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Digital archive of theses discussed at the University of Pisa


Thesis etd-05092016-154457

Thesis type
Tesi di dottorato di ricerca
Thesis title
Wireless Sensor/Actuator Networks for Smart Environments
Academic discipline
Course of study
tutor Prof. Anastasi, Giuseppe
tutor Prof. Marcelloni, Francesco
  • DSME
  • IEEE 802.15.4
  • IEEE 802.15.4e
  • MAC protocol
  • network formation
  • network technologies
  • smart city
  • smart factory
  • smart home
  • survey
  • TSCH
  • WSANs
Graduation session start date
Release date
Nowadays, Information and Communication Technologies (ICT) are quickly entering people's everyday lives, radically changing the way we all live and work. In this perspective, no wonder that new technologies are entering the environments where we live, in order to make them more comfortable and help people to achieve their tasks.
In fact, new and smart automatic systems will soon allow to manage the places where we spend most of time, such as our workplace, home, or city. By monitoring environments, these systems will be able to learn users' preferences and habits, and act on the environment itself in order to make it more welcoming, optimize consumption or offer better services to people.
To implement these capabilities, these "smart environments" must rely on sensor/actuator networks, so that the environment can be monitored and controlled. Obviously, deployment and operation of such a network must be as discreet as possible, so as to not bother users. Therefore, in this context, wireless technologies find an ideal application. Nevertheless, network communications must comply with specific constraints of reliability, latency and power consumption, depending on the requirements of the considered smart environment. Hence, designing a Wireless Sensor/Actuator Network (WSAN) is quite a complex task. Based on these observations, in this thesis, we examine the main WSAN technologies used in smart environments, and present possible extensions to improve their performance.
In particular, our analysis starts from the IEEE 802.15.4 standard, currently the most widespread technology. After an initial description of the 802.15.4 MAC protocol, we highlight that it suffers from some serious limitations in terms of reliability and scalability, mainly due to the improper setting of the CSMA/CA algorithm used for channel access. Therefore, we present JIT-LEAP, an adaptive algorithm which allows to change the 802.15.4 CSMA/CA parameters so as to provide the reliability level required by the application with minimum consumption.
Anyway, IEEE 802.15.4 may not be the best solution for critical applications that require low and predictable latency, high reliability and/or scalability. In this case, in fact, a time-slotted approach is preferable to the contention-based approach used in 802.15.4. Under these considerations, a new version of the standard - i.e., IEEE 802.15.4e - was released in 2012. The new version introduces many enhancements and five new MAC protocols, to support specific application domains. In this thesis we deeply describe the three most important MAC protocols (i.e., TSCH, DSME and LLDN) presenting in detail the related literature.
Despite the benefits introduced by the time-slotted approach, we have observed - through analysis and simulations - that, both with TSCH with DSME, the formation of the network may take an extremely long time. Therefore, in the final part of the thesis we introduce two mechanisms which allow to drastically reduce the time required to join the network and allocate communication resources, respectively in TSCH and DSME networks. Specifically, we describe a beacon scheduling algorithm for TSCH networks based on an analytical model that allows to minimize the waiting time for devices that want to join the network. Then, we present some enhancements for the channel access protocol of DSME, that allow to increase nodes' reception time and reduce collision probability, thus making communication more efficient.