Transcript Document 7711130

Time Synchronized Meshing
K. Pister
Prof. EECS, UC Berkeley
Founder & CTO, Dust Networks
This document is provided strictly for the purpose of gathering information leading to the development of an ISA
standard, recommended practice or technical report. Copies may be reproduced and distributed, in whole or in
part, but only for the following purposes:
Review of and comment on the ISA-SP100 draft proposal
Submission to ISA-SP100 Committee
Informing and educating others about the ISA-SP100 draft standard development process.
Standards
Certification
Education & Training
Publishing
Conferences & Exhibits
Goals
• Non-fanaticism
– TDMA & CSMA
– Centralized & decentralized management
– Efficient use of powered infrastructure when available
• Conceptually and practically simple
• 802.15.4 MAC w/ extensions
• Provide framework to approach limits of the radio
– 16x250kbps, ~1ms packets
•
Sept. 11th, 2006
2
Statement of Religious Alignment
• Time synchronization is required
– Application
– Low power
– Multi-channel
• Multi-channel is required
– Reliability
– Bandwidth, scale
Sept. 11th, 2006
3
802.15.4 Slot and superframe timing
•
Slot length
– When SO = 0  60 symbols  0.96ms
•
Active superframe duration
– 16 slots  15.36ms when SO=0
•
Superframe duration
– 15.36ms * 2BO ; BO = 0..14
– Up to 4 minutes (> 250,000 slots)
Semi-active
Channel-hopping
16|17|18|19|20|21|22|23|24|25|26|27|28|…
Sept. 11th, 2006
4
Timeslots and Frames
• Each mote-to-mote communication
happens within a scheduled timeslot
• All timeslots are contained within a
frame
• Frames repeat in time
• Multiple frames can operate
simultaneously within a network
Frame
Unallocated Slot
Allocated Slot
Sept. 11th, 2006
5
Slot Structure
Transmit Time Slot
Device
Current
RX start, CCA,
RX->TX
Transmit Packet: Preamble, SS,
Headers, Payload,MIC, CRC
Tx->Rx
Tg
ACK
RX ACK
Transmit operations (not to scale)
Sept. 11th, 2006
6
Idle listen (no packet exchanged)
Mote
Current
Radio RX startup
Empty RX
Sept. 11th, 2006
Energy cost (2004): 70 uC
7
Time Slot and Channel Mapping
D
Time
One Slot
Chan.
A
2.405 GHz
BA
2.470 GHz
CA
C
DA
B
BA
2.445 GHz
2.425 GHz
Slot links for devices
2.475 GHz
2.440 GHz
…
2.480 GHz
• The two links from B to A are dedicated
• D and C share a link for transmitting to A
• The shared link does not collide with the dedicated links
Sept. 11th, 2006
8
Frequency Hopping
Time
BA
BA
Channel
CA
BA
DA
BA
CA
BA
DA
CA
BA
DA
Cycle N
Cycle N+1
CycleN+2
Each link rotates through k available channels over k cycles.
Blacklisting can be defined globally and locally.
Sept. 11th, 2006
9
Link Types
one
destination
> one
•Contention free
one
source
•Collisions possible
> one
•Unicast
•ACKed
•Broadcast
•Duo-ACK?
Describes the assignments for a single cell = slot X channel_offset
Sept. 11th, 2006
10
Performance Limits
• Data collection
– 100 pkt/s per gateway channel
– 16*100 pkt/s with no spatial reuse of frequency
• Throughput
– ~80kbps secure, reliable end-to-end payload bits per second per
gateway
– 15 * 80k = 1.2Mbps combined payload throughput w/ no spatial
reuse of frequency
• Latency
– 10ms / PDR per hop
– Statistical, but well modeled
• Scale
– > 1,000 nodes per gateway channel
Sept. 11th, 2006
11
Industrial Automation Use Cases
Monitoring
Diagnostics
Configuration
Handheld
Peer to Peer
Phase II
Simulation of a 250 node network
(courtesy Bob Karschnia)
Sept. 11th, 2006
12
Multiple graphs  Multiple frames
Channel
Time
BA
CA
BA
BA
CA
BA
CA
BA
BA
BA
CA
BA
BC
B
CB
CB
Cycle M of red frame
Cycle M+1
A
C
B
Sept. 11th, 2006
13
Frames overlayed
Channel
Time
BA
BA
CA
BC
CB
CA
BA
BA
BA
CA
BA
BA
CB
CA
BA
• Cell collisions can be avoided by time or channel
partitioning
• Intentional scheduling collisions are resolved by
packet priority and graph priority
A
C
B
Sept. 11th, 2006
14
Subnetworks: single-hop, low latency
G
C
B
E
H
A
F
Black superframe
• All motes
• 1,000 slots (10 seconds)
• Data, Health reports up
