1. Computer Engineering and Networks Laboratory BTnodes A Distributed Environment for Prototyping Ad Hoc Networks Jan Beutel

2. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 Slide 2 Outline BTnode - Ad hoc networking prototyping platform Constructing network topologies using Bluetooth Implementation of a robust, self-healing tree topology Outlook on our current work: BTnode rev3 and Bluetooth v1.2

3. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 3 Prototyping ad hoc networks A myriad of interacting devices –node heterogeneity –sensing and actuation –user interaction Smart everyday objects by attaching sensor nodes: –self aware –context sensitive –cooperative –integration into computing environment NCCR-MICS Terminodes

4. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 4 Backend connectivity Infrastructure integration Local applications Mobile network gateways –GSM –SMS –Wireless LAN –interfacing to other sensor networks Debugging and monitoring –development –quantitative analysis BTnodes Bluetooth Gateway Internet Local Application

5. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 Slide 5 A look at platform competitors UC Berkeley motes – Crossbow, MoteIV (Culler) –Motes and IPAQ’s (Estrin) –Mote-on-a-chip “spec” – MoteInc (Hill) Bluetooth devices –Imotes – Intel Research (Kling) –Blue Wand – Beecon (Zitterbart) Testbeds –Microsoft wake-on wireless (Bahl) –UCLA i-Badge (Srivastava) –UCLA/WINS/Rockwell nodes (Srivastava) –PicoRadio Testbed (Rabaey) Other –TeCo Smart It’s (Beigl) –PicoBeacon (Rabaey) –WiseNet (Enz) –ParkTab (Weiser) –Active Bat (Hopper et al.) full custom radio proprietary limited availability complex and low integration low power reduced features full custom …

6. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 6 UCB Mica motes compared Originated in operating system research, now commercialized Less I/O and memory, same host MCU Custom radio frontend (Chipcon CC1000) –Baseband and MAC processing on host CPU –less free resources –much more fine grained RTOS –no standard wireless interface Mature system level know-how –TinyOS operating system –NesC language abstraction –TOSSIM simulation environment –TinyDB sensor query system –many sensor peripherals available

7. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 Slide 7 System and software and directions OS research –TinyOS in widespread use –many independent OS projects (~10-20 for AVR architecture alone) –core functionality/partitioning still unclear Distributed deployment –infrastructure integration –heterogeneous system services (EmStar, TinyDB…) –multihop still by large untouched Standardization efforts –IEEE 802.15.x (Bluetooth, ZigBee…) –success of open platforms –Bluetooth and 802.15.4 hardware (BTnode, Imote, Telos, MicaZ, MoteIV…)

8. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 8 BTnode architecture Lightweight wireless communication and computing platform based on a Bluetooth radio module and a microcontroller. Bluetooth has the advantage of –availability today for experimentation –compatibility to interface to consumer appliances –an abstract, standardized high level digital interface

9. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 9 Bluetooth prototyping platform Integrated hardware features –8-Bit RISC, max. 8 MIPS, 128 kB Flash, 64 kB SRAM, 180 kB data cache –operating from 3 cell batteries –generic sensor interfaces Event-driven lightweight OS –standard C language –system software available as library Current bill of material50 parts Parts60 USD Assembly5 USD Bluetooth 45 USD Unit cost @ 200 units110 USD

10. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 10 Large ad hoc network topologies How to construct an ad hoc network topology with Bluetooth –large network, many devices –all devices connected, supporting transparent multihop transport Understanding the limits and benefits of Bluetooth XHOP prototypeTreeNet topology

11. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 11 BTnode networking – definitions Four states –IDLE –MASTER –SLAVE –MASTERSLAVE Useful operations –inquiry() – find other nodes –connect() – open connection –roleSwitch() – change MS relation –sendData() – data transport Hardware limitations on the BTnodes/Bluetooth –max. 7 active slaves in one Piconet –while in inquiry() and connect() a node is not visible –while in SLAVE or MASTERSLAVE a node is not visible –while in SLAVE or MS a node cannot do inquiry() or connect() –inquiry() and connect() have long delays and no a priori guarantee Bluetooth only defines single hop Master-Slave data transport

12. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 12 Distributed Bluetooth Piconets Distributed inquiry() and connect() is a problem –nodes are uncoordinated –limited visibility –asymmetry: inquired node doesn’t notice Inquiry() and connect() have long delays –state change in remote node goes unnoticed –average delay in seconds [Kasten2001] –no a priori guarantee for success Inquiry() and connect() are highly nondeterministic (both in timing and function)

13. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 13 Bluetooth applied Purpose of this study: How can we construct ‘arbitrarily’ large trees in a robust and distributed way?

14. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 14 TreeNet simple tree construction Every node executes algorithm –until single tree is reached Formation of large topologies –robustness –simplicity –redundancy –distribution –self-healing Services and applications can break up trees later –forming other topologies –optimizing topology loop { inquiry(); forall (nodes_found) do { while (not_max_degree) connect(); }

15. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 15 TreeNet Demo at Monte Verita Shown at MICS Annual Review NCCR_MICS_MOBILE_INFORMATION_AND_COMMUNICATION_SYSTEMS

16. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 16 TreeNet discussion Nodes must all be in visible range Might not fully connect if multiple max_degree roots form –rebuilding of partial trees necessary if nodes cannot connect at root Simple greedy algorithm reduces inquiry() and connect() –better performance by caching and time-stamping inquiry() and connect() –try to connect() to node-last-seen first –exchange of topology data and adaptive connect() retries

17. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 Slide 17 After over 3 years of BTnodes 200 units with 16 research groups –smart objects –networking –wearable computing –perceptual computing –operating systems Good community interaction Open Source –BTnode System Software –examples –BTnode design data –development tools VTT, FI DSG, ETH Zurich, CH PCCV, ETH Zurich, CH TecO, University of Karlsruhe, GE PLAY, Interactive Institute, SE TIK, ETH Zurich, CH IFE Wearable Lab, ETH Zurich, CH NTT DoCoMo, Munich, GE Ptolemy Group, UC Berkeley, USA Art of Technology, Zurich, CH DistLab, Diku, Copenhagen, DK LAP, EPF Lausanne, CH CS Department, Lancaster University, UK LSL, EPF Lausanne, CH TinyOS Group, UC Berkeley, USA University of Uppsala, SE

18. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 Slide 18 BTnode future Need for more devices – keeping the modularity –design shrink, physical integration –lower power, integrated power supply –better networking support Make BTnodes available as a platform kit –open platform, manufacturing and resale through partner Rethinking of BTnode System Software –support of a threaded OS –tools: network reprogramming –…

19. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 19 BTnode rev3 architecture Multiple radio frontend BTnode –wake-up radio and low duty cycle power schemes Integrated modular extension port Integrated power management –power supply (2x AA) or DC input –main power switch and reset –switchable supplies for subsystems –power consumption 0.5-50 mA @ 3.3V (projected)

20. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 20 BTnode rev3 networking Zeevo Bluetooth 1.2 frontend –faster connection setup –Adaptive Frequency Hopping (AFH) –BT 1.2 Scatternets –7 active Slaves & 4 Masters –future class 1 operation supported –compatibility with ARM7/TinyOS port Chipcon CC1000 low power radio –315, 433, 868, 915 MHz ISM band –FSK 76.8 kBaud –UCB Mica mote compatible

21. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 21 BTnode rev3 status

22. BTnodes - Jan Beutel and Oliver Kasten March 4, 2004 22 To probe further… http://www.btnode.ethz.ch