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