Reliable End-to-End Data Transmission in Wireless Sensor Networks - PowerPoint PPT Presentation

Reliable End-to-End Data Transmission in Wireless Sensor Networks Wolf-Bastian Pöttner, March 19, 2014

Sines Refinery, Portugal galpenergia.com 35,000 sensors and actuators deployed in Sines refinery Connected to the control room using wires Wolf-Bastian Pöttner Page 2 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Wireless Industrial Monitoring and Control Motivation Monitoring and Control of industrial plants widely based on cables Cables have well known performance and reliability (Petrochemical) Industry physically rearranges plants regularly Benefits of Wireless Networks Increased flexibility and reduced cost Challenges Bounded end-to-end delay Guaranteed reliability Wolf-Bastian Pöttner Page 3 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Industrial Processes from a Network Perspective (Rather) Static network topologies of stationary stations TDMA medium access control for guaranteed delay Multi-hop data transport for extended distances Scalability for large plants Typical Requirements End-to-end delay: max. 1 s End-to-end reliability: min. 99 % How can wireless networks be made reliable enough for monitoring and control of industrial processes? Wolf-Bastian Pöttner Page 4 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Outline Motivation X Fundamentals Literature and Technology Reliability and Burstiness in TDMA networks Reliable TDMA Schedules for Real-Time WSNs Calculating topologies and schedules Measurement results Distributed Transmission Power Control Probe- and attenuation-based Transmission Power Control Measurement results Delay-Tolerant WSNs Wolf-Bastian Pöttner Page 5 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Wireless Process Automation in Literature WirelessHART Complex multi-channel design with up to 16 channels Wireless extension of the HART field bus Primarily for monitoring Proprietary centralized network manager automation.siemens.com Predictable single-channel design End-to-end solution: sensor to ERP/ERM Designed for monitoring and control T. O’Donovan et al.: The GINSENG System for Wireless Monitoring and Control: Design and Deployment Experiences , in TOSN 10, 1, Nov 2013 Wolf-Bastian Pöttner Page 6 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Underlying Technology Internet Wireless Sensor Networks Wireless Sensor Network Sink Network of low-power nodes Node IEEE 802.15.4 based radios Unstable links, mobility Sensor Multi-Hop User Node based on monet.postech.ac.kr Wireless Sensor Nodes Based on 8 or 16 bit microcontrollers ~16 kiB RAM, ~128 kiB ROM Battery powered → short duty cycles Wolf-Bastian Pöttner Page 7 Reliable End-to-End Data Transmission in Wireless Sensor Networks

From Topology to TDMA Schedule Physical Topology S" Location and role of nodes in the field C" B" Logical Topology A" Multi-hop tree structure rooted at sink TDMA Schedule Based on logical topology, traffic pattern and link reliability Wolf-Bastian Pöttner Page 8 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Time Division Multiple Access (TDMA) Time is divided into short time slots Slots are exclusively assigned to specific nodes Exclusive channel access allows to give timing guarantees TDMA"Schedule" Epoch"[1s]" S" Slot"[10ms]" C" A" B" B" C" A" B" B" C" Sender" B" B" S" S" S" Sleep" B" S" S" S" Receiver" A" TX"Power" 1" 2" 2" 1" 1" 2" 2" 1" t" Schedule: Seq. of multiple epochs: S = { e 1 , ..., e n } Wolf-Bastian Pöttner Page 9 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Reliability of Wireless Links Characteristics of Packet Loss Events Even on good wireless links, some packets will eventually get lost Packet loss events often occur in bursts Reliability in TDMA Systems TDMA schedules have to contain slots for retransmissions Worst-case burst loss has to be known in advance How to determine the number of retransmission slots? Wolf-Bastian Pöttner Page 10 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Outline Motivation X Fundamentals X Literature and Technology Reliability and Burstiness in TDMA networks Reliable TDMA Schedules for Real-Time WSNs Calculating topologies and schedules Measurement results Distributed Transmission Power Control Probe- and attenuation-based Transmission Power Control Measurement results Delay-Tolerant WSNs Wolf-Bastian Pöttner Page 11 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Life Cycle of a TDMA Schedule Node Deployment Offline Data Collection Logical Topology and Schedule Calculation Schedule Deployment Schedule Monitoring + Online Data Collection Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 12 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Measuring the Burstiness of Wireless Links Receiver Sender Probe ACK B max Probe Maximum unsuccessful probes in a row Here: B max = 2 Probe B min Probe Minimum successful probes after a ACK burst loss Here: B min = 1 t t Pattern: 1 0 0 1 Wolf-Bastian Pöttner Page 13 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Capturing the worst-case Burstiness of Links Burstiness of exemplary Link 40 35 Transmissions 30 25 20 15 10 5 0 12 14 16 18 20 22 00 02 04 06 08 10 12 Time of Day [h] B max B min 4 Packets Multiple measurements over one “period” of the environment Observed worst-case burstiness represents link Wolf-Bastian Pöttner Page 14 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Calculating Logical Topology and TDMA Schedule Valid Topology Generate valid logical Topology Acyclic tree rooted at sink Contains all nodes Calculate Schedule Valid Schedule No Schedule Based on valid topology valid? Follows individual traffic patterns Yes Respects B min and B max Not Evaluate Fulfils application requirements Better Schedule Better Best Schedule Save Schedule Valid schedule that minimizes ✏ Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 15 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Comparing two Schedules Optimization Goal Valid schedule fulfil delay and reliability requirements Minimized interference between neighbouring networks Minimizing Interference Approximation through energy signature ✏ Minimizing ✏ reduces interference k ✏ = P M i · D i = 0 k Slots, Slot Duration D , Transmission Power M i in Slot i Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 16 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Speed of Schedule Calculation Time for Schedule Calculation 5.67 h for 6 nodes and 32 power levels Exponential dependency on power levels and nodes Heuristic discards links that are unlikely to be used Unusable links Unreliable links Limit outgoing link list per node to T L = 5 links → Calculation with heuristic takes 0.054 h (or 3.24 min) for 13 nodes Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 17 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Results: Reliability in the Refinery 8 7 Initialization Phase Total Lost Packets [%] 6 5 4 3 2 1 0 0 500 1000 1500 2000 2500 3000 Time [s] Handpicked Schedule Computed Schedule Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 18 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Results: Long-term Reliability in Office Environment 1 0.8 Total Packet Loss [%] 0.6 0.4 0.2 0 0 50 100 150 200 250 300 Time [h] Computed Schedule Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 19 Reliable End-to-End Data Transmission in Wireless Sensor Networks

Results: Necessary Probing Effort 100 Correctly classified links [%] 80 60 40 20 0 20 40 60 80 100 120 140 Probing time [h] Office Environment Sines Refinery Wolf-Bastian Pöttner et al.: Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks , in TOSN, 10, 3, Aug 2014 Wolf-Bastian Pöttner Page 20 Reliable End-to-End Data Transmission in Wireless Sensor Networks