348859000012 ()978-1-4799-4903-8 (ISBN)
Konferens
IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Tillgänglig från: 2014-01-22 Skapad: 2014-01-22 Senast uppdaterad: 2016-09-13Bibliografiskt granskad
Čirkić, M. & Larsson, E. G. (2014). SUMIS: Near-Optimal Soft-In Soft-Out MIMO Detection with Low and Fixed Complexity. IEEE Transactions on Signal Processing, 62(12), 3084-3097
Öppna denna publikation i ny flik eller fönster >>SUMIS: Near-Optimal Soft-In Soft-Out MIMO Detection with Low and Fixed Complexity
2014 (Engelska)Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 62, nr 12, s. 3084-3097Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The fundamental problem of interest here is soft-input soft-output multiple-input multiple-output (MIMO) detection. We propose a method, referred to as subspace marginalization with interference suppression (SUMIS), that yields unprecedented performance at low and fixed (deterministic) complexity. Our method provides a well-defined tradeoff between computational complexity and performance. Apart from an initial sorting step consisting of selecting channel-matrix columns, the algorithm involves no searching nor algorithmic branching; hence the algorithm has a completely predictable run-time and allows for a highly parallel implementation. We numerically assess the performance of SUMIS in different practical settings: full/partial channel state information, sequential/iterative decoding, and low/high rate outer codes. We also comment on how the SUMIS method performs in systems with a large number of transmit antennas.

Ort, förlag, år, upplaga, sidor
IEEE Signal Processing Society, 2014
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:liu:diva-103671 (URN)10.1109/TSP.2014.2303945 (DOI)000338122400005 ()
Tillgänglig från: 2014-01-22 Skapad: 2014-01-22 Senast uppdaterad: 2017-12-06
Cirkic, M., Persson, D., Larsson, J.-Å. & Larsson, E. G. (2012). Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors. IEEE Transactions on Signal Processing, 60(12), 6421-6434
Öppna denna publikation i ny flik eller fönster >>Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
2012 (Engelska)Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, nr 12, s. 6421-6434Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present approximations of the LLR distribution for a class of fixed-complexity soft-output MIMO detectors, such as the optimal soft detector and the soft-output via partial marginalization detector. More specifically, in a MIMO AWGN setting, we approximate the LLR distribution conditioned on the transmitted signal and the channel matrix with a Gaussian mixture model (GMM). Our main results consist of an analytical expression of the GMM model (including the number of modes and their corresponding parameters) and a proof that, in the limit of high SNR, this LLR distribution converges in probability towards a unique Gaussian distribution.

Ort, förlag, år, upplaga, sidor
Institute of Electrical and Electronics Engineers (IEEE), 2012
Nyckelord
Fixed-complexity sphere-decoder; Gaussian mixture model; LLR distribution; MIMO detection; partial marginalization
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-87205 (URN)10.1109/TSP.2012.2217336 (DOI)000311805000024 ()
Anmärkning

On the defence date of the Licentiate Thesis the status of this article was Manuscript and the title was Approximating the LLR Distribution for the Optimal and Partial Marginalization MIMO Detectors.

Tillgänglig från: 2013-01-14 Skapad: 2013-01-14 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Čirkić, M. & Larsson, E. G. (2012). Near-Optimal Soft-Output Fixed-Complexity MIMO Detection via Subspace Marginalization and Interference Suppression. In: 2012 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP): . Paper presented at IEEE International Conference on Acoustics,Speech and Signal Processing (pp. 2805-2808). IEEE Signal Processing Society
Öppna denna publikation i ny flik eller fönster >>Near-Optimal Soft-Output Fixed-Complexity MIMO Detection via Subspace Marginalization and Interference Suppression
2012 (Engelska)Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE Signal Processing Society, 2012, , s. 4s. 2805-2808Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

The fundamental problem of our interest here is soft MIMO detection. We propose a method that yields excellent performance, atlow and at fixed (deterministic) complexity. Our method provides a well-defined tradeoff between computational complexity and performance. Apart from an initial step consisting of selecting columns,the algorithm involves no searching nor algorithmic branching; hence the algorithm has a completely predictable run-time, and it is readily and massively parallelizable.

Ort, förlag, år, upplaga, sidor
IEEE Signal Processing Society, 2012. s. 4
Nationell ämneskategori
Kommunikationssystem
Identifikatorer
urn:nbn:se:liu:diva-74097 (URN)10.1109/ICASSP.2012.6288500 (DOI)000312381402222 ()978-1-4673-0044-5 (ISBN)978-1-4673-0045-2 (ISBN)
Konferens
IEEE International Conference on Acoustics,Speech and Signal Processing
Tillgänglig från: 2012-01-23 Skapad: 2012-01-19 Senast uppdaterad: 2016-08-31Bibliografiskt granskad
Čirkić, M., Persson, D. & Larsson, E. G. (2011). Allocation of Computational Resources for Soft MIMO Detection. IEEE Journal of Selected Topics in Signal Processing, 5(8), 1451-1461
Öppna denna publikation i ny flik eller fönster >>Allocation of Computational Resources for Soft MIMO Detection
2011 (Engelska)Ingår i: IEEE Journal of Selected Topics in Signal Processing, ISSN 1932-4553, Vol. 5, nr 8, s. 1451-1461Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. Our main results are a formulation of the problem as a mathematical optimization problem with a well-defined objective function and constraints, and algorithms that solve this optimization problem efficiently computationally.

