Table Driven Protocols 8/7/20154 Distance Vector Protocols such
as: Wireless Routing Protocol (WRP) [MUR96] Destination Sequenced
Distance Vector (DSDV) routing protocol [PER94] Least Resistance
Routing (LRR) [PUR93] The protocol by Lin and Liu [LIN99]. Link
State Protocols such as: Global State Routing (GSR) [CHE98] Fisheye
State Routing (FSR) [PEI00a] Adaptive Link-State Protocol (ALP)
[PEI00a] Source Tree Adaptive Routing (STAR) [ACE99] Optimized Link
State Routing (OLSR) protocol [SHE03b] Landmark Ad Hoc Routing
(LANMAR) [PEI00b] However the most prominent protocol is DSDV
Slide 5
Table Driven Protocols 8/7/20155 Try to match the link state
and distance vector ideas to the wireless environment Each node
only needs to know the next hop to the destination, and how many
hops away the destination is: This information stored in each node
is often arranged in a table, hence the term table-driven routing
Such algorithm are often called distance vector algorithms, because
nodes exchange vectors of their known distances to all other nodes
An example is the Bellman-Ford algorithm, one of the first ones to
be used for routing in the Internet
Slide 6
Bellman-Ford Algorithm 8/7/20156 Consider a collection of
nodes, connected over bi-directional wired links of given delays.
We want to find the fastest route from each node to any other node.
An example network: Initially, each node knows the distances to its
direct neighbors, and stores them to its routing table. Nodes other
than their direct neighbors are assumed to be at an infinite
distance. Then, nodes start exchanging their routing tables.
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Stage 1 8/7/20157
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Stage 2 8/7/20158
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Stage 3 8/7/20159
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Table Driven Protocols 8/7/201510 As the number of nodes n
increases, the routing overhead increases very fast, like O(n 2 ).
When the topology changes, routing loops may form:
Slide 11
Destination Sequenced Distance Vector (DSDV) 8/7/201511 One of
the earlier ad hoc routing protocols developed Its advantage over
traditional distance vector protocols is that it guarantees loop
freedom Each routing table, at each node, contains a list of the
addresses of every other node in the network Along with each nodes
address, the table contains the address of the next hop for a
packet to take in order to reach the node In addition to the
destination address and next hop address, routing tables maintain
the route metric and the route sequence number.
Slide 12
Destination Sequenced Distance Vector (DSDV).. 8/7/201512 The
update packet starts out with a metric of one The neighbors will
increment this metric and then retransmit the update packet. This
process repeats itself until every node in the network has received
a copy of the update packet with a corresponding metric If a node
receives duplicate update packets, the node will only pay attention
to the update packet with the smallest metric and ignore the
rest
Slide 13
Destination Sequenced Distance Vector (DSDV).. 8/7/201513 To
distinguish stale update packets from valid ones, the original node
tags each update packet with a sequence number The sequence number
is a monotonically increasing number, which uniquely identifies
each update packet from a given node If a node receives an update
packet from another node, the sequence number must be greater than
the sequence number already in the routing table; otherwise the
update packet is stale and ignored
Slide 14
15/4/200314 DSDV Routing Protocol
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15/4/200315 DSDV Routing Protocol
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15/4/200316 Disadvantages of DSDV Protocol Routing is achieved
by using routing tables maintained by each node The bulk of the
complexity in generating and maintaining these routing tables If
the topological changes are very frequent, incremental updates will
grow in size This overhead is DSDVs main weakness, as Broch et al.
[BRO98] found in their simulations of 50- node networks
Slide 17
Virtual Base Station (VBS) All nodes are eligible to become
clusterhead / VBS Each node is at one hop from its clusterhead
Clusterhead / VBS is selected based on the smallest ID Gateways /
Boarder Mobile Terminals (BMTs) Clsuterheads and Gateways form the
virtual backbone of the network
Slide 18
VBS.. Every MT has an ID number, sequence number and my_VBS
variable Every MT increases its sequence number after every change
in its situation An MT my_VBS variable is set to the ID number of
its VBS; however, if that MT is itself a VBS, then the my_VBS
variable will be set to 0, otherwise it will be set to 1,
indicating that it is a VBS of itself
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VBS..
