Towards System Architecture for Tiny Networked Devices

1
Towards System Architecture for Tiny Networked
Devices

• David Culler
• http//www.cs.berkeley.edu/culler
• U.C. Berkeley
• Wireless hoo-hah
• 5/30/2000

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An End-to-end Perspective

• Desktops
• max out at few 100M
• in your face
• connected to the infrastructure

3
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
• gt efficient modularity
• gt migration across HW/SW boundary
• Robust Operation
• numerous, unattended, critical
• gt narrow interfaces

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Mote Initial Platform
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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

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TOS 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)()
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Composition
mapper
router
sensor appln
appln
Active Messages
packet
Serial Packet
Temp
Radio Packet
SW
byte
HW
UART
Radio byte
i2c
photo
bit
clocks
RFM
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Dynamics of Events and Threads

• Message Send Transition

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Empirical Breakdown of Effort

• can take apart time, power, space,
• 50 cycles threads ovhd, 10 cycle event ovhd

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Storage Breakdown (C Code)
3450 B code 226 B data
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Programming CAD

• Can assemble overall system using WV structural
  VHDL
• Scripts convert to all the make magic

12
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

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Looking forward

• Mote designed for experimentation this summer
• Lots of projects now small matter of
  programming
• Good basis for incorporating more exciting HW
  architectures