localized operations for distributed minimum energy multicast algorithm in mobile ad hoc networks

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Paper by Song Guo and Oliver Yang; supporting images and definitions from Wikipedia Presentation prepared by Al Funk, VT CS 6204, 10/30/07

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Paper by Song Guo and Oliver Yang; supporting images and definitions from Wikipedia Presentation prepared by Al Funk, VT CS 6204, 10/30/07. Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks. Table of Contents. Background and related work - PowerPoint PPT Presentation

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Page 1: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Paper by Song Guo and Oliver Yang; supporting images and definitions from Wikipedia

Presentation prepared by Al Funk, VT CS 6204, 10/30/07

Page 2: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Table of Contents

Background and related work Models: system, network, mobility DMEM algorithm Operations Performance Conclusions

Page 3: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Background and related work Multicast: communication technique which

enables a source to send a single packet to reach multiple receivers.

Objective: Create a distributed algorithm to solve the Minimum Energy Multicast (MEM) problem Definition of MEM: Find a route for multicast

transmission with the minimum total energy consumption for a given communication session.

Challenges: MANET changing network topology, lack of central authority; problem is NP-hard

Page 4: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Background and related work Prior research focused on:

Creating centralized, not distributed, algorithms

Efficient heuristic algorithm design Weaknesses of prior research

Examination of static, not dynamic, network topologies

Little examination of performance impact of node mobility

Page 5: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Models: System Model

Discrete Power Level Management Model Transmission range based on

power level, but power level increases at an exponential rate as distance increases

Identify discrete power levels appropriate to reach nodes at various distances from the transmitter Vary transmitter power in

granular increments to balance power use with the bandwidth usage necessary to constantly adjust transmission strength

Page 6: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Models: System Model

Pvu = Power level required to transmit from node v to node u

lvu = Layer (concentric ring from prior slide) of u relative to v

K = Number of discrete power levels of the transmitter (and therefore number of layers)

rK = Distance of ring K α = Parameter (2 to 4) representing rate

of signal attenuation

Page 7: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Models: Network Model

Represent network as a directed graph, G(N,A,p) N = set of nodes, A = set of arcs, p =

function representing power required for each arc

Rooted tree: directed acyclic graph with a source node that has no incoming arcs and where other nodes have a single incoming arc

Leaf vs. internal/relay nodes

Page 8: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Models: Network Model

For any node v in the rooted tree,there exists a single acyclic source route πv

Our goal is to set lv, the transmission layer of node v, to the minimum necessary for v to reach all of its child nodes

Once this is known, we can calculate pv, the necessary power level for the node

Page 9: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Models: Mobility

Mobility is a differentiator for the contribution, as alternative models require the significant overhead associated with central coordination.

Authors use “Random Waypoint Model” Calculate random speeds bounded by Vmin

and Vmax; assume random start and end points; introduce pause between journeys.

Objective: calculate the steady-state average speed:

Page 10: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Algorithm: Data Structure We need to store the forwarding

state at each tree node v. Membership status – sender, receiver,

forwarder (can be receiver and forwarder)

Source route π – directed path from the source to node v (used to avoid loops)

Tree neighborhood table TNv – stores neighbors, along with whether is a father, child or other, along with layer lvu

Page 11: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Algorithm: Tree Construction Minimum Spanning Tree: Given a

connected, undirected graph with weighted edges, an MST is a subgraph which connects all vertices together resulting in the minimum total weight.

Page 12: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Algorithm: Tree Construction MULTICAST-JOIN-REQUEST (MJREQ):

Broadcast message initiated by the source used when no route information is known

MULTICAST-JOIN-REPLY (MJREP):Response message sent to previous hop node

MJREQ: Transmitted at maximum transmission power

MJREP: Returned at necessary power Necessary power determined by strength of

the original MJREQ message

Page 13: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Algorithm: Tree Flood

MULTICAST-ALIVE (MA): Message sent periodically during session to refresh the tree (otherwise tree routes are cleared) Message sent at maximum power Used to adjust power dynamically Only sent if received from father (but then

always sent) Supports tree repair and energy saving

operations Nodes update neighborhood information to

identify nearby nodes

Page 14: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations

Normal Energy Saving (NES): Upon receipt of MA from children, node adjusts its transmission power to the minimum necessary. Reactive approach which could lower

total power utilization Keeps the tree connected but not with

maximum efficiency

Page 15: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: SHO Soft Hand-Off (SHO): Initiated by a

node that detects it is leaving its father’s transmission range (K). Goal is to identify a new father s.t.

and power utilization is minimized Node severs link with previous father

(via MULTICAST-LEAVE (ML) message), selects the new father

Tree is maintained.

