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Pilot Precoding and Combining in Multiuser MIMO Networks
KTH, School of Electrical Engineering (EES), Information Science and Engineering.ORCID iD: 0000-0002-5526-9213
KTH, School of Electrical Engineering (EES), Network and Systems engineering.ORCID iD: 0000-0001-6737-0266
KTH, School of Electrical Engineering (EES), Automatic Control.ORCID iD: 0000-0002-2289-3159
KTH, School of Electrical Engineering (EES), Information Science and Engineering.ORCID iD: 0000-0002-3599-5584
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2017 (English)In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. June, no 6Article in journal (Refereed) Published
Abstract [en]

Although the benefits of precoding and combining data signals are widely recognized, the potential of these techniques for pilot transmission is not fully understood. This is particularly relevant for multiuser multiple-input multiple-output(MU-MIMO) cellular systems using millimeter-wave (mmWave)communications, where multiple antennas have to be used both at the transmitter and the receiver to overcome the severe path loss.In this paper, we characterize the gains of pilot precoding and combining in terms of channel estimation quality and achievable data rate. Specifically, we consider three uplink pilot transmission scenarios in a mmWave MU-MIMO cellular system: 1) non-precoded and uncombined, 2) precoded but uncombined, and3) precoded and combined. We show that a simple precoder that utilizes only the second-order statistics of the channel reduces the variance of the channel estimation error by a factor that is proportional to the number of user equipment (UE) antennas.We also show that using a linear combiner design based on the second-order statistics of the channel significantly reduces multiuser interference and provides the possibility of reusing some pilots. Specifically, in the large antenna regime, pilot preceding and combining help to accommodate a large number ofUEs in one cell, significantly improve channel estimation quality, boost the signal-to-noise ratio of the UEs located close to the cell edges, alleviate pilot contamination, and address the imbalanced coverage of pilot and data signals.

Place, publisher, year, edition, pages
IEEE Press, 2017. Vol. June, no 6
Keywords [en]
multiuser MIMO, multiple antenna UEs, channel estimation, millimeter-wave, transceiver design
National Category
Signal Processing
Identifiers
URN: urn:nbn:se:kth:diva-207619DOI: 10.1109/JSAC.2017.2699398ISI: 000404242600017Scopus ID: 2-s2.0-85021270765OAI: oai:DiVA.org:kth-207619DiVA, id: diva2:1097331
Projects
Ericsson Research's HARALD project
Note

QC 20170523

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-07-11Bibliographically approved
In thesis
1. On Multiantenna Cellular Communications: From Theory to Practice
Open this publication in new window or tab >>On Multiantenna Cellular Communications: From Theory to Practice
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, wireless communications are an essential part of our everyday life. Both the number of users and their demands for wireless data have increasedtremendously during the last decade. Multiantenna communicationsis a promising solution to meet this ever-growing traffic demands. However, impairments that exist in most practical communication networks may substantially limit the performance of a multiantenna system. The characterizationof such a performance loss and how to minimize that are still largelyopen problems. The present thesis addresses this important research gap. Inparticular, we focus on three major impairments of a multiantenna cellularnetwork: impairment in the channel state information (CSI), interference andimpairment in the transceiver hardware components.To fully realize the benefits of multiantenna communications, the users need to acquire a certain level of information about their propagation environment; that is, their corresponding CSI. In practice, the CSI is not known bythe users and should be acquired by allocating part of the network resourcesfor pilot transmission. This problem is mainly important in the systems with a large number of antennas, as in general the required network resources for CSI acquisition scales with the number of transmitting antennas. Theproblem of CSI acquisition in a single-cell multiuser multiple-input multipleoutput(MIMO) system is addressed in this thesis. A linear spatial precodingand combining scheme for pilot transmission is proposed. This scheme requiresless number of network resources for channel estimation compared tothe conventional schemes. The gains of the proposed scheme are characterized by finding an upper-bound and a lower-bound on the channel estimation error.Moreover, as an ultimate performance metric, an achievable sum-rate ofthe network is formulated and analyzed numerically.Due to the broadcast nature of the wireless channels, the performanceof the users in a network is intertwined; the desired signal of one user mayinterfere other users. Hence, the interference is another major impairment inwireless communication systems. In this thesis, the practical challenges of aninterference management technique, namely MIMO interference alignment isinvestigated by implementation on a multiuser MIMO testbed. Then, in thecontext of interference alignment, the problem of optimal power allocation forpilot and data transmission is studied and verified by the measurements.The impairment in the hardware components of the transceivers, that is, any deviation of the components from their ideal behavior, degrades the performance of a communication system. In particular, the impact of nonlineartransmitter power amplifiers (PA)s is investigated in this thesis. First, consideringa memoryless third-order polynomial model for the PAs, a model forthe transmitted nonlinear distortion signal from a multiantenna transmitter isproposed and validated by measurements. This model implies that the spatialdirection of the transmitted distortion is dependent on the spatial directionof the desired signal. Then, this model is extended for a general arbitrary order polynomial model. Exploiting the developed distortion model, the energyefficiency of a multiantenna system operating at millimeter wave frequenciesis studied.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. p. 43
Series
TRITA-EE, ISSN 1653-5146 ; 050
National Category
Signal Processing
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-207623 (URN)978-91-7729-435-1 (ISBN)
Public defence
2017-06-09, Kollegiesalen, Brinellvägen 8, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20170523

Available from: 2017-05-24 Created: 2017-05-22 Last updated: 2017-05-24Bibliographically approved

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Fodor, GaborFischione, Carlo

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