a probabilistic and opportunistic flooding algorithm in wireless sensor networks

2. Introduction
The Purpose of Flooding
General forms
Typical Issues of Flooding
Another Issue in WSNs
POFA
Motivation
Key Idea
RA-MPR
RA-MPR Selection
Retransmission Policy
Numerical Result
Flooding Efficiency
Achieving the target Reliability
Conclusions
2Mobile Networking and Computing Lab.

3. 3Mobile Networking and Computing Lab.
The primary
Propagates a message throughout a networks for certain purpose
To make sure that all the nodes in a network receive the same
NOT Routing
Source
Relay
Destination
The application
Routing
Bridging

4. 4Mobile Networking and Computing Lab.
Blind flooding
All the nodes rebroadcast / relays / forwards the received message
An general form, also called as Simple Flooding
More transmission occurred, as the node density increases
Source
Relay
Destination
Advanced Flooding schemes
Probability-based
Area-based
Neighbor Knowledge Method-based / Topology-based / Tree-based

5. 5Mobile Networking and Computing Lab.
Efficiency or Reliability
Source
Relay
Destination
Tradeoff Relation
If # of the predetermined relay nodes is reduced, they could fail to receive a broadcast packet
If # of the predetermined relay nodes is increased, they could incur Broadcast Storm

6. 6Mobile Networking and Computing Lab.
Nasty Wireless Links
Hard to achieve high reliability
Retransmissions are needed / exploited
Source
Relay
New Question
How many times
Which node

7. 7Mobile Networking and Computing Lab.
Multipoint Relay (MPR) Selection
Algorithm used to solve MCDS problem, in OSLR
Known as optimum solution
Me
1-hop Nbr
2-hop Nbr
MPR
Every link presumed to be error-free
Not guarantee Reliability

8. 8Mobile Networking and Computing Lab.
Limitations of MPR Selection
Do not Aware Link error rates
Can not assure Reliability
Proposed scheme
to assure Reliability r
More 1-hop neighbors like MPR
More transmission (Retransmission / Rebroadcast)

9. 9Mobile Networking and Computing Lab.
Expected Delivery Probability (EDP)
𝑙𝑖𝑗 : Error Rate of the Link i to j
as 1 times
m
s
1 − 𝑙 𝑠𝑚 𝑖𝑓 𝑚 ∈ 𝑁1
m
Me
1-hop Nbr
2-hop Nbr
1 −
𝑘∈𝑁1
1 − 1 − 𝑙 𝑠𝑘 1 − 𝑙 𝑘𝑚 𝑖𝑓 𝑚 ∈ 𝑁2
𝐸𝐷𝑃𝑚 =
𝐸𝐷𝑃𝑚
𝑛
=
1 − 𝑙 𝑠𝑚
𝑛
𝑖𝑓 𝑚 ∈ 𝑁1
1 −
𝑘∈𝑁1
1 − 1 − 𝑙 𝑠𝑘
𝑛
1 − 𝑙 𝑘𝑚 𝑖𝑓 𝑚 ∈ 𝑁2
as n times
𝐸𝐷𝑃𝑚
𝑛
=
1 − 𝑙 𝑠𝑚
𝑛
𝑖𝑓 𝑚 ∈ 𝑁1
1 −
𝑘∈𝑁 𝑅
1 − 1 − 𝑙 𝑠𝑘
𝑛
1 − 𝑙 𝑘𝑚 𝑖𝑓 𝑚 ∈ 𝑁2

10. 10Mobile Networking and Computing Lab.
Reliability-aware multipoint relay (RA-MPR) Selection
To achieve a given Reliability
not to cover all 2-hop neighbors
𝐸𝐷𝑃 𝑛
RA-MPR Selection Algorithm
Me iteratively selects an RA-MPR among non-RA-MPR neighbors so as to increase the EDP most
Until the EDP satisfies the target reliability R
Me
1-hop Nbr
2-hop Nbr
0.2
0.12
0.02
0.1
0.14
0.1
0.07
1) R = 0.4
2) R = 0.95
=
𝑚∈𝑁1 𝑜𝑟 𝑁2
𝐸𝐷𝑃𝑚
𝑛
𝑁1 + 𝑁2

11. 11Mobile Networking and Computing Lab.
The result of the real world
either a success or a failure in contrast to the probabilistic calculation like 0.3141592…
The number of the received packet MUST be a Natural Number
ms
Opportunistic Retransmission
Overhearing / BACK(Broadcast ACK) handling
ms
Stop!
Online EDP : Recalculated EDP with Real Result
Implicit ACK explicit ACK
Success : 𝑙 𝑠𝑖 → 0
Failure : 𝑙 𝑠𝑖 → 1 − 𝑃 𝑀 𝐴 ,
𝑃 𝑀 ∩ 𝐴
𝑃 𝐴
=
=
𝑘=1
𝑛
𝑛
𝑘
1 − 𝑙 𝑘
𝑙 𝑛
=
𝑘=0
𝑛
𝑛
𝑘
1 − 𝑙 𝑘
𝑙 𝑛
= 1 −
𝑙 𝑛
𝑃 𝐴

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Link Error Rate
Can be controlled (?)

13. 13Mobile Networking and Computing Lab.
NTP
The total # of broadcasts divided by the # of nodes
As the link error rate increases
Not only a node, but also its 1-hop and 2-hop neighbors, probably, retransmit the packet more times
But can achieve high reliability (?)

14. 14Mobile Networking and Computing Lab.
ATR
The achieved Reliability divided by the target reliability
As the link error rate increases
if including all one-hop neighbors as RA-MPRs cannot make the EDP greater than the target reliability
A sender increments the # of transmissions
Optimum Efficiency

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Predetermining Technique
The Predetermined RA-MPRs only can forwards the received packets the Predetermined time(s)
But retransmits opportunistically (but little)
The opportunistic transmission
In ExOR, MORE and SOAR, any node amongst Forwarder Candidate can forward it
Future work
Contribution Level based Opportunistic Flooding for Wireless Multihop Networks, 2015. 6
– 1 time revised
Opportunistic Flooding in Low-Duty-Cycle Wireless Sensor Networks with Unreliable Links, 2014.11
- 16 times revised

16. Mobile Networking and Computing Lab.