David Malone | Maynooth University (original) (raw)

Papers by David Malone

The first part of the paper is of tutorial nature, offering an introduction to the basic operatio... more The first part of the paper is of tutorial nature, offering an introduction to the basic operation of CSMA/ECA and describing the benefits of this approach in a qualitative manner. The second part of the paper surveys related contributions, briefly summarizing the main challenges and potential solutions, and also introducing variants and derivatives of CSMA/ECA.

Proceedings of the 4th ACM SIGCOMM conference on Internet measurement - IMC '04, 2004

We extend two approaches for estimating the pro-portions of frame losses at an 802.11 station due... more We extend two approaches for estimating the pro-portions of frame losses at an 802.11 station due to collisions and other errors, in order to distinguish errors due to channel noise and hidden nodes. Our methods use local 802.11 measurements available in basic access mode and are based on MAC and PHY level measurements. We implement the estimators on experimen-tal testbeds using off-the-shelf hardware to evaluate them in real wireless environments. We show that the estimators are effective and provide practical insight into the radio environment.

25th IET Irish Signals & Systems Conference 2014 and 2014 China-Ireland International Conference on Information and Communities Technologies (ISSC 2014/CIICT 2014), 2014

2013 IEEE Globecom Workshops (GC Wkshps), 2013

2013 Proceedings IEEE INFOCOM, 2013

2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2013

ABSTRACT The standardized Medium Access Control (MAC) protocols for Power Line Communication (PLC... more ABSTRACT The standardized Medium Access Control (MAC) protocols for Power Line Communication (PLC) networks (Homeplug and IEEE 1901) are based on the Distributed Coordination Function (DCF) defined for IEEE 802.11. However, the backoff procedure is modified with the goal of decreasing the collision probability. In this work, the backoff procedure of PLC MAC protocols is compared to DCF in different traffic conditions and scenarios, including scenarios with all nodes in coverage range as well as topologies with hidden and exposed terminal problems. The goal is to demonstrate and quantify the pros and cons of each approach in each particular case. Results show that the modified backoff procedure of the Homeplug MAC reduces the collision probability when there is high contention. However, the performance is not always improved compared to DCF. Moreover, when Homeplug provides better performance than the vanilla DCF, we show that the DCF can be easily tuned to achieve similar gains.

18th IEEE International Symposium on Power Line Communications and Its Applications, 2014

ABSTRACT Power Line Communications standards, such as Homeplug and IEEE 1901, aim to provide stri... more ABSTRACT Power Line Communications standards, such as Homeplug and IEEE 1901, aim to provide strict channel access prioritisation in CSMA/CA mode. This is achieved by making lower-priority access categories postpone contention when packets belonging to categories with higher priority are pending for transmission. For this purpose, specific slots in which stations advertise the priority of the current packets to be transmitted are allocated. However, they are only present after the occurrence of successful frame exchanges. Thus, in lightly loaded conditions as well as after channel errors or collisions, the priority resolution mechanism is not employed. In this work, we evaluate the implications of these features on the QoS experienced by each access category. Results show the network provides a complex performance behaviour caused by the interdependence of higher-priority traffic contention and lower-priority traffic preemption.

2013 IEEE Global Communications Conference (GLOBECOM), 2013

2007 International Multi-Conference on Computing in the Global Information Technology (ICCGI'07), 2007

ABSTRACT The two main drawbacks of receiver-initiated Medium Access Control (MAC) protocols for W... more ABSTRACT The two main drawbacks of receiver-initiated Medium Access Control (MAC) protocols for Wireless Sensor Networks (WSNs) are that i) they require all nodes to send a beacon each time they wake up, and that ii) broadcast traffic is not efficiently supported. In this work, we propose addressing these limitations by extending receiver-initiated MAC protocols with scheduling, i.e, coordinating sensor nodes to wake up at nearly the same instant. Following this approach, only one sensor node in the neighborhood sends a beacon per wake-up period and, as all nodes are awake at the same time, broadcast transmissions are naturally supported. A distributed learning technique is used to establish the order of beacon transmissions. We present the protocol description and the time to convergence when a fully connected network is considered.

2013 Sustainable Internet and ICT for Sustainability (SustainIT), 2013

ABSTRACT Electricity is a major cost in running a data centre, and servers are responsible for a ... more ABSTRACT Electricity is a major cost in running a data centre, and servers are responsible for a significant percentage of the power consumption. With the rising cost of electricity and slow adoption of cleaner electricity-generating technology, servers should become more energy efficient. This paper looks at web servers, as HTTP is a common service provided by data centres. Reverse proxies are commonly used to improve the performance of web servers. In this paper, we consider how reverse proxies might be used to improve energy efficiency. We suggest that when demand on a server is low, it may be possible to switch off servers. In their absence, an embedded system with a small energy footprint could act as a reverse proxy serving commonly-requested content. When demand outstrips its capacity, the reverse proxy can power on the servers to meet this new load. Our initial results indicate that such a scheme could be practical and save significant power on servers with lower load.