On the impact of redirection on HTTP adaptive streaming services in federated CDNs

HTTP Adaptive Streaming (HAS) refers to a set of novel streaming services that allow clients to adapt video quality based on current network conditions. Their use of existing HTTP delivery infrastructure makes them perfectly suited for deployment on existing Content Delivery Networks (CDNs). Nevertheless, this leads to some new challenges, related to the distribution of content across servers and the latency caused by request redirection. The federation or interconnection of CDNs proliferates these problems, as it allows content to be distributed across networks and increases the number of redirects. This paper focuses on the second problem, assessing the impact of redirection on the Quality of Experience of HAS in CDN interconnection scenarios. Additionally, several novel inter-CDN request routing policies are proposed that aim to reduce the number of redirects. Our results indicate that redirection latency significantly impacts performance of HAS and more intelligent routing mechanisms are capable of solving this problem

Inter-Destination Multimedia Synchronization; Schemes, Use Cases and Standardization

Traditionally, the media consumption model has been a passive and isolated activity. However, the advent of media streaming technologies, interactive social applications, and synchronous communications, as well as the convergence between these three developments, point to an evolution towards dynamic shared media experiences. In this new model, geographically distributed groups of consumers, independently of their location and the nature of their end-devices, can be immersed in a common virtual networked environment in which they can share multimedia services, interact and collaborate in real-time within the context of simultaneous media content consumption. In most of these multimedia services and applications, apart from the well-known intra and inter-stream synchronization techniques that are important inside the consumers playout devices, also the synchronization of the playout processes between several distributed receivers, known as multipoint, group or Inter-destination multimedia synchronization (IDMS), becomes essential. Due to the increasing popularity of social networking, this type of multimedia synchronization has gained in popularity in recent years. Although Social TV is perhaps the most prominent use case in which IDMS is useful, in this paper we present up to 19 use cases for IDMS, each one having its own synchronization requirements. Different approaches used in the (recent) past by researchers to achieve IDMS are described and compared. As further proof of the significance of IDMS nowadays, relevant organizations (such as ETSI TISPAN and IETF AVTCORE Group) efforts on IDMS standardization (in which authors have been and are participating actively), defining architectures and protocols, are summarized.This work has been financed, partially, by Universitat Politecnica de Valencia (UPV), under its R&D Support Program in PAID-05-11-002-331 Project and in PAID-01-10, and by TNO, under its Future Internet Use Research & Innovation Program. The authors also want to thank Kevin Gross for providing some of the use cases included in Sect. 1.2.Montagud, M.; Boronat Segui, F.; Stokking, H.; Van Brandenburg, R. (2012). Inter-Destination Multimedia Synchronization; Schemes, Use Cases and Standardization. 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Development of Alkali-Activated Binders froRecycled Mixed Masonry-originated Waste

YesIn this study, the main emphasis is placed on the development and characterization of alkali-activated binders completely produced by the use of mixed construction and demolition waste (CDW)-based masonry units as aluminosilicate precursors. Combined usage of precursors was aimed to better simulate the real-life cases since in the incident of construction and demolition, these wastes are anticipated to be generated collectively. As different masonry units, red clay brick (RCB), hollow brick (HB) and roof tile (RT) were used in binary combinations by 75-25%, 50-50% and 25-75% of the total weight of the binder. Mixtures were produced with different curing temperature/periods and molarities of NaOH solution as the alkaline activator. Characterization was made by the compressive strength measurements supported by microstructural investigations which included the analyses of X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX). Results clearly showed that completely CDW-based masonry units can be effectively used collectively in producing alkali-activated binders having up to 80 MPa compressive strength provided that the mixture design parameters are optimized. Among different precursors utilized, HB seems to contribute more to the compressive strength. Irrespective of their composition, main reaction products of alkali-activated binders from CDW-based masonry units are sodium aluminosilicate hydrate (N-A-S-H) gels containing different zeolitic polytypes with structure ranging from amorphous to polycrystalline

Recent progress in low-carbon binders

The development of low-carbon binders has been recognized as a means of reducing the carbon footprint of the Portland cement industry, in response to growing global concerns over CO2 emissions from the construction sector. This paper reviews recent progress in the three most attractive low-carbon binders: alkali-activated, carbonate, and belite-ye'elimite-based binders. Alkali-activated binders/materials were reviewed at the past two ICCC congresses, so this paper focuses on some key developments of alkali-activated binders/materials since the last keynote paper was published in 2015. Recent progress on carbonate and belite-ye'elimite-based binders are also reviewed and discussed, as they are attracting more and more attention as essential alternative low-carbon cementitious materials. These classes of binders have a clear role to play in providing a sustainable future for global construction, as part of the available toolkit of cements

Polarization properties of stimulated Brillouin scattering in single-mode fibers

The polarization properties of stimulated brillouin scattering (SBS) in low birefringent optical fibers were evaluated using Stokes calculus. It was found that the Brillouin gain for orthogonally polarized pump and probe wave is half (in dB) of the gain for identical polarization, and not equal as often mentioned in literature. Therefore the polarization factor is K=11/2 for complete polarization scrambling, and not K=2. The spontaneous SBS has the same state of polarization as the pump, and its degree of polarization is 33.3% for low pump powers and near 100% for high pump powers. The experimental results agree very well with the calculation

Future telecommunication networks:major trend projections

\u3cp\u3eIntegrating synergistically the issues of traffic types, technologies, and competition, we create a view of the future of telecommunications that appears to be probable and review the technologies likely to be implemented in the future.\u3c/p\u3

System performance of a 4-channel PHASAR WDM receiver operating at 1.2 Gbit/s

Phased arrays are important key components in wavelength-division multiplexing (WDM) systems. We have realized a 4-channel WDM receiver combining a phased array with photodetectors on InP with a Si bipolar transimpedance amplifier. The channels are spaced at 2.0 nm with a 1.0-nm flat passband. On chip loss was 6-7 dB and detector efficiency was better than 90%. The optical cross talk remains below -20 dB. The electrical bandwidth per channel was 1 GHz. The electrical cross talk at 1 GHz after detection is below -25 dB. We have tested this receiver in a full 4-channel syste