The Flooding Time Synchronization Protocol

1
The Flooding Time Synchronization Protocol

• Miklos Maroti Branislav Kusy Gyula Simon Akos
  Ledeczi
• 
  Presented by
• 
  Rajat Khanda

2
Contents

• Introduction
• Approaches to the Synchronization
• What are the uncertainties in Radio Message
  Delivery?
• How does Flooding Time Synchronization Protocol
  Work?
• Comparison to existing protocols
• Results
• Conclusion

3
Introduction

• Potential Applications of WSN
• 1. Monitoring Applications
• 2. Mobile Commerce
• 3. Smart Office
• 4. Military Applications
• Goal of FTSP

4
Approaches to the Synchronization

• Network Time Protocol
• Reference Broadcast Protocol
• Timing-Sync Protocol for Sensor Network

5
Uncertainties of Radio Message Delivery

• Send Time
• Access Time
• Transmission time
• Propagation time
• Reception time
• Receive time

6
Uncertainties of Radio Message Delivery
7
Uncertainties of Radio Message Delivery

• Interrupt Handling Time
• Encoding Time
• Decoding Time
• Byte Alignment Time

8
Uncertainties of Radio Message Delivery
9
Working Principle of FTSP

• Assumptions
• 1. Every node in the network has an
  unique id
• 2. Each node has a local clock and
  can communicate to its neighbors over
  an unreliable link
• Goal
• To achieve a network wide
  synchronization with high precision

10
Working Principle of FTSP

• Time Stamping
• Broadcast message contains the senders time
  stamp (The estimated global time)
• synchronization point (a global local time pair )

11
Working Principle of FTSP

• Reduces the jitter of interrupt handling and
  encoding decoding times by recording multiple
  time stamps
• Receiver further corrects the average time stamp
  using the byte alignment time
• Accuracy depends on the number of time stamps
  taken to find the average time

12
Working Principle of FTSP

• Clock Drift Management
• 1. Local clocks does not a have a exact same
  frequency
• 2. Offset between clocks changes in linear
  fashion if the stability is good
• 3. Clock skew is estimated using linear
  regression on the received data points

13
Working Principle of FTSP
14
Working Principle of FTSP
15
Working Principle of FTSP

• Multi-hop Time Synchronization
• 1. Root node (a special node dynamically
  re-elected by the network, to which the whole
  network is synchronized)
• 2. A synchronized node can broadcast the
  synchronization message
• 3.Synchronization message contains-root-ID,
  time stamp, and Sequence number
• 4.Redundant information management

16
Working Principle of FTSP

• Root-ID ID of the root as known by the
  sender of the message
• Time stamp Global time estimate of the
  transmitter
• SeqNumber the sequence number set and
  incremented by the root when
• when a new synchronization round
  is started

17
Working Principle of FTSP
18
Working Principle of FTSP
19
Working Principle of FTSP

• Convergence Properties
• 1. Depends on the speed of information
  propagation in the network
• When
• NUMENTRIES_LIMITN
• ROOT_TIMEOUTM
• Broadcast Message is P and Radius of Network
  is R
• The total time to get synchronized is between
• P(M(N-1)R) and P(MNR)

20
Working Principle of FTSP

• A Synchronization Period
• When a root fails and the New network Radius is
  R , total time of reelection processltPRPMPR
  

21
Experimental Setup
22
Result
23
Comparison to Existing Protocols

• RBS improves accuracy by removing send and access
  delay.
• Average error for single hop is 29.1
  micro-second
• TPSN improves over RBS by removing byte alignment
  and propagation delay
• Average error for single hop 16.9 micro-second
• The draw back of this protocol is difficulties
  in implementing in different platform

24
Comparison to Existing Protocols

• FTSP uses a fine-grained clock, MAC layer time
  stamping with several jitter reducing techniques
  to achieve high precision.
• Average error for single hop is 1.48
  mico-second
• If the resynchronization period is T
• FTSP sends 1 message per T seconds
• TPSN sends 2 message per T seconds
• RBS sends 1.5 message per T seconds

25
Conclusion

• It performs better than the other existing time
  sync protocol in terms of precision
• Uses single broadcast message to establish
  synchronization point
• This is robust to topology changes and root or
  link failure

26
Questions?
27
Thank you