mobilné komunikácie lecture 3: d2d communication for 5g · 2020-03-26 · at present we have...
TRANSCRIPT
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Mobilné komunikácieLecture 3: D2D communication for 5G
Ján PapajKEMT – FEI – TUKE
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OutlineIntroductionEvolution towards 5G
Introduction – Why D2D CommunicationD2D CommunicationD2D Offloading
D2D Research at TCSStandardization of D2D CommunicationConclusion
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Can we Match to the Growth? Both backhaul as well as the access capacity should be increased Increasing Access Capacity…
Add more BTSs At present we have 7,36,654 BTS in India Tata Teleservices alone has 3000+ BTS in Bangalore New BTS will add CAPEX and OPEX
Release new spectrum Huge cost for the operators Seems to be a challenge
• Only 200+ MHz available in India Improve the spectral efficiency
Not possible always• Theoretical Limits are being reached
Usability is the key • Yet to deploy LTE Rel 8
» Spectral efficiency = 4-5Increasing Backhaul Capacity
Nationwide optical fibre backboneOnly a few operators can do this
CAPEX and OPEX issue again
Source – Huawei - The_full_spectrum_of_possibilities
Source – ITU -Link: http://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-M.2243-2011-PDF-E.pdf
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Preliminaries - What is device cooperation?
Device cooperation is a technique to exploit D2D(Device-to-Device) link in addition to the existing WWAN link for the following benefits. • Capacity enhancement• Reduction of power consumption
Related terminologies• Source device: The end device whom the data traffic to the BS is generated from or the data
traffic generated from the BS is targeting for• Cooperative device: The device who helps the source device(s) in UL or the BS in DL by
relaying or co-transmitting data and control information• Network lifetime: Duration of time until the first node (device) failure due to battery depletion
WWAN BSWWAN link
WWAN link (e.g. 802.16m)
D2D link
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Preliminaries - Device cooperation modes
Mobile relaying• A cooperative device performs the functionality of a RS(Relay Station). A cooperative device forwards the data of a source
device to the BS. For example, the source device send data traffic to the cooperative device through D2D link at T1, and the cooperative device send it to the BS at T2 as shown in Fig. 1. Additionally, a concept of group anchor where an anchor devicecollects data traffic from multiple source devices and forwards it to the BS, can be another example of mobile relaying.
Cooperative transmission• Both of a cooperative device and a source device transmit data traffic of a source device to the BS. In this mode, the data traffic
of the source device is shared with the cooperative device through the D2D link transmission in advance, and then the shared data traffic is transmitted to the BS from the source and cooperative device jointly. For example, the source device send data to the cooperative device at T1, and both of the source and cooperative devices transmit the data to the BS simultaneously at T2as shown in Fig. 2.
BS
Cooperative device
Source device
T1
T2
Fig. 1. Mobile relaying
(a) Mobile relaying (b) Group anchor
BS
Source device
Cooperative device
T1
T2
T2
Fig. 2. Cooperative transmission
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PurposeTo propose/design optimal scheduling algorithms for D2D uplink/downlink in data networks
such as HSPA, LTE, LTE-A, etc., networks. D2D communication model for LTE/LTE-A systems that can be used for mobile data offloading
Why D2D?Possible to have direct communication between close proximity UEs
Reuse of cellular resources –use cellular spectrum D2D users can use same resource blocks of the cellular users Higher and better network performance than WiFi, Bluetooth, etc. Viz: in social networking, online gaming, multimedia sharing, etc.
Gain and gain Reuse gain, proximity gain, hop gain Higher data rate, low end-to-end delay
Emergency services
D2D Communication
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● Securityo The security features of WiFi and Bluetooth are much less robust than
those used in public cellular systems. They would not be adequate for major public services and they would be unsuitable for public safety applications.
● Independence from cellular networkso WiFi and Bluetooth operate independently from cellular radio
technology such as LTE. Any form of device-to-device discovery based on them would have to run in parallel with cellular radio operation, which would be inefficient and would become a significant drain on device batteries.
