Abstract
In this paper, we concentrate on the robust multi-objective optimization (MOO) for the tradeoff between energy efficiency (EE) and spectral efficiency (SE) in device-to-device (D2D) communications underlaying heterogeneous networks (HetNets). Different from traditional resource optimization, we focus on finding robust Pareto optimal solutions for spectrum allocation and power coordination in D2D communications underlaying HetNets with the consideration of interference channel uncertainties. The problem is formulated as an uncertain MOO problem to maximize EE and SE of cellular users (CUs) simultaneously while guaranteeing the minimum rate requirements of both CUs and D2D pairs. With the aid of ε-constraint method and strict robustness, we propose a general framework to transform the uncertain MOO problem into a deterministic single-objective optimization problem. As exponential computational complexity is required to solve this highly non-convex problem, the power coordination and the spectrum allocation problems are solved separately, and an effective two-stage iterative algorithm is developed. Finally, simulation results validate that our proposed robust scheme converges fast and significantly outperforms the non-robust scheme in terms of the effective EE-SE tradeoff and the quality of service satisfying probability of D2D pairs.
Highlights
W ITH the proliferation of smart mobile services and the intrinsic spectrum scarceness, improving spectral efficiency (SE) has been widely treated as an essential target for the decade [1]
To generalize the proposed formulation to fit the extended system where each D2D pair can utilize multiple resource block (RB) and each RB can be occupied by multiple D2D pairs, we introduce the idea of virtual D2D pairs
It is assumed that there are one macro base stations (BSs) in the cell center, three pico BSs located at the circle with the radius of 200m, and randomly distributed D2D pairs as well as cellular users (CUs)
Summary
W ITH the proliferation of smart mobile services and the intrinsic spectrum scarceness, improving spectral efficiency (SE) has been widely treated as an essential target for the decade [1]. To tackle these difficulties, there is a general consensus that dense network deployment will play an important role, such as multi-tier heterogeneous networks (HetNets) and device-todevice (D2D) communications, especially when employed in combination [4]. D2D communications enable wireless point-to-point services directly between two mobile devices as well as offload the traffic of cellular base stations (BSs), which contribute to the improvement of the network EE and SE due to high spectral utilization and the physical proximity between D2D pairs [5], [6]. In D2D communications underlaying HetNets, spectrum allocation and power coordination mechanisms are more complicated in comparison with those in traditional homogeneous cellular networks, and they are essential to achieve the potential benefits from D2D communications and multi-tier HetNets
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