1 / 72

BSAC IAB 6 th Semi-annual Mini-Workshop on Wireless Sensor Networks

Join the 6th Semi-annual Mini-Workshop on Wireless Sensor Networks. Explore commercial perspectives, standards, and technology updates by industry experts. Learn about communication stacks, physical layers, and challenges in low-power industrial wireless sensor networks. Discover how RF energy, reflecting surfaces, and antenna distances impact signal strength and network performance. Gain insights into PHY layers, communication protocols, and simulation models. Explore the latest in wireless sensor network advancements and future trends in industrial automation.

rmiles
Download Presentation

BSAC IAB 6 th Semi-annual Mini-Workshop on Wireless Sensor Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BSAC IAB6th Semi-annualMini-Workshop onWireless Sensor Networks

  2. Agenda 1:00-2:00 Introduction • Technology & standards update (Kris Pister) 2:00-3:00 Commercial Perspectives I • Sensys Systems (Amine) • LV Sensors (Janus Bryzek) 3:15-3:30 Break 3:30-4:30 Commercial Perspectives II x 4:30-5:00 University Update

  3. Standards and Technology Kris Pister Prof. EECS, UC Berkeley Co-Director, Berkeley Sensor & Actuator Center (Founder & CTO, Dust Networks)

  4. Outline • Standards • The Stack • PHY • DLL • NET • TRAN • Applications

  5. WirelessHART • HART – Highway Addressable Remote Transducer • Wired standard, ~2 decades old • 25 million sensors deployed • Wireless HART • Based on TSMP 2.0 • Out to ballot 3/07

  6. Timing – perfect synchronization CCA: RX startup, listen, RX->TX A Transmit Packet: Preamble, SS, Headers, Payload,MIC, CRC RX startup or TX->RX RX ACK B RX startup RX packet Verify CRC Verify MAC MIC Calculate ACK MIC+CRC Transmit ACK RX/TX turnaround A transmits to B TX, RX ACK timing

  7. Timing – imperfect synchronization (latest possible transmitter) CCA: RX startup, listen, RX->TX A Transmit Packet: Preamble, SS, Headers, Payload,MIC, CRC RX startup or Tx->Rx Tg ACK RX ACK Tcrypto B RX startup Tg Tg RX packet Verify CRC Verify MAC MIC Calculate ACK MIC+CRC Transmit ACK RX->TX Expected first bit of preamble • TCCA = 0.512ms to be standards compliant • Worst case is a receive slot followed by a transmit slot to a different partner, as radio will be finishing up the ACK TX just as it needs to look for a clear channel, so • TCCA = TTX->RX + Tchannel assessment + TRX->TX = 0.192ms + 0.128ms + 0.192ms • With gold24, we believe we can do a faster turnaround, so we’d get 0.228 instead of 0.512 • Tpacket = 4.256ms for a maximum length packet • Preamble+SS+packet = 4+1+128B = 133B = 1064 bits  4.256ms @ 250kbps • Tcrypto needs to be chosen. For gold24 it will be about 0.25 or 0.5 ms. For the cc2420 it appears to be a bit slower – maybe 0.5 to 1 ms. • TgACK needs to be chosen. It is the tolerance to variation in Tcrypto and/or mote B’s turnaround time from RX to TX • TACK is a function of the ACK length. It is likely to be just under 1ms. • Tslot = TCCA+2*Tg+Tpacket+Tcrypto+TgACK+TACK = 0.512+2+4.256+1+0.1+1 = 9ms

  8. Announced Vendors • Emerson • Phoenix Contact • Vendor X (confidential?)

  9. ISA SP100 • ISA - International Society of Automation • SP100 - Standards Project 100 • Wireless standard for industrial automation • Political wrangling • Default PHY: 802.15.4 • Alternate PHY: NB/FHSS • Draft 2008?

  10. 802.15.4 • IEEE 802.15.4 • PHY, low-MAC • Basis for • Zigbee 2003 • Zigbee 2006 • Zigbee Pro • WirelessHART • SP100 • All incompatible • WirelessHART & SP100 goal: • Fold TSMP back into 802.15.4 (-2009?)

