Binary-PSO-based energy-efficient small cell deployment in 5G ultra-dense network

The energy-efficient deployment of small cells helps to reduce environmental pollution in an ultra-dense network. In contrast, demand for massive connectivity and higher data rate are the promise of the present cellular system and small cell networks. Hence, energy consumption is reduced if base stations are optimally used. One way to improve the energy efficiency is by shutting down the redundant BSs while sustaining the Quality of Service for each user. This paper proposes an efficient cell modeling (ECM) algorithm for small cell formation, and binary particle swarm optimization-based small cell deployment (BPSD) to optimize the deployment of small base stations in the small cell network. The small base stations (s-BSs) exist in two modes: active and sleep which is decided by the proposed algorithm without compromising the network performance. The proposed ECM and BPSD algorithms are implemented and evaluated in MATLAB. The results demonstrate that the proposed approaches improve the energy efficiency and connectivity in the ultra-dense small cell network.

     

Structural studies on the alloying behaviour of γ-Mn and the development of a high damping capacity in Mn-Cu alloys

Quenched Mn-Cu alloys undergo an unusual type of phase transformation and form metastable structures. A miscibility gap exists in these alloys, and the stability of the alloy phases is associated with the allotropic form of elemental Mn-atoms beyond the equi-atomic compositions. Quenched Mn-33.4 at% Cu alloy, which corresponds to the centre of the miscibility gap, upon ageing gives rise to a high damping capacity. The internal lattice strain which is the cause of the high damping capacity is thought to be due to interfacial misfit of the MnCu phase and elemental Mn in the proposed metastable structure of the alloy.     

Fatigue crack propagation in aluminum- lithium alloy 2090: Part I. long crack behavior

A study has been made of the mechanics and mechanisms of fatigue crack propagation in a commercial plate of aluminum-lithium alloy 2090-T8E41. In Part I, the crack growth and crack shielding behavior of long (≳5 mm) through-thickness cracks is examined as a function of plate orientation and load ratio, and results compared to traditional high strength aluminum alloys. It is shown that rates of fatigue crack extension in 2090 are, in general, significantly slower (at a given stress intensity range) than in traditional alloys, although behavior is strongly anisotropic. Differences in growth rates of up to 4 orders of magnitude are observed between the L-T, T-L, and T-S orientations, which show the best crack growth resistance, and the S-L, S-T, and L + 45, which show the worst. Such behavior is attributed to the development of significant crack tip shielding (i.e., a reduction in local crack driving force), primarily resulting from the role of the crack path morphology in inducing crack deflection and crack closure from the consequent asperity wedging. Whereas crack advance perpendicular to the rolling plane (e.g., L-T,etc.) involves marked crack path deflection and branching, thereby promoting very high levels of shielding to cause the slowest growth rates, fatigue fractures parallel to the rolling plane (e.g., S-L,etc.) occur by an intergranular, delamination-type separation, with much lower shielding levels to give the fastest growth rates. The implications of such “extrinsic toughening” effects on the fracture and fatigue properties of aluminum-lithium alloys are discussed in detail. R. O. RITCHIE, Professor and Director, Center for Advanced Materials, Lawrence Berkeley Laboratory     

BeSleep: Blockchain-enabled distributed sleeping strategies of small base stations in ultra dense networks

Small cell networks can fulfill the increasing demandfor the high data rate of wireless applications. Energy efficiency is an important design parameter of the ultra dense small cell network (UDSCN). The sleeping strategy of small base stations (s-BSs) is used to enhance the network's energy efficiency. An efficient sleeping strategy of s-BSs is required while preserving users' quality of service (QoS). The idle s-BSs can be switched to sleep mode. This paper proposes a blockchain-enabled solution for the sleeping strategy of s-BSs. Here, a blockchain-enabled small cell network is created between the s-BSs. The network is decentralized, which eliminates the workload of the macro base station (MBS). The proposed network architecture is enabled as a decentralized network through blockchain. The blockchain provides distributed control over the s-BS operations through a smart contract. Here, smart contracts act as distributed self organizing network features to handle self-transactions among small cells for switching off s-BSs in the network. All the software logic required to perform s-BS operations is written in a smart contract using Ethereum. The proposed solution improves energy efficiency and enables the ultra dense small cell network to be decentralized.