Reliable real-time communication for coach-assisted feedback systems in swimming

Kos, Anton (author), Hernández Casillas, Andrea (author), Tomažič, Sašo (author), Umek, Anton (author)

Wireless communication in aquatic environments faces major challenges as the radio channel is temporarily unavailable due to submersion and the movement of swimmers. These interruptions can lead to sudden and prolonged packet loss, making real-time biofeedback difficult to achieve with standard communication protocols. This paper presents a real-time swimmer monitoring system built around a novel Block Selective Repeat (BSR) communication protocol specifically designed for environments with cyclic channel interruptions. BSR extends the traditional selective repeat model by introducing dynamic packet composition, cumulative acknowledgements with loss indicators and buffered retransmission. These features enable efficient and reliable transmission of sensor data, even when the connection is temporarily interrupted. The system was implemented using low-cost, commercially available Wi-Fi enabled microcontrollers and tested under real swimming conditions in four swimming styles. Experimental results show that BSR achieves 100% data recovery, with consistent low-latency performance across all swimming styles, including high-loss scenarios such as breaststroke and butterfly. The protocol also preserves the temporal structure of the movement data, enabling accurate recognition of movement patterns for real-time coaching and performance analysis. These findings demonstrate the suitability of BSR for biofeedback systems in swimming and other applications where intermittent wireless connectivity is a constraint.

• Language: English
• Keywords: biofeedback system, block selective repeat protocol, cyclically interrupted channel, realtime communication, swimming, wearable device, wireless sensor device
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. 150091-150100
• Numbering: Vol. 13
• PID: 20.500.12556/RUL-174652
• UDC: 004.9:797.21
• ISSN on article: 2169-3536
• DOI: 10.1109/ACCESS.2025.3602904
• COBISS.SI-ID: 252192515
• Publication date in RUL: 08.10.2025

Record is a part of a journal

• Title: IEEE access
• Publisher: Institute of Electrical and Electronics Engineers
• ISSN: 2169-3536
• COBISS.SI-ID: 519839513

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: sistem z biološko povratno vezavo, blokovno selektivno ponovno pošiljanje, ciklično prekinjen kanal, komunikacija v realnem času, plavanje, nosljive naprave, brezžične senzorske naprave

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0246
• Name: ICT4QoL - Informacijsko komunikacijske tehnologije za kakovostno življenje