The cost of virtue : reward as well as feedback are required to reduce user ICT power consumption

This work was partly supported by the IU-AC project, funded by grant EP/J016756/1 from the Engineering and Physical Sciences Research Council (EPSRC).We show that students in a school lab environment will change their behaviour to be more energy efficient, when appropriate incentives are in place, and when measurement-based, real-time feedback about their energy usage is provided. Rewards incentivise `non-green' users to be `green' as well as encouraging those users who already claim to be `green'. Measurement-based feedback improves user energy awareness and helps users to explore and adjust their use of computers to become `greener', but is not sufficient by itself. In our measurements, weekly mean group energy use as a whole reduced by up to 16%; and weekly individual user energy consumption reduced by up to 56% during active use. The findings are drawn from our longitudinal study that involved 83 Computer Science students; lasted 48 weeks across 2 academic years; monitored a total of 26778 hours of active computer use; collected approximately 2TB of raw data.Publisher PD

Client-side energy costs of video streaming

Through measurements on our testbed, we show how users of Netflix could make energy savings of up to 34% by adjusting video quality settings. We estimate the impacts of these quality settings on the energy consumption of client systems and the network. If users exercise choice in their video streaming habits, over 100 GWh of energy a year could be saved on a global scale. We discuss how providing energy usage information to users of digital video could enable them to make choices of video settings to reduce energy usage, and we estimate savings on associated electricity costs and carbon emissions.Postprin

Control plane handoff analysis for IP mobility

Seamless host mobility is vital to future network mobility, and has been an active research area for a long time. Much research focuses on the performance of the data plane. In this paper, we present comprehensive analyses on the control (signalling) plane in the IETF Mobile IPv6, and compare it with the IRTF Identifier-Locator Network Protocol (ILNP). The control plane behaviour is important in order to assess the robustness and scalability of the mobility protocol. ILNP has a different mobility model from Mobile IPv6: it isa host-based, end-to-end architecture and does not require additional network-layer entities. Hence, the control signals are exchanged only between the end systems. We provide model-based analyses for handoff signalling, and show that ILNP is more efficient than MIPv6 in terms of robustness and scalability. The analytical models we present could also be adapted for other mobility solutions, for comparative assessment.Postprin

mHealth through quantified-self : a user study

This work was partly supported by the IU-ATC project, funded by grant EP/J016756/1 from the Engineering and Physical Sciences Research Council (EPSRC). Chonlatee Khorakhun is funded by the Scottish Informatics and Computer Science Alliance (SICSA).We describe a user study of a mHealth prototype system based on a wellbeing scenario, exploiting the quantified-self approach to measurement and monitoring. We have used off-the-shelf equipment, with opensource, web-based, software, and exploiting the increasing popularity of smartphones and self-measurement devices in a user study. We emulate a mHealth scenario as a pre-clinical experiment, as a realistic alternative to a clinical scenario, with reduced risk to sensitive patient medical data. We discuss the efficacy of this approach for future mHealth systems for remote monitoring. Our system used the popular Fitbit device for monitoring personal wellbeing data, the Diaspora online social media platform (OSMP), and a simple Android/iOS remote notification application. We implemented remote monitoring, asynchronous user interaction, multiple actors, and user-controlled security and privacy mechanisms. We propose that the use of a quantified-self approach to mHealth is particularly valuable to undertake research and systems development.Postprin

IEEE 802.11ac MU-MIMO Wireless LAN cells with legacy clients

We provide an empirical evaluation of an IEEE 802.11ac Wireless LocalArea Network (WLAN) cell with Multiple User Multiple Input MultipleOutput (MU-MIMO) technology. We conducted our experiments on a testbed comprising consumer equipment under different office scenarios using 40MHz and 80MHz channels. This is the first performance study of MU-MIMO with 802.11ac in an operational scenario using a commercial access point. We find that, for clients that do not support MU-MIMO,operating in a cell that has MU-MIMO enabled may result in reduced performance.Postprin

Impact of cell load on 5GHz IEEE 802.11 WLAN

We have conducted an empirical study of the latest 5GHz IEEE 802.11 wireless LAN (WLAN) variants of 802.11n (5GHz) and 802.11ac (Wave 1), under different cell load conditions. We have considered typical configurations of both protocols on a Linux testbed. Under light load,there is no clear difference between 802.11n and 802.11ac in terms of performance and energy consumption. However, in some cases of high cell load, we have found that there may be a small advantage with 802.11ac. Overall, we conclude that there may be little benefit in upgrading from 802.11n (5GHz) to 802.11ac in its current offering, as the benefits may be too small.Postprin