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### Radio Disjoint Multi-Path Routing in MANET

Carmelita Görg

Mobile Technology Research Center

TZI-ikom – University of Bremen

Abstract

- MANET research with focus on maintaining multiple routing paths mostly concentrate on the utilization of multiple paths as backup paths due to failures in the main routing path.
- Simultaneous use of multiple paths could be used to split packets of a flow or independent flows.
- This paper discusses an approach to choose multiple paths to be used simultaneously, reducing the effect of interference between nodes as far as possible, which is termed as radio disjoint paths.
- This paper discusses
- Simulation results of the use of multi-path routing considering the interference between them and different load conditions
- Implementation details of the algorithm to select the radio disjoint paths in DYMO protocol

CEWIT 2005

Biography

- Prof. Dr. Carmelita Görg MTRC:Mobile Technology Research CenterSFB 637:Collaborative Research Center tzi-ikom:University of Bremen, Germany
- Diploma degree, Department of Computer Science, University of Karlsruhe, Germany
- Dr. rer. nat. degree and Habilitation, Department of Electrical Engineering, Aachen University of Technology, Germany
- Research Interests: Performance Analysis of Mobile and Wireless Communication Networks, Stochastic Simulation, Mobility Support
- Joint work MTRC (K. Kuladinithi, M. Becker) and CEWIT (Samir Das)

CEWIT 2005

Agenda

- Previous research in multi-path routing & motivation
- Detailed analysis of the “Flow in the Middle Problem” with simultaneous use of multi-path routing
- How to select multiple routing paths to have better performance
- Implementation details (in DYMO in OPNET)
- Summary

CEWIT 2005

Research in Multi-path (Reactive MANET)

- Reactive MANET Protocols (Route Discovery & Route Maintenance) – Standards only keep a single path
- Multi-Path Routing for Reactive Protocols
- Use of an Alternate/Backup Path (to reduce the frequency of route discoveries)
- AODV-BR, AOMDV, SMR, etc.
- Load Balancing – per packet basis (SMR)

CEWIT 2005

Motivation

- Use of Multi-Path Routing simultaneously
- Balance the load in the network (Reduce the congestion/packet loss in the network)

but

- Probability of interference is higher when using multiple routes simultaneously (MANET nodes share the same channel)
- Higher interference -> Lower performance
- How to select Multiple Routing Paths with less interference (i.e. Radio Disjoint Multi-Path Routing)?

CEWIT 2005

Radio Disjoint Multi-Path Routing

- Multiple Routes with less interference,
- Try to avoid “Flow in the Middle Problem”
- Simulation of the “Flow in the Middle Problem”
- WLAN nodes set to ad hoc mode
- In a statically configured environment
- All nodes use the same frequency channel at 11Mbps

CEWIT 2005

Flow in the Middle Problem– Simulation Setup –

LP, MP & RP

- FD (Fully Radio Disjoint): All 3 paths are not in the interference of each other
- PD (Partially Radio Disjoint): Only the MP is in the interference of LP and RP
- ND (Non Radio Disjoint): All 3 paths are in the interference of each other

Right Path

(RP)

Left Path

(LP)

Middle Path

(MP)

CEWIT 2005

Flow in the Middle Problem (cont.)

- Results were taken for different loads
- LL (Low Load)
- ML (Medium Load)
- HL (Heavy Load): causes losses at the WLAN layer due to congestion (buffer overflows)
- 2 types of applications
- Unreliable Transmission, UDP (Video Transmission)
- Reliable Transmission, TCP (FTP Downloads)

CEWIT 2005

Flow in the Middle Problem - FTP

FTP Download Response Time in Seconds

No Flow in the Middle Problem

35%

-11.6%

1.8%

0.4%

CEWIT 2005

Flow in the Middle Problem - FTP

When using a download of 100,000 bytes – PD case

Use of 2 Paths Simultaneously

(No flow in the middle problem)

Use of 3 Paths Simultaneously

CEWIT 2005

FTP Results Analysis

- FD case:
- No interference between 3 paths
- Performance degrades for the Heavy Load due to congestion
- PD case:
- LL : Flow in the middle Problem is not visible for low loads
- ML : Avoiding MP (No flow in the middle problem) causes the performance to improve by 35%
- HL : Avoiding MP will not help due to the congestion
- ND case:
- All 3 paths are suffering heavily due to mutual interference
- Avoiding MP helps to gain ~2% performance improvement

CEWIT 2005

Flow in the Middle Problem – Video Transmission –

Mean Packets end-to-end delay in ms

20.5%

?

6%

?

