RRC and MAC call flow procedures for D2D communication through sidelink in LTE-A

Device-to-Device (D2D) communication is one of the most popular topic in the upcoming device communication. D2D provides access to services through direct or indirect connection path with neighboring devices with or/and without ENodeB (eNB) assistance. Some of the problems faced in this case are discovering process of neighbor user equipment (UE) and services, as well as designing suitable and secure protocols for D2D communication. In this paper, we propose a sidelink based D2D communication, wherein a separate unlicensed band apart from uplink and downlink is considered to be allocated for sidelink and is functional without the presence of eNB. In this paper we present a detailed study of operational procedures at Radio Resource Control (RRC) and Media Access Control (MAC) layers for sidelink based D2D communication along with this various messages handled for D2D communication for both scenarios using sidelink has been discussed. Two scenarios of D2D communications have been considered-for both UE's in-coverage and both UE's' out-of-coverage. The client side architecture of D2D communication with respect to RRC and MAC layers is also presented.