adhoc protocols comparison

Performance Comparison Of Mobile

Ad-Hoc Networks

By

Josh Broch, David A. Maltz, David B.Johnson, Yih-Chun Hu, Jorjeta Jetcheva

Presented by

Santhosh Ramaraju & Pradeep Godhala

Overview• Introduction

• Destination Sequenced Distance Vector (DSDV).

• Temporally Ordered Routing Algorithm (TORA).

• Dynamic Source Routing (DSR).

• Ad-hoc On-Demand Distance Vector Routing (AODV).

• Performance Metrics.

• Simulations.

• Conclusion.

Performance Comparison Of Mobile Ad-Hoc Networks 2

Introduction

• Ad-Hoc Network (Infrastructureless Networking).

• DSDV, TORA, DSR, AODV.

• ns-2 Network Simulator to include• Node Mobility

• Realistic Physical Layer• Radio propagation model supporting propagation delay

• Capture effects

• Carrier sense

• Radio network interfaces• Transmission power

• Antenna gain

• Receiver sensitivity

• 802.11 MAC using DCF

• ARP

• Packet Buffering


DSDV

• Table driven

• Hop by hop routing

• Sequence numbers to routes

• Increase or decrease route fidelity based on sequence numbers


Implementation decisions in DSDV

DSDV-SQ (Used for paper results):

•New sequence number triggers updates

•Broken links detected faster

•More overhead

DSDV:

•New metric triggers updates

•Less detected not as fast ov


TORA

• On demand routing

• Information flows like water flowing downhill

• Each node is assigned a "height" and information flows from nodes with greater height to nodes with lower height

• Three functions:

1) Route Creation

2) Route Maintenance

3) Route Erasure

• Builds DAG


Implementation Decisions in TORA

• Aggregation Delay

• Retransmission period and Timeout period

• IMEP's method of link status sensing is improved


Table: constants used in TORA

DSR

• DSR uses source routing rather than hop-by-hop routing.

• The Key Advantage of the source routing is that intermediate nodes do notneed to maintain up-to-date routing information in order to route thepacket.

• Route Discovery

• Route Request

• Route Reply

• Route Maintenance

• Reducing Route discovery process by maintain route cache.

• Route Error.


Implementation Decisions in DSR

• DSR protocol uses Unidirectional routes, since 802.11 is used it usesRTS/CTS/DATA/ACK exchange for all unicast packets limiting theprotocol to using bidirectional links.

• Implemented DSR to avoid Unidirectional links by using Route Reply toreverse back the same path as Route Request.

• Route Request packet maximum propagation limit (hop limit) set to zero,prohibiting form rebroadcasting it.

Table: Constants used in DSR


AODV

• Combination of DSR and DSDV.

• ROUTE REQUEST packets contain last known sequence number fordestination.

• When a node receives a ROUTE REQUEST packet for a destinationit has a route to it generates a ROUTE REPLY with the updatedsequence number and number of hops. Reverse route is also createdbefore forwarding the ROUTE REQUEST.

• Each node that forwards the reply back to the originator creates aforward path to the destination.

• Hello messages are used to maintain link state.

• Nodes remember only the next hop


Implementation Decisions in AODV

• Dropped periodic HELLO packets in favor of link layer breakagedetection (AODV-LL) thereby reducing Overhead.

• Problem with AODV-LL is its On Demand (link breakages can be detectedonly if there is a packet to be transmitted).

• Reduced ROUTE REPLY timeout to 6 seconds from 120 seconds.


Table: constants used in AODV

Methodology• Simulated network

• Took scenario files as input

• 210 total scenario files

• Describe motion of each node

• Exact sequence of packets(4 packets a second) to send from each node

• Exact Time change (in motion or packet origination) is to occur 50 wirelessnodes

• Flat rectangular area (1500m x300m)

• 900 seconds test time

• Following improvements made to all protocols:• Jittered response to periodic broadcast packets

• Routing packets queued ahead of other packets

• 802.11 MAC layer link breakage detection (except DSDV)Performance Comparison Of Mobile Ad-Hoc Networks 12

Movement Model and Communication

• Random Way-point Model

• 7 different pause times (0, 30, 60, 120, 300, 600, and 900 seconds)

• Nodes moved with a speed from 0-20m/s

• Also use simulations with max 1m/s for comparison

• Networks contained 10,20,30 CBR sources

• Did not use TCP

• 4 packets per second

• 64 byte packets

• Connections started uniformly between 0-180s


Performance Metrics

Fig: Packet delivery Ratio Fig: Routing Overhead


Performance metrics contd…..


Table: Rate of connection changes

Fig: Path Optimality between 1m/s and 20m/s

Simulation Results

Packet Delivery Ratio for DSDV and DSR


Packet Delivery Ratio for TORA and AODV-LL


Routing Overhead for DSDV and DSR


Routing Overhead for TORA and AODV-LL


Path Optimality


Fig: Path optimality for Different Protocols

Lower speed of node movement

Packet delivery ratio when packets

moving at 1m/s.

Routing Overhead when packets

moving at 1m/s.


Conclusion• ns network simulator can now evaluate ad-hoc routing protocols

• DSDV

• Good with low mobility and fails to converge when node mobility increases.

• TORA

• Large overhead; fails to converge with 30 sources but does good when using 10 and 20 sources. Large overhead but can deliver 95% of the data for 10 and 20 sources.

• DSR

• Very good at all rates + speed, but large packet overhead.

• AODV

• Almost as good as DSR, but has more transmission overhead


Thank youQuestions….?


adhoc protocols comparison

Engineering