Adhoc and sensor networks (IV CSE JNTUH)

1. TinyOS

2. Learning Objectives
• Understand TinyOS – the dominant open
source operating systems for WSN
– Hardware abstraction architecture (HAA)
– TinyOS architecture and component model
– Main characteristics of TinyOS 2
• Understand NesC programmng
• Learn representative WSN applications

3. Prerequisites
• Module 1
• Basic concepts of Operating Systems
• Basic concepts of Object-oriented Design and
Analysis
• Basic concepts of Computer Networks

4. http://www.tinyos.net 4
Software Challenges - TinyOS
• Power efficient
– Put microcontroller and radio to sleep
• Small memory footprint
– Non-preemptable FIFO task scheduling
• Efficient modularity
– Function call (event and command) interface between
commands
• Application specific
• Concurrency-intensive operation
– Event-driven architecture
– No user/kernel boundary

5. [TinyOS_1]: Table 2 5
TinyOS Hardware Abstraction
Architecture (HAA)
• Section 2.3 and Figure 2.5 of J. Polastre Dissertation:
http://www.polastre.com/papers/polastre-thesis-final.pdf

6. TinyOS Hardware Abstraction
Architecture (HAA)
Ref: Figure 2.4 of J. Polastre Dissertation
http://www.polastre.com/papers/polastre-thesis-final.pdf

7. Traditional OS Architectures
Problem with Large Scale Deeply embedded system..
• Large memory & storage requirement
• Unnecessary and overkill functionality ( address space isolation,
complex I/O subsystem , UI ) for our scenario.
• Relative high system overhead ( e.g, context switch )
• Require complex and power consuming hardware support.
VM I/O Scheduler
Application 1 Application 2
Monolith-kernel
HW
NFS I/O
Scheduler
Application 1
Micro-kernel
HW
IPC VM

8. NO Kernel Direct hardware manipulation
NO Process management Only one process on the fly.
NO Virtual memory Single linear physical address space
NO Dynamic memory allocation Assigned at compile time
NO Software signal or exception Function Call instead
Goal: to strip down memory size and system overhead.
TinyOS Architecture Overview (1)
I/O COMM . …….
Scheduler TinyOS
Application
Component
Application
Component
Application
Component

9. TinyOS Overview
• Application = scheduler + graph of components
– Compiled into one executable
• Event-driven architecture
• Single shared stack
• No kernel/user space differentiation
Communication
Actuating Sensing Communication
Application (User Components)
Main (includes Scheduler)
Hardware Abstractions

10. [TinyOS_4] 10
TinyOS Component Model
• Component has:
– Frame (storage)
– Tasks: computation
– Interface:
• Command
• Event
• Frame: static storage model - compile time
memory allocation (efficiency)
• Command and events are function calls
(efficiency)
Messaging Component
Internal StateInternal Tasks
Commands Events

11. The mote revolution: Low Powr
Wireless Sensor Network
12
Typical WSN Application
• Periodic
– Data Collection
– Network Maintenance
– Majority of operation
• Triggered Events
– Detection/Notification
– Infrequently occurs
• But… must be reported
quickly and reliably
• Long Lifetime
– Months to Years without
changing batteries
– Power management is the key
to WSN success
sleep
wakeup
processing
data acquisition
communication
Power
Time

12. The mote revolution: Low Powr
Wireless Sensor Network
13
Design Principles
• Key to Low Duty Cycle Operation:
– Sleep – majority of the time
– Wakeup – quickly start processing
– Active – minimize work & return to sleep

13. The mote revolution: Low Powr
Wireless Sensor Network
14
Minimize Power Consumption
• Compare to Mica2: a MicaZ mote with AVR mcu and 802.15.4 radio
• Sleep
– Majority of the time
– Telos: 2.4mA
– MicaZ: 30mA
• Wakeup
– As quickly as possible to process and return to sleep
– Telos: 290ns typical, 6ms max
– MicaZ: 60ms max internal oscillator, 4ms external
• Active
– Get your work done and get back to sleep
– Telos: 4-8MHz 16-bit
– MicaZ: 8MHz 8-bit

14. Power Consumption

15. Energy Consumption
• Idle listen:receive:send = 1:1.05:1.4

16. [Introduction_2]: Figure 3 17
TinyOS Radio Stack

17. [Introduction_2]: Table 2 18
Code and Data Size Breakdown

18. WSN Protocol Stack
Ref: [Introduction_1] “A Survey on Sensor Networks,” IEEE
Communications Magazine, Aug. 2002, pp. 102-114.