• Control info down
Red superframe
• Mote F is light switch
• Mote A is light
• 1 slot, ~10ms latency
Blue superframe
• Mote H is temp sensor
• Mote B is HVAC control point
• 100 slots, ~1second latency
Motes A and B are likely powered
All frames on all the time
All other motes run at <100uA
Sept. 11th, 2006
15
Subnetworks 2: reliable multi-hop control
Black superframe
• All motes
• 10s period
• Data, Health reports up
• Control info down
Red superframe
• ~2s latency
• Mote H is industrial process sensor
• Mote A is industrial process controller
G
C
B
E
A
H
F
Both frames on all the time
All motes run at <100uA
Sept. 11th, 2006
16
Subnetworks 3: query/response & log upload
A
C
B
E
H
F
G
Black superframe
• All motes
• Data, Health reports up
• Control info down
Red superframe
• Query/response from A to G
• 50 slots (0.5 second)
• Mean round-trip latency < 1s
Blue superframe
• Mote H sends a log file
• 2 slots, 1 payload delivered to A per cycle
• ~80kbps
Red & Blue frames are only on occasionally
All motes run at <100uA under “normal” conditions
Zero collisions, zero lost packets
Without black graph
Sept. 11th, 2006
17
Subnetworks 4, et cetera
G->E
W
E->C
D
C->A
A
Red frame:
1 packet delivered from G
to D every other slot
F
X
C
B
E
P
H
Y
H->C
C->A
B->A
W->X
X->Y
Blue frame:
1 packet delivered from H
to A every slot
G
R
Q
S
H->B
Y->Z
Gold frame:
1 packet delivered from W
to Z every other slot
Z
H->B
H->C
C->A
B->A
Sept. 11th, 2006
Green frame:
1 packet delivered from S
to P every slot
18
Many Knobs to Turn
• Trade performance and power
– Sample & reporting rate
– Latency
– High bandwidth connections
• Tradeoffs can vary with
– Time
– Location
– Events
• Use power intelligently if you’ve got it
– Highest performance with powered infrastructure
Sept. 11th, 2006
19
Communication Abstraction
• Packets flow along independent digraphs
• Digraphs/frames have independent periods
• Energy of atomic operations is known, (and
can be predicted for future hardware)
Network
Gateway
– Packet TX, packet RX, idle listen, sample, …
• Capacity, latency, noise sensitivity, power
consumption models match measured data
• Build connectivity & applications via gateway
or sensor interface
A
– Create & delete graphs
– Activate & deactivate graphs
– Add & delete links
C
B
E
H
G
Sept. 11th, 2006
F
20
Network Management
• Secure, Rapid Joining
– TJOIN = CT/PD
–
–
–
–
C = number of joining channels
T = mean time between advertising packet
P = PDR
D = duty cycle
– Seconds per mote for reasonable parameter values
• Continuous optimization
– Global knowledge of CIJ(t) useful, not required
– Optimization, not failure recovery - always have alternate paths
• Dynamic requirements
– Bandwidth on demand
– Shared links
– Pre-provisioned graphs turned on & off
– Wireless worker
Sept. 11th, 2006
21
Standards
Certification
Education & Training
Publishing
Conferences & Exhibits
50 motes, 7 hops
3 floors, 150,000sf
>100,000 packets/day
Oil Refinery – Double Coker Unit
•
•
•
GW
•
Scope limited to Coker facility
and support units spanning
over 1200ft
No repeaters were needed to
ensure connectivity
Gateway connected via
Ethernet port in control room
to process control network
Electrical/Mechanical
contractor installed per wired
practices
400m
Unamplified cc2420
85 dB SW-limited link margin
Sept. 11th, 2006
23
1 Protocol, Alternate Approaches
• All motes battery operated
– Intelligent Management: SmartMesh
– Minimal network management: Slotted aloha
• Some motes powered
– Hybrid: Sleepy Slotted Aloha
• Routers powered, leaf nodes minimum power
• Point-to-point
• Star networks
• Compare to CSMA approach for
– Latency
– Scalability
– Power consumption
Sept. 11th, 2006
24
Moving forward
• Radio RX current going down
– QIDLE < 10uC 
– listening every slot < 1mA
– 100ms latency/hop  100uA current
• Embedded microprocessor capabilities scaling at least 10x
– 32 bit cores, > 1MB flash, >128kB RAM, 100MHz
– Lower current!