  11. Communication Stack Source Destination L7 Application Application Session? Presentation? Transport Transport L4 Network Network L3 Link Medium Access Link Medium Access L2 L1 Physical Physical

  12. PHY – The Physical Layer

  13. Why a site survey cannot help in low power industrial wireless sensor networks

  14. Consider one path The energy received will depend mainly on distance RF energy is reflected, and now there are two waves received with two distances Add one reflecting surface (like anything metal) One transmits while the other receives Two motes in free space D1 D2 metal Now received energy depends on both distances. At some distances, the two waves will interfere constructively, and at others they interfere destructively. These nulls depend on wavelength and the relative distances

  15. R-2 -30dBm -60dBm The reflective surface is 10,000m away -90dBm 100m 1km 1m 10m

  16. R-2 -30dBm -60dBm The reflecting surface is 100m away -90dBm 100m 1km 1m 10m

  17. -30dBm The reflecting surface is 10m away -90dBm 100m 1km 1m 10m

  18. R-2 -30dBm -60dBm The reflecting surface is 1m away R-4 -90dBm 100m 1km 1m 10m

  19. -50dBm -70dBm The reflecting surface is 2m away from one node and 8m from the other -90dBm 100m 1km 1m 10m

  20. -50dBm Add a second reflecting surface 10m away from both antennas (like a metal ceiling) and it changes again -90dBm 100m 1km 1m 10m

  21. -50dBm Antenna 1 is 2m from surface 1. Antenna 2 is 9m from surface 1. Surface 2 is 17m from both antennas. -90dBm 100m 1km 1m 10m

  22. Simple Two Antenna Model

  23. Simple Propagation Model • Free space + U(0,40)dB -30dBm 100% -60dBm 98% 50% -90dBm 0% 100m 1km 1m 10m

  24. Simulations • 200 motes • 1 square km • Mean separation 70m • 1 mW TX, -90 Rx • R2 radius ~ 300m • R3.7 radius ~ 30m • Hack model 50% radius ~30m R-2 -90dBm R-2-40dB R-3.7 10m 100m 1km

  25. -40 -50 -60 -70 PR [dBm] -80 -90 -100 0 20 40 60 Distance [meters]

  26. PHY Conclusions • Things that you can not measure with a single antenna will make RF paths of a particular length vary by 40dB or more over frequency and time. • Any moving metal object can make a single RF path change by 40dB or more on one frequency, and not at all on another. • For any path in the 10m to 100m range that does not work on a particular channel, there is usually • A distance farther away that will work on that channel • A different channel that will work on that path • A different time at which that channel will work

  27. Antennas • PR = PT GT /(4 p R2) Aeff = PT GT GRl2/(4 p R)2 • Gdipole = 1.5 sin2(q) • Df/f h <= 2 (2pd/l)3

  28. DLL – The Data Link Layer • Medium Access Sublayer • Unsynchronized • Aloha • CSMA • Synchronized • Beacons • TDMA

  29. NET – the Networking Layer

  30. TRAN – The Transport Layer

  31. Applications • Emerson • Croda • Statoil Offshore platform • Annheuser Busch • Pittsburgh Steel • Milford Power • BP • GE • Sensing • Bently • Flow?

  32. Emerson Wireless Sensors and Actuators From CEO Dave Farr’s Analyst Presentation, Feb 2008

  33. Temperature Monitoring of Chemicals in Rail Cars • Application: Temperature monitoring of chemicals in moving railcars • Rate-of-rise temperature monitoring critical for safety and plant performance • Railcars continuously move, making hard wired measurement impractical • Employees had to climb on top of railcars for measurement; dangerous in winter • Smart Wireless solutions give early detection of potentially hazardous rising temperature rise of chemical and eliminate manual readings • Railcar position had no effect on self-organizing network performance; line of site not required • Safety improvement by eliminating operator trips to the top of the railcars • Early detection means early neutralization procedures, improved plant safety “There are savings of $14,600 per year in reduced operations and maintenance costs, but, the incalculable savings were in safety” —Denny Fetters, I&E Designer

  34. Next Generation • Localization • Public Key • Wibree?

  35. WiFi- based Location WiFi systems claim to utilize existing infrastructure, but that appears to be a bit misleading: AP density for location is approx 4x that for data Accuracy: 10 meters 90% and 5 meters 50% Battery life for tags: Up to 5 yrs on AA (e.g. 2 yrs at 20 sec reporting) Dust Networks Confidential 38

