1. A data delivery protocol for extremely resource constrained wireless sensors International Conference on Advances in ICT for Emerging Regions 2016/09/02 R.E. Hapuarachchi, A. Sayakkara, C. I. Keppetiyagama

2. Outline  Introduction & Motivation  Research question  Related work  Design & Architecture  Protocol implementation  Evaluation  Conclusion

3. Introduction & Motivation

4. Introduction  Monitoring applications are used widely.  Environmental Monitoring  Home & Office monitoring  Temperature  Light  Humidity  Sensor motes are used widely for these monitoring applications.

5. Sensor Motes  Motes contains number of sensors built in.  Contains a MCU & wireless transceiver  Capable of processing as well  Contains a real time OS (TinyOS, Contiki)  Programmable  Costs around $100  Implements the full IPv6 stack

6. Motivation  Number of conceptual application designs  Very few applications leverage dense networks  Most of the applications in small environments are not using multi-hop communication.  Processing power increased with the time.  Cortex M0 – M7  Battery life growth is relatively low.

7. Motivation  It is possible to build sensor nodes which are,  Cost effective ( Less than $15)  Resource constrained  Low power MCU  Low power wireless transceiver  Can use single hop communication in a small environment.  Eliminate complex routing mechanisms.  Save energy.  Will add more value to Home & Office context

8. Motivation IEEE 802.15.4 Frame

9. Research Question

10.  How to design a low complexity protocol to have low processing overhead in the sensor node?  How to achieve lower duty cycling mechanism to reduce the energy wastage?  Is it possible to achieve higher packet delivery ratio by using the proposed protocol?

11. Related Work

12. Data communication  Channel access is controlled by the MAC protocol.  Number of MAC protocols are available for data communication in wireless networks.  Focuses on,  Channel separation & access  Topology  Power  Transmission initiation  Traffic load and scalability  Range MAC Protocols

13. Mechanisms used in existing MAC protocols  S-MAC  Agree to SYNC time to communicate  Uses RTS/CTS packets.  Operates in a single layer  Uses link layer scheduling  ContikiMAC  Upon wakeup it keep sending data until sender receives ACK packet. (Avoid beacon retransmission)  B-MAC  Employs an adaptive preamble to reduce idle listening.  Eliminates control packet overhead by not using RTS/CTS packets.  Periodic channel check using Low Power Listening.  But preamble overhead is considerable.  For 36 bytes of data, preamble size 271bytes.  RI-MAC  Receiver initiated communication.

14. Mechanisms used in existing MAC protocols  Transmit Only  Consider that the C/A is unnecessary and wasteful.  Consists with multiple receivers to avoid collisions.  Used in dense wireless systems  Receivers are deployed in a way that each transmitter is within a single hop of one or more receivers.  Exploit the capture effect to reduce the effective contention between transmitters. Bernhard Firner, The State University of New Jersey

15. Energy Management  Energy waste factors in MAC protocols  Idle listening  Collisions  Control Packet Overhead  Overhearing  Over emitting  Packet Size

16. Energy Management  Energy saving mechanisms used in different MAC protocols  Duty cycling  Energy-efficient scheduling  Scheduled rendezvous  On-demand wake-up scheme

17. Design & Architecture

18. DispSense Architecture Sensor Node Mother Mote

19. Networking Stack Sensor MoteMother MoteOuter world

20. Protocol Architecture

21. Protocol Design

22. Hardware Implementation

23. Mother Mote  Raspberry PI  Arduino  PCDuino  Custom Device  Higher processing power  Wireless Transceiver  Networking capability

24. Mother Mote Arduino UNO NRf24L01 Image Source: http://blog.carr3r.com/content/public/upload/arduino-nrf24_1_o.jpg

25. Sensor Node ATtiny85 MCU NRf24L01 Wireless Transceiver 2x AA Battery

26. Protocol Implementation

27.  Arduino as coding environment for both Sensor node and the Mother Mote.  Mirf library.  Used Mirf SPI driver for the Mother mote and Mirf SPI 85 Driver for the Sensor node (ATtiny85 chip)  Used USBASP as the programmer for Attiny85 MCU.

28. Evaluation

29. Binary File Size Evaluation TinyOS

30. Binary File Size Evaluation ContikiOS Module Sizes

31. Binary File Size Evaluation  Attiny 85 Capacity= 8KB (8,192 bytes)  Compiled Binary Size = 2.19KB (2240 bytes)  ContikiOS binary size= 8082 bytes  TinyOS binary size = 9859 bytes

32. Binary File Size Evaluation

33. Protocol Evaluation  Used Parameters  Ttotal = 5S  Tdata = 4S  TnewNod= 1S  Twindow size is a variable.  Packet Size is 32 bytes for all experiments.  Evaluated with Single Mother Mote up to Four Mother Motes.