• Our standard should embrace these changes
Sept. 11th, 2006
25
Sept. 11th, 2006
26
Scalability: Outdoor Test Network
1,100 m
3.5
3.5
3.5
te
Mo
4
226
Mote
6
157
Mote
6
158
Mote
6
022
Mote
6
023
Mote
6
024
te
Mo
4
Mote
6
159
225
4
3
3
Mote
Mote
Mote
Mote
108
Mote
6
155
Mote
6
021
Mote
6
020
Mote
6
019
te
Mo
4
223
4.5
Mote
6
154
Mote
107
Mote
6
149
Mote
6
150
Mote
6
016
Mote
6
017
Mote
6
018
6
6
096
4.5
6
6
Mote
6
Mote
6
Mote
6
188
Mote
te
Mo
6
3
Mote
6
Mote
084
3
085
3
3
086
Mote
Mote
4.5
083
Mote
15
082
081
6
Mote
6
Mote
075
6
Mote
076
6
077
Mote
6
Mote
078
6
Mote
079
Mote
148
194
4.5
te
Mo
193
Mote
Mote
3
3
3
3
3
3
3
6
Mote
6
Mote
072
6
Mote
071
6
070
Mote
6
Mote
069
6
6
Mote
6
Mote
6
Mote
6
Mote
6
Mote
6
Mote
8
064
008
065
007
066
051
Mote
13
4.5
13
Mote
Mote
Mote
11.5
061
Mote
10
005
Mote
16
006
19
Mote
253
013
Mote
050
8
8
13
13
Mote
4.5
Mote
Mote
10
004
Mote
049
Mote
4.5
232
10.5
Mote
250
247
242
8
3
8
001
6
SmartMesh
Manager
4.5
Mote
Mote
Mote
9.5
Mote
1
Mote
4.5
233
Mote
11.5
4.5
4.5
11.5
Mote
4.5
6
264
255
252
027
Interferer
(PosC)
246
026
238
025
3
8
Mote
9
287
277
263
8
028
8
8
6
8
Mote
8
3
060
059
Mote
6
038
Mote
Mote
4.5
Mote
12.5
Mote
11.5
620
Mote
10
039
Mote
16
621
032
Mote
4.5
4.5
Mote
4.5
Mote
4.5
8
375
Mote
4.5
Mote
4.5
366
Mote
376
4.5
Mote
4.5
Mote
4.5
Mote
362
349
346
333
4.5
Mote
Mote
365
377
280
Mote
395
6
Mote
624
6
Mote
5
041
040
Mote
5
042
Mote
323
332
Mote
7
348
6.5
Mote
4.5
14
3-6m
Mote
397
4.5
4.5
422
4.5
Mote
445
460
5
634
Mote
Mote
6
633
5
Mote
5
643
Mote
3
4.5
425
4.5
Mote
Mote
424
Mote
Mote
442
16
9.5
6
651
Mo
te
650
Mote
6
649
Mo
te
Mote
559
648
5
Mote
6
044
Mote
5
658
Mote
6
659
13.5
Mote
Mote
560
Mot
SmartMesh
Manager
8
Mote
6
3
671
Mote
6
672
M
M
673
3
3
4.5
M
M
3
683
ot
3-6m
3
3
3
3
3
3
3-6m
3-6m
699
697
ot
57
3
M
57
2
M
ot
e
58
58
M
M
5
ot
ot
58
58
ot
59
59
ot
3
61
61
61
5
60
ot
e
60
7
e
60
8
9
M
0
ot
e
61
8
4.5
M
ot
e
61
7
4.5
M
2
M
4.5
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e
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61
6
4
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M
ot
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61
5
4
e
61
ot
1
5
4.
5
4.
ot
5
m
3-6
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4
M
4
M
60
M
5
4.
0
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6
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5
4.
5
4.
60
ot
4
4.5
M
4
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60
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4.5
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60
3
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3
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4.
N
5
4.
4
ot
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59
4.5
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60
59
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59
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5
4.
Netw ork deployed at 1 Thayer Road, Santa Cruz, CA, on rough
pasture. Modifications to Implementation plan due to deployment fit
into "thin and hourglass" shape of site (no minimum plan distances
compromised). All measurements given in meters, and accurate to
w ithin +/-25 centimeters (gopher hole offsets).
ot
e
e
59
M
4.5
M
ot
4
M
4
ot
9
4
M
6
M
OPEN SPACE DEPLOYMENT
58
8
7
e
58
e
e
e
4
M
ot
4
M
ot
4
4
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58
3
e
4
ot
ot
4
e
M
Forest Edge
M
4.5
M
5
4.
Mote
ot
4
M
Mote
1
4.5
Mo
te
5
4.
3-6m
M
Mote
684
6
59
4.5
565
e
0
5
4.
700
6
59
564
5
4.
696
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4.5
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59
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te
Mo
te
2
5
4.
Mote
Mote
ot
4.5
4.5
e
5
4.
3-6m
Mote
685
6
5
4.
701
6
695
M
563
566
ot
4.5
M
4.5
Mo
te
Mo
te
551
M
1
567
4.5
4.5
9
5
4.
Mote
Mote
58
Mo
te
550
57
e
2
552
3
e
0
5
4.
3-6m
Mote
686
5
58
5
4.
702
5
694
ot
4.5
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5
4.
Mote
Mote
5
4.