Packets are lost due to congestion

CEWIT 2005

Flow in the Middle Problem – Video Transmission –

Increase of Load and use of 3 paths simultaneously (except for FD case) causes

- Higher Packets delay variation (at the application)

- Higher Delay in WLAN

- More Data dropped at WLAN

CEWIT 2005

Result Analysis – Video Transmission –

- FD case:
- No interference between 3 paths
- Performance degrades for Heavy Load due to congestion
- PD case:
- LL : Flow in the middle Problem is not visible for low loads
- ML : Avoiding MP causes performance to improve by 20%
- HL : Avoiding MP will not help due to congestion (due to unreliable transmission)
- ND case:
- All 3 paths are suffering heavily due to mutual interference
- Avoiding MP helps to increase the performance by 6%

CEWIT 2005

Comparison of Single Path vs. Simultaneous use of Multi-Paths

- Scenario 1:
- FTP 1 – Download Response time for multiple downloads of the size of 100,000 bytes at each 5 sec.
- Video1 – Mean of packets end to end delay for uni-directional video transmission at the rate of 350bytes X 2 (5.6 kbps)
- Video2 – Mean of packets end to end delay for uni-directional video transmission at the rate of 350bytes X 2 (5.6 kbps)
- Scenario 2:
- FTP 1 – Download Response time for multiple downloads of the size of 100,000 bytes at 5 sec each.
- FTP 2 – Download Response time for multiple downloads of the size of 100,000 bytes at 5 sec each.
- Video 1 – Mean of packets end to end delay for uni-directional video transmission at the rate of 350bytes X 2 (5.6 kbps)

CEWIT 2005

Comparison of Single Path vs Simultaneous use of Multi-Paths

Scenario 1

w.r.t. delays in single path

Scenario 2

WLAN Delay

Single Path

Radio Disjoint

Multi-Path

Non-Radio Disjoint

Multi-Path

CEWIT 2005

Simultaneous Use of Multi-Path Routing to Improve Performance

- Selection of Multi-Path Routing
- Less Interference
- Best : Use of Fully Radio Disjoint Paths
- Ok : Use of Partially Radio Disjoint
- Less Load on a path (to avoid congestion)
- Distribution of Flows (Applications) to Multiple Paths
- Distribute the load so that paths will not be overloaded (to avoid congestion)
- To know the remaining capacity of the path and the capacity of application

CEWIT 2005

How to Compute Interference Level and Load of a Path?

NL – Node Load, PL –Path Load, HC – Hop Count

- NL = (packets transmitted and received by the node = X) + (packets heard from other nodes in the vicinity = Y)
- X ~ Current Load of the Node
- Y ~ Interference Level of the Node
- NL is computed by a weighted average over a periodical interval to consider the latest value

CEWIT 2005

How to Compute the Node Load?

- Example : NL is measured at each 1 sec and up to 4 measurements are held to compute weighted average of the NL (i.e. Avg. Of the past 4 sec)
- Current Node Load,

NL= 0.1 (X2+Y2) + 0.2 (X3+Y3) + 0.3(X4+Y4) + 0.4(X5+Y5)

X = packets transmitted and received by the node

Y = packets heard from other nodes in the vicinity

IP addr

MAC addr

X1 | Y1

X2 | Y2

X3 | Y3

X4 | Y4

X2 | Y2

X3 | Y3

X4 | Y4

X5 | Y5

Weighted average to consider the latest values

CEWIT 2005

How to Compute Interference Level between Paths?

- Pathload: PL = max [NL1, NL2 , NL3 , NL4 .. NLm ], where m – Number of nodes in a path
- Best Path: min(PL) considering also the Hop Count
- A path with less interference and less load
- Implementation Requirements

1. How to compute the path load during the route discovery?

- RREQ should be extended to include NL of each node
- Implementation – with interface set to promiscuous mode, X & Y could be computed and packets should be identified based on the MAC address

2. Max, number of paths to be selected

- Threshold value should be defined for max. number of routing paths to be used

3. Computation of path load periodically

- Sending a periodic packet to compute the path load even after the first route discovery

CEWIT 2005

Details of Simulation

- Based on DYMO Protocol (OPNET Simulator)

- DYMO – Reactive Protocol like AODV, but with path accumulation feature

I1

I2

I3

D

S

RREQ

RREQ

RREQ

RREQ

RREQ

RE-S

RE-S

RE-S

RE-S

RE-I1

RE-I1

RE-I1

RE-I2

RE-I2

RE-I3

RREP

RE-S Route Element with NL of S

RE-I1 Route Element with NL of I1

CEWIT 2005

Details of Simulation

Weighted Avg of NL

IP addr

X | Y

IP addr

MAC addr

X1 | Y1

X2 | Y2

X3 | Y3

X4 | Y4

- Open Issues
- Period for the computation of weighted average
- Any weight between X & Y?

CEWIT 2005

Summary

- Investigated the behavior of flow in the middle problem in a statically configured environment
- Simultaneous Use of Multiple Paths in MANET
- To achieve best performance while selecting less interfered and less loaded paths
- Discussed the implementation of radio disjoint multi-path routing in one of the reactive MANET protocols (DYMO)

CEWIT 2005

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