Experimental Study of Mobility in the Soccer Field with Application to Real-Time Athlete Monitoring Vijay Sivaraman † , Sarthak Grover † , Alexander Kurusingal † , Ashay Dhamdhere † , Alison Burdett ‡ † School of EE&T, University of New South Wales, Sydney, NSW 2052, Australia Emails: {vijay@unsw.edu.au, shahifaqeer@gmail.com, alex@ee.unsw.edu.au, ashay@unsw.edu.au} ‡ Toumaz Technology Limited, Abingdon, Oxfordshire, UK. Email: {alison.burdett@toumaz.com} Abstract— Live monitoring of athletes during sporting events can help maximise performance while preventing injury, and enable new applications such as referee-assist and enhanced television broadcast services. A major challenge is the extraction of athlete physiological data in real-time, since the radio range of body-worn sensor devices is limited, necessitating multi-hop routing mechanisms. However, little is known about the highly dynamic operating conditions on a soccer field under which communication protocols need to operate. In this work we conduct field experiments in which we outfit first-division soccer players with sensor devices and record their inter-connectivity during a real game. Our first contribution profiles the key properties of the dynamic wireless topologies arising in the soccer field, and highlights the consequences for routing mechanisms. We show that the topology is in general sparse, with short encounters and power-law distributed inter- encounters. Importantly, the co-ordinated movement of players in the field gives rise to significant correlations amongst links, an aspect that can potentially be exploited by routing. Our second contribution develops a model for generating synthetic topologies that mirror connectivity in a real soccer game, and can be used for simulation studies of routing mechanisms. Its novelty lies in explicitly modelling the underlying auto-correlation and cross-correlation properties of the links, from which derived measures such as inter-encounter times and neighbourhood distributions follow. Our study is an important first step towards understanding and modelling dynamic topologies associated with sports monitoring, and paves the way for the design of real-time routing algorithms for such environments. I. I NTRODUCTION Advances in sensing and communications technologies are enabling new low-cost and lightweight devices that allow measurement and remote monitoring of an individual’s vital physiological signs such as ECG, temperature and oxygen saturation levels. Such technology, though designed primarily for the healthcare industry, is being adapted to the massively popular and growing field of sports science, specifically for the purpose of athlete monitoring. Biomedical technology has long been used by professional coaches and trainers in striving to push their athletes’ bodies to the edge of its capabilities. However, much of this examination of the body has been performed under laboratory conditions where results attained in the artifical environment may not parallel those observed in competition [1]. Devices are now starting to emerge in the market that are making the leap from monitoring athletes in training (e.g. SPI Elite [2] platform from GPSports) to monitoring them during competition (e.g. e-AR [3] and VxSport [4]). We are partnering with Toumaz Tech- nologies in the UK who are manufacturing a platform called Sensium TM [5] that integrates low power wireless technology with miniaturised sensors and lightweight flexible batteries [6]. This platform, weighing just a few grams, will allow non-intrusive collection and real-time wireless transmission of athlete physiological data during competition. We seek to apply the above wearable platforms to moni- toring athletes in field sports, specifically soccer. Soccer is a hugely popular sport throughout the world, and attracts large financial investment, particularly in Europe. Several soccer clubs in the UK have expressed great interest in monitoring their athletes on the field, predominantly to reduce the risk of injury and improve player substitution decisions. Soccer organisers have also expressed some interest in using real-time position and impact information for referee-assist services, and television channels are eager to augment live broadcasts with player parameters (e.g. heart-rate during clutch events, speed and acceleration, impact levels during collisions, etc.) so as to heighten the level of engagement for audiences. While hardware platforms for athlete monitoring are ma- turing rapidly, there is much research needed in developing communication protocols that can operate under the unique conditions arising in the soccer field: (a) Rapid accelera- tion and impact are part of the sport, and this restricts the monitoring device to be small, lightweight, unobtrusive and non-protruding so that the players’ degree of freedom is not limited. This is in contrast to devices tried in sports such as rowing [7] or cross country skiing [8] that have form-factor akin to a mobile phone. Consequently, monitoring devices for soccer can be expected to have extremely limited battery power and restricted radio range, placing severe energy and reach constraints on the communication protocols. (b) The playing area in soccer is very large at over 4000m 2 . Given the limited transmission range of body-worn devices, coupled with attenuation effects arising from attachment to the human body (profiled in the next section), real-time extraction of player data would require multi-hop routing. One-hop communication from the device to base-station, such as proposed for ice- hockey in [9], or the protocols proposed in [10] for monitoring team-sports such as basketball and volleyball having a small playing area, would not suffice for soccer. (c) Soccer players move very rapidly in the field, and this makes the topology highly dynamic at short time-scales (seconds). Designing rout- ing mechanisms that can deliver data to base-stations within stringent time and energy constraints over multiple hops in this time-varying environment promises to be challenging. 2010 IEEE 6th International Conference on Wireless and Mobile Computing, Networking and Communications 978-1-4244-7742-5/10/$26.00 ©2010 IEEE 337