Approach for Reducing Control Packets in AODV-based MANETs

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Approach for Reducing Control Packets in
AODV-based MANETs

• Espes, D.   Teyssie, C.   IRIT-Paul Sabatier
  University, FranceUniversal Multiservice
  Networks, 2007. ECUMN '07. Fourth European
  Conference on ?????

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Outline

• 1. Introduction
• 2. Previous Work
• 3. Proposed routing algorithm
• 4. Simulation
• 5. Conclusion

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1. Introduction (1/3)

• Many routing protocols have been proposed for
  MANETs and they may be categorized as proactive
  such as OLSR or reactive protocols such as AODV.
• When reactive protocols create a route, they
  broadcast many control packets which may be
  useless.
• It is important to direct control packets only
  towards the destination, not in all directions.

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1. Introduction (2/3)

• In this paper , the authors go further in
  enhancing AODV capabilities by assuming that
  nodes use the GPS to determine their location.
• It is necessary that the destination sends its
  location to the source.
• Indeed, nodes have to use a high level (or extra)
  network to transmit their location.
• 
  

backbone network
no infrastructure is necessary to communicate
location-related information
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1. Introduction (3/3)

• Nodes use two frequencies, one for ad hoc network
  and another for backbone network.
• The backbone network frequency is the highest and
  has large coverage range. (only particular nodes)
• Data are transmitted over the ad hoc network
  frequency.
• Our objective in this paper is the proposal of a
  routing algorithm which
• Uses a backbone network to get the destination
  location.
• When a source knows the destination location, it
  broadcasts a route creation request limiting the
  search area.

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2. Previous Work (1/4)

• Backbone network

Backbone network
Regular ad hoc network
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2. Previous Work (2/4)

• High capacity nodes serve either Backbone Nodes
  (BNs) .They have a high capacity of storage, high
  processing resources, low power and high power
  radio modules which transmit and receive data and
  control packets using two different frequency
  bands simultaneously.
• Low capacity nodes act merely as Regular Nodes
  (RNs). RNs are limited in their power, storage,
  processing and communications assets and only use
  a single low power radio module.

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2. Previous Work (3/4)

• Ad hoc routing with localization information
• Greedy Perimeter Stateless Routing (GPSR)
• The next hop of a route is always the mobile
  terminal closest to the destination.
• The authors make an assumption that there exists
  a location server ? node has to know the server
  address to call

D
S
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2. Previous Work (4/4)

• Location-Aided Routing protocol (LAR) Routing
• Requests are not flooded in the network, but
  forwarded only towards the destination to reduce
  the routing overhead.
• However, sources dont determine destination
  location.

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3. Proposed routing algorithm(1/15)

• Reducing the zone during route request broadcast
  decreases the number of control packets and
  prevents some nodes from hearing the request.
• It has two routing levels
• one to find destination locations ( location
  routes )
• another to select routes ( data routes ?AODV )

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3. Proposed routing algorithm(2/15)

• Destination localization
• When nodes find the destination location, they
  use the backbone network
• Avoids disturbing the regular nodes.
• Each backbone node knows the list of nodes which
  are associated with it.
• When a source needs a destination location, it
  broadcasts a request on the backbone network.

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3. Proposed routing algorithm(3/15)

• When a source, which is a regular node, needs the
  location of a destination, it sends a Location
  Request (LReq) to its backbone node. When its
  backbone node receives this LReq packet, it keeps
  in its location route table the source address.
• When a source, which is a backbone node, needs
  the location of a destination, it directly
  broadcasts a LReq packet on the backbone network.

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3. Proposed routing algorithm(4/15)

• When the destination (which may be a backbone
  node or a regular node) receives a LReq packet,
  it sends a Location Response (LRep) packet to the
  source via the reverse location route.
• The LRep packet contains the destination
  coordinates.
• When the source receives the LRep packet, it
  creates and broadcasts to its neighbors an AODV
  route request composed of
• traditional parameters
• destination and source addresses, sequence
  numbers, and hop count
• location-oriented parameters
• the distance from the source to the destination,
  destination coordinates

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3. Proposed routing algorithm(5/15)

• Data route selection
• Our routing algorithm is based on AODV protocol
  and enables to decrease the number of RREQ
  request

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3. Proposed routing algorithm(6/15)

• Property 1 Given a line Y aX b passing
  through points S and D where a ?0

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3. Proposed routing algorithm(7/15)

• Property 2? Yd ?Yd1 , Yd2 if
• XDgtXS ? agt0 ? XDltXS ? alt0 , Yd gtYD else
  Yd ltYD.

