Rep

TOWARDS RELIABLE DATA

DELIVERY FOR HIGHLY DYNAMIC

MOBILE ADHOC NETWORKS

Project Guide:

Ms D.Usha M.C.A., M.Phil, M.Tech,

Submitted By

M.Subhashri

M.Saranya

K.Sureka

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CONTENTS

ABSTRACT

INTRODUCTION

EXISTING SYSTEM

PROPOSED SYSTEM

MODULES

MODULES DESCRIPTION

SYSTEM ARCHITECTURE

FLOW DIAGRAM

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ABSTRACT

Mobile Ad-hoc Network is an infrastructureless and decentralized network which

need a robust dynamic routing protocol. Many routing protocols have been proposed to

accommodate the needs of communications for MANET.

In this project, there is problem in delivering data packets for highly dynamic mobile ad hoc

networks in a reliable and timely manner. Most existing ad hoc routing protocols are

susceptible to node mobility, especially for large-scale networks. Driven by this issue, an

efficient Position based Opportunistic Routing protocol (POR) was introduced. It takes

advantage of the stateless property of geographic routing and the broadcast nature of wireless

medium. When a data packet is sent out, some of the neighbor nodes that have overheard the

transmission will serve as forwarding candidates, and take turn to forward the packet if it is

not relayed by the specific best forwarder within a certain period of time.

The additional latency incurred by local route recovery is greatly reduced and the

duplicate relaying caused by packet reroute is also decreased. In case of communication hole,

a Virtual Destination based Void Handling (VDVH) scheme is further proposed to work

together with POR. To enhance the robustness of POR in the network where nodes are not

uniformly distributed and large holes may exist, a complementary void handling mechanism

based on virtual destination is proposed.

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1. INTRODUCTION

A Mobile Ad-hoc Network (MANET) is a self-configuring infrastructure less network

of mobile devices connected by wireless links. The topology of the MANET may change

uncertainly and rapidly due to the high mobility of the independent mobile nodes, and

because of the network decentralization, each node in the MANET will act as a router to

discover the topology and maintain the network connectivity.

The following are the advantages of MANETs:

They provide access to information and services regardless of geographic position.

These networks can be set up at any place and time.

The set of applications for MANETs is diverse, ranging from large-scale, mobile, highly

dynamic networks, to small, static networks that are constrained by power sources. Besides

the legacy applications that move from traditional infrastructure environment into the ad hoc

context, a great deal of new services can and will be generated for the new environment.

Some of the applications of MANETs are

Military or police exercises.

Disaster relief operations.

Mine cite operations.

Urgent Business meetings.

Due to the error prone wireless channel and the dynamic network topology, reliable

data delivery in MANETs, especially in challenged environments with high mobility

remains an issue. Traditional topology based MANET’s routing protocols are quite

susceptible to node mobility. Owing to the constantly and even fast changing network

topology, it is very difficult to maintain a deterministic route. The discovery and recovery

procedures are also time and energy consuming. Once the path breaks, data packets will

get lost or be delayed for a long time until the reconstruction of the route, causing

transmission interruption. No end-to-end routes need to be maintained, leading to high

efficiency and scalability. The neighbor which is relatively far away from the sender is

chosen as the next hop. If the node moves out of the network the transmission will fails.

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There will be n number of candidates among the network, if the best candidate does not

forward the packet in certain time slots, suboptimal Candidates will take turn to forward

the packet according to a locally formed order.

2. EXISTING SYSTEM

In Existing system there are so many protocols are used. Some of the protocols are

Dynamic Source Routing (DSR)

Ad Hoc On-Demand Distance Vector Routing (AODV)

Greedy Perimeter Stateless Routing(GPSR)

Dynamic Source Routing

The Dynamic Source Routing (DSR) protocol is an on demand routing protocol that is based

on the concept of Source Routing. Source Routing is a technique where by the sender of a

packet can specify the route that a packet should take through the network. .The DSR

protocol is composed of two mechanisms of Route Discovery and Route maintenance, which

works together to allow nodes to discover and maintain source routes to destination in the

adhoc network.

Route Discovery, by which a node S wishing to send a packet to a destination node D

obtains a source route to D. Route Discovery, is used only when S attempts to send a packet

to D and does not already know a route to it.

When Route Maintenance indicates that a source route is broken, S can attempt to use

any route to D or it can invoke Route discovery again to find a new route. Route Maintenance

is used only when S is actually sending packets to D.

The Disadvantages of the DSR are

Packet header size grows with route length due to source routing

Flood of route requests may potentially reach all nodes in the network 

Potential collisions between route requests propagated by neighboring nodes

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Increased contention if too many route replies come back due to nodes replying using their local cache

Route Reply: A->B ->C ->F ->C ->D ->E Repeated node

Fig 2.1

The fig2.1 shows that source node A wishes to send the packet to the destination node E.

Because of source routing, the node C is repeated. This may lead to wastage of time to reach

destination.

Adhoc on- Demand Routing Protocol (AODV) The AODV Routing protocol uses an on-demand approach for finding routes, ie, a route

is established only when it is required by a source node for transmitting data packets. When a

source node desires to send to some destination node and does not already have a valid route

to that destination, it initiates a path discovery process to locate the destination.

Disadvantage of this protocol is that intermediate nodes can lead to inconsistent routes if the

source sequence number is very old and the intermediate nodes have a higher but not the

latest destination sequence number, thereby having stale entries. Also, multiple Route Reply

packets in response to a single Route Request packet can lead to heavy control overhead.

Another disadvantage of AODV is unnecessary bandwidth consumption due to periodic

beaconing.