19. TinyOS 2
• An operating system for tiny, embedded, and
networked sensors
• NesC language
– A dialect of C Language with extensions for components
• Three Limitations
– Application complexity
– High cost of porting to a new platform
– reliability
• Little more that a non-preemptive scheduler
• Component-based architecture
• Event-driven
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded Sensor
Networks”

20. TinyOS 2
• Static binding and allocation
– Every resource and service is bound at compile time and all
allocation is static
• Single thread of control
• Non-blocking calls
– A call to start lengthy operation returns immediately
– the called component signals when the operation is
complete
– Split phase
– See this link for one example
http://docs.tinyos.net/index.php/Modules_and_the_TinyOS_Exe
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded Sensor
Networks”
• Ref: [TinyOS_3] Section 2.1

21. TinyOS 2
• The scheduler has a fixed-length queue, FIFO
• Task run atomically
• Interrupt handlers can only call code that has the async
keyword
• Complex interactions among components
• Event
– In most mote applications, execution is driven solely by
timer events and the arrival of radio messages
• ATmega128 has two 8-bit timers and two 16-bit timers
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded Sensor
Networks”

22. TinyOS 2
• sync code is non-preemptive,
– when synchronous (sync) code starts running, it does not relinquish the
CPU to other sync code until it completes
• Tasks
– enable components to perform general-purpose "background"
processing in an application
– A function which a component tells TinyOS to run later, rather than
now
• The post operation places the task on an internal task queue
which is processed in FIFO order
• Tasks do not preempt each other
• A Task can be preempted by a hardware interrupt
• See TinyOS lesson:
– Modules and the TinyOS Execution Model

23. 802.15.4 and CC2420
• CC2420 hardware signals packet reception by
triggering an interrupt
• The software stack is responsible for reading
the received bytes out of CC2420’s memory;
• The software stack sends a packet by writing it
to CC2420’s memory then sending a transmit
command
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded Sensor
Networks”

24. TinyOS 2
• Platforms
– MicaZ, Mica2, etc;
– Compositions of chips
• Chips
– MCU, radio, etc
– Each chip follows the HAA model, with a HIL
implementation at the top
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded Sensor
Networks”

25. TinyOS 2
• A T2 packet has a fixed size data payload
which exists at a fixed offset
• The HIL of a data link stack is an active
message interface
• Zero-copy
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded
Sensor Networks”

26. Scheduler in TinyOS 2.x
SchedulerBasicP.nc of TinyOS 2.x

27. TinyOS Serial Stack
• Ref: P. Levis, et al. “T2: A Second Generation OS For Embedded Sensor
Networks”

28. Device Drivers in T2
• Virtualized
• Dedicated
• Shared
• Ref: Section 3 of [Energy_1]

29. [TinyOS_1]: Section 5 30
T2 Timer Subsystem
• MCU comes with a wide variation of hardware
timers
– ATmega128: two 8-bit timers and two 16-bit times
– MSP430: two 16-bit timers
• Requirement of Timer subsystem
– Different sampling rates: one per day to 10kHz

30. T2 Timer Subsystem
• See interface at:
– tos/lib/timer/Timer.nc

31. One Example TinyOS Application -
BlinkC
• http://docs.tinyos.net/index.php/TinyOS_Tutor
ials

32. One Example of Wiring
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

33. AppM
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

34. AppM
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

35. Sensor Interface
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

36. Initialize Interface
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

37. SensorC
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

38. AppC
• Ref: D. Gay, et al. “Software Design Patterns for TinyOS”

39. Notation

40. CTP Routing Stack

41. Parameterized Interfaces
• An interface array
•Ref: D. Gay, et al. “Software Design Patterns for TinyOS”, Section 2.3

42. unique and uniqueCount
• Want to use a single element of a
parameterized interface and does not care
which one, as long as no one else use it
• Want to know the number of different values
returned by unique
•Ref: D. Gay, et al. “Software Design Patterns for TinyOS”, Section 2.4

43. section 4.5 "TinyOS Programming
manual"
44
async
• Functions that can run preemptively are
labeled with async keyword
• Command an async function calls and events
an async function signals must be async
• All interrupt handlers are async
• atomic keyword
– Race conditions, data races

44. Generic Components and Typed
Interface
• Have at least one type parameter
• Generic Components are NOT singletons
– Can be instantiated within an configuration
– Instantiated with the keyword new (Singleton
components are just named)

45. /tos/lib/timer/VirtualizeTimerC.n 46
Example - VirtualizeTimerC
• Use a single timer to create up to 255 virtual timers
• generic module VirtualizeTimerC(typedef
precision_tag, int max_timers)
• Precision_tag: A type indicating the precision of the Timer being
virtualized
• max_timers: Number of virtual timers to create.
• How to use it?
– Components new VirtualizeTimerC(TMilli, 3) as TimerA
• This will allocate three timers
– Components new VirtualizeTimerC(TMilli, 4) as TimerB
• This will allocate three timers
• Ref:
– /tos/lib/timer/VirtualizeTimerC.nc
– Section 7.1 of “TinyOS Programming Manual”

46. Virtualized Timer

47. Figure 4 of [TinyOS_1] 48
Timer Stack on MicaZ/Mica2

48. Timer Subsystem
• HplTimer[0-3]C provide dedicated access to
the two 8-bit and two 16-bit timers of
ATmega128 MCU
• T2 subsystem is built over the 8-bit timer 0
• Timer 1 is used for CC2420 radio

