Slide 2 1 Modeling Clock Synchronization in the Chess gMAC WSN
Protocol Mathijs Schuts Feng Zhu Faranak Heidarian Julien Schmaltz
Frits Vaandrager QFM09 FM09 Slide 3 2 Plan Intro to WSN and Chess
case study A first model + analysis A second model +
counterexamples Conclusions & Future Work Slide 4 3 WSN but
with a twist! Main challenges: Energy efficiency (battery operated
or energy harvesting lifetime) Robustness (RF spectrum is extremely
noisy, very busy and unreliable) Scalability (10 1 10 2 10 3 10 4
10 5 nodes with a single protocol) Self-adaptable (constantly
changing network topology, density, mobility) Limited resources
(CPU processing speed, available memory, fysical size) There are
many available WSN protocols, e.g.: Wifi Bluetooth Zigbee Z-wave
Neither of these technologies addresses all challenges! Slide 5 4
WSN but with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Slide 6 5
WSN but with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Slide 7 6
WSN but with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Slide 8 7
WSN but with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Slide 9 8
WSN but with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Slide 10
9 WSN but with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Slide 11
10 WSN but with a twist! Communication inspired on biology and
human interaction Epidemic communication Analogy: spreading a rumor
or a virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Page
10 Slide 12 11 WSN but with a twist! Communication inspired on
biology and human interaction Epidemic communication Analogy:
spreading a rumor or a virus MYRIANED GOSSIP protocol RF broadcast
(2.4 Ghz ISM) Page 11 Slide 13 12 WSN but with a twist!
Communication inspired on biology and human interaction Epidemic
communication Analogy: spreading a rumor or a virus MYRIANED GOSSIP
protocol RF broadcast (2.4 Ghz ISM) Page 12 Slide 14 13 WSN but
with a twist! Communication inspired on biology and human
interaction Epidemic communication Analogy: spreading a rumor or a
virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz ISM) Page 13
Slide 15 14 WSN but with a twist! Communication inspired on biology
and human interaction Epidemic communication Analogy: spreading a
rumor or a virus MYRIANED GOSSIP protocol RF broadcast (2.4 Ghz
ISM) Slide 16 15 Properties of GOSSIP In a nutshell: Flooding
provides robustness Local caching prevents overhead Absense of
routing provides scalability Inherently self-configuring Supports
node mobility Automatic adoption to network density But what about
energy efficiency? Slide 17 16 RF ANTENNA RF TRANCEIVE R (NORDIC
SEMI) CPU (ATMEL XMEGA128) I/O INTERFACES Slide 18 17 Case Study
for EU Quasimodo Project Model and analyze Chess WSN, based on
1.informal specification in deliverable 2.discussions with experts
Slide 19 18 Our Focus: Clock Synchronization TXRX idle Time is
considered as a sequence of Time Frames. A time frame is composed
of a fixed number (C) of Time Slots. In a time slot the hardware
clock of the sensor node ticks a fixed number (k 0 ) of times. A
Time Frame tsn Slide 20 19 Goal: Minimalize Energy Consumption RX
Time Slot TX Time Slot Guard Time Slide 21 20 Uppaal Model FM09 20
Slide 22 21 Results FM09 Paper Full parametric analysis for clique
networks Parameter constraints found using Uppaal Proof fully
checked using Isabelle/Hol (> 5000 lines) Correctness also
studied for line topologies Slide 23 22 Results FM09 Paper Full
parametric analysis for clique networks Parameter constraints found
using Uppaal Proof fully checked using Isabelle/Hol (> 5000
lines) Correctness also studied for line topologies Model does not
correspond to Chess implementation! Slide 24 23 How Current
Implementation Works Clocks only synchronized once per frame
Implementation computes median of phase errors of all messages
received in frame Offset = median * gain Radio switching time is
relevant Slide 25 24 Structure of Uppaal Model Slide 26 25 Clock
Slide 27 26 Sender Slide 28 27 Receiver Slide 29 28 Controller
Slide 30 29 Synchronizer Slide 31 30 compute_phase_correction() if
(number of received messages == 0) offset = 0; else if (number of
received messages
