Transcript (D2D) Communications

Device-to-Device (D2D) Communication
Networks Lab, TCS Research
TSDSI SG1 F2F meeting,
IEEE Bangalore, July 2015
Outline
 Introduction
 Evolution towards 5G
 Introduction – Why D2D Communication
 D2D Communication
 D2D Offloading
 D2D Research at TCS
 Standardization of D2D Communication
 Conclusion
Experience certainty.
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Growth of Networks
 Challenges for future wireless communication  Massive growth in connected devices
 Smart phones, laptops, sensor devices, etc
 Massive growth on network traffic
 Almost 1000+ times or more
 61% CAGR expected
 Wide range of applications and their requirements
 Social media, video on demand, live TVs, gaming, IoT, etc
Experience certainty.
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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
Source – Huawei - The_full_spectrum_of_possibilities
 Not possible always
• Theoretical Limits are being reached
 Usability is the key
• Yet to deploy LTE Rel 8
» Spectral efficiency = 4-5
 Increasing Backhaul Capacity
 Nationwide optical fibre backbone
 Only a few operators can do this
 CAPEX and OPEX issue again
Source – ITU -Link: http://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-M.2243-2011-PDFE.pdf
Experience certainty.
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D2D Communication
 Purpose
 To 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
Experience certainty.
5
Device to Device (D2D) Communications
 Big Question
 Is it possible for UEs in proximity to communicate among themselves ?
Control Path (C-Plane)
Data Path
eNB
Control Path (C-Plane)
Data Path
eNB
D2D (U-Plane)
Regular Communication Model
In coverage D2D Communication Model
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Experience certainty.
6
D2D vs. M2M and Ad-hoc Networks
 Machine to Machine (M2M) Communication
 Machine Type Communication – 3GPP TR 22.368
 D2D vs. M2M
D2D
M2M
Describes 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. Ad-hoc Networks
D2D
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
Experience certainty.
7
D2D Communication - Classification
 Classification based on Frequency of use
 In-band - Network assisted
 Out-band - Independent
 Classification based on Services
 Emergency services (both in/out band)
 Commercial services (in-band only)
eNB
D2D
Emergency Services
Control Path
Control Path
Data Path
Data Path
eNB
D2D
Commercial Services
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Experience certainty.
8
Technology behind D2D Communication
 Discovery and classifications
 Discovery types
 Proactive – Discovery signal is per group of UEs or all UEs
 Reactive – Discovery signal is per UE
 eNB Classifies D2D and Cellular pairs
 Based on - location, distance, power control, interference, etc.
 Restructuring of the Scheduling procedures
 Scheduling of cellular and D2D transmissions
 Overlapping - non-interfering same RB scheduling
 Non-overlapping – unused cellular RBs used for D2D
RBs can be re-used
through scheduling
 D2D frame usage
 In TDD – UL sub-frame (U) will be used
 In FDD – UL spectrum will be used
TDD Frame structure
Experience certainty.
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Challenges in D2D Communications
 Communication Challenges
 Location of the devices
 Ensure accuracy
 Signaling techniques need to be amended
 Signaling overhead to be evaluated
 New Modulation Schemes can be proposed
 Cellular: SC-FDMA Tx (UE-eNB) and OFDMA Rx (eNB-UE)
 D2D: SC-FDMA receiver in UE (UE-UE)
 Interference Management
 To ensure interference below threshold in case of overlapping D2D
 Power control model
 Select the transmit power depending on distance/channel characteristics
 Channel model
 Short distance (indoor/outdoor) channel model can be explored
 D2D traffic characterization
 What percentage of the users are D2D?
Experience certainty.
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Why LTE D2D Communication ?
LTE-D2D
Strong Resource
Management
Better
Performance
Reliability and
Scalability
Tighter
spectrum reuse
Higher data rate,
low end-to-end
delay
Operator
initiated
Services
Offloading can
be achieved
Energy Efficient
Security can be
guaranteed
Experience certainty.
Regulatory and
Standardization
Under 3GPP and
TSD
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D2D Communication @ 3GPP
 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
ProSeAPP
LTE- Uu
S1
UE -1
E -UTRAN
PC 5
LTE- Uu
SGi
EPC
(MME,
S/PGW)
HSS/SLP
ProSeAPP
PC 4
UE-2
 Usage
Commercial /Social
Public Safety (with and without coverage)
Network Offloading
PC 3
PC 2
ProSe Function
PC 6
PC 1
Source - 3GPP-23.703-V12.0.0
ProSe System Architecture
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Experience certainty.
ProSeAPP
Server
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D2D Use Cases
 Usecase – 1
 M2M communication using D2D underlaying LTE
 eNB classifies, schedules the communication
 Usecase – 2
 M2M communication using D2D offloading
 Offloader can relay data
Experience certainty.
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Direct M2M under LTE
 Direct M2M for close proximity devices
 Communicate directly whenever close to receiver (UE/eNB/AP)
 eNB takes care of Interference and control management
 Classification, scheduling, etc. through APPs
 M2M offloading for bad-channel devices
 Remote sensors, non-LOS connections
 Foreign and unpredictable channel conditions
 Offload message packet to a nearby offloader
 Improved spectral efficiency and system utilization
 Examples
 Offloading of images from cam to mobile
 Direct songs/images transfer from smartphone to
car/home AP
Experience certainty.
