Date post: | 03-Jul-2015 |
Category: |
Education |
Upload: | phearin-sok |
View: | 159 times |
Download: | 4 times |
Distance and Probabilistic Routing Protocol using History of Encounters
and Transitivity (DPRoPHET) in Delay Tolerant Network (DTN)
Advisor Professor: Keecheon Kim
Phearin Sok
MBC Laboratory
Computer, Information, and Communication Engineering
Konkuk University
Published in International Conference on Applied Materials and Electronics Engineering (AMEE) 2013, Hong Kong
Friday, May 31, 2013
Contents• Background
PRoPHET Overview
• Problems Statement
• Solution: DPRoPHET Routing Protocol in DTN
Distance Mechanism
Cross Layer Model
DPRoPHET Delivery Probability
DPRoPHET Scenarios
• Simulation and Evaluation
• Conclusion
• Key References
Background
PRoPHET in DTN• Probabilistic Routing Protocol using History of Encounters and
Transitivity
• All data forwarding happens at opportunistic encounters
• Using probabilistic metric called Delivery Predictability (DP)
a: DP generator Node
b: Destination Node
A
B
C
S
Note: P(a, b) > P(c, b) : Bundles for destination B
are likely to be forwarded to A rather than C
P(a, b)∈[0,1]
The Three DP Calculations
• Transitivity Equation
initoldbaoldbaba PPPP )1( ),(),(),(
oldbaba PP ),(),(
βPPPPP (b,c)(a,b)old(a,c)old(a,c)(a,c) )1(
A B
S
A
C
B
S
Pinit∈[0,1]: Initialization constant
γ∈[0,1): Aging constant
κ: Number of time units
β∈[0,1]: Impact scaling constant
• Direct Encounter – Main Equation
• Aging Equation
PRoPHET Principal Phases
• New Neighbor Awareness
Done by lower layers
PRoPHET is notified if neighbor nodes are in range
• Two-part Information Exchange Phase
1st part: exchange summary vector (Hello procedure)
o Delivery Predictability Values
o Bundle Information, Buffer Size…
2nd part: forward the bundles
Problems Statement
PRoPHET Drawbacks
• Lack of distance awareness
Impact: Introduce delay
• More resource consumption for equal DP value
Impact: Storage shortage, Bundles dropping
• Highly fluctuating DP value
Impact: Fault forwarding decision
• No Acknowledgement
Impact: Stale copies of delivered message
Solution
DPRoPHET Routing Protocol
• Modified from PRoPHET protocol based on Neighbor
Node Distances
Therefore, Neighbor Node Distance can be
retrieved:4
22
Pr L
hhGGPd rtrtt
Ld
hhGGP rtrtt
4
22
Pr
• Received Power Strength of Two-ray Ground
Reflection Model
Cross Layer Model
Application
Bundle (DTN)
Transport
Network
Link
Physical
Sh
are Reg
istry
DTN Cross Layer Model
4
22
Pr L
hhGGPd rtrtt
initoldbaoldbaba PPPP )1( ),(),(),(
New Delivery Predictability
‽ Which message is suitable for distance retrieval?
