Department of Information EngineeringUniversity of Padova, Italy

COST273 May 30-31, 2002 HelsinkiCOST273 May 30-31, 2002 Helsinki TD (02)-062TD (02)-062

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On the performance of On the performance of AODV and FSR routing AODV and FSR routing

algorithms on Bluetooth algorithms on Bluetooth scatternets: preliminary scatternets: preliminary

resultsresults

Department of Information EngineeringUniversity of Padova, Italy

Andrea Zanellazanella@dei.unipd.it

COST273 May 30-31, 2002 HelsinkiCOST273 May 30-31, 2002 Helsinki TD (02)-062TD (02)-062

May 30-31, 2002 COST273 TD(02)-062 3

Outline of the contentsOutline of the contents

Bluetooth basic Ad-hoc routing algorithms

Ad-hoc On demand Distance Vector (AODV) Fisheye State Routing (FSR)

Simulation model Experimental results Conclusions and future work

May 30-31, 2002 COST273 TD(02)-062 4

Bluetooth TechnologyBluetooth Technology

What is Bluetooth? A wireless technology

Proposed as cable replacement for leakage portable electronic devices, BT provides short-range low-power point-to-(multi)point wireless connectivity

A global industry standard in the making Initially developed by Ericsson, now BT is promoted by an

industry alliance called Special Interest Group (SIG)

May 30-31, 2002 COST273 TD(02)-062 5

Bluetooth piconetBluetooth piconet

Two up to eight Bluetooth units sharing the same channel form a piconet

In each piconet, a unit acts as master, the others act as slaves

Channel access is based on a centralized polling scheme

active slavemaster

parked slavestandby

slave1

slave2

slave3

master

May 30-31, 2002 COST273 TD(02)-062 6

FH & TDDFH & TDD

Each piconet is associated to frequency hopping (FH) channel The pseudo-random FH sequence is imposed by the master Time is divided into consecutive time-slots of 625 s Each slot corresponds to a different hop frequency

Full-duplex is supported by Time-division-duplex (TDD) Master-to-slave (downlink) transmissions start on odd slots Slave-to-Master (uplink) transmissions start on even slots

625 s

t

t

master

slave

f(2k) f(2k+1) f(2k+2)

May 30-31, 2002 COST273 TD(02)-062 7

Bluetooth scatternetsBluetooth scatternets Piconets can be interconnected by Inter-piconet Units (IPUs) IPUs may act as gateways, forwarding traffic among adjacent

piconets IPUs must time-division their presence among the piconets Time division can be realized by using SNIFF mode

May 30-31, 2002 COST273 TD(02)-062 8

Next in the line…

Bluetooth basic Ad-hoc routing algorithms

Ad-hoc On demand Distance Vector (AODV) Fisheye State Routing (FSR)

Simulation model Experimental results Conclusions and future work

May 30-31, 2002 COST273 TD(02)-062 9

Motivations of the workMotivations of the work

Bluetooth gets out typical MANET scenario Physical proximity does not imply connection Connection set-up may take infinite time Broadcast is supported only within piconets

Hence, MANET algorithms have to be tested in Bluetooth environment Table-driven algorithms: LSR, DSDV,WRP,FSR On demand algorithms: DSR,TORA,AODV?

May 30-31, 2002 COST273 TD(02)-062 10

IP-layer routingIP-layer routing

Routing is performed at IP layer, making use of IP addresses

Pros No address-mapping Independence of the network details

Cons Each node must support IP functionalities IP datagrams must be reassembled before

forwarding Access CodeAccess Code Layer 2 Layer 2

HeaderHeaderLayer 2 PayloadLayer 2 Payload

SCIDSCID DCIDDCID L2CAP PayloadL2CAP Payload

Source IP Source IP AddressAddress

Destination IP Destination IP AddressAddress

IP PayloadIP Payload

May 30-31, 2002 COST273 TD(02)-062 11

AODV Algorithm (1)AODV Algorithm (1) Route discovery

Broadcast Route Request packet (RREQ), containing source and destination IP addresses