Ort, förlag, år, upplaga, sidor
IEEE conference proceedings, 2011
Nationell ämneskategori
Signalbehandling
Identifikatorer
urn:nbn:se:liu:diva-69612 (URN)10.1109/JSTSP.2011.2162719 (DOI)000297348500006 ()
Anmärkning
©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Mirsad Čirkić, Daniel Persson and Erik G. Larsson, Allocation of Computational Resources for Soft MIMO Detection, 2011, accepted IEEE Journal of Selected Topics in Signal Processing Tillgänglig från: 2011-07-06 Skapad: 2011-07-06 Senast uppdaterad: 2016-08-31
Čirkić, M., Persson, D., Larsson, E. G. & Larsson, J.-Å. (2011). Gaussian Approximation of the LLR Distribution for the ML and Partial Marginalization MIMO detectors. In: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP) (pp. 3232-3235). IEEE conference proceedings
Öppna denna publikation i ny flik eller fönster >>Gaussian Approximation of the LLR Distribution for the ML and Partial Marginalization MIMO detectors
2011 (Engelska)Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP), IEEE conference proceedings, 2011, s. 3232-3235Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

We derive a Gaussian approximation of the LLR distribution  conditioned on the transmitted signal and the channel matrix for the  soft-output via partial marginalization MIMO detector. This detector  performs exact ML as a special case. Our main results consist of  discussing the operational meaning of this approximation and a proof  that, in the limit of high SNR, the LLR distribution of interest  converges in probability towards a Gaussian distribution.

Ort, förlag, år, upplaga, sidor
IEEE conference proceedings, 2011
Serie
IEEE International Conference on Acoustics, Speech and SignalProcessing, ISSN 1520-6149
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-64368 (URN)10.1109/ICASSP.2011.5946710 (DOI)000296062403161 ()978-1-4577-0537-3 (ISBN)
Tillgänglig från: 2011-01-20 Skapad: 2011-01-20 Senast uppdaterad: 2016-08-31
Čirkić, M., Persson, D. & Larsson, E. G. (2011). New Results on Adaptive Computational Resource Allocation in Soft MIMO Detection. In: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) (pp. 2972-2975). IEEE conference proceedings
Öppna denna publikation i ny flik eller fönster >>New Results on Adaptive Computational Resource Allocation in Soft MIMO Detection
2011 (Engelska)Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), IEEE conference proceedings, 2011, s. 2972-2975Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

The fundamental problem of our interest is soft MIMO detection for  the case of block fading, i.e., when the transmitted codeword spans  over several independent channel realizations. We develop methods  that adaptively allocate computational resources to the detection  problems of each channel realization, under a total per-codeword  complexity constraint. The new results consist of a new algorithm, a  new performance measure, and a thorough complexity discussion.

Ort, förlag, år, upplaga, sidor
IEEE conference proceedings, 2011
Serie
IEEE International Conference on Acoustics, Speech and Signal Processing, ISSN 1520-6149
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-64367 (URN)10.1109/ICASSP.2011.5946281 (DOI)000296062403096 ()
Tillgänglig från: 2011-01-20 Skapad: 2011-01-20 Senast uppdaterad: 2016-08-31
Čirkić, M. (2011). Optimization of Computational Resources for MIMO Detection. (Licentiate dissertation). Linköping: Linköping University Electronic Press
Öppna denna publikation i ny flik eller fönster >>Optimization of Computational Resources for MIMO Detection
2011 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

For the past decades, the demand in transferring large amounts of data rapidly and reliably has been increasing drastically. One of the more promising techniques that can provide the desired performance is the multiple-input multiple-output (MIMO) technology where multiple antennas are placed at both the transmitting and receiving side of the communication link. One major implementation difficulty of the MIMO technology is the signal separation (detection) problem at the receiving side of the MIMO link. This is due to the fact that the transmitted signals interfere with each other and that separating them can be very difficult if the MIMO channel conditions are not beneficial, i.e., the channel is not well-conditioned.

For well-conditioned channels, low-complexity detection methods are often sufficiently accurate. In such cases, performing computationally very expensive optimal detection would be a waste of computational power. This said, for MIMO detection in a coded system, there is always a trade-off between performance and complexity. The fundamental question is, can we save computational resources by performing optimal detection only when it is needed, and something simpler when it is not? This is the question that this thesis aims to answer. In doing so, we present a general framework for adaptively allocating computational resources to different (“simple” and“difficult”) detection problems. This general framework is applicable to any MIMO detector and scenario of choice, and it is exemplified using one particular detection method for which specific allocation techniques are developed and evaluated.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2011. s. 26
Serie
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1514
Nationell ämneskategori
Kommunikationssystem
Identifikatorer
urn:nbn:se:liu:diva-72368 (URN)978-91-7393-011-6 (ISBN)
Presentation
2011-12-19, Campus Valla, Linköpings universitet, Linköping, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2011-11-28 Skapad: 2011-11-28 Senast uppdaterad: 2020-02-03Bibliografiskt granskad
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