An overview about the new feature proposed for LTE Release 12 and beyond: Proximity Services (ProSe) / D2D. It covers the D2D features: Discovery, Communication, Security and also shows some use-cases.

1. D2D
Device to Device Communication
Aluno: Francisco Bento da Silva Neto
MO611 - Teleprocessamento e Redes
Professor: Nelson Fonseca, Ph.D
Instituto de Computação

2. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

3. Background
● Challenges for future wireless communication:
o Massive growth in the number of connected devices. (50 billion)
o Massive growth in traffic volume (1000x in 10 years) due to new
users / communicating machines
o Increasingly wide range of applications with varying requirements and
characteristics: Multi-Gbps in specific scenarios, Tens of MBps almost
everywhere, communicating machines

4. Background
● Needed enhancements to support future wireless communication:
o General enhancements applicable to a wide range of scenarios and use cases
o Enhancements specifically targeting small-cell/local-area deployments.
o Enhancements specifically targeting new use cases, such as machine-type
communication (MTC) and national security and public safety services (NSPS).
● LTE evolution: LTE Release 12 and beyond (LTE-B)
o Proximity Services (ProSe):
 D2D discovery
 D2D communication

5. Background
● D2D in one image:

6. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

7. ● Security
o 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 networks
o 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

8. ● Unlicensed spectrum
o 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 pairing
o 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

9. Wireless technologies comparison

10. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

11. D2D Overview
● Devices communicates with each other without intermediate nodes
(Offloads traffic from the core network)
● Uses cellular spectrum (licensed band)
● Proximity of equipments provides:
o High bit rates / low delays
o Low energy consumption
● Radio resources may be simultaneously used by cellular and D2D links so
that the same spectral resource can be used more than once within the
same cell (reuse gain)
● Uses the same pre-existing cellular infrastructure: supports more services
and improves current services and applications

12. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

13. D2D Discovery
● Devices can discover the presence of other devices in their vicinity
● Proximity discovery is a natural trigger for direct communication
● Proximity discovery can be used as a standalone service and not trigger
communication (social networking)
● General requirements:
o Fast discovery
o Low energy consumption
o Minimize additional interference to the WAN and resource degradation

14. 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

15. D2D Discovery:
Node/Peer discovery
● Before two devices can directly communicate with one another, they must
first discover that they are near each other
● Two peer devices need to meet in space, time and frequency
● No 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

16. D2D Discovery:
Beacon
Sadly not this:
● Beacon: A known synchronization or reference signal sequence
○ Similar to secondary synchronization sequence in LTE or frequency
hopping sequence (FHS) in bluetooth

17. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

18. D2D Discovery:
Priori discovery
● Network (and/or devices themselves) detects D2D candidates before the
start of the communication session between the devices
● Extreme approach:
o Network assigns beacon resources to the devices
o Beacon are broadcast in the coverage area of the cell, so D2D
devices can readily find one another
● Alternative approach:
o Device willing to engage in D2D communication sends a request to the network
to indicate its interest
o Device can provide information about the specific service it is interested in.
Network will initiate the discovery process when a pair of devices are likely to
benefit from D2D communication (passive)

19. D2D Discovery:
Priori discovery

20. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

21. D2D Discovery:
Posteriori discovery
● Use case: Network realizes that two D2D enabled devices with an ongoing
communication session (cellular mode) are in the proximity of each other
● Does not provide the same flexibility of supporting localized services as
priori methods, but it is limited to offloading localized traffic
● Devices agree on a token that is unique to the already ongoing
communication (similar to HTTP_SESSION mechanics)
● Once token is established devices register the token at the serving eNB
(evolved Node B)
● Alternatively the eNB can analyze the source and destination IP addresses
to detect D2D pairs communicating within the same cell (same subnet)

22. D2D Discovery:
Posteriori discovery

23. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

24. ● Licensed band:
o Better interference avoidance under a controlled environment
o Ex: Femtocells / picocells work under LTE-A licensed band
● Classified in:
o Inband D2D:
 Underlay
 Overlay
o Outband D2D
 Controlled
 Autonomous
D2D communication

25. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

26. ● 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

27. ● Pros:
o Underlay D2D increase the spectral efficiency of cellular spectrum
o Any cellular device is capable of using inband
o QoS is easy because the cellular spectrum can be fully managed by
the eNB
o Transmission distance ~ 1km.
o Data rate ~ 1Gbps
● Cons
o Cellular resources might be wasted in overlay
o Interference mgmt among D2D and cellular transmission is very
challenging/complex
D2D communication
Inband: Pros and cons

28. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

29. ● Communication occurs under unlicensed spectrum
● Aims to eliminate the interference issue between D2D and cellular links
● Requires 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 / Android beam
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

30. ● Pros:
o No interference with cellular communication (unlicensed spectrum)
o Users can have simultaneous cellular and D2D transmission
● Cons
o Cellular devices requires two wireless interfaces (e.g. LTE and WiFi)
o Power consumption of the extra interface (WiFi)
o Lower transmission distance
o Lower transmission data rate
D2D communication
Outband: Pros and cons

31. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

32. D2D security
1. Network access security:
o Security interactions between the user and access network, which
provides protection against attacks on the radio access link;
1. Network domain security:
o it enables the secure data/control signal exchange among network
elements, which provides protection against attacks on wire-line
network;
1. User domain security (3):
o it secures the access to the mobile station;

33. D2D security
4. Application domain security:
o it is an end-to-end security between the application on user equipment
and on servers;
4. Visibility and configuration security:
o the set of features controls the availability and configuration of certain
security service.

34. D2D security
[1] Network access security [2] Network domain security [3] User domain security [4] Application
domain security [5] Visibility and configuration security

35. Agenda
● Background
● D2D vs Ad-hoc
● D2D overview
● D2D discovery
o Priori
o Posteriori
● D2D communication
o Inband
o Outband
● D2D security
● D2D use cases
● Conclusion

36. ● Two categories:
o Simple D2D: sender and receiver exchange data with each other
o Relay: D2D user forward data from and to other users
● 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

37. ● V2V - Vehicle to Vehicle communication:
o Collision avoidance system requires a very low latency for example to
coordinate braking between vehicles
o 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

38. ● Multiuser cooperative communication (MUCC)
o Benefited user (BU) is in an area with poor cellular signal
o Another 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

39. ● D2D communications with network coding
o Users requesting the same content can form cooperative clusters to
achieve higher energy efficiency
o eNB transmits the content to the cluster heads
o Cluster heads multicasts the contents to the other devices within the
cluster through D2D links
o Eg: world cup games
o IPTV:
o Multicast of linear channels, Pay-Per-View, Video Recording
D2D use cases

40. ● 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 capability
o US government has expressed desire to move to LTE for public safety
o 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

41. ● 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
apps
 Bad: Privacy concerns, device battery consumption
o D2D communication:
 Good: Offloading traffic, High data rate speeds
 Bad: Interference / deterioration of existing services
Conclusion

42. Questions ?

43. Thank you!
Francisco Bento da Silva Neto, Jun 2014.
References:
●Shahid Mumtaz et al., "Odyssey of LTE-A D2D Communication:Tutorial Approach", IEEE
Communications Surveys and Tutorials, Dec. 2013
●Gábor et. al. “Design Aspects of Network Assisted Device to Device Communication”, IEEE
communication Magazine March 2012
●K. Doppler, M. P. Rinne, P. Janis, C. Ribeiro, and K.Hugl, “Device-to-Device Communications;
Functional Prospects for LTE-Advanced Networks”. IEEE International Conference on
Communications Workshops, 2009, Jun. 2009, pp.1– 6
●M. Hajiaghayi, C. Wijting, C. Ribeiro, M. T. Hajiaghayi, "Efficient and practical resource block
allocation for LTE-based D2D network via graph coloring", Springer Science+Business Media, New
York, 2013
●Alastair Brydon, "Opportunities and threats from LTE Device-to-Device (D2D) communication",
Unwired insight - The wireless blog, Feb. 2014