Introduction to D2D communications

Device-to-device (D2D) communication enables researchers to merge together the achievements of long-term development in previously two disjoint networking techniques, that is, ad-hoc networking and centralized networking. D2D can support local area services such as content distribution, local advertisement, and location aware services very effectively through unicast, groupcast, and broadcast transmission. The diversity of cellular communication provides lots of flexibility for D2D communication in terms of link establishment, resource allocation, energy efficiency, as well as applications and services. D2D communication in cellular spectrum enables direct communication between devices that are in close proximity, and it is an exciting and innovative feature for next generation of cellular networks. In terms of spectrum usage, D2D is primarily classified into two categories, in-band and out-band. D2D provides benefit in terms of performance improvement, spectral, and energy efficiency, but there are few challenges while integrating D2D in long term evolution-advanced network.