It is expected that the LTE (Long Term Evolution) system will allow for an increased usage of device to device communication. The LTE system and LTE-A (LTE Advanced) system comprises the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), and the Evolved Packet Core (EPC). The E-UTRAN typically comprises a plurality of base station entities, typically referred to as eNBs (evolved NodeBs) for macro-cells and HeNBs (Home-eNBs) for femto-cells, as well as the cellular terminals (or user equipments).
Device to device communication is currently being defined as a work item in the context of 3GPP (Third Generation Partnership Project), Release 12. The basic principle of LTE device to device communication (LTE D2D) is the possibility to allow for a direct communication between at least two devices (or user equipments) supporting a device to device communication mode. Within the context of the device to device communication, standardized in 3GPP, two modes are part of the 3GPP definitions: an infrastructure-based device to device communication mode and a direct device to device communication mode.
A further feature of the device to device communication is the so-called “discovery” functionality which allows at least two device-to-device-communication-enabled devices (or user equipments) to identify each other if these devices (or user equipments) are in the vicinity of each other. Within the context of the so-called “communication” functionality, the at least two device-to-device-communication-enabled devices involved in the discovery are enabled to initiate a direct communication between each other.
The discovery feature is of interest to critical communication users as well as commercial cellular mobile operators in order to explore new business opportunities with targeted mobile advertising as well as supporting the growing trend of social networking where the environment of the current location of the user equipment (i.e. the proximity of the current location) plays a more and more important role. Additionally, device to device communications, and especially proximity services, are likewise interesting for automotive applications in order to establish new services, e.g., for car-to-car communication, traffic management and traffic alert.
The device to device discovery and/or device to device communication allows for direct interactions between at least two devices based on radio resources being allocated to the devices by the supporting mobile communication network. Typically, the mobile communication network is involved in determining the location of devices in order to provide location based services. For example, the location of one device may be provided, by the supporting mobile communication network, to another device such that an absolute position may be used to determine a relative distance between the devices, which typically requires a centralized system for the determination of the relative distance. However, this might lead to situations in which the network load increases with increasing number of relative distances to be determined by the mobile communication network. Furthermore, the usage of device-to-device communication is limited due to reception failures or weak signals related to the communication of the devices with the supporting mobile communication network, in particular in public safety applications.