Device-to-Device (D2D) Communication

Transcription

1 Device-to-Device (D2D) Communication Networks Lab, TCS Research TSDSI SG1 F2F meeting, IEEE Bangalore, July 2015

2 Introduction Evolution towards 5G Outline Introduction Why D2D Communication D2D Communication D2D Offloading D2D Research at TCS Standardization of D2D Communication Conclusion

3 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 times or more 61% CAGR expected Wide range of applications and their requirements Social media, video on demand, live TVs, gaming, IoT, etc

4 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 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 = 4-5 Increasing Backhaul Capacity Nationwide optical fibre backbone Only a few operators can do this CAPEX and OPEX issue again Source Huawei - The_full_spectrum_of_possibilities Source ITU -Link: E.pdf

5 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

6 Big Question Device to Device (D2D) Communications Is it possible for UEs in proximity to communicate among themselves? Control Path (C-Plane) Data Path Control Path (C-Plane) Data Path enb enb D2D (U-Plane) Regular Communication Model In coverage D2D Communication Model

7 D2D vs. M2M and Ad-hoc Networks Machine to Machine (M2M) Communication Machine Type Communication 3GPP TR D2D vs. M2M D2D M2M Describes connectivity Services Direct device to device communication Access specific Local comm. improves spectral efficiency D2D vs. Ad-hoc Networks D2D Licensed and Free Spectrum QoS can be ensured Seamless Connectivity Security is guaranteed Application Oriented Remote devices communicates through a centralized node Access agnostic Not applicable Ad-hoc Networks Free Spectrum No QoS guarantee Manual Connectivity Security is a challenge

8 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) Control Path Data Path Control Path Data Path enb enb D2D Emergency Services D2D Commercial Services

9 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 D2D frame usage In TDD UL sub-frame (U) will be used In FDD UL spectrum will be used RBs can be re-used through scheduling TDD Frame structure

10 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?

11 Why LTE D2D Communication? LTE-D2D Strong Resource Management Better Performance Reliability and Scalability Regulatory and Standardization Tighter spectrum reuse Higher data rate, low end-to-end delay Operator initiated Services Under 3GPP and TSD Offloading can be achieved Energy Efficient Security can be guaranteed

12 D2D 3GPP Standardization attempts under 3GPP Rel 12/13 (ProSe) - 3GPP TR / TR / TR / TR 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 UE -1 LTE-Uu E -UTRAN S1 EPC (MME, S/PGW) SGi PC5 LTE -Uu HSS/SLP ProSeAPP Usage Commercial /Social Public Safety (with and without coverage) Network Offloading UE-2 PC3 PC1 PC 4 ProSe Function PC 6 Source - 3GPP V PC 2 ProSe System Architecture ProSeAPP Server

13 Usecase 1 D2D Use Cases D2D communication underlaying LTE Usecase 2 enb classifies, schedules the communication D2D offloading Offloader can relay data

14 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

15 Evaluation of D2D Communications (2/3) Simulations 30% average D2D users considered Static users only Discovery and classification Assumed 3GPP specifications for discovery Proximity based classification by enb - proactive Optimal D2D scheduling under LTE Two phase scheduling Modelled as a Binary Integer Program Solved using Matlab 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 UE1 UE3 UE3 enb enb UE1 UE2 UE2 Simulation topology: Cellular vs. D2D

16 Emulations Evaluation of D2D Communications (3/3) 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. TDD scheduling scheme implemented D2D & cellular transmissions on same channel Time synchronization is assumed APP based deployment JAVA API for enb Desktop with Ubuntu as enb Livetek WiFi adapter Android APP for Tx, Rx (UEs) Lenovo Nexus 5, Android KitKat Test-bed Topology Control Flow Diagram for D2D

17 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 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 Challenges in D2D Offloading Traffic characterization Distorted user discovery Synchronization between UEs Network assisted vs. independent Interference management and Scheduling Energy consumption due to sensing and location updates D2D enb D2D D2D Control Path Data Path Offloading Path

18 Simulations D2D Offloading Evaluations Matlab based offloading scheduling under LTE 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

19 Practical Deployment Scenario Single operator case D2D Offloading - Discussions 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

20 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 Conclusion 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 and standardization

21 References References Alastair Brydon,"Opportunities and threats from LTE Device-to-Device (D2D) communication",, Unwired insight - The wireless blog, Feb 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 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 , GPP TR , Study on architecture enhancements to support proximity services (ProSe) (Release 12), v , February, GPP TR , Feasibility study for Proximity Services (ProSe) (Release 12), v , June, 2013.

22 Thank You