5G Research @ Aalto

5G Research @ Aalto
http://5g-research.aalto.fi/en/
Researchers
Assist. Prof. Katsuyuki Haneda, Radio science and
technology
mm-wave channel sounders, channel modeling,
antenna design
Prof. Risto Wichman, Signal Proc. for
communications
MIMO for LTE, Massive MIMO (channel estimation),
full-duplex radio, Dirty RF, Geolocation
databases for TVWS, Stochastic geometry
Lecturer Kalle Ruttik, Communications Engineering
Software Defined Radio, C-RAN, implementation
studies
Prof. Jyri Hämäläinen, Mobile communications
Network architectures, relays, small cells, DAS,
HetNets, RRM, public safety communications,
3GPP compliant simulation tools
Prof. Olav Tirkkonen, Communications theory
Prof. Tarik Taleb, Networking technology
Self-organization, flexible spectrum user, D2D
Coding theory (codebooks for massive MIMO),
RF imprirments, Statistics for communications
Implementation studies
Radio access networks, cloud-communications
Prof. Riku Jäntti, Communications engineering
Staff Scientist Jose Costa Requena, Networking
technology
Flexible spectrum use, interference modeling and
control (ultradense networks), MTC
(capillary/sensor networks, wireless automation),
indoor DAS, Implementation studies
Packet core virtualization, Software Defined
Networking, implementation studies
5G challenges
• 1000 x more capacity
• Ultra-reliable communications
5G challenges
Author
NSN
Huawei
NTT Docomo
Zander & Mähönen
Spectral
Total Capacity
Spectrum Efficiency Densification Increase
10X
10X
10X
1000X
3X
3.3X
10X
100X
2.8X
24X
15X
1000X
3X
5X
66X
1000X
I Spectrum
Spectrum
• Most of the current mobile radio systems operate on overcrowded
bands between 450MHz and 3.5GHz.
• On the other hand, between 3.5GHz and 60GHz there is currently
around 7GHz unlisenced spectrum available, including large
contiguous bands
• New access frequency can be made available much more easily on
10-60GHz than below 3.5GHz frequencies.
• In the following we introduce some new directions for the mobile
systems research on mm-wave frequencies making – somewhat
strong - assumptions on the channel properties.
From multipath communication to
dominant path communication
Some mm-wave channel
characteristics:
– Received power in isotropic
antenna is decreasing when
TX
RX
carrier frequency increases
– Diffraction losses are
tremendously large on high
RX
frequencies
– Signal wall penetration losses
are heavy
Dominant path communication:
– Signal reflections occur but
• Major part of the received power
signal power decreases heavily
comes through line-of-sight and/or
in each reflection
first reflected signal component.
Mm-Wave Channel Modeling
Field scattering is limited only to
single-bounce
5
Mm-Wave Channel Modeling
1. Are mm-wave radio channels sufficiently multipath-rich
to support spatial multiplexing in MIMO transmission?
– Yes they are, often as much as lower frequency channels do.
x!
Window!
Pillar!
Table!
y!
Shelf!
7 m!
Tx!
Rx!
5!
7!
4!
6!
12! 17!
11! 16!
3!
10! 15!
2!
9!
14!
8!
13!
1!
Tables!
Tx w/o NLOS meas.! Chairs!
6.75 m!
9
Implications from dominant
path presumption
• Cell shapes
– The cell shapes become quasi-deterministic
– The cell edges will be sharp
– Coverage areas will be usually defined by surrounding physical
obstacles
– Currently used shadow fading model becomes irrelevant
• Coverage vs interference
– If cell overlap exists, overheard signals are usually strong.
– Shot noise type of interference occurs – unless coordinated
communication is applied.
• Control approaches
– Reactive control structures: Based on e.g. UE and eNB
measurements.
– Proactive control: Traces and traffic statistics could be used.
– Out of band control (<3.5 GHz)?
• Multiantenna systems
– Integrated antenna arrays become feasible even in mobile devices
– Beamforming/steerable directive antennas provide means to overcome
heavy attenuation losses.
– Due to frequent LOS and large BWs the importance of spatial
multiplexing decreases.
