Location Based Routing for MANETS

1
Location Based Routing for MANETS

• Author Ljubica Blazevic
• Author Jean-Yves LeBoudec
• Author Silvia Giordan
• Presenter Douglas Pepelko

2

• Problem Holes
• Holes are areas where the are few/no nodes
• Old solution was to route in geographic direction
  until hole was hit
• Then route around hole in perimeter mode
• Not the best way. Ex Going from to Egypt from
  France would cause us to travel down to Italy,
  then Greece, and around.

3
Problem Mobility

• When nodes move finding them with old routing
  techniques no longer work
• A nodes location may be very transient. Suppose
  the node is in a car moving 60mph

4
Solution Terminode Routing

• Link state mechanism
• Nodes maintain some routing information
• Anchor areas
• Allows nodes to route around holes
• Restricted Local Flooding (RLF)
• Allows us to search a limited area using
  flooding
• If a node has moved, it can still be found

5
Overview of Routing Methods

• Terminode Remote Routing (TRR)
• Routing when destination is more than 2 hops
• Link state routing
• Similar to geographic routing except that anchors
  are used
• Terminode Local Routing (TLR)
• Broadcast using RLF or use TLR table when
  destination is within two hops

6
Anchors

• Anchors are geographic areas
• Similar to a zip code
• Not a specific node
• Used to select a route to a destination
• I would have called them zip codes or anchor
  areas or something else to avoid conflicting
  with the common use of the term anchor

7
Friends

• Friend Assisted Path Discovery (FAPD)
• Helps nodes find routes (Knows how to get places)
• Certain percentage of node preconfigured to be
  FAPD responders
• Can find other friends

8
Other Terms

• EUI - End-system Unique Identifer
• An address (like an IP address)
• LDA - Location Dependent Address
• Geograpical Coordinates (x, y)
• RLF - Restricted Local Flooding
• Described later
• TLR,TRR - Terminode Remote/Local Routing
• Routing techniques used throughout

9
Restricted Local Flooding

• RLF is used when local communication is needed
  but the exact location is not known
• Packets are sent with a source location, a max
  distance and the RLF flag set
• Any node that receives a packet at a distance
  greater than the max distance from source
  location and the RLF flag set does NOT repeat the
  message
• Otherwise the message is repeated just as in
  regular flooding

10
Friends Finding Friends

• All preconfigured FAPD nodes use RLF
• Broadcast a get_friends_request
• Four (4) packets are sent in opposite directions
• Presumably North South East and West
• Sent with no destination address EUI
• Sent with a location LDA
• Other friends respond with their lists
• Lists are merged and sent to other friends on
  request

11
Nodes in the 'hood'

• A node must know its neighbourhood
• Broadcasts a HELLO with LDA and EUI
• Listens for other HELLOs and builds a TRL table'
• Table has links up to two (2) hops away
• Creates a Gabriel Graph
• Spatial proximity
• A node may posses density maps to assist in
  Geographic Map-based Path Discovery (GMPD)

12
There and Back Again

• A node wants to send a packet
• Destination is local Easy, just turn on Use
  TLR bit and send via the TLR table
• Destination is remote Several steps
• Obtain an LDA (a geographic location)
• Send using TRR without Anchors.
• Send to closest neighbour in the TLR table
• Obtain feedback about route taken
• Attempt to optimize route using anchors

13
Forwarding a Packet

• A node receives a packet
• For me? Keep it
• Local? Use the TRL table
• TRR termination
• If location is in transmission range but packet
  is not in TRL table
• Attempts to find node using RLF (flooding)
• Sends six (6) packets in different direction
• Max distance is set to twice the transmission
  range

14
What about Anchor Paths

• Geographic routing produces poor path in some
  cases
• If a node sends a packet and then determines that
  the path taken was non-optimal it can attempt to
  compute a better anchor path
• Node sends an anchored path request using RLF in
  four (4) directions.

15
An FAPD Receives an Anchor Request

• A FAPD gets a request
• If it is closer to the destination or has an
  anchor path to the destination it appends its
  geographic location (and the rest of the path if
  available) to the list
• Otherwise it sends the packet on to the
  destination
• TABU index
• How far backwards the packet can move from the
  destination
• If no friends are closer to destination, head
  backwards, but increment tabu
• Check that tabu never exceeds max_tabu of two (2)

16
Destination Receives Anchor Path Search Packet

• Destination gets a long list of anchors
  accumulated in packet
• Destination simplifies path
• Reduce number of anchors
• Set timers on path freshness

17
Source uses GMPD to find path

• If a node knows network density it can use this
  determine a good path.
• High node density areas are towns
• Towns are connected by highways
• Much like a second layer of connectivity
• Use an atlas to get you across the country
• Use a city map to get you to a street

18
(No Transcript)
19
Performance

• The authors claim that this method works better
  than all other methods
• As good as GPSR when location accuracy is high,
  but better when location accuracy is low
• Better than GPSR when there are holes
• Same as AODV and LAR1 with small nets but better
  than both in a large network or when dealing with
  mobility

20
What did they test?

• Packet deliver fraction
• Ratio of packets delivered / total packets
  generated by CBR (constant bit rate) source
• Average end-to-end delay
• How long did it take to get the data there
• Includes delay in route discovery and waiting for
  LDA
• Normalized routing load
• Number of control packets per data packet
  delivered at destination

21
Nodes movin' and groovin'

• To simulate a real network nodes must move
• Random nodes
• Node chooses a random waypoint then moves at a
  random speed (1-20m/sec)
• Node pauses at destination for a random time
• Restricted Random nodes
• Some nodes are town nodes and are more likely to
  stay in town
• Some nodes are commuters and move between towns.
• Finally some are stationary nodes. They don't
  move.

22
Small unobstructed network
It certainly seems better tan LAR1 or AODV
23
GPSR is hurt by holes. GMPD seems the winner
here.
24
RLF (restricted local flooding) helps quite a
bit If a node has moved, it usually has not gone
too far. RLF can find it.
25
Conclusions

• Terminode is a mish-mash of several things
• Should have been separated into different papers
• RLF Assumes nodes are going to move after being
  located. Assumes that they don't move too far.
  Broadcasts in the area of the last known location
• Could be improved by calibrating the distance
  based on the measured mobility of nodes
• Could use the LDA dest as center of Broadcast
  area
• TRR using towns/highways (GMPD) seems like a good
  idea
• Results show it is one of the better algorithms
• Requires density maps though

26
References

• 1 BLAZEVIC05 http//people.cs.vt.edu/irchen/
  6204/pdf/BLA05-sensor-routing.pdf
• 2 SAVCHENKO http//cgm.cs.mcgill.ca/godfried/
  teaching/projects.pr.98/sergei/project.html
• 3 MAURO http//www.i-cherubini.it/mauro/blog/2
  005/10/17/the-gabriel-graph/