Real-time vital data monitoring for athletes during training and game is essential for planning effective training menus and avoiding injuries and diseases. Especially for team sports such as footfall and rugby, how to reliably collect vital data from many players spread in a large field is a key issue. In our previous work [1], we developed a real-time vital data collection system in which a wireless sensor node attached at the waist position of each player broadcasts packets to data collection nodes placed around a football field. Our field experiments showed that, (1) for the 920 MHz band, the packet success rate can be almost 1.0 when using 3 or 4 data collection nodes, whereas for the 2.4 GHz band, the packet success rate is less than 0.85 even when using 6 data collection nodes, and (2) the suitable antenna height of the data collection node is 2 meters. In this paper, we discuss a suitable packet forwarding method from the data collection nodes to a sink node at a technical trainer or a coach. By field experiments, we compare the packet error rate between a single-hop packet forwarding in the 920 MHz band and a multi-hop packet forwarding in the 2.4 GHz band. Furthermore, we show some interesting events on the packet error rates for different player positions such as forward, midfielder, defender and goalkeeper.
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