A Scalable Joint Routing and OFDMA Resource Allocation in LTE-D2D Networks

In this paper, we address the scalability issue in designing LTE-D2D-based offloading schemes. We propose a scalable method, named JRW-D2D-SC, that offloads the intracellular unicast/multicast traffic using a side-links network of User Equipments (UEs). The devised scheme does this while keeping the control plane inside the LTE-A base station (eNB). By selecting relays and allocating OFDMA resources, the eNB manages to reroute the unified-model traffic from sources to destinations alleviating the cellular infrastructure from the data-plane overhead. To increase the utility of the LTE-D2D relaying network, the eNB solves the routing and the resource block allocation problem simultaneously. Like its counterpart in our previous work, JRW-D2D-SC addresses factors that limit the spectrum reuse and other LTE-D2D limitations such as half-duplex operation and contiguity in resource block allocations. However, we base our proposal on a novel formulation for the problem. The scheme employs an algorithm based on the Branch-and-Cut method to solve the resulted Mixed-Integer Linear Problem (MILP). In doing so, JRW-D2D-SC is more scalable than its counterpart in the previous work and can handle more dense deployments of UEs which is typical in the targeted crowded-platform scenarios: such as in stadiums, waiting-halls in airports and train stations. Based on our home-grown LTE-D2D module for NS-3, extensive network simulations demonstrate that JRW-D2D-SC maintains the same performance metrics or better in small-scale deployments of the LTE-D2D relays while being able to extend the advantage of the offloading system to large-scale deployments.