Ad-Hoc Networking Course

Instructor: Carlos Pomalaza-Ráez

A Paper Presentation of ”Multihop Sensor Network Design for Wide-Band Communications”

Proceedings of the IEEE, VOL.91, NO.8, August 2003

Terho Hautala13.1.2004

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Outline

• Introduction• New Cluster-Based Network• AODV• Mobility and handoff• Ipv6-in-IPv4 Tunneling• IEEE 802.11• Measurements• Conclusions

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Introduction

• New cluster-based network architecture• Mixture of two different types of network:

• Infrastructure (master-and-slave)• Ad-hoc

• Slave Nodes (SN) are communicating via their respective Master Nodes (MNs)

• Base stations (MNs) are mobile (AODV routing)

• MNs act as a Home Agent (HA) and gateways for the cluster

• All nodes in a cluster typically move as a group

• If node changes cluster MIPv6 is deployed

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Introduction

Static addressing Mobile IP Mobile IP + Ad-hoc routing

Ad-hoc MobilityRelatively fixed

Increasing mobility

Wired and wirelessWireless only

Headquarters Airbase

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Introduction

• Traditional cluster-based networking has difficulties when the number of nodes increases

• routing complexity

• network management

• large overheads

• In the paper a simple cluster networking is proposed. There WLAN is utilized. The goal is to provide a wide-band access for multimedia communication (video).

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New Cluster-Based Network

Ad-hoc channel

Infrastructure channel

APLAN

WLAN

WLANLANAP

Master node 4 (MN4)

Master node 3 (MN3)

APLAN

WLAN

WLANLANAP

Master node 2 (MN2)

APLAN

WLANMaster Node 1 (MN1)

Slave Node (SN)

GW

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AODV

• AODV is used to manage routes between Master Nodes.

• Instead of AODV DSR could also have been used, but it was not further investigated in the paper.

• AODV discovers routes by means of route request (RREQ) and route reply (RREP).

• Each node will reply to RREQ if it is either destination node or an intermediate node.

• In the case on link breakage error message (RERR) will be sent back to the source.

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Mobility and handoff

• If SN moves to a new cluster mobile IPv6 (MIPv6) handoff is performed.

• SN will automatically configure link-local address and care-of-address (CoA) address based on the router advertisements.

• The home-agent is informed of the new CoA, so it can tunnel packets arriving to the home network (original cluster) to the new location.

• If SN receives a tunneled packet it should inform the source SN of the new location (route optimization).

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Mobility and handoff

APLAN

WLAN

WLANLANAP

APLAN

WLAN

WLANLANAP

(MN1) (MN3)

(MN4) (MN2)

Router Advertisement by IPv6 ROUTER

• SN automatically configures care-of-address (CoA) address based on the router advertisements

BU

SN sends Binding Update to inform Master Node 1 about the movement. Binding Cache is updated. BUs should also be sent to Correspondent Nodes (CNs) of SN

BACK

Master Node1 (HA for SN1) replies with Binding Acknowledgement and tunnels the packets to SN1

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IPv6-in-IPv4 Tunneling

• IPv6 is used for operation in the infrastructure mode.

• The communication in the ad-hoc mode (between the master nodes) is based on IPv4 and AODV.

• If SN communicates with SN in another cluster, IPv6-in-IPv4 tunneling is used.

• Master node encapsulates the IPv6 packets received from SN and sends them to the master node of the destination cluster.

• The source address in IPv4 header is the address of the master node.

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IPv6-in-IPv4 tunneling

APLAN

WLAN

APLAN

WLAN(MN1)

(MN3)

WLANLANAP

(MN2)

Data packets

MN1 encapsulates the IPv6 packets received from SN1

IPv6

SN1

Packets are sent to the master node of the destination cluster.The source address in IPv4 header is the address of the master node.

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IEEE 802.11

• IEEE 802.11 supports direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS) modes.

• The DSSS mode is preferred if the number of clusters if small.

• If the number of clusters is large, FHSS can be more suitable.

• FHSS can select 79 possible hopping sequences to avoid inteference.

• IEEE 802.11 is allowed several retransmission attempts (the number retransmission affects the performance)

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Experimental setup

• Stationary , throughput and delay• Retrans = 0 and retrans = 3• Bitrate = 128 / 384 / 768 kb/s

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Experimental setup

APLAN

WLAN

APLAN

WLAN(MN1)

(MN3)

WLANLANAP

(MN2)

SN1

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Scenarios

(MN1)

(MN2)

WLANLANAP

(MN3)

APLAN

WLAN

WLANLANAP

SN-D

1-hop case:

Same radio channel resources are overwhelmed at higher bit rates

SN-S 2 hops case:SN-S

SN-D

3-hops case:

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Results(throughput)

Fig.1. Throughput performance for one node

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Results(throughput)

Fig.2. Throughput performance for two node

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Results(delay)

Fig.3. Propagation delay distributions for 1-hop communication

(time resolution 10ms)

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Results(delay)

Fig.4. Propagation delay distributions for 2-hop communication

(time resolution 10ms)

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Results(delay)

Fig.5. Propagation delay distributions for 3-hop communication

(time resolution 10ms)

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Results(delay)

Fig.6. Average delay

(time resolution 10ms)

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AODV Route Change Scenario

• Cluster is moving (routes change), delay + tput

• Route change: 2-hop => 3-hop• At low bitrate delay remains almost

the same• At high bitrate delay increases• Route change a->b, duration about 2

sek

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AODV route change scenario

(MN2)(MN1)

(MN3)2-hops

SN-S

SN-D

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(MN2)(MN1)

(MN3)

AODV route change scenario

3-hops

SN-S

SN-D

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AODV route change results

Fig.7. Delays in AODV route change

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Mobile IP handoff scenario

• SN is moving (MIPv6 handover ja tunneling + BUs), delay + troughput

• Route A (original)• Route B (BU has sent to HA and it is

receiving packets from CN)• Route C ( CN has received BU because

SN sent it after receiving a tunneled packet)

• Handover delay remains same regardless the bitrate and max retries

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(MN3)

(MN1)

(MN2)

SN-D

Mobile IP handoff scenario

SN-S

SN-D

Route A: SN-S MN-2 MN-1 SN-DRoute B: SN-S MN-2 MN-1 MN-2 MN-3 SN-DRoute B: SN-S MN-2 MN-1 MN-2 MN-3 SN-D

Route C: SN-S MN-2 MN-3 SN-D

HA

CN

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Mobile IP handoff scenario

• In he pa

Fig.8. Average packet loss in Mobile IP

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Mobile IP handoff scenario

Fig.9. Delays in Mobile IP

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Future work

• In he pa• Use forward error correction (FEC) codes at the application layer

• Use Dynamic Source Routing (DSR) and Optimized Link State Routing (OLSR)

• Measure the network performance when a larger number of clusters have been utilized

• Develop robust error resilient coding for video streaming

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Conclusions

• In he pa• Assumption was that all the nodes within each cluster move as a group• To allow handoffs for some isolated nodes Mobile IP has been considered• AODV routing protocol has been used for ad-hoc routing• Experimental testbed was developed for video based sensor network and was successfully tested

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Thanks!

• In he pa