D2D vs Ad-hoc
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● Unlicensed spectrumo WiFi and Bluetooth operate in unlicensed spectrum, without any
centralised control of usage or interference. This is not generally a problem when usage densities are low, but it would become a major limitation as proximity-based services proliferate. Throughput, range and reliability would all suffer.
● Manual pairingo WiFi and Bluetooth rely on manual pairing of devices to enable
communication between them, which would be a serious stumbling block for autonomous, dynamic proximity-based services.
● Transmission distance and data transfer rate (see next slide)
D2D vs Ad-hoc
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Machine to Machine (M2M) Communication Machine Type Communication – 3GPP TR 22.368
D2D vs. M2M
D2D vs. Ad-hoc NetworksD2D Ad-hoc Networks
Licensed and Free Spectrum Free Spectrum
QoS can be ensured No QoS guarantee
Seamless Connectivity Manual Connectivity
Security is guaranteed Security is a challenge
D2D M2MDescribes connectivity Services Application Oriented
Direct device to device communication Remote devices communicates through a centralized node
Access specific Access agnostic
Local comm. improves spectral efficiency Not applicable
D2D vs. M2M and Ad-hoc Networks
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Big Question Is it possible for UEs in proximity to communicate among themselves ?
Regular Communication Model In coverage D2D Communication Model
eNB
Data PathControl Path (C-Plane)
D2D (U-Plane)
eNB
Control Path (C-Plane)Data Path
Device to Device (D2D) Communications
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D2D Discovery: Posteriori discovery
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D2D Discovery●●●
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Devices can discover the presence of other devices in their vicinity Proximity discovery is a natural trigger for direct communicationProximity discovery can be used as a standalone service and not trigger communication (social networking)General requirements:o
o
o
Fast discoveryLow energy consumptionMinimize additional interference to the WAN and resource degradation
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D2D Discovery: Methods● D2D provides 2 methods of discovery:
● Network discovery (Radio)o A device is able to discover and be discovered by other devices in
radio proximity● User assisted discovery (Application Layer)
o A user of a service or social networking application is able to discover and be discovered by other users of the same service or social networking application
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D2D Discovery: Node/Peer discovery
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● Before two devices can directly communicate with one another, they must first discover that they are near each otherTwo peer devices need to meet in space, time and frequencyNo coordinated discovery: Peer discovery is a randomized procedure, in which a device sends signals without any knowledge about the location of the intended peer (energy consuming)Coordinated discovery: The network uses its knowledge of approximate device locations to recognize devices which could benefit from D2D communications. When a D2D pair has been found, the network coordinates the time and frequency allocation for sending/scanning for beacons
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Overlay and Underlay D2D
Higher spectrum efficiency by spatial reuseNeed to cope with interference
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Dedicated resources for D2DReduce the concern about interferenceNeed explicit resource allocation
D2D
Cellular
Underlay
D2D
Cellular
Overlay
Cellular
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● Communication occurs under licensed spectrum: Cellular spectrum is used for both cellular link and D2D
● High control over cellular (licensed) spectrum● Underlay:
o Cellular and D2D communication share the same radio resources● Overlay:
o Cellular and D2D are given dedicated cellular resources (a cellular resource is subtracted from cellular users)
● Underlay is more popular than overlay: probably due to its hight spectral efficiency
D2D communication Inband: Overview
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● Pros:- Underlay D2D increase the spectral efficiency of cellular spectrum Any cellular device is capable of using inband
- QoS is easy because the cellular spectrum can be fully managed by theeNB,
- Transmission distance ~ 1km. - Data rate ~ 1Gbps
D2D communication Inband: Pros and cons
● Conso
oCellular resources might be wasted in overlayInterference mgmt among D2D and cellular transmission is very challenging/complex
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●●●●
Communication occurs under unlicensed spectrumAims to eliminate the interference issue between D2D and cellular linksRequires an extra interface, usually Wi-Fi direct, ZigBee or Bluetooth Classified in:o Controlled