3-6m
Mote
687
6
ot
58
e
537
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e
5
4.
3
6
693
5
4.
703
Mote
M
Mot
536
M
ot
4.5
M
5
5
4.
Mote
Mote
688
5
3-6m
5
692
57
4
8
4.5
M
e
4
57
e
5
4.
Mote
3-6m
Mote
689
6
ot
4
e
4
13
3
3
3
698
Mote
5
4.
691
3
57
7
5
4.
6
690
Mote
57
6
5
4.
Mote
57
Mo
te
5
4.
3
674
6
682
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5
4.
Mote
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571
5
4.
3
3
3
3
3
3
675
6
681
M
Mote
5
4.
Mote
ot
4.5
Mote
16
3
676
5
048
6
5
4.
Mote
Mote
4.5
562
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te
5
4.
677
6
047
6
5
4.
Mote
Mote
Mo
te
4.5
549
5
4.
045
5
046
5
5
4.
Mote
Mote
5
4.
678
6
680
6
5
4.
679
Mote
Mote
ot
4.5
Mote
3
5
670
3
3
Mote
3
6
669
5
Mo
te
Mote
5
4.
3
Mote
3
5
4.5
553
538
8
Mo
te
3.5
5
h
es
tM er
ar ag
Sm Man
661
Mote
Mote
Mo
te
4.5
548
5
4.
Mote
668
6
Mo
te
568
Mo
te
e
5
19
9
6
667
Mote
4.5
4.5
554
4
561
662
8
Mote
Mo
te
e
539
Mot
5
5
663
4.5
547
4
3.5
535
Mote
5
Mote
5
6
664
Mote
5
Tree
Stump
3
6
665
3
3
3.5
3.5
5
666
Tree
Trunk
Mote
Mo
te
660
Mote
Mote
Mo
te
4.5
555
Mo
te
5
657
5
Mote
16
6
656
Mote
4.5
569
4.5
3
3
3
3
3
3
3
Mote
Mo
te
e
540
534
6
655
570
Mo
te
4.5
4
Mot
13.5
528
Mo
te
4.5
556
5
546
Mote
Mote
529
Mote
Mo
te
e
3
3
5
4.5
4.5
545
Mot
8
Mote
Mo
te
5.5
5
541
647
458
443
4
652
Mote
508
4
653
5
3
3
Mote
Mote
5
654
6
16
459
4
Mote
533
Mote
16
646
4
Mote
507
457
4.5
558
16
530
Mote
4.5
645
Mote
Mote
Mo
te
557
542
Mote
3
Mote
e
4
6
3
3
3
Mote
Tree
Stump
444
398
4
4.5
Mote
632
6
644
Mot
4
642
3
3
Mote
641
527
506
4.5
544
5.5
8
6
640
4.5
Mote
3-6m
Mote
Mote
8
Mote
3
3
3
3
6
639
483
Mo
te
8
Mote
036
Mote
3 Trees
526
505
4.5
Mote
6
543
Mote
3
6
Mote
515
4
4
635
Mote
482
4
636
5
4
484
4.5
Mote
378
4
Mote
4
9.5
e
4
637
6
Mote
4
481
4.5
4.5
Mote
4
Mote
Mote
Mote
4
461
456
9.5
9.5
9.5
423
Mote
Mot
4
638
6
4.5
Mote
Mote
Mote
Mote
441
4.5
Mote
Mote
6
531
532
Mote
525
504
4.5
4.5
307
035
6
600 m
9.5
Mote
Mote
282
Mote
631
3
630
3
629
3
043
3
628
3
627
3
626
Mote
4
485
4.5
Mote
3
6
Mote
4
480
4.5
4
Mote
524
4.5
4
5
Mote
4
Mote
14
5
5
516
4
Mote
Mote
5
6
14
514
4
Mote
Mote
Mote
4.5
Mote
16.5
14
509
Mote
Mote
4
462
4.5
Mote
Mote
4
6
Mote
4.5
4.5
4.5
14
503
Mote
057
6.5
Mote
Mote
4
486
Mote
16
622
3
3
3
3
3
3
6
523
4.5
4.5
363
522
4.5
4.5
Mote
4
479
4.5
4.5
4.5
4.5
Mote
Mote
426
421
Mote
14
517
502
4.5
Mote
4
Mote
455
Mote
14
513
Mote
4
487
4.5
Mote
4.5
4.5
Mote
446
Mote
14
510
Mote
463
454
447
Mote
440
427
4.5
399
Mote
14
501
4.5
Mote
4
478
4.5
14
14
4.5
SmartMesh
Manager
Mote
4
488
4.5
Mote
4
464
Mote
Mote
4.5
4.5
Mote
Mote
4.5
Mote
14
439
428
4.5
Mote
Mote
034
Mote
4.5
Mote
Mote
Mote
9
10.5
379
6
623
4.5
521
500
4.5
Mote
4
477
4.5
Mote
4.5
420
400
Mote
Mote
4
489
4.5
Mote
4
465
429
419
4.5
308
520
4.5
4.5
Mote
4.5
Mote
8
Mote
Mote
4.5
306
Mote
14
518
512
7
Mote
14
452
453
4.5
3-6m
4.5
4.5
396
380
8
Mote