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VBS Illustrated
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VBS Illustrated..
Slide 24
CGSR infrastructure Creation CGSR uses the Least Cluster Change
(LCC) clustering algorithm No clusterheads in the same transmission
range Each Cluster has a different code to eliminate the
interference, typically the suggest 4 Walsh codes
Slide 25
CGSR Illustrated
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CGSR Illustrated..
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Simulation Results
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Simulation Results..
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15/4/200332 Range of node #1 Routing in VBS Some issues about
pure Cluster-based Routing (VBS)
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15/4/200333 Some issues about pure Cluster-based Routing
(VBS)
Slide 34
15/4/200334 Routing in VBS Some issues about pure Cluster-based
Routing (VBS)
Slide 35
Drawback of VBS 8/7/201535 All the nodes require the aid of
their VBS(s) all the time, so this results a very high MAC
contention on the VBSs the periodic hello message updates are not
efficiently utilized by MTs (other than VBSs and BMTs) The power of
the nodes with small IDs drain down much faster than that with
large IDs
Slide 36
36 Nodes Classifications: myCH = 0 Clusterhead myCH = -1 Free
node myCH > 0 Zone_MT WEAC Infrastructure Creation Protocol
4/29/2008 An MT is eligible to be a clusterhead and willing to
accept other MTs to be under its supervision if these MTs have a
lower EL An MT ignores any merge request messages that are sent to
it by other MTs. However, if the MT is serving as a clusterhead, it
will remain a clusterhead If an MT is serving as a clusterhead, it
sets its warningThreshold flag to true, informing its zone_MTs to
look for another clusterhead, nonetheless, they can remain with it
till its BPL drains down to THRESHOLD_3 An MT ignores any merge
request messages and will send iAmNoLongerYourCH message to all the
nodes under its supervision, if it was serving other nodes
Slide 37
List of MTs 5 WEAC Infrastructure Creation Protocol.. Merge REQ
Merge Accpt. myCH = 20myCH = -1 myCH = 0 20 5 BPL > THRESHOLD_1
BPL < THRESHOLD_1 An MT sends a merge-request message to another
MT if the latter has a higher energy level and it should be >
Threshold_1 8/7/201537
Selecting Gateways The least number of neighbors method The
highest energy level method The Gateway Selection Algorithm
8/7/201542
Slide 43
The Gateway Selection Algorithm 1.if(there is more than one
access to DEST){ 2. Select the MT with EL > THRESHOLD_2; 3.
if(more than one with EL THRESHOLD_2){ 4.
getTheLeastNumberOfNeighbors(); 5. select the one with the least
number of neighbors; 6. } 7. elseif(MTs EL < THRESHOLD_2) 8.
choose the one with the highest EL(); } 8/7/201543
Slide 44
Table update for zone_MTs 1.if(myCH > 0) 2. if(DEST my
neighbor || DEST my neighbors neighbor){ 3. set this neighbor as
the next hop; 4. if(more than one neighbor to the DEST) 5. run
Gateway Selection Algorithm(), 6. } 7. else 8. set myCH as the next
hop 8/7/201544
Slide 45
Table update for clusterheads and free_MTs 1.if(myCH 0) 2.
update routing table according to the received tables 3. if(the
DEST my neighbor || my neighbor s neighbor){ 4. set this neighbor
as the next hop 5. if(more than one neighbor to the DEST) 6. run
Gateway Selection Algorithm(); } 7. else if(available route to the
DEST) 8. keep the current route till the next update; 9. else 10.
set the DEST to null; 8/7/201545