eprintid: 10042595 rev_number: 28 eprint_status: archive userid: 608 dir: disk0/10/04/25/95 datestamp: 2018-02-06 10:51:12 lastmod: 2021-09-25 23:11:46 status_changed: 2019-10-07 10:46:53 type: article metadata_visibility: show creators_name: Tang, J creators_name: So, DKC creators_name: Alsusa, EA creators_name: Hamdi, KA creators_name: Shojaeifard, A creators_name: Wong, KK title: Energy-Efficient Heterogeneous Cellular Networks with Spectrum Underlay and Overlay Access ispublished: pub divisions: UCL divisions: B04 divisions: C05 divisions: F46 keywords: Interference, Resource management, Bandwidth, Optimization, Cellular networks, Quality of service, Power demand note: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. abstract: IEEE In this paper, we provide joint subcarrier assignment and power allocation schemes for quality-of-service (QoS)-constrained energy-efficiency (EE) optimization in the downlink of an orthogonal frequency division multiple access (OFDMA)-based two-tier heterogeneous cellular network (HCN). Considering underlay transmission, where spectrum-efficiency (SE) is fully exploited, the EE solution involves tackling a complex mixed-combinatorial and non-convex optimization problem. With appropriate decomposition of the original problem and leveraging on the quasi-concavity of the EE function, we propose a dual-layer resource allocation approach and provide a complete solution using difference-of-two-concave-functions approximation, successive convex approximation and gradient-search method. On the other hand, the inherent inter-tier interference from spectrum underlay access may degrade EE particularly under dense small-cell deployment and large bandwidth utilization. We therefore develop a novel resource allocation approach based on the concepts of spectrum overlay access and resource efficiency (RE) (normalized EE-SE trade-off). Specifically, the optimization procedure is separated where the macro-cell optimal RE and the corresponding bandwidth is first determined, then the EE of small-cells utilizing the remaining spectrum is maximized. Simulation results confirm the theoretical findings and demonstrate that the proposed resource allocation schemes can approach the optimal EE with each strategy being superior under certain system settings. date: 2018-03 date_type: published official_url: https://doi.org/10.1109/TVT.2017.2773506 oa_status: green full_text_type: other language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1427262 doi: 10.1109/TVT.2017.2773506 lyricists_name: Shojaeifard, Arman lyricists_name: Wong, Kai-Kit lyricists_id: ASHOJ33 lyricists_id: KWONG98 actors_name: Wong, Kai-Kit actors_id: KWONG98 actors_role: owner full_text_status: public publication: IEEE Transactions on Vehicular Technology volume: 67 number: 3 pagerange: 2439-2453 issn: 0018-9545 citation: Tang, J; So, DKC; Alsusa, EA; Hamdi, KA; Shojaeifard, A; Wong, KK; (2018) Energy-Efficient Heterogeneous Cellular Networks with Spectrum Underlay and Overlay Access. IEEE Transactions on Vehicular Technology , 67 (3) pp. 2439-2453. 10.1109/TVT.2017.2773506 <https://doi.org/10.1109/TVT.2017.2773506>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10042595/1/1610.09683v1.pdf