4.5
Mote
401
4.5
3
4.5
283
Mote
14
448
4.5
418
402
Mote
Mote
Mote
14
14
511
4.5
Mote
4
476
4.5
4.5
Mote
4.5
3-6m
4.5
Mote
Mote
14
499
4.5
Mote
4
466
4.5
Mote
4.5
4.5
Mote
4.5
394
4.5
364
Mote
14
438
4.5
3
10
033
6
625
Mote
16
381
3
258
Mote
Mote
417
403
4.5
Mote
Mote
14
430
4.5
4.5
4.5
347
Mote
Mote
4.5
281
Mote
4.5
Mote
4.5
305
3
3
4.5
Mote
4.5
4.5
404
393
382
4
490
4.5
4.5
4.5
SmartMesh
Manager
Mote
Mote
Mote
4
475
Mote
451
431
Mote
4.5
Mote
4.5
Mote
4
467
450
449
437
Mote
14
519
498
4.5
Mote
Mote
4.5
4.5
Mote
8
324
Mote
14
6
392
383
Mote
4
491
4.5
4.5
322
309
Mote
14
Mote
4.5
416
4.5
Mote
Mote
Mote
14
432
415
4.5
Mote
4.5
8
Mote
3
Mote
4.5
Mote
4.5
405
Mote
16
4.5
4.5
4.5
4.5
4.5
Mote
4.5
4.5
4.5
361
350
345
4.5
Mote
Mote
325
4.5
284
Mote
Mote
4.5
367
360
4.5
Mote
8
3
8
031
6
Mote
Mote
Mote
259
13
4.5
351
4.5
4.5
406
4.5
4.5
4.5
4.5
Mote
055
13
Mote
Mote
4.5
Mote
4.5
391
384
374
368
359
4.5
3
3
Mote
4.5
4.5
260
030
4.5
344
Interferer
(PosB)
4.5
4.5
390
Mote
Mote
4
474
4.5
4.5
Mote
4.5
3.5
321
Mote
3
304
285
279
3
Mote
Mote
Mote
19
Mote
058
Mote
Mote
16
385
Mote
3-6m
4.5
Mote
257
Mote
8
373
Mote
Mote
8
4.5
4.5
4.5
261
3
4.5
335
326
4.5
Mote
3.5
310
4.5
Mote
Mote
Mote
Mote
Mote
334
4.5
303
3
3
3
3
8
10.5
244
6
3
Mote
029
245
Mote
236
4.5
331
Mote
4
320
Mote
3.5
4.5
286
278
243
8
8
Mote
235
Mote
4.5
Mote
Mote
4.5
4.5
262
256
12.5
Mote
4.5
237
054
8
234
Mote
6
13
13
056
Mote
6
Mote
Mote
Mote
Mote
Mote
Mote
4
311
3
3
3
3
4
037
Mote
10
4.5
327
3-6m
Mote
4.5
468
433
4.5
4.5
Mote
4.5
4.5
4.5
302
Mote
4.5
369
4.5
3-6m
4.5
4.5
4.5
Mote
8
Mote
8
Mote
Mote
4.5
319
Mote
4
4.5
4.5
4.5
SmartMesh
Manager
4.5
Mote
Mote
Mote
Mote
Mote
4.5
358
4.5
Mote
352
Interferer
(PosE)
343
328
4.5
Mote
4.5
3-6m
3-6m
336
312
3
3
4
Interferer
(PosA)
Mote
4.5
301
Mote
4.5
353
4.5
Mote
Mote
Mote
5
318
4.5
5
Mote
288
276
Interferer
(PosD)
3
Mote
4.5
342
4.5
Mote
497
4.5
4.5
4.5
4.5
Mote
5
313
4.5
4.5
4.5
4.5
4.5
Mote
Mote
Mote
Mote
Mote
Mote
4.5
9.5
337
4.5
4.5
4.5
4.5
4.5
4
10
2
SmartMesh
Manager
4.5
619
251
8
8
SmartMesh
Manager
9
002
8
Mote
8
8
Mote
8
Mote
5
300
289
4.5
Mote
4
492
4.5
Mote
Mote
Mote
4.5
414
4.5
4.5
Mote
4
473
4.5
4.5
4.5
Mote
4.5
407
389
Mote
4
469
434
4.5
Mote
4.5
8
372
4.5
4.5
329
4.5
4.5
4.5
275
Mote
5.5
317
4.5
4.5
Mote
Mote
Mote
4.5
265
Mote
5.5
314
299
4.5
354
Mote
4.5
413
4.5
4.5
Mote
4.5
370
496
4.5
4.5
4.5
Mote
4.5
408
388
386
371
Mote
4.5
357
4.5
4.5
Mote
4.5
Mote
4
493
4.5
4.5
4.5
Mote
4.5
4.5
4.5
5.5
4.5
290
4.5
4.5
4.5
Mote
4.5
356
4.5
Mote
4.5
341
338
316
Mote
8
Mote
6
Mote
Mote
Mote
274
4
003
3-6m
355
4.5
Mote
4.5
8
4.5
4.5
4.5
Mote
315
298
4.5
4.5
266
254
10.5
Mote
4.5
239
053
3
Mote
Mote
Mote
Mote
Mote
Mote
6
4.5
291
4.5
4.5
Mote
Mote
4.5
273
267
13
248
8
8
Mote
Mote
Mote
240
231
Mote
3-6m
340
4.5
4.5
Mote
4.5
Mote
3-6m
339
330
297
4.5
4.5
Mote
Mote
8
Mote
Mote
Mote
Mote
Mote
4.5
292
272
4.5
