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Distributed Interference Management in Two-Tier CDMA Femtocell Networks
Duy Trong Ngo,Long Bao Le,Le-Ngoc, T.,Hossain, E.,Dong In Kim IEEE 2012 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.11 No.3
<P>This paper proposes distributed joint power and admission control algorithms for the management of interference in two-tier femtocell networks, where the newly-deployed femtocell users (FUEs) share the same frequency band with the existing macrocell users (MUEs) using code-division multiple access (CDMA). As the owner of the licensed radio spectrum, the MUEs possess strictly higher access priority over the FUEs; thus, their quality-of-service (QoS) performance, expressed in terms of the prescribed minimum signal-to-interference-plus-noise ratio (SINR), must be maintained at all times. For the lower-tier FUEs, we explicitly consider two different design objectives, namely, throughput-power tradeoff optimization and soft QoS provisioning. With an effective dynamic pricing scheme combined with admission control to indirectly manage the cross-tier interference, the proposed schemes lend themselves to distributed algorithms that mainly require local information to offer maximized net utility of individual users. The approach employed in this work is particularly attractive, especially in view of practical implementation under the limited backhaul network capacity available for femtocells. It is shown that the proposed algorithms robustly support all the prioritized MUEs with guaranteed QoS requirements whenever feasible, while allowing the FUEs to optimally exploit the remaining network capacity. The convergence of the developed solutions is rigorously analyzed, and extensive numerical results are presented to illustrate their potential advantages.</P>
Duc Duy Le,Soon‑Ku Hong,Trong Si Ngo,Jeongkuk Lee,Yun Chang Park,홍순익,나영상 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6
Microstructural properties of as-grown and annealed CoCrFeMnNi high entropy alloy (HEA) oxynitride thin films wereinvestigated. The CoCrFeMnNi HEA oxynitride thin film was grown by magnetron sputtering method using an air gas, andannealed under the argon plus air flow for 5 h at 800 °C. The as-grown film was homogeneous and uniform composed ofnanometer-sized crystalline regions mixed with amorphous-like phase. The crystalline phase in the as-grown film was facecentered cubic structure with the lattice constant of 0.4242 nm. Significant microstructural changes were observed afterthe annealing process. First, it was fully recrystallized and grain growth happened. Second, Ni-rich region was observed innanometer-scale range. Third, phase change happened and it was determined to be Fe3O4spinel structure with the latticeconstant of 0.8326 nm. Hardness and Young’s modulus of the as-grown film were 4.1 and 150.5 GPa, while those were 9.4and 156.4 GPa for the annealed film, respectively.
Resource Allocation for Virtualized Wireless Networks with Backhaul Constraints
LeAnh, Tuan,Tran, Nguyen H.,Ngo, Duy Trong,Hong, Choong Seon IEEE 2017 IEEE communications letters Vol.21 No.1
<P>In this letter, we study resource allocation for wireless virtualized networks considering both the backhaul capacity of the infrastructure provider (InP) and the users' quality-of-service (QoS) requirements. We focus on the profit gained by a mobile virtual network operator (MVNO), which is a middleman who buys physical resource from the InP, bundling them into virtual resources called slides before selling off the service providers. The objective of the MVNO is to maximize its profit while guaranteeing the backhaul constraint and users' QoS by jointly allocating the slices and the uplink transmit power to the users. To solve the formulated mixed integer non-convex problem, we propose a distributed solution framework based on Lagrangian relaxation to a find suboptimal decision about slice and transmit power allocations. We further propose a low-complexity solution based on the concept of a matching game that does not require any global information. Numerical results are provided to evaluate the performance of the proposed schemes.</P>