♣ The control of the second interface is under the cellular network● Similar to Android NFC / Androidbeam
o Autonomous♣ D2D controlled by the users: second interface is not under cellular control
● Transmission distance and data transfer rate is extremely lower than Inband
D2D communication Outband: Overview
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● Pros:o
oNo interference with cellular communication (unlicensed spectrum) Users can have simultaneous cellular and D2D transmission
● Conso
o
o
o
Cellular devices requires two wireless interfaces (e.g. LTE and WiFi) Power consumption of the extra interface (WiFi)Lower transmission distance Lower transmission data rate
D2D communication Outband: Pros and cons
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D2D Interference ManagementPossible solutions
Resource allocation (OFDMA)Throughput maximizationRevenue maximization Energy consumptionIncentive
MIMO techniques, such as interference alignment
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Classification based on Frequency of use In-band - Network assistedOut-band - Independent
Classification based on ServicesEmergency services (both in/out band)Commercial services (in-band only)
Emergency Services Commercial ServicesD2D
eNB
Control PathData Path
D2D
eNB
Control PathData Path
D2D Communication - Classification
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TDD Frame structure
Technology behind D2D CommunicationDiscovery and classifications
Discovery typesProactive – Discovery signal is per group of UEs or all UEsReactive – Discovery signal is per UE
eNB Classifies D2D and Cellular pairsBased on - location, distance, power control, interference, etc.
Restructuring of the Scheduling procedures Scheduling of cellular and D2D transmissions
Overlapping - non-interfering same RB schedulingNon-overlapping – unused cellular RBs used for D2D
D2D frame usageIn TDD – UL sub-frame (U) will be usedIn FDD – UL spectrum will be used
RBs can be re-used through scheduling
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Challenges in D2D CommunicationsCommunication Challenges
Location of the devices Ensure accuracy
Signaling techniques need to be amendedSignaling overhead to be evaluated
New Modulation Schemes can be proposedCellular: SC-FDMA Tx (UE-eNB) and OFDMA Rx (eNB-UE) D2D: SC-FDMA receiver in UE (UE-UE)
Interference ManagementTo ensure interference below threshold in case of overlapping D2D
Power control modelSelect the transmit power depending on distance/channel characteristics
Channel modelShort distance (indoor/outdoor) channel model can be explored
D2D traffic characterizationWhat percentage of the users are D2D?
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Why LTE D2D Communication ?LTE-D2D
Strong Resource Management
Tighter spectrum reuse
Offloading can be achieved
Better Performance
Higher data rate, low end-to-end
delay
Energy Efficient
Reliability and Scalability
Operator initiated Services
Security can be guaranteed
Regulatory and Standardization
Under 3GPP and TSD
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Standardization attempts under 3GPP Rel 12/13 (ProSe) - 3GPP TR 21.905 / TR 22.803 / TR 36.814/ TR 36.843 Discovery for ProSe
UEs at proximity should identify each other using E-UTRA/EPC
ProSe D2D communication Communication between two UEs in proximity Path can be established directly or through eNB
UsageCommercial /SocialPublic Safety (with and without coverage)Network Offloading
UE -1
ProSeAPP LTE - Uu
E - UTRAN
UE-2
ProSeAPP
EPC (MME,
S/PGW)
S 1
ProSeAPP Server
SGi
ProSe Function
PC 4 PC 2
PC 5 LTE - Uu
PC 3
PC 1
PC 6
HSS/SLP
Source - 3GPP-23.703-V12.0.0
ProSe System Architecture
D2D Communication @ 3GPP
HSS/SLP
4
PC
EPC
(MME, S/PGW)
6
PC
1
PC
3
PC
Uu
-
LTE
5
PC
2
PC
ProSe Function
SGi
Server
ProSeAPP
1
S
ProSeAPP
UE-2
UTRAN
-
E
Uu
-
LTE
ProSeAPP
UE -1
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D2D Use CasesUsecase – 1
M2M communication using D2D underlaying LTEeNB classifies, schedules the communication
Usecase – 2 M2M communication using D2D offloading
Offloader can relay data
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● Two categories:o
oSimple D2D: sender and receiver exchange data with each other Relay: D2D user forward data from and to other users
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Use cases examples: Local Data Service
♣
♣
♣
♣
♣
♣
Information sharing (bittorrent) Mobile multiplayer gaming
Mobile advertising (proximity services)Streaming services (IPTV, google chromecast, apple airplay) Social (Tinder, Waze, Facebook)
Community services
D2D use cases
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● V2V - Vehicle to Vehicle communication:o Collision avoidance system requires a very low latency for example to
coordinate braking between vehicleso V2V can provide not only information about the nearest car in front,
but also from other cars within the communication range, including traffic (waze ?)