4.5
Mote
241
8
4.5
4.5
4.5
268
249
Mote
Mote
Mote
052
Mote
495
4.5
Mote
4
472
Mote
4.5
Mote
4
470
435
4.5
296
Mote
4.5
4.5
Mote
4.5
412
4.5
4.5
Mote
293
271
Mote
4.5
409
4.5
4.5
Mote
4.5
4.5
4.5
8
063
Mote
4.5
387
Mote
Mote
Mote
014
Mote
16
269
062
Mote
4.5
4.5
4.5
3
3
3
3
3
3
3
Mote
Mote
Mote
4
494
471
436
4.5
Mote
295
294
270
147
067
Mote
4.5
411
4.5
4.5
4.5
Mote
068
4.5
073
Mote
4.5
410
4.5
Mote
Mote
Mote
Mote
Mote
Mote
4
8
015
080
8
074
196
195
4.5
te
Mo
4.5
187
Mote
Mote
198
4.5
197
4.5
te
Mo
4.5
te
Mo
4.5
190
Mote
4.5
6
3
Mote
3
6
087
3
088
3
089
Mote
te
Mo
4.5
4.5
203
192
6
201
4.5
te
Mo
4.5
te
Mo
Mote
16
Mote
202
4.5
4.5
16
094
3
010
3
093
3
3
009
3
092
3
091
6
te
Mo
4.5
te
Mo
4.5
16
Mote
16
Mote
8
4.5
090
Mote
4.5
200
4.5
te
Mo
4.5
204
191
Mote
205
te
Mo
4.5
199
4.5
te
Mo
4.5
Mote
095
3
097
3
3
3
6
098
te
Mo
4.5
206
4.5
te
Mo
4
8
3
6
099
3
6
100
3
3
101
Brush
Pile
Tree
4.5
212
14
Mote
207
4.5
te
Mo
4
Mote
208
4.5
te
Mo
4
211
te
Mo
14
Mote
te
Mo
4
210
4.5
te
Mo
4
189
Mote
209
4.5
te
Mo
4
214
213
152
te
Mo
4
te
Mo
4.5
te
Mo
4
4.5
151
4
216
4.5
215
4.5
4
Mote
6
te
Mo
4
224
153
SmartMesh
Manager
Mote
19
106
Stump
"Well"
Mote
6
156
3.5
Mote
6
109
3
218
217
4.5
8
3
105
Mote
Mote
6
SmartMesh
Manager
Mote
3.5
Mote
011
6
3.5
6
3.5
6
104
103
Mote
3
102
Mote
110
6
3.5
6
Stump
Tree
Mote
3.5
Mote
012
6
3.5
6
Mote
6
Mote
111
6
3
6
112
Mote
te
Mo
te
Mo
te
Mo
Mote
4
4.5
te
Mo
4
222
4.5
160
219
4
221
4.5
3.5
Mote
119
3.5
Mote
6
118
3.5
Mote
6
117
3.5
Mote
3.5
6
3.5
Mote
116
3
3
3
6
115
3.5
Mote
220
4.5
te
Mo
3
6
114
3
Mote
3
6
113
3
Mote
4
te
Mo
te
Mo
4.5
4.5
te
Mo
4
227
4.5
230
4
228
te
Mo
161
3.5
3.5
te
Mo
229
4.5
te
Mo
4.5
Mote
6
162
4.5
te
Mo
174
Mote
6
163
-1400 Motes
-20 Managers
- 32 Acres
3.5
3.5
3.5
Mote
6
164
Mote
6
173
3.5
Mote
6
165
175
Mote
6
172
3.5
Mote
6
166
3.5
3.5
3.5
3.5
3.5
Mote
6
167
Mote
6
176
Mote
6
171
3.5
Mote
120
3.5
Mote
Mote
6
170
186
Mote
6
177
3.5
6
121
Mote
6
169
Mote
6
185
Mote
6
178
3.5
Mote
6
122
Mote
6
168
3.5
Mote
3.5
3.5
133
Mote
6
Mote
6
179
3.5
3
Mote
3
Mote
Mote
184
Mote
6
180
3.5
6
6
132
Mote
6
181
134
6
183
3.5
3
3
3
Mote
123
3
3
3
6
124
Mote
6
131
3
Mote
Mote
Mote
Mote
9.5
135
3.5
6
125
Mote
6
136
3
Mote
6
Mote
6
182
146
Mote
6
3
6
126
Mote
130
3
3
3
Mote
6
129
Mote
Mote
6
Mote
137
3
Mote
Mote
145
6
3
6
128
6
138
3
Mote
Mote
3
6
127
Mote
144
6
139
3
Mote
3
3
Mote
6
3
3
6
140
3
Mote
143
Mote
3
6
142
6
141
3
Mote
Mote
M
ot
e
61
4
Approaching 8 mote-centuries
Sept. 11th, 2006
27
Additional link types
•
“Primary”, “secondary” parent
Sept. 11th, 2006
28
Slotted Aloha performance
• Peak payload bandwidth
– 100 slots/sec * 80B/packet = 8kB/s = 64kbps
• Peak payload goodput with collisions
– 64kbps * e-1 = 23.5kbps
• Average power consumption, non-congested
– IRX * (2ms/10ms) = 0.2 IRX
• Average latency, non-congested
– 10ms/hop
• Relative to Aloha w/ 80B ACKed payloads
