Periklis Chatzimisios – författare

This book constitutes the refereed proceedings of the 12th European Conference on Ambient Intelligence, AmI 2015, held in Athens, Greece, in November 2015. The 21 revised full papers presented together with 5 short papers were carefully reviewed and selected from 48 submissions. Over the past 20 years, the vision of Ambient Intelligence has gradually materialized into a plethora of technologies and devices, which are being introduced into almost every aspect of everyday life, thus affecting our abilities, activities, behavior and in the end,shaping a new way of thinking.

Following the success of the First MOBILIGHT 2009 in Athens, Greece, the Second International Conference on Mobile Lightweight Systems (MOBILIGHT) was held in Barcelona, Spain on May 10-12, 2010. It was not an easy decision to carry on organizing a scientific event on wireless communications, where competition is really enormous. This decision was motivated by discussion with many colleagues about the current unprecedented demand for lig- weight, wireless communication devices with high usability and performance able to support added-value services in a highly mobile environment. Such devices follow the users everywhere they go (at work, at home, while travelling, in a classroom, etc. ) and result in exciting research, development and business opportunities. Such scenarios clearly demand significant upgrades to the existing communication paradigm in terms of infrastructure, devices and services to support the “anytime, anywhere, any device” philosophy, providing novel and fast-evolving requirements and expectations on - search and development in the field of information and communication technologies. The core issue is to support wireless users' desire for 24/7 network availability and transparent access to "their own" services. In this context, we continue to envision an international forum where practitioners and researchers coming from the many areas involved in lightweight wireless systems’ design and deployment would be able to interact and exchange experiences.

This book constitutes the refereed proceedings of the 5th International Workshop on Multiple Access Communications, MACOM 2012, held in Maynooth, Ireland, in November 2012. The 13 full papers and 5 demo and poster papers presented were carefully reviewed and selected from various submissions. The papers are organized in topical sections on network coding, handling interference and localization techniques at PHY/MAC layers, wireless access networks, and medium access control.

Wireless Sensor Networks (WSNs) and the Internet of Things are facing tremendous advances both in terms of energy-efficiency as well as in the number of available applications. Consequently, there are challenges that need to be tackled for the future generation of WSNs. After giving an overview of the WSN protocols and IEEE 802.15.4 standard, this book proposes IEEE 802.15.4 Medium Access Control (MAC) sub-layer performance enhancements by employing not only RTS/CTS combined with packet concatenation but also scheduled channel poling (MC-SCP). Results have shown that the use of the RTS/CTS mechanism improves channel efficiency by decreasing the deferral time before transmitting a data packet. Furthermore, the Sensor Block Acknowledgment MAC (SBACK-MAC) protocol enables more efficiency as it allows the aggregation of several acknowledgement responses in one special Block Acknowledgment (BACK) response packet. The throughput and delay performance have been mathematically derived under both ideal conditions (a channel environment with no transmission errors) and non-ideal conditions (with transmission errors). Simulation results successfully validate the proposed analytical models. This research reveals the importance of an appropriate design for the MAC sub-layer protocol for the desired WSN application. Depending on the mission of the WSN application, different protocols are required. Therefore, the overall performance of a WSN application certainly depends on the development and application of suitable e.g., MAC, network layer protocols.

Demand for wireless data exchange is perpetually increasing, leading to pressure on deployed wireless capacity. As systems enhance their spectral efficiency to attempt to address this, evermore complex processing techniques are being employed. Such techniques increase power consumption, leading to greater heat output from processers in network elements and increasing powered cooling. Moreover, the requirement for wideband linearity of radio frequency circuitry in state-of-the-art OFDM systems, twinned with high transmission power capability on the network side and the inefficiencies of components when operating at such limits, leads to greater inefficiency hence further heat power output and the need for greater cooling. All of these ingredients significantly affect the power consumption of communications equipment. Indeed, merely considering raw transmission power, the Shannon-Hartley theorem implies that necessary transmission power increases exponentially with required capacity. Such power consumption issues can be mitigated through cognitive radio (CR) techniques.The use of greater bandwidths through CR and in some cases the aggregation of bandwidths, as well as the opportunistic use of spectrum of more appropriate propagation characteristics or with better interference management, can reduce necessary transmission power for devices and systems. Moreover, CR techniques may achieve greater spatial/temporal awareness of connectivity options and their inherent power consumptions, as well as the power consumptions of chosen radio access characteristics. They might be able to use this awareness to dynamically switch to connections that better manage loads and interference, or might be able to minimize the power consumption of radio frequency circuitry through switching radio access technique given a required traffic load. At a simpler level, they may be able to appropriately select nearer connectivity options minimizing path loss/shadowing hence necessary transmission power, in consideration of experienced/predicted traffic loads and channel characteristics.Such capabilities are particularly relevant considering that, at least in terms of the transmission power to from-the-socket power consumption ratio, lower power equipment such as wireless LAN access points achieves far better efficiency than higher-power equipment such as macro-cell base stations. This manifestation is not only because of favorable path loss characteristics, but also because of the better efficiencies of the lower power components in such access points. CR might also assist in making other areas of life more environmentally friendly. The application of CR to intelligent transportation, for example, facilitating the sharing of information in a timely manner and with appropriate data rates among vehicles and between vehicles and roadside infrastructure through enhancing the capabilities of systems such as IEEE 802.11p, could lead to the better management of traffic signals and better collaborative automated management of traffic speeds, limiting unnecessary vehicular start/stop cycles and greatly reducing the burning of fossil fuels.Moreover, the presence of CR capability in a wide range of future machines will facilitate those machines talking to each other more ubiquitously than today. Such machine-to-machine communications could greatly enhance the energy efficiency of everyday living. One example of this is smart grids and smart homes, facilitating the usage of energy locally, only when needed, and catering for the integration, better prediction of and capitalization from renewable resources. Among other benefits, such solutions would decrease wastage in the home through better management of appliances and heating/cooling options.