1. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
September, 2008
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Time Slotted, Channel Hopping Field Experience] Date Submitted: [1 Sep, 2008] Source: [Kris Pister, Lance Doherty, Rick Enns, Kuor Hsin Chang, Clint Powell, José A. Gutierrez, Ludwig Winkel] Companies [Dust Networks, Freescale, Emerson, Siemens AG] Address [30695 Huntwood Avenue, Hayward, CA USA; 890 N. McCarthy Blvd, Suite 120, Milpitas, CA USA; 8000 West Florissant Avenue St. Louis, Missouri USA; Siemensallee 74, Karlsruhe, Germany] Voice:[+1 (510) , +1 (650) , +1 (408) , +1 (480) , +1 (314) , +49 (721) ] ] Re: [n/a] Abstract: [This document proposes extensions for IEEE MAC] Purpose: [This document is a response to the Call For Proposal, IEEE P ] Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
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2. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
<11 January, 2008r>
doc.: IEEE <doc#>
doc.: IEEE <doc#>
September, 2008
Time Slotted, Channel Hopping
(TSCH) Field Experience
Kris Pister – UC Berkeley/Dust Networks
Lance Doherty Dust Networks
Rick Enns - Consultant
Kuor Hsin Chang - Freescale
Clinton Powell - Freescale
José A. Gutierrez – Emerson
Ludwig Winkel – Siemens
September, 2008
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3. Overview
This is the first of many more examples will be showing later.
Present empirical result from a multi-channel multi-hop Industrial Deployment
Measurement was taken for 26 days on all pairwise channels in the network

4. Printing Factory Field Experience Topics
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Printing Factory Field Experience Topics
Network Topology & Location
Network Protocols
Time-Averaged Statistics
Time Series Data
Reliability in Uncertain Conditions
Summary of Results
Kris Pister et al.
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5. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Network Topology
44 Nodes
Gateway circled
2.5 hop mean
Printing factory
Kris Pister et al.
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6. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Kris Pister et al.
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7. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Kris Pister et al.
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8. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
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9. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Network Protocols
Each node has two parents
Childparent connection is a path
TDMA hopping over 16 channels of 2.402.48 GHz
Each path composed of 16 path-channels
Stability is the packet success rate
We measured stability on all path-channels
Child
Parent
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10. Time-Averaged Stability for All Path-Channels
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September, 2008
Time-Averaged Stability for All Path-Channels
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11. Time-Averaged Stability per Path
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September, 2008
Time-Averaged Stability per Path
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12. An Example Low-Stability Path
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September, 2008
An Example Low-Stability Path
What does a path-channel look like?
How does it vary with time?
Let’s look at all 16 channels for a single path over time
Kris Pister et al.
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13. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
26 Days: 2417 Path
2.48GHz
2.40GHz
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14. doc.: IEEE 802.15-<doc#>
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doc.: IEEE <doc#>
September, 2008
Three Paths 56 44 47 17
Are paths geographically correlated?
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15. Three Paths - Stability Averaged over Time
<11 January, 2008r>
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September, 2008
Three Paths - Stability Averaged over Time
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16. Three Paths - Stability Averaged over Time
<11 January, 2008r>
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September, 2008
Three Paths - Stability Averaged over Time
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17. Three Paths - Channel 5 Over 26 Days
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September, 2008
Three Paths - Channel 5 Over 26 Days
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18. Strategies to Overcome Variance
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doc.: IEEE <doc#>
September, 2008
Strategies to Overcome Variance
Path diversity
Have multiple parents for each node
Frequency diversity
Hop equally over all available channels
Time diversity
Link-layer ACKs and retries
Tolerate duplicates
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19. Reliability in the Midst of Variance
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September, 2008
Reliability in the Midst of Variance
44 nodes, 80B payload per packet
33 packets per 15 min per node
3.6 million packets, 17 lost
% reliability over 26 days
All data secure and encrypted
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20. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Expected Lifetime
Duty Cycle
TX Current=20mA
RX Current=10mA
TX Current=60mA
RX Current=30mA
0.1%
hr (= 11.4 yr)
33333 hr (= 3.8 yr) 1%
10000 hr (= 1.1 yr)
3333 hr (= 4.6 mo)
10 %
1000 hr (= 1.4 mo)
333 hr (= 0.5 mo)
100 %
100 hr (= 4.2 days)
33 hr (= 1.4 days)
Assuming 2xAA batteries (3000mAh)
Kris Pister et al.
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21. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Summary of Results
Average over time and frequency  good paths
Individual frequencies have periods of poor performance
Time-varying behavior unpredictable
Use network protocols to get mean behavior
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22. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
September, 2008
Conclusions
Industrial environments have varying channels
Low-power single-channel system will have failures
Cannot predict performance
Average-case modeling software not applicable
Site surveys cannot capture behavior
Problems would be more severe with interference
Can appropriately overprovision to get reliability
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