  36. Predictive Maintenance "Unscheduled downtime is the largest single factor eroding plant performance. Over $20 Billion, or almost 5 percent of total production, is lost each year in North America alone due to unscheduled downtime." ARC, 2002 “Electric motors consume approximately 60% of all electricity generated in the United States.“ US DoE, December 2002 • Ubiquitous monitoring of motors, pumps, and bearings: • Vibration • Temperature • Acoustic

  37. Industrial Process Monitoring “…this wireless technology enabled us to do things we simply could not do before, either because of cost or physical wiring obstacles. Through the trials, we found that Emerson's wireless approach is flexible, easy to use, reliable, and makes a step-change reduction in installed costs." Dave Lafferty BP Engineering Materials Labor Other Emerson Wireless 90% Savings Over Wired Installation 0% 10% 100% "Wireless promises to enable us to put more monitoring in the plant at one-tenth the cost of wired technology” John Berra, President Save up to 90% on installation The cost of wire, additional hardware and labor drives up the cost of any project, large or small. Wireless solutions enable cost-effective implementation of new measurement points.

  38. “Dust Inside” Industrial Products • End Users • Oil & Gas • Power • Food • Pharma • Chemical • Steel Smart Wireless

  39. Algorithm 1 • At layer2, sending mote • Keeps a list of its communication partners • For each new partner, it makes a few attempts at establishing L2CC (layer 2 compression capable) • keeps track of the last Nk packets that it has sent to each of k L2CC partners • Periodically analyzes the Nk packets for patterns • Sends an ADD_pattern packet to partner. If ack==ok, this pattern is added to the senders list • When sending to an L2CC partner • If a packet matches an established pattern, the compressed packet is sent instead • If the packet is not ACKed, its pattern’s FAIL counter is incremented. If it is successfully ACKed, the FAIL counter is set to zero. If enough FAILs happen (possibly just 1) the packet is sent uncompressed, and patterns are verified using List_pattern • At layer 2, receiving mote:

  40. Packet and information flow Layer 3 Verify Headers, MIC, CRC Generate Headers, MIC, CRC L2CC Control L2CC? L2CC? Decompress N CMD? Layer 2 N Y Partner ADDR1 Y Compress Partner ADDR2 Partner ADDR3 ID Pattern FAILs ID Pattern FAILs ID Pattern FAILs ID1 Pattern FAILs ID Pattern FAILs ID Pattern FAILs ID Pattern FAILs ID Pattern FAILs ID2 Pattern FAILs Y Packet1 Packet2 N L2CC sublayer Layer 1

  41. L2CC packets All of these use some non-standard, recognizable (by layer 2) 15.4 formatting. • Use invalid 15.4 packet structure, with non-standard MIC calculation (e.g. MIC over the message concatenated with the string “L1CC”) • Hello(version) • Hello_ACK • OK, BAD_VERSION, … • Add_pattern(ID, pattern) • Add_pattern_ACK • OK, NO_ROOM, … • Delete_pattern(ID) • Delete_pattern_ACK • OK, NO_SUCH • List_pattern (ID_list) • Request all (ID, pattern) pairs matching ID_list • List_patterns_ACK

  42. L2CC patterns • Identical bytes • Duh. • Counters • Are these even worth compressing? Probably. • Are they detectable? Maybe. • If it’s a 4 bytes counter (e.g. 15.4 security) then 3 bytes will be identified as the same, and every 256 packets the pattern will need to be updated. • Known checksums • E.g. UDP • Questionable if this is worth it. • Others?

  43. Stateful Header Compression Kris Pister UC Berkeley Dust Networks

  44. The Motivation Working in IEEE to fix this • In many sensor networks, >90% of packets • Flow along paths with lots of shared state • Final destination, sometimes source • Link and end-to-end crypto • Source & destination ports • Route • … • Have very short “fundamental” payloads • 2B, 4B not uncommon. Data, or (data, timestamp) • Today’s minimum multi-hop overhead • Application: 0-20B • Transport+Network: 12B (HC1, HC2_UDP) • Link: 11B + 9B (security) • PHY: 6B • >10x overhead • Why fix our part?

  45. Example • Once per second, mote A wakes up and sends a packet with exactly the same • 5B: Mesh header • 3B: Dispatch, HC1, HC2 • 1B: UDP compressed ports • For a period of hours or days (thousands to millions of packets) this information doesn’t change

More Related