34. Single Mother Mote Node Placement

35. Single Mother Mote

36. Node Placement

37. Single Mother Mote

38. Node Placement

39. Single Mother Mote

40. Comparison D < 1M1M <D < 3M 3M < D < 5M

41. Packet Delivery with Distance (M)

42. Two Mother Motes Node Placement

43. Two Mother Motes

44. Mother Mote 1Mother Mote 2

45. Three Mother Motes Node Placement

46. Three Mother Motes

47. Mother Mote 1Mother Mote 2 Mother Mote 3

48. Four Mother Motes Node Placement

49. Four Mother Motes

50. Mother Mote 1Mother Mote 2 Mother Mote 3Mother Mote 4

51. Duty Cycle Analysis

53. Clock Drift Analysis

54. Conclusion & Future Work

55. Conclusion Binary File size is smaller than ContikiOS and TinyOS binary files. TinyOS does not fit in to Attiny85 Chip. ContikiOS binary files almost take up the entire memory. Using about 4 Mother Motes, a large area can be coverd.. Protocol performs well up to 4 Mother Motes and can handle 20 sensor nodes while maintaining over 98% PDR. Have lower Duty Cycle ratio than X MAC, RI MAC and Wise MAC protocols. But ContikiMAC protocol has a lower Duty Cycle ratio. Higher data rates are not evaluated

56. Future Work  Evaluate protocol for dense networks.  Using simulator  Using real devices  Evaluate performance of the protocol in real applications.  Remove the overhead of community libraries used in the implementation.  Mirf  SPI  SPI85  nRF24L01

57. Thank you

58. MCU Comparison ModuleRAMROMInst.Current (uA) ATtiny85512B8KB8bit300@1 MHz MSP430G2553512B16KB16bit330@1 MHz MSP430F161110KB48KB16bit330@1 MHz Cortex-M0+4KB16KB32bit1400@12 MHz Cortex-M464KB512KB32bit47810@80 MHz

59. Wireless Transceivers Comparison

68. Duty Cycle Analysis

71. SPI RF-SETUP (RF_PWR) RF Output Power DC current consumption 110dBm11.3mA 10-6dBm9.0mA 01-12dBm7.5mA 00-18dBm7.0mA nRF24L01power consumption on different power levels

72. Existing MAC protocols  S-MAC  Agree to SYNC time to communicate  Uses RTS/CTS packets.  Operates in a single layer  Uses link layer scheduling S-MAC Timing relationship of a receiver and multiple senders by W. Ye, J. Heidemann

73. Existing MAC protocols  ContikiMAC  Uses Duty Cycling  Upon wakeup it keep sending data until sender receives ACK packet. (Avoid beacon retransmission) ContikiMAC Overview by A.Dunkels

74. Existing MAC protocols  B-MAC  Employs an adaptive preamble to reduce idle listening.  Eliminates control packet overhead by not using RTS/CTS packets.  Periodic channel check using Low Power Listening.  But preamble overhead is considerable.  For 36 bytes of data, preamble size 271bytes. B-MAC Overview by J. Cabra

75. Existing MAC protocols  RI-MAC  Nodes have own schedule.  Receiver sends a beacon and sender will transmit the data.  Receiver acknowledgement will also invite the next packet. RI-MAC Overview by Y. Sun et al.

77. Energy Management  Sleep & wake mechanism to conserve energy.  Different D/C mechanisms available.  Answers to the Idle listening problem.  Disadvantage  D/C will stop working of the whole network or portion of the network.  SMAC uses adaptive D/C to overcome this. Duty Cycling

78. Energy Management  Efficient scheduling according to the demand of the network.  This will reduce the energy consumption at all levels of the network.  Common design goal:  Maximize the network lifetime.  Scheduling mechanism can be classified into two major categories:  Distributed scheduling mechanisms in a nonhierarchical networks  Distributed scheduling mechanisms in hierarchical networks Energy Efficient Scheduling

79. Energy Management  Neighbors of a node will have a prescheduled rendezvous time to wake up and communicate.  All the nodes will sleep until the next rendezvous time.  Guarantee that whenever a node wakes up, all the neighbors are also awake at the moment.  Used in environmental monitoring.  Strict scheduling and clock drifting might affect the protocol significantly. Scheduled Rendezvous

80. Energy Management  Multiple radios are being used.  One radio which consume less energy will broadcast a wake-up tone to neighbors.  No data encoded in the wake-up tone.  Use the other node to transfer data.  Advantage  Receiver has only to detect the energy of the channel without attempting to decoding a data packet.  Disadvantage  Increased complexity.  All the neighbors will wakeup because of the wake-up tone.  Additional radios will add extra cost. On Demand Wake-up scheme

81. Single Mother Mote <1M Range

82. Single Mother Mote <3M Range

83. Single Mother Mote <5M Range

84. Two Mother Motes

85. Three Mother Motes