Towards System Architecture for Tiny Networked Devices David

Towards System Architecture for Tiny Networked Devices David Culler http: //www. cs. berkeley. edu/~culler U. C. Berkeley Wireless hoo-hah 5/30/2000 wireless hoo hah

An End-to-end Perspective • Scalable Infrastructure – – highly available persistent state (safe) databases, agents service programming environment Service Path • Desktops – max out at few 100 M – in your face – connected to the infrastructure • Ubiquitous Devices – billions – sensors / actuators – PDAs / smartphones / PCs – heterogeneous 5/30/2000 wireless hoo hah 2

Key Characteristics of TNDs • Small physical size and low power consumption • Concurrency-intensive operation – flow-thru, not wait-command-respond • Limited Physical Parallelism and Controller Hierarchy – primitive direct-to-device interface • Diversity in Design and Usage – application specific, not general purpose – huge device variation => efficient modularity => migration across HW/SW boundary • Robust Operation – numerous, unattended, critical => narrow interfaces 5/30/2000 wireless hoo hah 3

‘Mote’ Initial Platform 5/30/2000 wireless hoo hah 4

TOS Tiny OS • Scheduler and Graph of Components – constrained two-level scheduling model: threads + events • Component: – Frame – Threads (concurrency) – Commands, and Handlers (events) • Constrained Storage Model – frame per component, shared stack, no heap • Very lean multithreading • Layering – components issue commands to lower-level components – event signal high-level events, or call lower-level commands 5/30/2000 wireless hoo hah 5

msg_send_ done (success) msg_rec(type, data) send_msg(ad dr, type, data) power(mode) init TOS Component send_msg_thread. Internal State 5/30/2000 TX_packet _done (success) RX_packet_ done (buffer) init Power(mode) TX_packet(buf) Messaging Component /* Messaging Component Declaration */ //ACCEPTS: char TOS_COMMAND(AM_SEND_MSG)(char addr, char type, char* data); void TOS_COMMAND(AM_POWER)(char mode); char TOS_COMMAND(AM_INIT)(); //SIGNALS: char AM_MSG_REC(char type, char* data); char AM_MSG_SEND_DONE(char success); //HANDLES: char AM_TX_PACKET_DONE(char success); char AM_RX_PACKET_DONE(char* packet); //USES: char TOS_COMMAND(AM_SUB_TX_PACKET)(char* data); void TOS_COMMAND(AM_SUB_POWER)(char mode); char TOS_COMMAND(AM_SUB_INIT)(); wireless hoo hah 6

Composition mapper appln router sensor appln Active Messages packet Radio Packet Serial Packet Temp Radio byte UART i 2 c SW byte HW photo bit clocks RFM 5/30/2000 wireless hoo hah 7

Dynamics of Events and Threads • Message Send Transition Timing diagram of event propagation 5/30/2000 wireless hoo hah 8

Empirical Breakdown of Effort Components AM Packet Ratio handler Radio decode thread RFM Radio Reception Idle Total Packet reception Percent CPU work breakdown Utilization 0. 05% 1. 12% 26. 87% 5. 48% 66. 48% 100. 00% 0. 20% 0. 51% 12. 16% 2. 48% 30. 08% 54. 75% 100. 00% Energy (nj/Bit) 0. 33 7. 58 182. 38 37. 2 451. 17 1350 2028. 66 • can take apart time, power, space, … • 50 cycles threads ovhd, 10 cycle event ovhd 5/30/2000 wireless hoo hah 9

Storage Breakdown (C Code) 3450 B code 226 B data 5/30/2000 wireless hoo hah 10

Programming CAD • Can assemble overall system using WV structural VHDL • Scripts convert to all the make magic 5/30/2000 wireless hoo hah 11

Projects this Term • Device Proxy Architecture – mobile-IP RDP variant • Integration with infrastructure – JINI and Ninja • Multithreaded vs federated archtiecture • Pluggable adaptive MAC layer – often periodic, moment of crisis – sleep cycling • Ad Hoc routing component • Connectivity-based location detection • smart badge + sensor in smart space 5/30/2000 wireless hoo hah 12

Looking forward • Mote “designed for experimentation” this summer • Lots of projects now “small matter of programming” • Good basis for incorporating more exciting HW architectures 5/30/2000 wireless hoo hah 13