Optimal Device-to-Device Cell Association and Load Balancing

A key characteristic of the emerging and future wireless networks (aka 5G) is the enabling of direct Device-to-Device (D2D) communications between mobile nodes. D2D communication will not only provide ultra-low power, reduced latencies and increased spatial capacity in such networks but will also unlock a plethora of new location-aware applications. Since these D2D links will be mainly controlled by the network, it is crucially important to reduce the overall overhead and also allow for mitigated traffic imbalance by controlling a potentially large number of D2Ds. In this paper, an optimization framework is introduced to firstly reduce signalling load and latency in network control-based D2D links and secondly to balance the load among neighbouring cells. To this end, under the assumption of future small cell-based ecosystems, a set of integer linear programs is introduced for D2D links that fall within the coverage area of different neighbouring base stations (BSs) with the aim to equilibrate load across cells and reduce signalling overhead by associating D2D links with only one BS. Through a wide set of numerical investigations, the benefits of the proposed schemes are evaluated showing significant performance gains in terms of load balancing and cost-based resource block (RB) allocation for orchestrating D2D links.