Nuno Pereira

Models and Tools

An accurate planning and dimensioning of the network parameters and resources is paramount for the overall system to behave as expected. This is particularly important when there are more demanding quality-of-service requirements to be met, namely related to the correct and timely execution of the tasks and transmission of messages. This chapter outlines a set of analytical and simulation models and tools to help the system designer to setup and fine tune all relevant settings and parameters, as well as to anticipate hardware problems and identify the network behavior and its performance limits.

Energy-Efficiency in Data Centers

Moving from a still on-going work [1], this section reports the progress being developed towards energy-efficient operations and the integrated management of cyber and physical aspects of data centers. In particular, an integrated system composed by wired and wireless sensors is presented: it monitors power consumptions of the servers and environmental conditions, with the goal of achieving an overall reduction of data centers’ energy consumptions. As like as the EMMON system ( Chap. 8), the architecture proposed is intended to be hierarchical, modular and flexible enough to achieve high temporal and spatial resolution of the sensor measurements, with negligible latencies of sensors’ reports to the data center management control station.Overall, the advantage of having fine-grained power and environmental measurements in this application scenario is twofold: (i) measuring the power consumption at the single server level has enormous benefits for the business logic of data centers’ owners, since they can offer services and billing to their customers based on the actual consumption, and (ii) although there are in literature models to predict heat-flows used in commercial Computer Room Air Cooling (CRAC) systems, those models often lack of spatial resolution, so the availability of micro-climate conditions would help improving those models as well as continue feeding them with real data will improve the reliability and accuracy of their forecasts. Fine-grained measurements are also the basis to provide different views of the system, each of them customized to different users. The proposed architecture allows to set the desired resolution of the readings upon user’s requests, for example to investigate some problems in a specific area (row, room or floor) of the data center building. Every single sensor can be configured by setting user defined alarms and trigger measurements reports adaptively, by changing or (re-)configuring specific thresholds at run-time.

Amendments to the IEEE 802.15.4 Protocol

This chapter presents specific amendments to the IEEE 802.15.4, so that some of the open issues that have been previously identified. In particular, a new implicit GTS allocation mechanism (i-GAME) is proposed that over performs the default one. Then, a node grouping mechanism (H-NAMe) is proposed so that the hidden nodes problem is mitigated and consequently energy-efficiency, throughput and latency are improved. Also, we present a very simple mechanism to exploit differentiate the traffic based on multiple priority. Finally, an overview of several improvements affecting the security and privacy of the messages against external attacks and spoofing is presented. Importantly, all these mechanisms have been implemented and integrated in the 15.4 protocol stack and experimentally validated.

The Effect of a Static Magnetic Field on the Flow of Iron Oxide Magnetic Nanoparticles Through Glass Capillaries

Iron oxide nanoparticles were developed using solvothermal synthesis and suspended in a physiological fluid constituted by erythrocytes in order to perform studies of flow behaviour in glass microchannels. The main purpose of this work was to study the influence of different iron oxide nanoparticles and magnetic fields in the plasma layer thickness and also the influence of the magnetic field in the area composed of nanoparticles attracted to the wall of the microchannel. The results obtained show that nanoparticles with magnetic characteristics promote the thinning of the plasma layer, in contrast to the behaviour observed with nanoparticles without magnetic characteristics. It was also observed upon application of magnetic fields with different intensities, the plasma layer tend to disappear in some areas depending on the type of particles. Moreover, the area of nanoparticles attracted to the microchannel wall increases with the increase of the magnetic field intensity.

Structural Health Monitoring

This chapter proposes an extension of our preliminary work [1] to address COTS-based accurate and scalable Structural Health Monitoring (SHM) systems by means of WSN, trying to overcome most if not all of the limitations identified in this field, namely by: (i) using adequate synchronization between all nodes in the network; (ii) relying on standard communications protocols, while most proposals use IEEE 802.15.4-compliant devices that neither implement the IEEE 802.15.4 medium access control (MAC) nor ZigBee protocols; (iii) building upon a standard de facto operating system (OS) for WSNs platforms (TinyOS); (iv) relying on COTS technologies (more cost-effective); and (v) providing adequate scalability to monitor large infrastructures in an effective way, i.e., with a consistent time correlation of samples.

Snapshot of the IEEE 802.15.4 and ZigBee Protocols

This chapter presents the most important features of the IEEE 802.15.4 and ZigBee protocols. It particularly focuses on the Data Link and Network Layers, which are the most relevant in the context of this book. Finally, a brief discussion on the issues that the standards still leave open is presented. A possible set of solutions to those problems will be formulated as amendments in the second part of the book.

Performance Analysis and Network Dimensioning

This Chapter provides an overview of the performance limits of the 15.4 and ZigBee custer-tree protocols, building on the models and tools that have been presented in Chap. 3. A thorough performance analysis permitted to identify some limitations in the standard protocols, some of which we resolve with the add-ons that are presented in the second part of the book (Chaps. 5 and 6).

Amendments to the ZigBee Protocol

Similarly to the previous one, this chapter focuses on several amendments to the ZigBee network layer, as proposed by the standard. In particular, a cluster scheduling solution is proposed and paramount to achieve networking at larger scales, while still be able to meet the quality of service requirements. Then new routing algorithms are proposed based on the possibility to group several nodes based on some common property, such as, e.g., their geographical position. Finally, using the mechanisms defined at the Data Link layer, new security and privacy mechanisms are available at the higher layers of the protocol stack.