Long-term evolution represents an emerging technology that promises a broadband and ubiquitous Internet access. But several aspects have to be considered for providing effective multimedia services to mobile users. In particular, in this work, we consider the design of a quality-of-service (QoS) aware packet scheduler for real-time downlink communications. To this aim, a novel two-level scheduling algorithm is conceived. The upper level exploits an innovative approach based on discrete-time linear control theory. Instead, at the lower level, a proportional fair scheduler has been properly tailored to our purposes. The performance and the complexity of the proposed scheme have been evaluated both theoretically and by using simulations. A comparison with recently proposed scheduling strategies has been also presented, considering several network conditions and real-time multimedia flows. Particular attention has been devoted to the evaluation of the quality-of-experience (QoE) provided to end users. Results have clearly shown that the proposed approach is able to greatly outperform the existing ones especially in the presence of real-time video flows.

We have witnessed the Fixed Internet emerging with virtually every computer being connected today; we are currently witnessing the emergence of the Mobile Internet with the exponential explosion of smart phones, tablets and net-books. However, both will be dwarfed by the anticipated emergence of the Internet of Things (IoT), in which everyday objects are able to connect to the Internet, tweet or be queried. Whilst the impact onto economies and societies around the world is undisputed, the technologies facilitating such a ubiquitous connectivity have struggled so far and only recently commenced to take shape. To this end, this paper introduces in a timely manner and for the first time the wireless communications stack the industry believes to meet the important criteria of power-efficiency, reliability and Internet connectivity. Industrial applications have been the early adopters of this stack, which has become the de-facto standard, thereby bootstrapping early IoT developments with already thousands of wireless nodes deployed. Corroborated throughout this paper and by emerging industry alliances, we believe that a standardized approach, using latest developments in the IEEE 802.15.4 and IETF working groups, is the only way forward. We introduce and relate key embodiments of the power-efficient IEEE 802.15.4-2006 PHY layer, the power-saving and reliable IEEE 802.15.4e MAC layer, the IETF 6LoWPAN adaptation layer enabling universal Internet connectivity, the IETF ROLL routing protocol enabling availability, and finally the IETF CoAP enabling seamless transport and support of Internet applications. The protocol stack proposed in the present work converges towards the standardized notations of the ISO/OSI and TCP/IP stacks. What thus seemed impossible some years back, i.e., building a clearly defined, standards-compliant and Internet-compliant stack given the extreme restrictions of IoT networks, is commencing to become reality.

The IEEE 802.15.4 standard represents one of the most successful technologies for enabling low-rate wireless personal area networks (LR-WPANs). Accordingly, the properties of its protocols (at physical and MAC layers) have been widely studied in the scientific literature to derive performance bounds on throughput, delays, and frame losses. At the same time, to the best of the authors’ knowledge, a complete characterization of the frame-error-rate process, including also the correlation among loss events, is still missing. This kind of investigation is particularly relevant in noisy industrial environments, which, as well known, introduce bursty frame losses. To this end, this paper proposes a Markov model to account for the different changing conditions under which an IEEE 802.15.4 channel is seen at the MAC layer. The model is able to reproduce synthetic traces having a cumulative distribution function and an autocorrelation coefficient that closely resemble experimental measurements. In this way, it becomes a valuable tool for further refining existing theoretical models and simulation platforms for IEEE 802.15.4 LR-WPANs and for helping the designer and researcher working on industrial Internet of things.

In network measurement systems, packet sampling techniques are usually adopted to reduce the overall amount of data to collect and process. Being based on a subset of packets, they introduce estimation errors that have to be properly counteracted by using a fine tuning of the sampling strategy and sophisticated inversion methods. This problem has been deeply investigated in the literature with particular attention to the statistical properties of packet sampling and to the recovery of the original network measurements. Herein, we propose a novel approach to predict the energy of the sampling error in the real time estimation of traffic bitrate, based on spectral analysis in the frequency domain. We start by demonstrating that the error introduced by packet sampling can be modeled as an aliasing effect in the frequency domain. Then, we derive closed-form expressions for the Signal-to-Noise Ratio (SNR) to predict the distortion of traffic bitrate estimates over time. The accuracy of the proposed SNR metric is validated by means of real packet traces. Furthermore, a comparison with respect to an analogous SNR expression derived using classic stochastic tools is proposed, showing that the frequency domain approach grants for a higher accuracy when traffic rate measurements are carried out at fine time granularity.

A method of downloading a multimedia content from a server (110) to a client (105) through a wireless communication network (100) is proposed. The multimedia content is subdivided into a plurality of portions (cki) and for each portion the server storing a plurality of versions (seg i,j ) thereof each of which is encoded with a specific encoding quality (br i,j ). The method comprises: selecting, among the plurality of versions (seg i,j ) of each portion (ck i ) of the multimedia content, a version (seg i,j ) of said portion (ck i ) of the multimedia content to be downloaded on the basis of wireless communication parameters determined at at least two different layers of a wireless communication network OSI protocol stack at the client (105).