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Cell-Free Massive MIMO
Giovanni InterdonatoEricsson AB – Linköping University
25 November 20165Gwireless Public Talk – Giovanni Interdonato 1
Introduction
¡ Industrial Ph.D. candidate at Linköping University,Communication Systems division (ISY).
¡ Researcher at Ericsson AB, Linköping. WirelessAccess Networks department, Ericsson Research.
¡ Early Stage Researcher (ESR) at “5Gwireless”Marie-Curie Innovative Training Network (ITN).Ø http://www.h2020-msca-etn-5gwireless.eu/
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5Gwireless topics
5Gmassive MIMO
Cell-free massive MIMO
mmWave communications
full-duplex communications
device-to-device communications
network-coded protocols
stochastic geometry, game
theory
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Concepts and definitions
¡ Spectral Efficiency: the maximum amount of data that can be transmitted over a given bandwidth with the fewest transmission errors [bit/s/Hz].
¡ Energy Efficiency: the maximum amount of energy needed to transfer a certain quantity of data [bit/J].
¡ Throughput: a measure of how many bits of information a communication system can process in a given amount of time [bit/s].
¡ Coverage probability: probability of a base station to guarantee a successful communication to a terminal.
¡ Signal blocking probability: probability that a signal is blocked due to the presence of obstacles along the propagation channel (it depends also on the signal frequency).
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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What is Massive MIMO?
¡ MIMO: Multiple-Input Multiple-Output
¡ Multi-antenna transmission: many parallel transmissions spatially focused to each desired user (spatial multiplexing)
¡ Massive: Base station with >100 antenna elements
¡ Keys: o Many more antennas than users
o Small antennas and transceiver chains (not massive size)
o Very directive signals (beamforming)
160 antenna elements, LuMaMi testbed, Lund University
60 c
m
NOT massive
size
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Why Massive MIMO?
¡ To cope the increasing number of connected devices and data traffic growth
¡ Increase spectral efficiency in 5Go >20-fold gain over 4G networks (i.e., LTE and LTE advanced) are foreseen
¡ Increase network throughput (5G design goal: up to 1000x improvements)o 𝑇ℎ𝑟𝑜𝑢𝑔ℎ𝑝𝑢𝑡 [𝑏𝑝𝑠/𝑘𝑚1] = 𝐶𝑒𝑙𝑙 𝐷𝑒𝑛𝑠𝑒 ∗ 𝐴𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒 𝑆𝑝𝑒𝑐𝑡𝑟𝑢𝑚 ∗ 𝑆𝑝𝑒𝑐𝑡𝑟𝑎𝑙 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦
¡ Favorable propagation in most propagation environments
o Channels from BS to users are “sufficiently different”
o Simultaneous multiple transmissions with no interference
¡ Resource allocation and processing are simplified, not complicated
o Spatial resource allocation: each user gets the whole bandwidth.
o Linear signal processing (maximum ratio, zero-forcing, etc.)
¡ Many potential deployments (e.g., Cell-free massive MIMO)
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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What is Cell-free massive MIMO?
Figure: conventional massive MIMO (left) vs Cell-Free massive MIMO (right)
Cell-freeMassive MIMO
= Massive MIMO
+ cell-freetopology
distributedarchitecture
+
CPU
UE
APantennas no cell
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Why Cell-free massive MIMO?
¡ Improves spatial multiplexing
o Introduces macro-diversity gain
¡ Reduces interference among users
¡ Improves coverage probability
¡ Improves energy efficiency
Advantages of a distributed cell-free topology:
¡ More suitable for high throughput applications, no cell-edge users
¡ Support of huge number of connections, no scalability limit
The reliability of a signal is improved if it is transmitted from antennas situated in different sites by using channels with different characteristics. This diversity improves the strength and the quality of the signal at the receiver.
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Why Cell-free massive MIMO?
¡ Supporting both cellular and high (mmWave) frequencies
o Signal blocking probabilityis smaller compared to in a centralized architecture
¡ Indoor applications
¡ Improving resilience
¡ Avoiding large and visible BS installations
¡ Easier to deploy
Practical reasons to prefer a distributed cell-free topology:
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Readings about massive MIMO
¡ T. L. Marzetta, “Noncooperative cellular wireless with unlimited numbers of base stationantennas,” IEEE Trans.Wireless Commun., Nov. 2010.
¡ H. Q. Ngo, E. G. Larsson, and T. L. Marzetta, “Energy and spectral efficiency of very largemultiuser MIMO systems,” IEEE Trans. Commun., Apr. 2013.
¡ E. G. Larsson, F. Tufvesson, O. Edfors, and T. L. Marzetta, “Massive MIMO for nextgeneration wireless systems,” IEEE Commun. Mag., Feb. 2014.
¡ E. Björnson, E. G. Larsson, T. L. Marzetta, “Massive MIMO: 10 Myths and One CritcalQuestion,” IEEE Commun. Mag., Feb. 2016.
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Readings about Cell-free massive MIMO
¡ H. Q. Ngo, A. E. Ashikhmin, H. Yang, E. G. Larsson, and T. L. Marzetta, “Cell-free massiveMIMO versus small cells,” IEEE Trans. Wireless Commun., Feb 2016. Available onhttp://arxiv.org/abs/1602.08232
¡ G. Interdonato, H. Ngo, E. G. Larsson, and P. Frenger, “On the Performance of Cell-FreeMassive MIMO with Short-Term Power Constraints” in IEEE 21st International Workshopon Computer Aided Modelling and Design of Communication Links and Networks(CAMAD), Oct 2016. Available on https://arxiv.org/abs/1608.05121
¡ G. Interdonato, H. Ngo, E. G. Larsson, and P. Frenger, “How much do downlink pilotsimprove Cell-Free massive MIMO?” in Proc. IEEE Global Comm. Conference(GLOBECOM), Dec 2016. https://arxiv.org/abs/1607.04753
25 November 20165Gwireless Public Talk – Giovanni Interdonato
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Thank [email protected]
twitter.com/gio_interdonato
linkedin.com/in/interdonatogiovanni
researchgate.net/profile/Giovanni_Interdonato
arxiv.org/a/interdonato_g_1
Contacts and Social Media
25 November 20165Gwireless Public Talk – Giovanni Interdonato