● Group handover of multiple users (for example in a Bus)o By using D2D the devices in a group inform each other about the
handover and its parameters with minimal signaling from the network
D2D use cases
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● Multiuser cooperative communication (MUCC)o
oBenefited user (BU) is in an area with poor cellular signalAnother user is in an area with good cellular signal. This user may help BU to improve its signal and act as a supporting user (SU)
D2D use cases
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● D2D communications with network coding
- Users requesting the same content can form cooperative clusters to achieve higher energy efficiency
- eNB transmits the content to the cluster heads- Cluster heads multicasts the contents to the other devices within the cluster
through D2D links Eg: world cup games - IPTV:
o Multicast of linear channels, Pay-Per-View, VideoRecording
D2D use cases
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● Public safety (police, fire and ambulance services)o Many of these organisations uses relatively old technology such as
TETRA system developed in the 90’s with limited capabilityo US government has expressed desire to move to LTE for public safetyo Crucial requirement for these users is the ability to communicate with
each other outside of a mobile network (walkie talkie), which is not supported by LTE, but is one of LTE D2D objectives
D2D use cases
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Direct M2M under LTEDirect M2M for close proximity devices
Communicate directly whenever close to receiver (UE/eNB/AP)eNB takes care of Interference and control managementClassification, scheduling, etc. through APPs
M2M offloading for bad-channel devicesRemote sensors, non-LOS connectionsForeign and unpredictable channel conditionsOffload message packet to a nearby offloaderImproved spectral efficiency and system utilization
ExamplesOffloading of images from cam to mobileDirect songs/images transfer from smartphone to
car/home AP
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Evaluation of D2D Communications (1/3)Network assisted D2D is considered
Carrier frequency – 2 GHzeNB needs to identify the D2D and cellular pairs
3GPP’s D2DSS signaling for discoveryTwo types of communications will exist
Existing cellular communications and D2DShould not interfere in case of overlapping communication
Broad AssumptionsD2D does not use the full duplex on a given carrierMobility – 3km/hrFull synchronization between UEs and UE to eNB is possibleUnicast communication only
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Evaluation of D2D Communications (2/3)Simulations
30% average D2D users consideredStatic users only
Discovery and classificationAssumed 3GPP specifications for discoveryProximity based classification by eNB - proactive
Optimal D2D scheduling under LTE Two phase schedulingModelled as a Binary Integer ProgramSolved using Matlab
Power control Simultaneous transmission : non-interfering
QoS ImprovementReduced delayEnergy efficientImproved spectral efficiency
Network and per-user spectral efficient improved15% at-least
Simulation topology: Cellular vs. D2D
UE1
UE2
UE3eNB
UE1
UE2
UE3eNB
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Evaluation of D2D Communications (3/3)Emulations
Through test-bed level implementationWiFi AP as LTE eNB, smartphones as UEs
Discovery based on signal strength and locationService classification – D2D/Cellular
Depending on location, distance, interference, etc.Power control mechanism for smartphones
eNB computes required Tx power for small D2D distanceeNB notifies UE the reduced Tx power, modulation, timing, etc.
