Effective but Lightweight Online Selftest for Energy-Constrained WSNs - PowerPoint PPT Presentation

Effective but Lightweight Online Selftest for Energy-Constrained WSNs SenseApp 2018 Ulf Kulau, Daniel Szafranski and Lars Wolf, 01.10.2018 Technische Universität Braunschweig, IBR

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors What are Soft Errors? 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 2

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors What are Soft Errors? Unexpected state changes in digital circuits 1 → 0 Bit-flips, stuck-at errors, ... x 0 → 1 Occur randomly and temporary x + ¯ y ¯ Can lead to malfunction of components 1 Overall system is often not affected y → Very hard to detect 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 2

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors What are Soft Errors? Unexpected state changes in digital circuits 1 → 0 Bit-flips, stuck-at errors, ... x 0 → 1 Occur randomly and temporary x + ¯ y ¯ Can lead to malfunction of components 1 Overall system is often not affected y → Very hard to detect Causes In space applications: cosmic rays Undervolting Large temperature variations Faulty units, ageing and wear, ... 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 2

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors Effects of soft errors in computer systems 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 3

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors Effects of soft errors in computer systems Soft errors can occur in any component ... ... 0x10 0x11 0x12 Program Counter (PC) → unpredictable program flow Arithmetic logic unit (ALU) → incorrect calculations ... ... 0x11 0x11 0x12 RAM → data corruption Peripheral components, ... 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 3

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors Effects of soft errors in computer systems Soft errors can occur in any component ... ... 0x10 0x11 0x12 Program Counter (PC) → unpredictable program flow Arithmetic logic unit (ALU) → incorrect calculations ... ... 0x11 0x11 0x12 RAM → data corruption Peripheral components, ... Can propagate and lead to unpredictable malfunction of the entire system 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 3

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors Effects of soft errors in WSNs Disadvantages Malfunction of WSN nodes Can significantly decrease the overall energy efficiency of WSNs Kulau et.al., Energy Efficiency Impact of Transient Node Failures when using RPL , WoWMoM, 2017 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 4

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors Effects of soft errors in WSNs Disadvantages Malfunction of WSN nodes Can significantly decrease the overall energy efficiency of WSNs Kulau et.al., Energy Efficiency Impact of Transient Node Failures when using RPL , WoWMoM, 2017 Advantages Safe indicator of an malfunctioning MCU due to undervolting Can be used to detect unreliable WSN node Kulau et.al., IdealVolting – Reliable Undervolting on Wireless Sensor Nodes , ACM Transactions on Sensor Networks (TOSN), 2016 → Soft error detection is both, necessary and beneficial 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 4

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Soft Errors Project goal: Effective but Lightweight Online Selftest for Energy-Constrained WSNs Reliability Reliability → High soft error detection rates Low overhead Focus on most error-prone components → Increase energy efficiency Genericity Use a software implementation instead of addidtional hardware Genericity Low overhead → usable on different MCUs 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 5

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics Online Selftest - Basics 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 6

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics Online Selftest - Basics Well-known Algorithm-Based Fault Tolerance (ABFT) Used for fault tolerance in complex computer systems Error correction requires huge overhead 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 6

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics Online Selftest - Basics Well-known Algorithm-Based Fault Tolerance (ABFT) Used for fault tolerance in complex computer systems Error correction requires huge overhead Online Selftest for energy-constrained MCUs ALU is one of the most error-prone components → Based on checksum based fault tolerant matrix multiplication Checksum is implemented as a sum function Small dimensional matrices Online capable implementation Focus on error detection instead of correction 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 6

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics 1) Starting with 2 Matrices A ∈ R m × n and B ∈ R n × r     a 1 , 1 a 1 , 2 · · · a 1 , n b 1 , 1 b 1 , 2 · · · b 1 , r a 2 , 1 a 2 , 2 · · · a 2 , n b 2 , 1 b 2 , 2 · · · b 2 , r      ∈ R m × n ,  ∈ R n × r A = B =  . . .   . . .  ... ... . . . . . .     . . . . . .   a m , 1 a m , 2 · · · a m , n b n , 1 b n , 2 · · · b n , r 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 7

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics 2) Adding column and row sums to A and B a 1 , 1 a 1 , 2 · · · a 1 , n   a 2 , 1 a 2 , 2 · · · a 2 , n   m . . .  ...  ∈ R ( m + 1 ) × n , ∑ A c = . . . a m + 1 , j = a i , j with j = [ 1 , ..., n ]   . . .   i = 1   a m , 1 a m , 2 · · · a m , n   a m + 1 , 1 a m + 1 , 2 · · · a m + 1 , n b 1 , 1 b 1 , 2 · · · b 1 , r b 1 , r + 1   b 2 , 1 b 2 , 2 · · · b 2 , r b 2 , r + 1 r    ∈ R n × ( r + 1 ) , ∑ B c = b i , r + 1 = b i , j with i = [ 1 , ..., n ]  . . . .  ... . . . .   . . . . j = 1  b n , 1 b n , 2 · · · b n , r b n , r + 1 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 8

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics 3) Multiplication and results review  c 1 , 1 c 1 , 2 · · · c 1 , r c 1 , r + 1  c 2 , 1 c 2 , 2 · · · c 2 , r c 2 , r + 1    . . . .  ... A c · B c = C c = . . . .   . . . .     c m , 1 c m , 2 · · · c m , r c m , r + 1   c m + 1 , 1 c m + 1 , 2 · · · c m + 1 , r c m + 1 , r + 1 No soft errors At least one soft error m m ∑ ∑ ∀ j ∈ [ 1 , ..., r + 1 ] : c m + 1 , j = c i , j ∃ j ∈ [ 1 , ..., r + 1 ] : c m + 1 , j � = c i , j i = 1 i = 1 r r ∑ ∑ ∀ i ∈ [ 1 , ..., m + 1 ] : c i , r + 1 = c i , j ∃ i ∈ [ 1 , ..., m + 1 ] : c i , r + 1 � = c i , j j = 1 j = 1 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 9

Introduction and Motivation Online Selftest Automatic test equipment Evaluation Summary Online Selftest - Basics Implementation Optimization   c 1 , 1 c 1 , 2 · · · c 1 , r c 1 , r + 1   · · · c 2 , 1 c 2 , 2 c 2 , r c 2 , r + 1     . . . .  ...  C c = . . . .   . . . .    c m , 1 c m , 2 · · · c m , r c m , r + 1      c m + 1 , 1 c m + 1 , 2 · · · c m + 1 , r c m + 1 , r + 1 Alternating row and column multiplication Checksums can be verified online → reduce the overhead Square matrices ( n = m = r ) are used to simplify implementation 01.10.2018 Ulf Kulau, Daniel Szafranski Effective but Lightweight Online Selftest for Energy-Constrained WSNs Page 10