Intermediate nodes that receive the RREq for the first time

Increment by one the hop count field in the packet Add an entry containing: source IP, destination IP,

predecessor IP Broadcast the RREQ packet

Source nodeSource node

IP1IP1

Destination nodeDestination node

IP7IP7

IP2IP2

IP3IP3

IP4IP4

IP5IP5

IP6IP6

1IP1IP1IP7

1IP1IP1IP7 2IP2IP1IP7

3IP4IP1IP7

3IP4IP1IP7

4IP5IP7IP1

May 30-31, 2002 COST273 TD(02)-062 12

AODV Algorithm (2)AODV Algorithm (2) Destination responds to the RREQ by unicasting a Route

Reply (RREP) packet to the source The RREP flows backward along the path traced by the RREQ Intermediate nodes that process the RREP update their entry Entries that are not updated expire after a given timeout

1IP1IP1IP7

1IP1IP1IP7 2IP2IP1IP7

3IP4IP1IP7

3IP4IP1IP7

4IP5IP1IP7

Source nodeSource node

IP1IP1

IP7IP7

Destination nodeDestination node

IP2IP2

IP3IP3

IP4IP4

IP5IP5

IP6IP6

4IP2IP7IP1

1IP7IP7IP1

3

3IP7IP7IP1

3

2IP7IP7IP1

2

May 30-31, 2002 COST273 TD(02)-062 13

AODV Algorithm (3)AODV Algorithm (3)

In case of link failure, AODV propagates a Route Error (RERR) message to the upstream nodes

Receiving an RERR, nodes set to infinity the distance to the destination

If the path is still needed, nodes start a new path discovery procedure

Source nodeSource node

IP1IP1

IP7IP7

Destination nodeDestination node

IP2IP2

IP3IP3

IP4IP4

IP5IP5

1IP1IP1IP7 2IP2IP1IP7

3IP4IP1IP7

4IP5IP1IP7

4IP2IP7IP1

1IP7IP7IP1

3

3IP7IP7IP1

3

2IP7IP7IP1

2

X

X

X

X

X

X

X

X

May 30-31, 2002 COST273 TD(02)-062 14

FSR Algorithm (1)FSR Algorithm (1) Each node maintains link state information for every other

node

FSR generates route update on a periodic basis

Routing information is propagated to neighbours only

Updates occur on the basis of the Fisheye algorithm:

Nodes are divided in scopes, on the basis of their distance to the

source

Routing information for a given destination is updated with a

frequency that is inversely proportional to the scope of the

destination

May 30-31, 2002 COST273 TD(02)-062 15

FSR Algorithm (2)FSR Algorithm (2)

Fisheye scope= set of nodes within a given number of hops

Closer nodes are update more frequently than farther ones

3 or more hops3 or more hops

2 hop2 hop

1 hop1 hop

Reference nodeReference node

May 30-31, 2002 COST273 TD(02)-062 16

FSR Algorithm (3)FSR Algorithm (3)

Getting close to the destination, the routing information becomes progressively more accurate

