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

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

Introduction & Motivation

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

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

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.

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

Motivation IEEE Frame

Research Question

 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?

Related Work

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

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.

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

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

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

Design & Architecture

DispSense Architecture Sensor Node Mother Mote

Networking Stack Sensor MoteMother MoteOuter world

Protocol Architecture

Protocol Design

Hardware Implementation

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

Mother Mote Arduino UNO NRf24L01 Image Source:

Sensor Node ATtiny85 MCU NRf24L01 Wireless Transceiver 2x AA Battery

Protocol Implementation

 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.

Evaluation

Binary File Size Evaluation TinyOS

Binary File Size Evaluation ContikiOS Module Sizes

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

Binary File Size Evaluation

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.

Single Mother Mote Node Placement

Single Mother Mote

Node Placement

Single Mother Mote

Node Placement

Single Mother Mote

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

Packet Delivery with Distance (M)

Two Mother Motes Node Placement

Two Mother Motes

Mother Mote 1Mother Mote 2

Three Mother Motes Node Placement

Three Mother Motes

Mother Mote 1Mother Mote 2 Mother Mote 3

Four Mother Motes Node Placement

Four Mother Motes

Mother Mote 1Mother Mote 2 Mother Mote 3Mother Mote 4

Duty Cycle Analysis

Clock Drift Analysis

Conclusion & Future Work

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

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

Thank you

MCU Comparison ModuleRAMROMInst.Current (uA) MHz MHz MHz MHz MHz

Wireless Transceivers Comparison

Duty Cycle Analysis

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

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

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

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

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.

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

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

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

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

Single Mother Mote <1M Range

Single Mother Mote <3M Range

Single Mother Mote <5M Range

Two Mother Motes

Three Mother Motes