49. message_t
• tos/types/message.h
• Ref. TEP 111
• Every link layer defines its header, footer, and
metadata structures

50. Relationship between CC1000 Radio
Implementation and message_t
• tos/chips/cc1000/CC1000Msg.h

51. Relationship between CC2420 Radio
Implementation and message_t
• tos/chips/cc2420/CC2420.h

52. Relationship between Serial Stack
Packet Implementation and message_t
• tinyos-2.x/tos/lib/serial/Serial.h

53. Active Message (AM)
• Why do we need AM?
– Because it is very common to have multiple
services using the same radio to communicate
– AM layer to multiplex access to the radio
• make micaz install,n
– n: unique identifier for a node

54. Active Message
• Every message contains the name of an event handler
• Sender
– Declaring buffer storage in a frame
– Naming a handler
– Requesting Transmission
– Done completion signal
• Receiver
– The event handler is fired automatically in a target node
 No blocked or waiting threads on the receiver
 Behaves like any other events
 Single buffering
 Double Check!!!!!!!

55. TinyOS Component
• Two types of components
– Module: provide implementations of one or more
interfaces
– Configuration: assemble other components
together

56. TinyOS Component Model
• Component has:
– Frame (storage)
– Tasks: computation
– Interface:
• Command
• Event
• Frame: static storage model - compile time
memory allocation (efficiency)
• Command and events are function calls
(efficiency)
Messaging Component
Internal StateInternal Tasks
Commands Events

57. Structure of a Component
TinyOS Component
Command Handlers
Event Handlers
Set of Tasks
Frame
(containing state information)

58. TinyOS Two-level Scheduling
• Tasks do computations
– Non-preemptable FIFO scheduling
– Bounded number of pending tasks
• Events handle concurrent dataflows
– Interrupts trigger lowest level events
– Events prempt tasks, tasks do not
– Events can signal events, call commands, or post tasks
Hardware
Interrupts
events
commands
FIFO
Tasks
POST
Preempt
Time
commands

59. TinyOS Applications
• In most mote applications, execution is driven
solely by timer events and the arrival of radio
messages

60. How to Program motes Under TinyOS
• make telosb install,n mib510,/dev/ttyUSB0
• make telosb install,1 mib510,/dev/ttyUSB0

61. Representative WSN Applications
• BaseStation – Listen – BlinkToRadio
– One-hop WSN application to collect sensed values
• OscilloScope
– one-hop WSN application with GUI interface
• MultiOscilloScopre
– multihop WSN application
• Octopus
– multi-hop WSN application with a more dynamic display
of network topology and data dissemination functions

62. Application Example - BaseStation,
Listen and BlinkToRadio

63. Application Example - Oscilloscope

64. Application Example -
MultihopOscilloscope

65. Application Example - MViz

66. MViz

67. Application Example - Octopus
• http://csserver.ucd.ie/~rjurdak/Octopus.htm

68. Octopus

69. BaseStation – Listen - BlinkToRadio

70. OscilloScope

71. MultihopOscilloscope

72. MViz

73. Octopus

74. Lab 1
• a) Write a PingPong application that runs on
two nodes. When a node boots, it sends a
broadcast packet using the AMSend interface.
When it receives a packet, it a) wait one
second; b) sends a packet; c) toggle an LED
whenever a node sends a packet.

75. Lab 2
• b) Please add the reliable data transmission feature to the PingPong
application from the Application and Link layer, respectively. Suppose
that two motes A and B are talking to each other.
I. Application Layer: When mote A sends a broadcast pack P to node B,
mote A will start a timer T. When mote B receives the packet P, mote B
will send an ACK to node A.
b.1 If the timer T expires before mote A receives the ACK from mote B
(either the packet P or the ACK is lost), mote A will retransmit the packet;
b.2 If mote A receives the ACK from mote B before the timer T expires,
mote A will do nothing when the timer T expires.
b.3 If mote B receive a packet which has already been received (based on
sequence number), node B just drop this packet.
There is a sequence number included in the payload of the packet P. The
sequence number starts from 0. When a packet P is received, the receiver
will display the bottom three bits (through LEDs) of the sequence number
in the packet P.

76. Lab 2 - continue
• II. Link Layer: In TEP 126 (http://www.tinyos.net/tinyos-
2.x/doc/html/tep126.html), it says:
“PacketLink: This layer provides automatic retransmission
functionality and is responsible for retrying a packet
transmission if no acknowledgement was heard from the
receiver. PacketLink is activated on a per-message basis,
meaning the outgoing packet will not use PacketLink unless it
is configured ahead of time to do so”
Therefore, as an alternative, you may also configure
PacketLink to provide automatic retransmission functionality.

77. Assignment
• 1. What is the relationship among all the
application components in the Oscilloscope
application?
• 2. please give two examples of split-phase
operations in TinyOS 2.
• 3. What is the usage of Active Message in
TinyOS 2?
• 4. Why doesn’t TinyOS 2 make every
statement async?