– Paradigm shift from passive isotropic/sectorized to active directive
radio communication
Much can be infered from RSS
• RSS based fingerprints (Radio maps) can be utilized to
discover samall cells in HetNets
• RSS based inference: devicer free localization,
breathing rate estimation, …
Most accurate indoor localization
technology
Evaluating AAL Systems through Competitive Benchmarking
September 2012
Award for "Most accurate indoor localization technology" at the
"Evaluating AAL Systems through Competitive Benchmarking"
2012 International Competition.
mm-wave antennas
Mm-Wave Antennas
• Integrated lens antenna with beam-steering capability
– Reduction of internal reflections with low permittivity material
– Reduction of side-lobe levels, increased cross-polarization
discrimination and mutual coupling
Mm-Wave Antennas
• On-chip beam-steering antenna
Bulk process
500 µm thick HR silicon
Metal
BCB membrane
10.5mm
membrane
3.3mm
monopole
Y
Bulk silicon substrate
CPW
X
gold
Z
port 1
port 2
port 3 port 4
Z
Membrane process
Metal
BCB membrane
port 5
Max gain 3.8 dBi
Mm-Wave Antennas
• Dielectric rod waveguide antenna
Si HR
Y
X
Radiation
15
efficiency 84 %
– Very wide operating frequency range:
from 75 GHz to 1.1 THz
– Radiation pattern is almost independent
of frequency
– Easily integrated into RF components,
e.g., directional couplers, phase shifters,
amplifiers, and power sensors
II Spectral efficiency
Massive and networked MIMO
• Practical massive MIMO
– Remove the pilot contamination problem
– Channel estimation based on subspace approach,
random matrix theory
– Codebooks for massive MIMO
– Closed form low coherence frames / Grassmannian
codebooks for k-dimensional subspaces in 2m –
dimensional spaces, some optimal
– Stiefel & Grassmannian codebooks
– Convergence of gradient search for low-dimensional
matrix completion in high-dimensional spaces
– Minimum distance bounds on Stiefel and Grassmannian
manifolds
• Distributed antenna systems
– Over the air synchronization of remote radio units
– Centralized base band processing
Self-backhauling
(Large system) analysis of full-duplex/half-duplex trade-offs taking into account the self-interferference
Multihop local area network with full-duplex access points/relays
Routing + precoding + interference cancellation
Goal: Design a local area network using practical performance figures for full-duplex transceivers
0.8
One hop
1-2 hop Half Duplex
1-2 hop FD, 80 dB attenuation
1-2 hop FD, 90 dB attenuation
1-2 hop FD, no self-interference
0.7
0.6
0.5
CDF
•
•
•
•
0.4
0.3
0.2
0.1
0
0.2
0.4
0.6
0.8
1
1.2
Throughput [bps]
1.4
1.6
1.8
2
9
x 10
Full-duplex antenna
• Simultaneous receiving and
• Transmitting / jamming
• Spectrum sensing
• Full-duplex
Full-duplex antenna design
• Relays
• Access points
• System design
• 50dB attenuation on self-interference by
antenna design
• Nonlinear cancellation of self-interference
(~40 dB additional gain by analog and
digital cancellation)
Full-duplex tranceiver design
Cancellation of self-interference by digital signal processing
III Densification
Virtualization
• In Cloud Radio Access Networks (C-RAN), the radio access network
(RAN) functionality is moved to the cloud computing infrastructure.
• Remote radio units (RRU) of different cells are connected to the cloud
via a high speed front-haul link, such as a fiber network.
• Unlike classical cellular system where a baseband processing unit is
deployed in each cell cite, C-RAN has a central processing system in
the cloud.
• Advantages:
– RRU’s have much less energy consumption and require less CAPEX and OPEX
than traditional basestations
– C-RAN provides flexibility in terms of signal processing complexity and
coordination among cells and networks such that resources can be used
efficiently.
Aalto C-RAN based TD-LTE testbed Physical
Architecture
• Network densification with low power cells provides high
capacity especially in hotspots. However, in this scenario,
interference is the biggest challenge. Hence, inter-cell
coordination and joint processing, which are inherent to C-RAN,
are vital to achieve the maximum capacity gain.
Aalto eMME Architecture
AALTO TD-LTE TESTBED
• TD-LTE System
– Implementation of TD-LTE tesbed (Rel. 8) on
general purpose processors and non-real-time
operation system
– Over 30 000 lines of C++ code
– PHY and limited set of RRC and MAC functions
– Cloud-RAN setup
– Base station can run on virtual server
– Flexible spectrum use
– Can interact with Fairspectrum geo-location data base
– TVWS operation
– D2D implementation
– Network controlled D2D
Cloud RAN architecture
– Reliable D2D links
– DAS implementation
– Antenna port selection
– Open loop transmit diversity
Remote radio units
IV Ultra-reliable communications
Ultra-reliable / mission critical MTC
• Ultra-reliable low latency
D2D communications
– Overlay D2D
– CQI feedback
– Protected D2D resources
• Distributed antenna system
– Resilience against HW
failures
– Improved coverage
Summary
• 5G requirements imposes many challenges
– Capacity
– Latency
– Reliability
• Enabling technologies
–
–
–
–
–
New control architectures
mm-wave
massive and networked MIMO
ultra dense networks
Scalability and flexibility through Cloud technologies