1. Mobile Ad hoc Networks COE 549 Routing Protocols I
Tarek Sheltami
KFUPM
CCSE
COE
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2. Outline Routing Algorithms Classifications Proactive Routing:
Table Driven Protocols
Cluster-based Protocols
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3. Routing Algorithm Classifications
Routing Algorithms
Proactive
Reactive
Hybrid
Table Driven
Cluster-based
On-Demand
Cluster-based
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4. Table Driven Protocols
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
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5. Table Driven Protocols
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
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6. Bellman-Ford Algorithm
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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7. Stage 1
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8. Stage 2
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9. Stage 3
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10. Table Driven Protocols
As the number of nodes n increases, the routing overhead increases very fast, like O(n2).
When the topology changes, routing loops may form:
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11. Destination Sequenced Distance Vector (DSDV)
One of the earlier ad hoc routing protocols developed
Its advantage over traditional distance vector protocols is that it guarantees loop freedom
Extends the classical DBF by tagging each distance entry dik(j) by a sequence number (SN) that is originated by the destination node j.
Each routing table, at each node, contains a list of the addresses of every other node in the network
Along with each node’s 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.
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12. Destination Sequenced Distance Vector (DSDV)..
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
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13. Destination Sequenced Distance Vector (DSDV)..
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 equal to or greater than the sequence number already in the routing table; otherwise the update packet is stale and ignored
If the sequence number matches the sequence number in the routing table, then the metric is compared and updated as previously discussed
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14. DSDV Routing Protocol
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15. DSDV Routing Protocol
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16. 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 DSDV’s main weakness, as Broch et al. [BRO98] found in their simulations of 50-node networks
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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

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

19. VBS..

20. VBS..

21. VBS..

22. VBS Illustrated

23. VBS Illustrated..

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

25. CGSR Illustrated

26. CGSR Illustrated ..

27. CGSR Illustrated..

28. Simulation Results

29. Simulation Results

30. Simulation Results..

31. Simulation Results..

32. Some issues about pure Cluster-based Routing (VBS)
Range of node #1
Routing in VBS
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33. Some issues about pure Cluster-based Routing (VBS)
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34. Some issues about pure Cluster-based Routing (VBS)
Routing in VBS
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35. Drawback of VBS
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
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