Abstract
In this paper, the tradeoff between spectrum efficiency (SE) and energy efficiency (EE) is investigated in terms of interference management and power allocation for heterogeneous networks (HetNets) with non-orthogonal multiple access (NOMA). The EE and SE tradeoff is modeled as a multi-objective problem (MOP) under the maximum power and quality of service (QoS) constraints, which is non-convex. The MOP is relaxed into a convex single objective problem (SOP) by adopting a weighted sum strategy with the hypograph transformation. The SOP is solved in two steps. In the first step, we propose a power allocation technique based on non-cooperative (NC) game for EE and SE in NOMA HetNets. In the proposed NC game, the macro base station (MBS) and the small BSs (SBSs) compete with an equal priority in order to optimize their transmit powers towards maximizing the weighted sum of SE and EE. In the second step, a closed-form formula is proposed to control the power allocated to users while taking into account both QoS constraint and successive interference cancellation (SIC) condition. From simulations, the proposed technique can, in some dedicated settings, considerably improve the tradeoff between EE and SE over conventional techniques.
Highlights
Towards more efficient communication systems, spectrumefficient (SE) and energy-efficient (EE) cellular systems need to be maximized to meet the critical demand for high data rates while saving energy for the green communication objective
SUi,1 and MU1 are randomly distributed over an area of ranges d[iS,1] and d[1M] far from the center of their BSs, respectively, while SUi,2 and MU2 are randomly spread over an area of ranges d[iS,2] and d[2M], respectively
Simulation results compare the performance in terms of the achieved EE and spectrum efficiency (SE) among techniques; 1) NC-SE [9], where only SE is taken into account, 2) NC-EE [8], where only EE is taken into account, and 3) the proposed NCEE-SE scheme #1
Summary
Towards more efficient communication systems, spectrumefficient (SE) and energy-efficient (EE) cellular systems need to be maximized to meet the critical demand for high data rates while saving energy for the green communication objective. Two notable wireless technologies can be deployed to this achieve this end. The first one is the heterogeneous networks (HetNets), where the SE can be achieved by deploying small-cell (SCs) tiers with a short-range small base station (SBS) under the coverage of a macro-cell (MC) tier with a powerful macro BS (MBS) [1]. The second technology is the non-orthogonal multiple access (NOMA), where users are multiplexed on the same time/frequency/space resources while distinguishing them by allocating different power levels to users according to several criteria including quality of service (QoS) or relative channel gains [2], [3]. Due to the resource sharing among different tiers, HetNets with NOMA suffers from co-tier and cross-tier interference [4]–[7], while acquiring the advantages of NOMA HetNets depends on mitigating these types of interference
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