– Payload goodput = ~150kbps * e-2 =
– Average Current = IRX
– Non-congested Latency 5ms/hop
• Relative to Aloha w/ 10B ACKed payloads
Sept. 11th, 2006
29
Duty Cycling
• Slotted aloha
– Any fractional slot duty cycle a possible with varying frame length
– Use x links in a y slot frame to get a = x/y duty cycle
–
–
–
–
Current decreases proportional to a
Latency increases as 1/a
10% slot duty cycle  100ms latency per hop.
Radio duty cycle is still lower, i.e. 2% (=10% slot duty cycle * 20% radio
duty cycle in slot)
• Aloha
– “chunky-ness” of the duty cycle will set latency
– Typical approaches (e.g. Millennial) use long sleep intervals, e.g. 6
seconds on, 54 seconds off to get 10% duty cycle
– Latency is tens of seconds, radio duty cycle is same as overall duty
cycle, =10%
Sept. 11th, 2006
30
Powered routers
Sept. 11th, 2006
31
Point to point links
• Use scheduled communication, e.g. one Tx and one RX
link in a two slot frame
– Available guaranteed bandwidth
– 50 slots/sec in each direction
– =50 payloads/sec = 4kB/s = 32kbps full duplex
– Idle current
– 50 listens/sec * 2ms/listen = 100ms/s = 10% radio duty cycle
– Average latency = 1 slot = 10ms
Or…
• Use bandwidth on demand (slotted aloha), e.g. one
aloha slot in a one slot frame
– Available one-way bandwidth is 100 packets/sec = 64kbps
– Average One-way latency is 5ms
Sept. 11th, 2006
32
Star connected networks
• 1 hub, N end-points
• Scheduled communication
– 1 downstream broadcast, N upstream links in a 1+N slot frame
– Downstream bandwidth = 100 packets/sec / (1+N)
– Average Latency = 10ms * (1+N)/2
• Bandwidth on demand
–
–
–
–
–
–
1 downstream broadcast, 1 aloha in a 2 slot frame
Downstream bandwidth = 50 packets/sec
Peak upstream bandwidth, 1 mote = 50 packets/sec
Average Query/response latency = 3 slots = 30ms
End-point radio duty cycle = 50% slot * 20% rx/slot = 10%
Reducing endpoint duty cycle
– E.g. 5 downstream slots/sec
– Average query/response latency = 120ms
– End-point radio duty cycle = 5% * 20% = 1%
Sept. 11th, 2006
33
Variable slot length
• Slot length will be a variable number of 1/1024ths of a
second, hereafter referred to as milliseconds for
convenience.
• Expected values for slot length are 8-20ms.
• Single slot length networks
– All slots, frames, and motes in a network will use the same slot
size, chosen by the first mote in the network (e.g. the gateway)
– There will be no provision for changing the slot length of an
existing network without restarting the network. Hence, a “slow”
mote (e.g. without hardware crypto) would not be able to join a
fast network.
– Problem: Rob won’t go for it for “bad customer experience”
• Multi- slot length networks
– Different frames could have different slot lengths
– Different paths could have different slot lengths. Manager blocks
out the appropriate amount of time for each link.
