Wireless Communication on Wearable Systems CORECO I, WEMS II + III Jan Beutel, Computer Engineering and Networks Lab Mathias Stäger, Holger Junker, Electronics Lab December 4, 2002

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 The Body Area Networking Difference Distributed Configurable Computing Platform – heterogeneous components – communication centric – low power – varying configurations and requirements – many components (~20…50) Display Context Sensor Array Camera, light, microphone, GPS Distributed Reconfigurable Computer Body Area Network Wired and wireless Access Networking Bluetooth, WLAN variants, GSM, UMTS, Thuraya Sensors Interaction with ubiquitous appliances Audio

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 Competitors Wearable Systems – single garment, wired-up solutions MIThril (DeVaul) – custom box-type computer (Starner) Sensor Networks – low bit-rate SOC transceivers (Rabaey) – COTS sensor networks (Pister et al) Power Management – dynamic power saving states (De Micheli, Gupta) – low power frontends (Enz, Meng)

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 Our Research Issues Scalable low power networking on Wearable Systems – optimal use of resources – low power body area networking transceivers – fast prototyping for the implementation of real life scenarios Design parameters from the network view – network topology – spatial capacity – link data rates – latency/burstiness – transceiver architectures – protocol features

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 Investigation of Standard Concepts Why standardized wireless devices? – operational components available today for prototypes – foundation of methodical approach to distributed systems Goals – knowledge to select the right hard/software architectures – optimal duty cycle performance dependant on the application – future replacement by custom components Our contribution – characterization and benchmarking of existing wireless communication devices, protocols and transmission schemes – results are used in the modeling of communication channels for Design Space Exploration of Wearable Systems [Anliker et al, submitted to TOC] – implementation of a Bluetooth protocol stack on Linux and uC

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 Communication Model The Problem optimal device configuration for each link Power Consumption and Delay Assumptions – multiple periodic inputs – deadline associated to data – four operating states: standby, idle, transmit, receive continuous duty cycle 1 burst duty cycle 2/3

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 BTnodes – Bluetooth Smart Nodes Programmable networking node for fast prototyping – 8-Bit RISC CPU, (max. 8 8 MHz) – 128 k Flash, 64 k SRAM, 4k EEPROM – generic sensor interfaces – power and frequency management – Bluetooth with integrated antenna – MHz, 3.3V<0.5 mW – MHz, 3.3V150 mW Status – initial sw kit, drivers and demo applications available – current deployment ~ 200 (12 research groups worldwide) – [Beutel et al, submitted to MobiSys]

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 Integrated Network Protocols using BTnodes Bluetooth Multihop Prototype – integrated scalable application protocol – based on Dynamic Source Routing (CMU) – routing across piconet borders to support >8 nodes Status – first implementation on BTnodes available – integration with the Physical Activity Detection Network PADnet (Demo)

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 Comparison Transceiver Architectures Goal – dedicated architecture for on-body sensor network – short distance (50 cm) – low bit rate (0.1 ~ 1 kbit/s) – low power consumption (100  W targeted) Comparison of – traditional far field architectures – near field systems – magnetic induction – capacitive coupling – ultra wideband architecture UWB as promising new candidate – simplicity of implementation – relatively new research field

Polyproject Wearable Computing, ETH Zürich, December 4, 2002 The Road so Far Interfacing within the Polyproject – modeling of communication systems ► Design Space Exploration CORECO IV – BTnode ► user activity network and reconfigurable computing CORECO I + IV In two years… – a refined communication model – on-line tradeoff and application of different interface types – UWB channel characterized and suitable architecture implemented – integration into the demonstrator platform