Hello message to exchange DP value during the encounter
d
initold(a,b)old(a,b)(a,b) εPPPP 1
ε∈[0,1): Distance scaling constant
d: Distance between nodes from the Share Registry
Note: Larger ε, higher impact on the delivery predictability
• Direct Encounter Calculation for DPRoPHET
• Transitivity Equation
oldbaba PP ),(),(
βPPPPP (b,c)(a,b)old(a,c)old(a,c)(a,c) )1(
• Direct Encounter – Main Equation
• Aging Equation
DPRoPHET Delivery Predictability
d
initold(a,b)old(a,b)(a,b) εPPPP 1
Maintained from
PRoPHET
DPRoPHET Scenarios
Equal Delivery Predictability
A
B
C
D
E
F
SP(b,d)=0.6
P(a,d)=0.6
Near-equal Delivery Predictability
A
B
C
D
E
F
S
P(a,d)=0.605
P(b,d)=0.6
Simulation and Evaluation
Simulation
• Simulation Setup
Parameter Value
NS2 Version 2.35
Mobility Model Random Waypoint (RWP)
Area 2000m x 2000m
Number of nodes 40
Speed 2.5 – 20 m/s
Radio Propagation
ModelTwo-ray ground reflection
Message size 100 KB
Buffer size Up to 100 MB
Bundle lifetime 750 seconds
Transmission Timeout 1000 seconds
Simulation time 5000 seconds
Constants Value
Pinit 0.75
β 0.25
γ 0.98
ε 0.3
Simulation Setting
Protocol Constants Setting
• Languages:
C++
OTcl
DPRoPHET Implementation
• Node Distance double TwoRayGround::getDist(double Pr, double Pt, double
Gt, double Gr, double hr, double ht, double , double )
{ /* Get quartic root */
return sqrt(sqrt(Pt * Gt * Gr * (hr * hr * ht * ht) / Pr));
}
Double TwoRayGround::Pr(PacketStamp *t, PacketStamp *r, WirelessPhy *ifp){
……
if(loc_d <= crossover_dist) {
Pr = Friis(t->getTxPr(), Gt, Gr, lambda, L, d);
dist = getDist(Pr,t->getTxPr(),Gt,Gr,ht,hr,0.0,0.0);
r->getNode()->add_neigh_dist(t->getNode()->nodeid(), (double)dist,
Scheduler::instance().clock());
return Pr;
}
else{
Pr = TwoRay(t->getTxPr(), Gt, Gr, ht, hr, L, d);
dist = getDist(Pr,t->getTxPr(),Gt,Gr,ht,hr,0.0,0.0);
r->getNode()->add_neigh_dist(t->getNode()->nodeid(), (double)dist,
Scheduler::instance().clock());
return Pr;
}
}
DPRoPHET Implementation• Protocol Implementation void BundleAgent::recv(Packet* pkt, Handler*) {
hdr_ip* iph=hdr_ip::access(pkt);
hdr_bundle* bh=hdr_bundle::access(pkt);
if (((u_int32_t)iph->daddr()==IP_BROADCAST) && (bh->type ==3)){
// Hello Message & Update neighbor information
int found=0, i=0;
while ((found == 0)&&(i < neighbors)) {
if (neighborId[i] == iph->saddr())
found=1;
else
i++;
}
If(found==0){
…… //initialize new DP
}
……
dist = dist_table[neighborId[i]];
ownDP[i]=ownDP[i] + (1-ownDP[i]) * 0.75 + pow(0.3, dist);
……
}//end Hello Message (type=3)
……
}
Evaluation
• Message Delivery Ratio Improves the performance
Produces a higher ratio
Average Increment: 5%
35%40%
60%
70%
83%
33%
42%
65%
77%
92%
0%
20%
40%
60%
80%
100%
20 40 60 80 100
Message D
eliv
ery
Ratio
Buffer Size (MB)
Message Delivery Ratio vs. Buffer Size
PRoPHET DPRoPHET
Evaluation
• Average Delay
220
330
430
455480
215
310
400420 435
0
100
200
300
400
500
20 40 60 80 100
Avera
ge D
ela
y (s
)
Buffer Size (MB)
Average Delay vs. Buffer Size
PRoPHET DPRoPHET
Reduce the delay of bundles delivery
Average Reduction: 30s
Evaluation
• Message Overhead
11500
22000
31000
36500
48000
11000
20000
28000
33000
44000
0
10000
20000
30000
40000
50000
20 40 60 80 100
Avera
ge F
orw
ard
ed M
essage
Buffer Size (MB)
Average Forwarded Messages vs. Buffer Size
PRoPHET DPRoPHET
Reduce the overhead of message exchange
Average Reduction: 2600 messages
Conclusion
To Conclude…
• A popular routing protocol in DTN – PRoPHET routing protocol and its drawbacks
• DPRoPHET considering the distance metric as an addition operant to produce better delivery predictability
• DPRoPHET produces equal or better performancesthan PRoPHET, in terms of
Increasing Delivery Ratio
Reducing Delivery Delay
Less Protocol Exchange Overhead
Key References
• Sok, P., Lee, S., & Kim, K.C. (2013). “DPRoPHET in Delay Tolerant Network.” 2nd International Conference on Applied Materials and Electronics Engineering (AMEE2013). Advanced Materials Research Vol. 684 (2013) pp 543-546
• Lindgren, A. et al., "Probabilistic Routing Protocol for Intermittently Connected Networks," IETF 6693, August 2012
• Lindgren, A., Doria, A., & Schelén, O. (2003). “Probabilistic routing in intermittently connected networks.” ACM SIGMOBILE Mobile Computing and Communications Review, 7(3), 19-20.
• …
Thank You…