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Analysis of Alternative Massive MIMO Designs: Superimposed Pilots and Mixed-ADCs
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The development of information and communication technologies (ICT) provides the means for reaching global connectivity that can help humanity progress and prosper. This comes with high demands on data traffic and number of connected devices which are rapidly growing and need to be met by technological development. Massive MIMO, where MIMO stands for multiple-input multiple-output, is envisioned as a fundamental component of next generation wireless communications for its ability to provide high spectral and energy efficiency, SE and EE, respectively. The key feature of this technology is the use of a large number of antennas at the base stations (BS) to spatially multiplex several user equipments (UEs).

In the development of new technologies like Massive MIMO, many design alternatives need to be evaluated and compared in order to find the best operating point with a preferable tradeoff between high performance and low cost. In this thesis, two alternative designs for signal processing and hardware in Massive MIMO are studied and compared with the baseline operation in terms of SE, EE, and power consumption. The first design is called superimposed pilot (SP) transmission and is based on superimposing pilot and data symbols to remove the overhead from pilot transmission and reduce pilot contamination. The second design is mixed analog-to-digital converters (ADCs) and it aims at balancing high performance and low complexity by allowing different ADC bit resolutions across the BS antennas.

The results show that the baseline operation of Massive MIMO, properly optimized, is the preferred choice. However, SP and mixed ADCs still have room for improvement and further study is needed to ascertain the full capabilities of these alternative designs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. , p. 62
Series
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1803
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:liu:diva-145677DOI: 10.3384/lic.diva-145677ISBN: 9789176853238 (print)OAI: oai:DiVA.org:liu-145677DiVA, id: diva2:1190586
Presentation
2018-04-13, Algoritmen, B-huset, ing 27/29, Campus Valla, Linköping, 13:15 (English)
Opponent
Supervisors
Note

Mindre typografiska fel är korrigerade i den elektroniska versionen. / Minor typographic errors are corrected in the electronic version.

Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2019-10-12Bibliographically approved
List of papers
1. Joint UL and DL Spectral Efficiency Optimization of Superimposed Pilots in Massive MIMO
Open this publication in new window or tab >>Joint UL and DL Spectral Efficiency Optimization of Superimposed Pilots in Massive MIMO
2017 (English)In: Proceedings of 2017 IEEE Globecom Workshops (GC Wkshps), IEEE, 2017, p. 1-7Conference paper, Published paper (Refereed)
Abstract [en]

The reuse of pilot sequences in a Massive MIMO system leads to pilot contamination, which reduces the channel estimation quality and adds coherent interference in the data transmission. A standard method to reduce pilot contamination, known as regular pilots (RPs), is to increase the pilot overhead and reuse pilots more sparsely in the network. Another approach, denoted as superimposed pilots (SPs), is to send a superposition of pilot and data symbols which allows the system to reuse pilots far more sparsely. This work performs a comparative analysis of RPs and SPs in Massive MIMO considering the joint spectral efficiency (SE) of the uplink (UL) and downlink (DL) communications. A rigorous DL lower bound on the capacity with SPs is derived and multiobjective optimization theory is used to compare the UL and DL SE between RPs and SPs. Numerical results indicate that RPs and SPs give comparable SE when both methods are optimized.

Place, publisher, year, edition, pages
IEEE, 2017
Series
IEEE Globecom Workshops
Keywords
MIMO communication, channel estimation, data communication, optimisation, DL spectral efficiency optimization, SP, channel estimation quality, data symbols, data transmission, joint spectral efficiency, massive MIMO system, pilot contamination, pilot overhead, pilot sequences, superimposed pilots, Antennas, Contamination, Interference, Optimization, Uplink
National Category
Telecommunications
Identifiers
urn:nbn:se:liu:diva-145678 (URN)10.1109/GLOCOMW.2017.8269159 (DOI)000426984700128 ()9781538639207 (ISBN)9781538639214 (ISBN)
Conference
4-8 Dec 2017 Globecom Workshops (GC Wkshps), Singapore, Singapore
Note

Funding agencies: Swedish Foundation for Strategic Research (SSF); ERC Starting MORE [305123]; Swedish Research Council; ELLIIT

Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2020-02-27Bibliographically approved
2. Hardware Design and Optimal ADC Resolution for Uplink Massive MIMO Systems
Open this publication in new window or tab >>Hardware Design and Optimal ADC Resolution for Uplink Massive MIMO Systems
2016 (English)In: IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM), Rio de Janeiro, Brazil, July 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 1-5Conference paper, Published paper (Refereed)
Abstract [en]

This work focuses on the hardware design for the efficient operation of Massive multiple-input multiple-output (MIMO) systems. A closed-form uplink achievable data rate expression is derived considering imperfect channel state information (CSI) and hardware impairments. We formulate an optimization problem to maximize the sum data rate subject to a constraint on the total power consumption. A general power consumption model accounting for the level of hardware impairments is utilized. The optimization variables are the number of base station (BS) antennas and the level of impairments per BS antenna. The resolution of the analog-to-digital converter (ADC) is a primary source of such impairments. The results show the trade-off between the number of BS antennas and the level of hardware impairments, which is important for practical hardware design. Moreover, the maximum power consumption can be tuned to achieve maximum energy efficiency (EE). Numerical results suggest that the optimal level of hardware impairments yields ADCs of 4 to 5 quantization bits.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
Series
Sensor Array and Multichannel Signal Processing Workshop (SAM), E-ISSN 2151-870X ; 2016
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-137324 (URN)10.1109/SAM.2016.7569654 (DOI)9781509021031 (ISBN)9781509021048 (ISBN)
Conference
IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) 2016, 10-13 July 2016, Rio de Janerio, Brazil
Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2020-01-15Bibliographically approved

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Analysis of Alternative Massive MIMO Designs: Superimposed Pilots and Mixed-ADCs(618 kB)290 downloads
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Verenzuela, Daniel

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