D2D Multihop Energy-Efficient Routing and OFDMA Resource Allocation in 5G Networks

In face of the rapidly increasing cellular traffic, 5G will employ offloading techniques to relieve the cellular infrastructure. The idea is to carry the traffic locally by User-Equipment (UE) relays or by other coexisting radio access technologies such as WiFi, Bluetooth, etc. To this end, in this paper, we propose an offloading scheme using multi-hop LTE-D2D communications and assisted by the operator. LTE-D2D UEs cooperate to carry intra-cell unicast/multicast traffic from sources to destinations by exploiting i) sidelink interfaces and ii) multi-hop paths. To increase the lifetime of the offloading system and to reduce the impact of the relaying process on the battery-limited UEs, we propose our energy-aware approach, named JRRA-EE, to solve jointly the routing and the OFDMA resource block allocation. We formulate our problem as a 0-1 Integer Linear Programming (ILP) model which is elaborated to take into consideration the realistic LTE-D2D capabilities and constraints. To gauge the effectiveness of our proposal, we implement the whole 3GPP LTE-D2D protocol stack in the NS-3 network simulator to simulate our approach. Based on extensive simulations, the obtained performances of JRRA-EE are better compared to other one-sided optimal strategies, including an energy non-aware variant, in terms of i) the network lifetime, ii) the packet loss and iii) the service interruption rate.