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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 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 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