Page 16: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: MTR Multicast Tree Repair (MTR): In the

case where loss of a node results in a tree partition, we need a way to repair the multicast tree. Occurs when a forwarder or receiver fails

to receive successive MAs from its father Nodes furthest from the source attempt

to reconnect first MULTICAST-JOIN-SOLICITATION (MJS):

Hop-limited message

Page 17: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: MTR Disconnected node closest to source

notifies the subtree that it is initiating repair procedures using an MA message

The closest node to the source initiates an MJREP message and attempts to reconnect the subtree back to the multicast tree

If an appropriate node responds, the tree is reconnected; if not, other nodes in the subtree attempt to reconnect, and the node(s) that failed must rejoin through a network flood.

Page 18: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: AES Advanced Energy Savings (AES): A proactive

method of reallocating child nodes s.t. overall power utilization of the system is reduced. The major contribution of the paper We must be able to retain the MST structure for

multicast Operation performed as part of MA Approach: Each child node attempts to

extend its transmission range to become the parent of a current child of its father – but only if such a change reduces the total power utilization of the system

More sophisticated than NES They are not mutually exclusive

Page 19: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: AES Using the MA message header means that no

separate message is necessary for the operation

Use of MA messages fits the algorithm -- father to child propagation enables communication of power levels and supports child decision-making. At each transmission from its father, a node

modifies header with its own information and propagates to its neighbors

Because MA messages are at full power, neighbors of multicast tree nodes will receive. As a result, non-multicast tree nodes can join, but

must consider potential added cost of the link from a father node

Page 20: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: AES AES-REQUEST: When a node

identifies a power savings, it sends an AES-REQUEST to the source

Source reviews AES-REQUEST messages and sends AES-REPLY to the node with the greatest power savings

Page 21: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: AES Finalizing the update

Selected node sends local broadcast TREE-UPDATE and assigns itself as father to the node to move

Moving node leaves father, sending MULTICAST-LEAVE.

If selected node is a non-tree node, it must find a father It will be a forwarding node only, otherwise it

would have been part of the original tree Multiple nodes may become children of the

selected node if power savings justify

Page 22: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Localized Operations: AES Examples of AES tree revision

Page 23: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation

Simulations Ad hoc network with size 1,000 meters

sq. Each node can transmit 250 meters K=10 α = 2 Modeled max node movement speeds of:

1, 5, 10, 15, 20 and 25 m/s Multicast groups 5, 25, 50, 75, 100 Static networks considered 50 scenarios for each multicast group

Page 24: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation

Measures Relative tree power: Ratio of actual total

tree power for heuristic algorithm vs. ideal of MST algorithm

Average tree power: Power used over time for the tree

Communication overheads: Overhead for AES, SHO and MTR as a total number of these operations over each simulation

Page 25: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation

Static network evaluation Compared DMEM against prior work Not key to the paper, but demonstrates

that DMEM is a useful heuristic compared with prior research

Page 26: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation

Mobile network evaluation: Consider with and without optional protocol components

Page 27: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation

Examine AES performance considering node speed and multicast group size.

Page 28: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation

Examine SHO operations given node speed and multicast group size.

Page 29: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Performance Evaluation MTR operations considering node

speed and multicast group size.

Page 30: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Conclusions

In a static network, DMEM is superior to alternative algorithms for medium and large multicast groups. Measures heuristics, but major contribution is on

dynamic network DMEM is efficient in reducing energy

utilization AES provides significant value relative to base

case SHO is mostly redundant when using AES

DMEM proven correct for maintaining tree structure using localized operations

Page 31: Localized Operations for Distributed minimum energy multicast algorithm in mobile ad hoc networks

Critique

Graphs are not presented in such a way to visually support the analysis e.g., authors require visual comparison of separate

charts to compare AES and SHO, rather than presenting a single chart

Is it scalable? Authors indicate that AES becomes saturated; this seems to occur rapidly in “large” networks even at slow speed. Authors indicate that it is scalable with regard to

mobility – but AES saturation seems to put this in question, as do some of their comments right before the conclusion

If scalability is an issue, possible approaches to address it would have been welcome

Do the arbitration performed by the source node along with the broadcast approach amount to centralization that reduces scalability and creates a bottleneck?