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Evaluation of D2D Communications (1/3)
 Network assisted D2D is considered
 Carrier frequency – 2 GHz
 eNB needs to identify the D2D and cellular pairs
 3GPP’s D2DSS signaling for discovery
 Two types of communications will exist
 Existing cellular communications and D2D
 Should not interfere in case of overlapping communication
 Broad Assumptions
 D2D does not use the full duplex on a given carrier
 Mobility – 3km/hr
 Full synchronization between UEs and UE to eNB is possible
 Unicast communication only
Experience certainty.
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Evaluation of D2D Communications (2/3)
 Simulations
 30% average D2D users considered
 Static users only
UE3
UE3
 Discovery and classification
eNB
 Assumed 3GPP specifications for discovery
 Proximity based classification by eNB - proactive
UE1
UE1
UE2
 Optimal D2D scheduling under LTE
 Two phase scheduling
 Modelled as a Binary Integer Program
 Solved using Matlab
eNB
UE2
Simulation topology: Cellular vs. D2D
 Power control
 Simultaneous transmission : non-interfering
 QoS Improvement
 Reduced delay
 Energy efficient
 Improved spectral efficiency
 Network and per-user spectral efficient improved
• 15% at-least
Experience certainty.
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Evaluation of D2D Communications (3/3)
 Emulations
 Through test-bed level implementation
 WiFi AP as LTE eNB, smartphones as UEs
 Discovery based on signal strength and location
 Service classification – D2D/Cellular
• Depending on location, distance, interference, etc.
 Power control mechanism for smartphones
 eNB computes required Tx power for small D2D distance
 eNB notifies UE the reduced Tx power, modulation, timing, etc.
Test-bed Topology
 TDD scheduling scheme implemented
 D2D & cellular transmissions on same channel
 Time synchronization is assumed
 APP based deployment
 JAVA API for eNB
 Desktop with Ubuntu – 14.04 as eNB
 Livetek WiFi adapter
 Android APP for Tx, Rx (UEs)
 Lenovo Nexus 5, Android KitKat 4.4.2
Experience certainty.
Control Flow Diagram for D2D
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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 planned
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Multiple UEs may be involved
Effective data rate/spectral efficiency can be improved
Energy saving can be achieved
Both licensed and un-licensed spectrums can be used
Control Path
Data Path
Offloading Path
eNB
 Challenges in D2D Offloading
 Traffic characterization
 Distorted user discovery
 Synchronization between UEs
 Network assisted vs. independent
D2D
D2D
D2D
 Interference management and Scheduling
 Energy consumption due to sensing and location updates
Experience certainty.
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D2D Offloading Evaluations
 Simulations
 Matlab based offloading scheduling under LTE
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Static users, 30% are distorted (poor signal)
Cell radius: 300 mt,
D2D range: 5-30 mts
Fixed/adaptive modulation scheme
 Channel modelling
 Channel between UE-eNB and UE-UE
 Short term, long term fading is considered
 Scheduling
 Round robin scheduling
 D2D transmission scheduled prior to relay
 QoS Improvement
 Guaranteed delivery for distorted users
 Low delay due to reduced failure rate
 Improved spectral efficiency
 User and system throughput improved : 30-40%
 Better system utilization
Experience certainty.
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D2D Offloading - Discussions
 Practical Deployment Scenario
 Single operator case
 Billing is the key issue
 Traffic characteristics
• Data usage pattern of UEs
• Signaling for distorted users – eNB assited/Distributed
 Multiple operators case
 Further research required
 Standardization
 Mobility modeling & dynamic classification
 Location of UEs – discovery and classification
 Modeling the mobile channel
 Secure D2D communication
 Control signaling, authentication, connection timing, etc.
 Power-control at UE
 Equipment manufacturers should be involved
Experience certainty.
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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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Experience certainty.
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Thank You
 References
 Alastair Brydon ,"Opportunities and threats from LTE Device-to-Device (D2D)
communication",, Unwired insight - The wireless blog, Feb. 2014
 X. Lin, J. G. Andrews, A. Ghosh, and R. Ratasuk, “An overview of 3GPP device-todevice proximity services,” IEEE Communications Magazine, December 2013
 X. Wu, S. Tavildar, S. Shakkottai, T. Richardson, J. Li, R. Laroia, and A. Jovicic,
“FlashLinQ: A synchronous distributed scheduler for peer-to-peer ad hoc
networks,” in IEEE Allerton Conference on Communication, Control, and
Computing, 2010, pp. 514–521
 K. Doppler, M. Rinne, C. Wijting, C. Ribeiro, and K. Hugl, “Deviceto-device
communication as an underlay to LTE-advanced networks,” IEEE
Communications Magazine, vol. 47, no. 12, pp. 42–49, 2009
 3GPP TR 23.703, “Study on architecture enhancements to support proximity
services (ProSe) (Release 12),” v. 12.0.0, February, 2014
 3GPP TR 22.803, “Feasibility study for Proximity Services (ProSe) (Release 12),”
v. 12.2.0, June, 2013.
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Experience certainty.
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