0:{1}0:{1} 22

1:{0,2,3}1:{0,2,3} 11

2:{5,1,4}2:{5,1,4} 22

3:{1,4}3:{1,4} 00

4:{5,2,3}4:{5,2,3} 11

5:{2,4}5:{2,4} 22

0:{1}0:{1} 22

1:{0,2,3}1:{0,2,3} 11

2:{5,1,4}2:{5,1,4} 22

3:{1,4}3:{1,4} 00

4:{5,2,3}4:{5,2,3} 11

5:{2,4}5:{2,4} 22

TT HopTT Hop

0:{1}0:{1} 22

1:{0,2,3}1:{0,2,3} 22

2:{5,1,4}2:{5,1,4} 11

3:{1,4}3:{1,4} 11

4:{5,2,3}4:{5,2,3} 00

5:{2,4}5:{2,4} 11

0:{1}0:{1} 22

1:{0,2,3}1:{0,2,3} 22

2:{5,1,4}2:{5,1,4} 11

3:{1,4}3:{1,4} 11

4:{5,2,3}4:{5,2,3} 00

5:{2,4}5:{2,4} 11

TT HopTT Hop

0:{1}0:{1} 11

1:{0,2,3}1:{0,2,3} 00

2:{5,1,4}2:{5,1,4} 11

3:{1,4}3:{1,4} 11

4:{5,2,3}4:{5,2,3} 22

5:{2,4}5:{2,4} 22

0:{1}0:{1} 11

1:{0,2,3}1:{0,2,3} 00

2:{5,1,4}2:{5,1,4} 11

3:{1,4}3:{1,4} 11

4:{5,2,3}4:{5,2,3} 22

5:{2,4}5:{2,4} 22

TT HopTT Hop

11

22

33

44

55

00

May 30-31, 2002 COST273 TD(02)-062 17

Next in the line…

Bluetooth basic Ad-hoc routing algorithms

Ad-hoc On demand Distance Vector (AODV) Fisheye State Routing (FSR)

Simulation model Experimental results Conclusions and future work

May 30-31, 2002 COST273 TD(02)-062 18

Simulation platform Simulation platform

Simulator Tool: OPNET Modeler Ver. 8.0 The simulator does support

Baseband protocols Frequency Hopping, Paging, Inquiry, Scan

Link manager (LM) protocol Link layer control and adaptation protocol

(L2CAP) Connection setup/release, Sniff Mode

The simulator does not support Handover for Bluetooth units Multi-slot data packets

May 30-31, 2002 COST273 TD(02)-062 19

Model assumptionsModel assumptions

Pre-formed Scatternet Roles of master/slave/gateway are preassigned

Pure Round Robin polling strategy Nodes in a piconet have the same priority and

get polled in cyclic order 2 piconets per IPU

IPU divides it time equally between the piconets by means of the sniff mechanism

IPUs are not coordinated Network layer routing algorithms: AODV &

FSR

May 30-31, 2002 COST273 TD(02)-062 20

Scatternet topologyScatternet topology

May 30-31, 2002 COST273 TD(02)-062 21

Next in the line…

Bluetooth basic Ad-hoc routing algorithms

Ad-hoc On demand Distance Vector (AODV) Fisheye State Routing (FSR)

Simulation model Experimental results Conclusions and future work

May 30-31, 2002 COST273 TD(02)-062 22

Average end-to-end delay Average end-to-end delay (1)(1)

Simulation parameters CBR traffic: 20 kbit/sec

5 hops connection

2 gateway units (IPUs)

Results End-to-end delay grows

almost linearly with the

Sniff period

Short IP datagrams better

exploit the pipeline effect

May 30-31, 2002 COST273 TD(02)-062 23

Average end-to-end delay Average end-to-end delay (2)(2)

Simulation parameters Sniff period: 100 slots 5 hops connection

Results Short IP dtgs achieve

lower end-to-end delay but saturate earlier

Long IP dtgs incur in higher end-to-end delay but increase capacity utilization

May 30-31, 2002 COST273 TD(02)-062 24

AODV: route discovery delay AODV: route discovery delay (1)(1)

Simulation parameters Sniff period: 100 slots Route length increasing

Results Using Link Layer (AODV-

LL) messages to refresh table entries the discovery time is shorter

Path discovery query ends one hop earlier

Route discovery delay grows almost linearly with the distance of the destination

May 30-31, 2002 COST273 TD(02)-062 25

AODV: route discovery delay AODV: route discovery delay (2)(2)

Simulation parameters Sniff period ranges from

50 to 200 slots 5 hops connection

Results Route discovery delay

grows almost linearly with the Sniff period

AODV-LL shows much better performance than AODV-std

Impact of Sniff period is higher on longer path

May 30-31, 2002 COST273 TD(02)-062 26

Fisheye: control trafficFisheye: control traffic Simulation parameters

Sniff time: 50 slots Different Refresh periods Different number of scopes

Remark: # Scope=0 is the Global State Routing

Results As expected, the more the

number of scopes the less the control traffic

Refresh Times less than 0.1s absorb more than 10% of the system capacity

Refresh time must be longer than 0.1s, but this increases the route updating delay