• Dual slot length
– 8-10ms slot length
– M2135 motes can only handle even-numbered slots
Sept. 11th, 2006
34
Timing – perfect synchronization
A
CCA: RX startup,
listen, RX->TX
B
RX
startup
Transmit Packet: Preamble, SS,
Headers, Payload,MIC, CRC
RX packet
Verify
CRC
Verify MAC
MIC
RX startup
or TX->RX
RX ACK
Calculate ACK
MIC+CRC
Transmit
ACK
RX/TX
turnaround
A transmits to B
TX, RX ACK timing
Sept. 11th, 2006
35
Timing – imperfect synchronization (latest possible transmitter)
A
CCA: RX startup,
listen, RX->TX
B
RX
startup
Tg
Tg
Transmit Packet: Preamble, SS,
Headers, Payload,MIC, CRC
RX packet
Tcrypto
Verify
CRC
RX startup
or Tx->Rx
Verify MAC
MIC
Tg
ACK
RX ACK
Calculate ACK
MIC+CRC
Transmit
ACK
RX->TX
Expected first bit of preamble
•
TCCA = 0.512ms to be standards compliant
–
–
–
•
Tpacket = 4.256ms for a maximum length packet
–
•
•
•
•
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
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
Sept. 11th, 2006
36
Late TX, early neighbor TX next slot
X
X
Preamble+SS, 160us
TX, RX ACK (late)
TX, RX ACK (early)
Expected first bit of preamble
CCA = 178us
Expected first bit of preamble
First bit of late transmitter shows up at +X relative to network-wide clock. That late
transmitter performed a CCA starting 178us earlier.
The early transmitter in the next slot wakes up early enough to perform a CCA and get
the first bit of its preamble out at –X relative to network-wide clock.
The last bit of the late transmitter is done before the first sniff of the early CCA has
taken place.
Sept. 11th, 2006
37
Tg
Early
TC
CA
Perfect
Late
Tg
Tg
Transmit Packet: Preamble, SS,
Headers, Payload,MIC, CRC
TC
CA
Tcrypto
CA
TC
CA
Transmit Packet: Preamble, SS,
Headers, Payload,MIC, CRC
TC
TACK
Tcrypto
TACK
Transmit Packet: Preamble, S
Headers, Payload,MIC, CRC
TC
CA
Transmit Packet: Preamble, SS,
Headers, Payload,MIC, CRC
Tcrypto
TACK
Tg
Transmit Packet: Pre
Headers, Payload,M
TC
CA
Transmit Pa
Headers, P
Tcomm = Tpacket+Tcrypto+TACK
Tslot = 2Tg+Tcomm+TCCA
Tcrypto includes TgACK and all CRC, crypto, and radio turnaround times. It’s the time
from the last bit of the packet to the first bit of the preamble of the ACK.
Sept. 11th, 2006
38
Star-mesh or Star-LAN
Q: Star-connectivity is known to be death for reliability, so why
do it?
A: Don’t trust the motes, don’t think that they have the power to
be routers.
Sept. 11th, 2006
39
Star-mesh or Star-LAN
What if WiFi gets jammed (easier to do than freq-hopping 802.15.4)?
What if you lose ethernet? (power failure, cable, …)
Sept. 11th, 2006
40
Mesh, with backbone
Use powered infrastructure when you have it.
Lower latency
Lower power
But, if it goes away…
Sept. 11th, 2006
41
Mesh, with backbone
Assume that the motes are smart, and that their radios are good.
Use protocols that leverage those capabilities:
Time-synchronized, TDMA, Channel Hopping MAC
Mesh routing
Sept. 11th, 2006
42
TSMP Dedicated Services
• Periodic traffic
• Time Division Multiplexing assigned to slots in frames
• Dedicated access and Quality of Service
–
–
–
–
Deterministic latency
Bandwidth assignment
Configurable latency
Transport and resource priority
• Connectivity
– One-to-one
– One-to-many
Sept. 11th, 2006
43
TSMP Shared Services
• Used for burst traffic
– Provides pool of available slots as needed
– Low latency alarms
– High-speed on-demand file transfer
• Slotted Aloha assigned to slots in frames
–
–
–
–
Time slots can be configured to be shared
MAC level ACK detects collisions
Exponential back off algorithm
Transport and resource priority
• Connectivity
– Many-to-one
– Many-to-many
Sept. 11th, 2006
44
TSMP Network Management
• Unified resource allocation
• Dynamic:
– Adapts to changing RF environment – global response to local
changes
– Robust against network device failures
– Responds to application resource requests and provides QOS
• Optimized: allocation of resources across the network
• Flexible: Network management and device
interoperability do not require the standardization of how
resources are allocated
– Innovations can be added after the standard is released
– Specialized network managers can target vertical markets
• Secure: Critical functions are removed from physically
unsecured locations
Sept. 11th, 2006
45