An experimental study of wireless connectivity and routing in ad hoc sensor networks for real-time soccer player monitoring

Live physiological monitoring of soccer players during sporting events can help maximise athlete performance while preventing injury, and enable new applications for referee-assist and enhanced television broadcast services. However, the harsh operating conditions in the soccer field pose several challenges: (a) body-mounted wireless sensor devices have limited radio range, (b) playing area is large, necessitating multi-hop transmission, (c) wireless connectivity is dynamic due to extreme mobility, and (d) data forwarding has to operate within tight delay/energy constraints. In this paper, we take a first step towards characterising wireless connectivity in the soccer field by undertaking experimental work with local soccer clubs, and assess the feasibility of real-time athlete monitoring. We make three specific contributions: (1) We develop an empirical profile of radio signal strength in an open soccer field taking into account distance and body orientation of the athlete. (2) Using data from several soccer games we profile key characteristics of wireless connectivity, highlighting aspects such as small power-law inter-encounters and link correlations. (3) We develop practical multi-hop routing algorithms that can be tuned to achieve the right balance between the competing objectives of resource consumption and data extraction delay. We believe our study is the first to characterise the wireless environment for mobile sensor networks in field sports, and paves the way towards realisation of real-time athlete monitoring systems.