Case a gt 0
Case a lt 0
Yd YD
Yd YD
XS XD
XD XS
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3. Proposed routing algorithm(8/15)

• Property 3 Given a line Y b passing through
  points S and D, ? Xd1 XD -ß, Xd2 XD ß Xd1,
  Xd2 are the X-coordinates of points with a
  distance ß to D.
• If XD gtXS ? Xd XD ß else if XD ltXS ? Xd
  XD -ß

Y b
Xs XD Xd
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3. Proposed routing algorithm(9/15)

• Property 4 Given a line Y aX b passing
  through points S and D, the point C has the
  coordinates
• The point C has the coordinates

sin?
Sdtana
Sdtanacos?
sin?
?
Sdtanasin?
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3. Proposed routing algorithm(10/15)

• Property 5 Given a line X b passing through
  points S and D,
• if YD gtYS ? Yd YD ß, else if YD ltYS ?
  Yd YD -ß

X b
Yd YD Ys
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3. Proposed routing algorithm(11/15)

• Property 6 Given a line X b passing through
  points S and D, the point C has the coordinates
• The point C has the coordinates

X b
Sdtana
Yd
Xc Xc
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3. Proposed routing algorithm(12/15)

• When a source needs a data route to a destination
• First obtain the destination location using the
  localization phase .
• Transmit the AODV RREQs , which including (XD,
  YD), (XS, YS) and the value of a.
• It calculates the search area. If it is inside
  this area, it transmits the data route request.
• Route search may fail for a selected zone. In
  this case, a timer should be used to be able
  either to make another search or to use standard
  AODV protocol.

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3. Proposed routing algorithm(13/15)

• Route repair mechanism
• When a link breakage is detected by the source,
  it must recreate a route if still needed to send
  data.
• We propose that during data transmission, the
  destination periodically sends its location and
  eventually some parameters (such as its new
  speed, direction) to the source.

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3. Proposed routing algorithm(14/15)

• Two methods can be used to transmit location
  information to the source by the backbone
  network.
• The first one is to broadcast location packets
  over the backbone network.
• A second one is that
• During LReq forwarding , backbone nodes keep in
  their location route table the previous backbone
  node .
• When a data route is created, the destination
  sends a movement packet (Mov) to the source at
  regular intervals via the backbone network.
• At the reception of a Mov packet, the backbone
  node forwards it to the previous node towards the
  source.

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3. Proposed routing algorithm(15/15)

• As all the nodes in the network may move, regular
  nodes (in particular source and destination) may
  loose their association with their backbone
  nodes, or backbone node may break down.
• For a destination node, the former association
  backbone node of this destination detects the
  association loss and then it sends via the
  location route a repair location warning (RLWar)
  to each backbone node associated with appropriate
  sources.
• For a source node, to recreate location route.

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4. Simulation (1/4)

• Simulation model
• Simulator NS-2.
• Nodes movement uses the Random Way Point (RWP)
  model.
• Square with length equal to 1000m
• Maximum velocity of 20 m/s.
• All nodes are associated with a backbone node.
• The data packet length is 500 bytes/s.
• The number of flows is randomly fixed.

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4. Simulation (2/4)

• Results
• Figure 4 shows the number of requests per
  connection according to the number of nodes in
  the network.

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4. Simulation (3/4)

• Figure 5 shows the percentage of paths not found
  with the number of nodes in the network. The
  numbers of route not found during the connection
  establishment phase decreases with the value of a
  and the number of nodes.

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4. Simulation (4/4)

• Figure 6, the average time to obtain the
  destination location is equal to 1.4 ms. Such a
  time is low.

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5. Conclusion (1/1)

• In this paper, we present a location-based
  routing protocol for MANETs.
• To reduce the number of control packets, we
  modify the AODV protocol to limit the search
  area.
• We preserve the coherence in the backbone network
  to inform periodically the source of destination
  movements. So, source reinitiates the route
  without use the localization phase.
• The algorithm decreases the number of requests by
  60 compared to the LAR algorithm.