Implementation aspects of hierarchical radio resource management scheme for overlay D2D

Capacity, reliability and latency are key requirements of machine type communications (MTC) in future wireless networks. Device to device (D2D) communication is seen as a solution to fulfill these requirements for the aforementioned applications. To this end, a portion of resources for D2D communications is reserved (overlay) and the overlay resources are scheduled to D2D users in a semi-persistent manner. However, the required reliability and latency for MTC applications are achieved at the cost of capacity wastage. Since MTC applications generate relatively small payloads, the semi-persistent scheduling of resources leads to further wastage of resources. Shortening transmission time interval (sTTI) in the current long-term evolution (LTE) technology and the hierarchical radio resource management scheme, i.e. sub-granting, are two solutions to tackle the resource wastage. In this paper, we discuss novel algorithms in physical and MAC layer of LTE in order to realize the subgranting scheme. We developed a system level simulator and studied both schemes in terms of uplink throughput, overhead and transmission time for device to infrastructure (D2I) and D2D users. The results show that the sub-granting scheme outperforms the sTTI scheme.