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Aspects of Power Allocation in Massive MIMO
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The past decades have seen a rapid growth of mobile data trac, both in terms of connected devices and data rate. To satisfy the ever growing data trac demand in wireless communication systems, the current cellular systems have to be redesigned to increase both spectral eciency and energy eciency. Massive MIMO (Multiple-Input-Multiple-Output) is one solution that satisfy both requirements. In massive MIMO systems, hundreds of antennas are employed at the base station to provide service to many users at the same time and frequency. This enables the system to serve the users with uniformly good quality of service simultaneously, with low-cost hardware and without using extra bandwidth and energy. To achieve this, proper resource allocation is needed. Among the available resources, transmit power is one of the most important degree of freedom to control the spectral eciency and energy eciency. Due to the use of excessive number of antennas and low-end hardware at the base station, new aspects of power allocation compared to current systems arises. In the rst part of the thesis, a new uplink power allocation schemes that based on long term channel statistics is proposed. Since quality of the channel estimates is crucial in massive MIMO, in addition to data power allocation, joint power allocation that includes the pilot power as additional variable should be considered. Therefore a new framework for power allocation that matches practical systems is developed, as the methods developed in the literature cannot be applied directly to massive MIMO systems. Simulation results conrm the advantages brought by the the proposed new framework. In the second part of the thesis, we investigate the eects of using low-end ampliers at the base stations. The non-linear behavior of power consumption in these ampliers changes the power consumption model at the base station, thereby changes the power allocation. Two dierent scenarios are investigated and both results show that a certain number of antennas can be turned o in low load scenarios.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. , 32 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1767
National Category
Communication Systems Telecommunications Computer Engineering Signal Processing Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:liu:diva-132784ISBN: 9789176856185OAI: oai:DiVA.org:liu-132784DiVA: diva2:1049450
Presentation
2016-12-20, Visionen, hus B, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2016-11-24 Created: 2016-11-24 Last updated: 2016-11-25Bibliographically approved
List of papers
1. MIMO Capacity under Power Amplifiers Consumed Power and Per-Antenna Radiated Power Constraints
Open this publication in new window or tab >>MIMO Capacity under Power Amplifiers Consumed Power and Per-Antenna Radiated Power Constraints
2014 (English)In: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Institute of Electrical and Electronics Engineers (IEEE), 2014, 179-183 p.Conference paper (Refereed)
Abstract [en]

We investigate the capacity of the multiple-input-multiple-output channel taking into account the consumed power in the power amplifiers. The mutual information is optimized with a limitation of total consumed power and per-antenna radiated power for a fixed channel with full channel state information at both the transmitter and receiver. The capacity is thus obtained by optimizing the input distribution to maximize the mutual information. Since the optimization problem is non-convex, direct computation of the capacity suffers from high computational complexity. Hence upper and lower bounds on the capacity are given as benchmarks for different ad-hoc schemes. An efficient suboptimal algorithm is also presented. Numerical results show that the suboptimal algorithm performs close to the capacity.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2014
Series
, IEEE International Workshop on Signal Processing Advances in Wireless Communications, ISSN 2325-3789
Keyword
MIMO capacity; power amplifier; consumed power constraint; per-antenna power constraint
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-114602 (URN)10.1109/SPAWC.2014.6941397 (DOI)000348859000037 ()9781479949038 (online) (ISBN)9781479939121 (USB) (ISBN)9781479949021 (PoD) (ISBN)
Conference
IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC),June 22-25, Toronto, Canada
Available from: 2015-02-26 Created: 2015-02-26 Last updated: 2016-11-24Bibliographically approved
2. Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios
Open this publication in new window or tab >>Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios
2015 (English)In: 2015 IEEE International Conference on Communications (ICC), IEEE , 2015, 1697-1702 p.Conference paper (Refereed)
Abstract [en]

For both maximum ratio transmission (MRT) and zero forcing (ZF) precoding schemes and given any specific rate requirement the optimal transmit power, number of antennas to be used, number of users to be served and number of pilots spent on channel training are found with the objective to minimize the total consumed power at the base station. The optimization problem is solved by finding closed form expressions of the optimal transmit power and then search over the remaining discrete variables. The analysis consists of two parts, the first part investigates the situation when only power consumed in the RF amplifiers is considered. The second part includes both the power consumed in the RF amplifiers and in other transceiver circuits. In the former case having all antennas active while reducing the transmit power is optimal. Adaptive scheme to switch off some of the antennas at the base stations is found to be optimal in the latter case.

Place, publisher, year, edition, pages
IEEE, 2015
Series
, IEEE International Conference on Communications, ISSN 1550-3607 (Print), 1938-1883 (online)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-127290 (URN)10.1109/ICC.2015.7248569 (DOI)000371708101150 ()9781467364324 (online) (ISBN)9781467364317 (USB) (ISBN)9781467364300 (PoD) (ISBN)
Conference
IEEE International Conference on Communications (ICC), 8-12 June, London, UK
Available from: 2016-04-20 Created: 2016-04-19 Last updated: 2016-11-24Bibliographically approved

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