Recent progress of long-term evolution device-to-device in third-generation partnership project standardisation

Device-to-device (D2D) is considered as a promising technique to increase resource utilisation and to provide new application in future wireless networks. This study reviews the standardisation progress of D2D in third-generation partnership project. Three scenarios, in-coverage, partial-coverage and out-of-coverage, are defined. For these scenarios, channel model is obtained by the amendment of existing channel model. The function of D2D operation is divided into three building blocks: synchronisation, discovery and communication. The synchronisation procedure and synchronisation signal/channel are discussed first. Then the design aspects of D2D discovery and communication are discussed in detail, including channel structure design, resource allocation mechanisms, interference management and so on. Future works towards post Rel-12 releases are also briefly outlined.