The present document contains the result of the Device to Device (D2D) study item. The Feasibility Study on Proximity-based Services (FS_ProSe, TR 22.803) has identified services that could be provided by the 3GPP system based on UEs being in proximity to each other. The identified areas include services related to commercial services and Public Safety that would be of interest to operators and users. The objectives of this feasibility study are to evaluate LTE Device to Device proximity services, as follows:

  In particular:

1. Define an evaluation methodology and channel models for LTE device to device proximity services, including scenarios to compare different technical options to realize proximal device discovery and communication, appropriate performance metrics, and performance targets (e.g. range, throughput, number of UEs supported). [RAN1]
2. Identify physical layer options and enhancements to incorporate in LTE the ability for devices within network coverage: [RAN1]:
   • to discover each other in proximity directly in a power-efficient manner.
   • to communicate directly, including enhancements to LTE interference management and scheduling that allow the LTE network to enable, manage, and continuously control all direct, over the air, device to device communications.
3. Identify and evaluate options, solutions and enhancements to the LTE RAN protocols within network coverage [RAN2 primary, RAN3 secondary]:
   • to enable proximal device discovery among devices under continuous network management and control,
   • to enable direct communication connection establishment between devices under continuous network management and control,
   • to allow service continuity to/from the macro network
4. Consider terminal and spectrum specific aspects, e.g. battery impact and requirements deriving from direct device to device discovery and communication [RAN4].
5. Evaluate, for non public safety use cases, the gains obtained by LTE device to device direct discovery with respect to existing device to device mechanisms (e.g. WiFi Direct, Bluetooth), and existing location techniques for proximal device discovery (e.g. in terms of power consumption, and signaling overhead) [RAN1, RAN2].
6. The possible impacts on existing operator services (e.g. voice calls) and operator resources should be investigated [RAN1].
7. For the purposes of addressing public safety requirements, identify and study the additional enhancements and control mechanisms required to realize discovery and communication outside network coverage [RAN1, RAN2].

The identified options/enhancements should reuse the features of LTE as much as possible. The study will cover:

• Single and multi-operator scenarios, including the spectrum sharing case where a carrier is shared by multiple operators (subject to regional regulation and operator policy)
• LTE FDD and LTE TDD operations

In this study item, the study of direct communication shall address at least public safety requirements and use cases. It is assumed that aspects related to service authorization, system level architecture, security, and lawful interception are covered in the 3GPP TSG SA Working Groups.