1 Photo: San Onofre Nuclear Generating Station Radio Channel Quality in Industrial Sensor Networks Daniel Sexton, Jay Werb SICon 05 February 9 th 2005 2 3 Generic Mesh Network Features Bi-directional Acknowledgements and commands Multi-hop Extend solutions and resiliency Self-healing Reliable and flexible Standards IEEE Secure Symmetric link to link encryption 4 Anatomy of an installed system Bridge nodes interface the sensor network to the IP world Mesh nodes form a reliable backbone for routing sensor data Sensors connect to end nodes to access the network 5 Value Proposition Motor Replaced = 25.61C 6 IEEE Standard Desirable features 250 kbps Flexibility, low duty cycle 2.4 GHz International Lightweight MAC low complexity Simple ASIC many sources low cost Network Security But will it work in a harsh factory environment? 7 Does the promise match the reality? Research focuses on radio reliability in factories Channel fading & multipath Channel coherence Radio performance In simulation On the wire Statistical: lost packets in factories Will channel diversity help? 8 Channel Fading Multipath effects Varies by position Varies by frequency Varies over time Overcome with diversity Path diversity Costs more routing nodes Frequency diversity Free with certain protocols 9 Fading Factors Path Loss: L(dB) = *N*LogD L= path loss at 2.4GHz D = distance in meters N=Exponential Path Loss Factor N=2 for free space Observed values of N: 1.310 dB Frequency diversity is free Some path diversity also provides redundancy Increase 2.4 GHz radio power to about 15 dBm Bluetooth/WiFi coexistence Hostile radio environment, line of sight often unavailable Range consistent with scale of industrial applications Likely range somewhat less than 100 meters Multihop architecture is necessary More testing needed in a wider variety of sites