During the past few years, architectures for cellular radio networks like 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) have evolved towards flatter topologies with fewer centralized nodes, shifting more and more radio‐related processing towards the base station or even further into so‐called remote radio heads near the antennas. With Internet Protocol (IP) traffic growth, user traffic lost its predictability, which resulted in the need for the over‐dimensioning of processing and forwarding resources in the radio path. This is especially true in upcoming picocell and femtocell configurations in heterogeneous cellular architectures. To hold down costs resulting from these emerging architectures and deployments, we developed a concept of a cloud base station. Developed as a candidate for a lightRadioTM evolution, this cloud base station leverages virtualization techniques such as dynamic and elastic allocation of baseband processing resources between small and large cell sites, as well as load balancing between temporarily overloaded sites and their less utilized neighbors. A cloud base station in a virtualized radio access network (RAN) can serve to ease a smooth standards migration towards LTE‐Advanced with the same deployed equipment, and in the future, support the transformation of dedicated baseband hardware into general purpose processing platforms. In this paper, we discuss the tight networking requirements of a cloud base station in a virtual radio access network, architecture challenges, and our cloud management solutions. We also demonstrate research results on the concept, provide validation based on simulations, and discuss business case related implications. © 2013 Alcatel‐Lucent.

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The power splitting ratio of Y-branches based on step index waveguides has been calculated using threedimensional (3-D) finite-difference beam propagation method (FD-BPM). Due to interference of the guided mode with quasiguided modes generated at distortions of the waveguide the splitting ratio depends on the wavelength and design parameters of the Y-branch. The simulations show how variations of the splitting ratio can be minimized using a mode-filter in the input section without significant increase of losses or component size.

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An influence of the chemical composition, porosity and ageing on mechanical behaviour of light, multifunctional aluminium alloys (AlSi8Cu3 and AlSi7MgCu0.5) subjected to creep and low cycle fatigue (LCF) was investigated. The materials were tested to verify their applicability as the cylinder heads in car engines. During creep tests, a strain response of the materials was observed under a range of the step-increased stresses and different temperatures. The LCF tests were carried out under strain control in three blocks of 100 cycles each with a constant strain amplitude. The results of creep and LCF tests were analysed with regard to chemical composition, type of porosity and ageing of the materials tested. An influence of porosity on the creep resistance and lifetime was considered. The results of the LCF tests were compared for the materials in the as-received state and after ageing. An experimental evaluation of cyclic behaviour because of the LCF was carried out to check whether the hardening or softening effects can be observed in the materials. Taking into account the various history of loading, a stress response of the materials was investigated.Creep and LCF Tests of Aluminium Alloys : A. Rutecka et al.