TDD scheduling scheme implementedD2D & cellular transmissions on same channelTime synchronization is assumed
APP based deploymentJAVA API for eNB
Desktop with Ubuntu – 14.04 as eNBLivetek WiFi adapter
Android APP for Tx, Rx (UEs)Lenovo Nexus 5, Android KitKat 4.4.2
Control Flow Diagram for D2D
Test-bed Topology
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D2D
eNB
Control PathData PathOffloading Path
D2DD2D
D2D Offloading If the load at eNB is high or if the channel between the UE - eNB is poor
Offloading via another UE can be plannedMultiple UEs may be involved Effective data rate/spectral efficiency can be improvedEnergy saving can be achievedBoth licensed and un-licensed spectrums can be used
Challenges in D2D OffloadingTraffic characterization
Distorted user discoverySynchronization between UEs
Network assisted vs. independentInterference management and SchedulingEnergy consumption due to sensing and location updates
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D2D Offloading EvaluationsSimulations
Matlab based offloading scheduling under LTE Static users, 30% are distorted (poor signal)Cell radius: 300 mt,D2D range: 5-30 mtsFixed/adaptive modulation scheme
Channel modellingChannel between UE-eNB and UE-UEShort term, long term fading is considered
SchedulingRound robin scheduling D2D transmission scheduled prior to relay
QoS ImprovementGuaranteed delivery for distorted users
Low delay due to reduced failure rateImproved spectral efficiency
User and system throughput improved : 30-40% Better system utilization
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D2D Offloading - DiscussionsPractical Deployment Scenario
Single operator caseBilling is the key issueTraffic characteristics
Data usage pattern of UEs Signaling for distorted users – eNB assited/Distributed
Multiple operators caseFurther research required
StandardizationMobility modeling & dynamic classification
Location of UEs – discovery and classificationModeling the mobile channel
Secure D2D communicationControl signaling, authentication, connection timing, etc.
Power-control at UEEquipment manufacturers should be involved
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● Although basic requirements are set, details are being still studied/developed
● Big impact of the new technologies proposed:o D2D discovery
♣
♣
Good: Might be a key tool for social networking and other internet appsBad: Privacy concerns, device battery consumption
o D2D communication:♣
♣
Good: Offloading traffic, High data rate speeds Bad: Interference / deterioration of existing services
Conclusion
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Conclusion D2D provides one more mechanism for network offloading Is now on the way towards standardization through 3GPP
Rel 12 ProSe Discovery, ProSe Communication One-to-Many ProSe UE-to-NW relay (with no RAN impact), ECP support for WLAN
Rel 13 Communication: One-to-One communication; direct and via eNB, Service continuity Discovery: Interaction with 3rd party apps & UE terminal apps
LTE-D2D is being positioned for emergency services in the US Is a new tool for social networking Many issues are still being unresolved and thus a fertile ground for research
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Mobilné komunikácie�Lecture 3: D2D communication for 5GOutlineCan we Match to the Growth? Preliminaries - What is device cooperation?Preliminaries - Device cooperation modesD2D CommunicationD2D vs Ad-hocD2D vs Ad-hocD2D vs. M2M and Ad-hoc NetworksDevice to Device (D2D) CommunicationsD2D Discovery: Posteriori discoveryD2D DiscoveryD2D Discovery: MethodsD2D Discovery: Node/Peer discoveryOverlay and Underlay D2DD2D communication Inband: OverviewD2D communication Inband: Pros and consD2D communication Outband: OverviewD2D communication Outband: Pros and consD2D Interference ManagementD2D Communication - Classification�Technology behind D2D CommunicationChallenges in D2D CommunicationsWhy LTE D2D Communication ?D2D Communication @ 3GPPD2D Use CasesD2D use casesD2D use casesD2D use casesD2D use casesD2D use casesDirect M2M under LTEEvaluation of D2D Communications (1/3)Evaluation of D2D Communications (2/3)Evaluation of D2D Communications (3/3)D2D Offloading D2D Offloading EvaluationsD2D Offloading - DiscussionsConclusionConclusionSlide Number 41