Self-stabilizing energy-efficient multicast for MANETs
Mobile Ad hoc Networks (MANETs)
Network Model mobile nodes (PDAs, laptops etc.) multi-hop routes between nodes no fixed infrastructure
A
B
C
D
A
D
B
CNetwork Characteristics Dynamic Topology Constrained resources
battery power
Links formed and broken with mobility
Applications Battlefield operations Disaster Relief Personal area networking Multi-hop routes generated among nodes
Self-stabilization in Distributed Computing
Valid State
Invalid State
Applied to Multicasting in MANETs
Convergence
ClosureFault
Topological Changes and Node Failures for MANETs.
Local actions in distributed nodes.
Self-stabilizing distributed systems• Guarantee convergence to valid state through
local actions in distributed nodes.• Ensure closure to remain in valid state until any
fault occurs.
Can adapt to topological changes• Is it feasible for routing in MANETs?
Self-stabilizing Multicast for MANETsMulticast source
Topological Change
Converge
nce
Based on
Loca
l acti
ons
• Maintains source-based multi-cast tree.
• Actions based on local information in the nodes and neighbors.
• Pro-active neighbor monitoring through periodic beacon messages.
• Neighbor check at each round (with at least one beacon reception from all the neighbors)
• Execute actions only in case of changes in the neighborhood.
Self-Stabilizing Shortest Path Spanning Tree (SS-SPST)
Self-stabilizing Multicast Tree Construction
S BA
D C
G
FE
H
I
J
First Round – source (root) stabilizes level of root is 0.
Arbitrary Initial State – no multicast tree Parent of each node NULL. Level of each node 0.
Second Round – neighbors of root stabilizes level of root’s neighbors is 1. parent of root’s neighbors is root.
And so on ……
Pruning of the tree in a bottom-up manner.
Tolerance to topological changes.Problem – energy-efficiency
is not considered
SS-SPST
Energy-Efficiency in Self-stabilization
Energy Consumption Model
Ti reaches all nodes in range
i
Ti
Overhearing at j, k, and l
i
j
k
lnon-intended neighbor
No communication schedule during broadcast in random access MAC (e.g. 802.11).
Transmission energy of node i
• Variable through Power Control
• One transmission reaches all in range
Cost metric for node i Ci = Ti + Ni x R
• Reception energy at intended neighbors.
• Overhearing energy at non-intended neighbors.
Reception cost at all the neighbors
intended neighbor
Ci = Ti + 7R
What is the additional cost if a node selects a parent?
Energy Aware Self-Stabilizing Protocol (SS-SPST-E)
A BF
C
E
D
X
Select Parent with minimum Additional Cost
Minimum overall cost when parent is locally selected
Execute action when any action trigger is on
Tree validity – Tree will remain connected with no loops.
Not in tree
Loop Detected
Potential Parents of XAdditionalCost (A → X) = TA + 2R
AdditionalCost (B → X) = TB + R
Actions at each node (parent selection)
• Identify potential parents.
• Estimate additional cost after joining potential parent.
• Select parent with minimum additional cost.
• Change distance to root.
Action Triggers
• Parent disconnection.
• Parent additional cost not minimum.
• Change in distance of parent to root.
SS-SPST-E Execution
S BA
D C
FE
H
No multicast tree parent of each node NULL. hop distance from root of each node infinity. cost of each node is Emax.
First Round – source (root) stabilizes hop distance of root from itself is 0. no additional cost.
Second Round – neighbors of root stabilizes hop distance of root’s neighbors is 1. parent of root’s neighbors is root.
2
2
2 2
2
2
2
31
AdditionalCost (S → {A, B, C, D}) = Ts + 4R
No potential parents for any node.
Potential parent for A, B, C, D, F = {S}.
Potential parent for E = {D, F}.
AdditionalCost (F → E) = TF + 2RAdditionalCost (D → E) = TD + 3R
Potential parent for F = {S, C}.
AdditionalCost (S → F) = TS + 5RAdditionalCost (C → F) = TC + 3R
And so on ……
Tolerance to topological changes.
AdditionalCost (D → E) = TD + 3R
Convergence - From any invalid state the total energy cost of the graph reduces after every round till all the nodes in the system are stabilized.
Proof - through induction on round #.
Closure: Once all the nodes are stabilized it stays there until further faults occur.
G1
1
Multicast source
AdditionalCost (S → F) = Ts + 5R
Simulation Results – Varying Beacon Interval
Energy Consumption per Packet Delivered Vs. Beacon Interval
0
10
20
30
40
1 2 3 4
Beacon Interval (sec)
Ener
gy (m
Joule
s)
SS-SPST-E
SS-SPST
Energy consumption per packet delivered increases due to decrease in number of packets delivered.
Simulation Results – Varying Beacon IntervalPDR Vs. Beacon Interval
0
0.2
0.4
0.6
0.8
1
1 2 3 4
Beacon Interval (sec)
PDR SS-SPST-E
SS-SPST
PDR decreases with less beaconing
What is the optimum beacon interval?
Improvements to self-stabilizing multicast
• Fault-localization to reduce stabilization time– Incorporate fault-containment mechanism
• Optimize the beacon interval to minimize overhead energy– depends on data traffic arrival– depends on changes in link status– depends on what level of reliability to attain
• Management plane required at the network layer to control protocol parameters
Application-aware Adaptive Optimization Sub-layer
Sample Result
Additional Slides
Simulation Results – Varying Node Mobility
1m/s 5m/s 10m/s 15m/s 20m/s
Low packet delivery with high dynamicity
ODMRP has high PDR due to redundant routes
Simulation Results – Varying Node Mobility
Energy Consumption per Packet Delivered
0
10
20
30
40
50
60
Average Node Velocity
Ener
gy (m
Joul
es)
1m/s 5m/s 10m/s 15m/s 20m/s
SS-SPST-E leads to energy-efficiency
ODMRP has high overhead to generate redundant routes
Simulation Results - Varying Multicast Group Size
PDR Vs. Multicast Group Size
00.10.20.30.40.50.60.70.80.9
Number of Nodes in Multicast Group
PDR
10 20 30 40 50
Self-stabilizing protocols scale better.
MAODV has highest delay due to reactive tree construction