May 30-31, 2002 COST273 TD(02)-062 27

Fisheye: update delay (1)Fisheye: update delay (1)

Simulation parameters 5 hops connection 2 scopes Sniff period: 50 slots Refresh period ranges

from 0.1 to 0.25 s Results

A refresh period of 0.1 s updates nodes 6-hop faraway from the source within 1 s

May 30-31, 2002 COST273 TD(02)-062 28

Fisheye: update delay (2)Fisheye: update delay (2)

Simulation parameters 2 scopes Sniff perriod ranges from

50 to 300 slots Refresh period:0.25 s Path length increasing

Results Update delay mainly due

to the path length Sniff period has smaller

impact

May 30-31, 2002 COST273 TD(02)-062 29

Next in the line…

Bluetooth basic Ad-hoc routing algorithms

Ad-hoc On demand Distance Vector (AODV) Fisheye State Routing (FSR)

Simulation model Experimental results Conclusions and future work

May 30-31, 2002 COST273 TD(02)-062 30

Final RemarksFinal Remarks Datagram size and Sniff period have a considerable

impact on IP end-to-end delay and AODV route discovery time

FSR refresh time must be carefully chosen AODV appears suitable in case of

Sparse connections Relaxed latency constraints Semi-static topology

FSR appears more convenient for Dense connections Dynamic and wide topology

May 30-31, 2002 COST273 TD(02)-062 31

Future workFuture work

Coming Soon (maybe…) Mathematical analysis of the scatternet

efficiency

Simulator enhancements Multi-slot packets

Handover

Comparison with Link Layer Routing algorithms

Implementation of dynamic scatternet formation

algorithms

May 30-31, 2002 COST273 TD(02)-062 32

Spare slides…Spare slides…

May 30-31, 2002 COST273 TD(02)-062 33

Table-Driven algorithmsTable-Driven algorithms Each node maintains one or more tables

with routing information for every other node

Nodes periodically exchange tables information

Algorithms differ for the number of routing-related tables and updating strategy

Examples Fisheye State Routing (FSR) Hierarchical State Routing (HSR) Wireless Routing Protocol (WRP)

May 30-31, 2002 COST273 TD(02)-062 34

On Demand On Demand algorithmsalgorithms

Nodes maintain route information only to the nodes for which there is an actual need

Routes are built on a demand basis, by means of a route discovery mechanism

Changes on the network topology are propagated only to the interested nodes

Examples Ad hoc On demand Distance Vector (AODV) Cluster Based Routing (CBR) Dynamic Source Routing (DSR) Associativity Based Routing (ABR)

May 30-31, 2002 COST273 TD(02)-062 35

Routing on Bluetooth Routing on Bluetooth scatternetscatternet

Bluetooth baseband packets contain AMA_ADDR Temporary and local meaning only

Routing must be performed above the baseband

layer!

Possible approaches Data Link Layer: Routing performed between L2CAP and IP

Routing Vector Method (RVM)

Bluetooth Network Encapsulation Protocol (BNEP)

Network Layer: routing performed at IP layer MANET algorithms

May 30-31, 2002 COST273 TD(02)-062 36

Data Link layer routingData Link layer routing

RVM lies above L2CAP and beneath IP It uses 3 bit local IDs to identify the piconets Routing is performed by means of the routing vector

mechanism Pros: simplicity, bandwidth conservation, low resources

requirement Cons: Topological changes determine address re-mapAccess CodeAccess Code Layer 2 Layer 2

HeaderHeaderLayer 2 PayloadLayer 2 Payload

FFFF DADA BFBF RVFRVF Layer 3 PayloadLayer 3 Payload

Layer 3 HeaderLayer 3 Header Layer 3 PayloadLayer 3 Payload