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Why we want a 5G?
• Sustained mobile traffic growth (it won’t slow down anytime soon)
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• Radically new applicative scenarios
• Tight and contradictingrequirements
LTE alone will not be enough
• Design compromises to work well in mostsituations (e.g. reference symbols density)
• Not well suited to emerging usage patterns, like M2M or very high speed
• Innovation limited by compatibility with legacyequipment
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Future use cases
Expected usage scenarios for the 2020 decade:
• 50 Mbps everywhere• High speed train• Sensor networks• Tactile internet• Automatic traffic control / driving• Broadcast-like services• Dense urban society
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50 Mbps everywhere
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• Provide broadband access in low ARPU areas
• High throughput, coverage and mobility shouldbe provided in a cost-effective manner
High speed train
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• Fast, reliable connection on very fast train lines
• The train can act as a relay node for itspassengers
• Need to avoidperformance degradationdue to doppler effect
Sensor networks
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• Massive Machine-to-Machine (M2M) deployments over cellular networks
• Generates a huge number of transmissions with very small payloads
• Needs specifically optimized random accessprotocols
Tactile internet
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• Wireless interaction with real and virtual objects• A very low latency is required to perceive a real-
time control• Strong levels of security and reliability should be
guaranteed
Automatic traffic control / driving
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• Vehicle-to-Vehicle communication enablescooperative driving, road traffic balancing and prevention of dangers
• Direct communication among vehicles shouldsupport low latency and high reliability
Broadcast-like services
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• Support multicast/broadcast services to localizedgroups of users, exploiting the shared nature of the wireless medium
• Needs high coverage and a feedback channel in the uplink
Dense urban society
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• Provide broadband connection to many users in crowded urban centers
• Needs high levels of resource reuse, togetherwith effective interference management / mitigation
NGMN vision
• For more information on the 5G vision, pleaseread the NGMN white paper: https://www.ngmn.org/uploads/media/NGMN_5G_White_Paper_V1_0.pdf
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5G Architecture
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5G Architecture
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• Separation of network resources, functions / capabilities, and business models
• Extensive use of Software Defined Network (SDN) and Network Functions Virtualization(NVF) paradigms
• All aspect of 5G operation should be controllableby suitable APIs
5G Architecture
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5G Architecture
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• 5G will be organized in different «slices» spanning all domains of the network
• Slices are sets of resources, functions and parameters tailored for the delivery of a specificservice
• Multiple concurrent slices can share functionsand resources
Flexible frame structure
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Flexible frame structure
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• Frames can have different numerologies (i.e. duration, sub-carrier spacing, number of symbols) in each part of the available bandwidth
• The parameters are optimized for the requirements of each service
• Numerologies are multiples of the LTE frame structure, to ease co-existence and hardware reuse
New waveforms
New waveforms are proposed, with improvementsover CP-OFDM
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FBMC P-OFDM ZT-s-OFDM UF-OFDM
Lower OOB emissions X X X X
Asyncronous TX X X X X
No cyclic prefix X X
OFDM coexistence X X X
Robust to doppler effect X X
Massive MIMO
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• Large antenna arrays can be used to transmitmany concurrent streams
• … but there is ah high overhead for channelestimation in downlink!
TDD
• TDD mode simplifies channel estimation: reciprocity allows the DL channel to be derivedfrom the UL channel
• UL estimation cost is much lower than UL cost in a Massive MIMO setting
• Inter-cell interference becomes the limitingelement (see the «pilot contamination» problem)
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Millimeter waves
• Lots of usable bandwidth in the 30-300 GHz frequency range
• However, propagation losses are drasticallyhigher than current wireless systems
• Indoor propagation is also blocked
• Can be useful in femtocells• Small antennas make Massive MIMO easier• Precise beamforming can compensate for the
increased path loss
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Non-Orthogonal Multiple Access
• Superposition coding in the power domain increases spectral efficiency
• Successive Interference Cancellation (SIC) isused at the decoder to separate the signals
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Interference management
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Interference management
• 5G will inherit many techniques from LTE to reduce interference and increase spectralefficiency (small cells, CoMP, massive MIMO…)
• Most of them may be active concurrently in the same places
• A general framework for interferencemanagement will coordinate them to maximizethe target objective (e.g. throughput, fairness…)
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Predictor antenna for fast vehicles
• A row of antennas is mounted on top of the vehicle
• Channel estimation is based on the (expected) future position of the antennas
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Massive access protocols
• LTE uplink requires strict time sinchronizationamong transmitting devices
• The RACH procedure with timing advance (TA) is costly for sporadic transmission of small packets
• New waveform can permit one-shot transmissionwith only coarse synchronization in time and frequency
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Massive access protocols
• Coded Random Access applies the decode-and-subtract approach to multiple copies of the packets
• Advanced multi-user detection techniques (e.g. Compressive Sensing) allow higher by decodingnon-singleton slots as well
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Advanced channel coding
• New channel coding method can reduce errorrates compared to LTE, particularly with short packets
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Broadcast transmissions
• Broadcast in LTE (with Multicast-Broadcast Single Frequency Network) is SISO-only and unidirectional: no CQIs nor ACKs
• MIMO beamforming can be used in 5G to serve different multicast groups concurrently
• An additional unicast channel allows for CQI reporting, dynamic service creation and ad-hoc retransmissions
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Early tests
• On february 2016, USA operator Verizonconducted tests with real prototype equipment
• The top recorded speed was 10 Gbit/s, usingmmWave at 28 GHz, beamforming and massive MIMO
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