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B D E

C

F

A

Fig 2.2: The data packet was not delivered to the destination In this fig 2.2, Routing discovery happens when a node wants to communicate with a

destination while it obtains no proper route entry for that destination. In this situation, this

source node (originator) will broadcast an RREQ (Routing REQuest) message to all its

neighbors. Each neighbor who receives this RREQ will check in its own routing table if it

contains the route entry for that destination. If not, it will set up a reverse path towards the

originator of RREQ and rebroadcast this routing request. Any node which receives this

RREQ will generate a RREP (Routing REPly) message if it either has a fresh enough route to

satisfy the request or is itself the destination. Then this intermediate or destination node will

generate an RREP message and unicast it to the next hop toward the originator of the RREQ,

as indicated by the routing entry for that originator. When a node receives an RREP message,

it first updates some fields of the route table and the routing reply, and then forwards it to the

next hop towards the originator. When a Source node receives a RERR (Routing ERRor)

message, it shows that the packets are not reached the destination successfully.

Greedy Perimeter Stateless Routing (GPSR)

Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless

datagram networks that uses the positions of routers and a packet’s destination to make

packet forwarding decisions. GPSR makes greedy forwarding decisions using only

information about a router’s immediate neighbors in the network topology. When a packet

reaches a region where greedy forwarding is impossible, the algorithm recovers by routing

around the perimeter of the region.

Greedy forwarding great advantage is its reliance only on knowledge of the forwarding

node’s immediate neighbors. The state required is negligible and dependent on the density of

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nodes in the wireless network, not the total number of destinations in the network. On

networks where multi-hop routing is useful, the number of neighbors within a node’s radio

range must be substantially less than the total number of nodes in the network. The

disadvantages of this protocol are

Fig 2.3

In fig 2.3 the greedy forwarding method is used. X is the source node which has two nearest neighbors w and y. But w and y are farther from D which is destination node. So the greedy forwarding failure will occur.

3. PROPOSED SYSTEM:

There are some disadvantages in the existing protocols, to overcoming that protocol by using

new routing protocols namely

Position based Opportunistic Routing Protocol (POR)

Virtual Destination based Void Handling Mechanism (VDVH)

3.1 Position based Opportunistic Routing Protocol (POR)

The design of POR is based on geographic routing and opportunistic forwarding. The nodes

are assumed to be aware of its own location and the positions of its direct neighbors.

Geographic Routing (GR) uses location information to forward data packets, in a hop-by-hop

routing fashion. The concept of opportunistic forwarding is to select and prioritize the

forwarding candidates. The forwarding candidates cache the packet that has been received

using MAC interception. If the best forwarder does not forward the packet in certain time

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slots, suboptimal candidates will take turn to forward the packet according to a locally

formed order. We analyze the effect of node mobility on packet delivery and explain the

improvement brought about by the participation of forwarding candidates. Due to the

selection of forwarding area and the properly designed duplication limitation scheme, POR’s

performance gain can be achieved at little overhead cost.

3.1.1 Selection and prioritization of forwarding Candidates

One of the key problems in POR is the selection and prioritization of

forwarding Candidates. Only the nodes located in the forwarding area would get the chance

to be backup nodes. The forwarding area is determined by sender and the next hop node.

A node located in the forwarding area, satisfies following two conditions:

It makes positive progress towards the destination.

Its distance to the next hop node should not exceed half of their transmission range of

a wireless node (i.e. R/2}.

The priority of a forwarding candidate is decided by its distance to the destination. The nearer

it is to the destination, the higher priority it will get.

Algorithm Used:

Candidate selection algorithm:

First, initialize the candidate selection to select and prioritize the forwarder list. Only the

nodes specified in the candidate list will act as forwarding candidates. The lower index of

the node in the candidate list has higher priority. Thus the candidate selection algorithm is

used to select best forwarding candidates in the POR routing protocol.

3.1.2 Limitation on Possible Duplicate Relaying

Due to collision and nodes movement, some forwarding candidates may

fail to receive the packet forwarded by the next hop node or higher-priority candidate, so that

a certain amount of duplicate relaying would occur .To limit such duplicate relaying, only the

packet that has been forwarded by the source and the next hop node is transmitted in an

opportunistic fashion and is allowed to be cached by multiple candidates.

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3.1.3 MAC Modification and Complementary Techniques

3.1.3.1 MAC Interception

The broadcast nature of 802.11 MAC was all nodes within the

coverage of the sender would receive the signal. However, its RTS/CTS/DATA/ACK

mechanism is only designed for unicast. It simply sends out data for all broadcast packets

with CSMA. Therefore packet loss due to collisions would dominate the performance of

multicast like routing protocols. Here, did some alteration on the packet transmission

scenario. In the network layer, just send the packet via unicast, to the best node which is

elected by greedy forwarding as the next hop. In this way, make full utilization of the

collision avoidance supported by 802.11 MAC .It is then further processed by POR. Hence the

benefit of both broadcast and unicast (MAC support) can be achieved.

3.1.3.2 MAC Callback

When the MAC layer fails to forward a packet, the function

implemented in POR –Mac_ callback will be executed. The item in the forwarding table

corresponding to that destination will be deleted and the next hop node in the neighbor list

will also be removed. If the transmission of the same packet by a forwarding candidate is

overheard, then the packet will be dropped without re-forwarding again, otherwise it will be

given a second chance to reroute. The packets with the same next hop in the interface queue

which is located between the routing layer and MAC layer will also be pulled back for

rerouting. As the location information of the neighbors is updated periodically, some items

might become obsolete very quickly especially for nodes with high mobility.This scheme

introduce a timely update which enables more packets to be delivered.

3.1.3.3 Interface Queue Inspection

One of the key points of POR is that when an intermediate node

receives a packet with the same ID (i.e. same source address and sequence number), it means

a better forwarder has already taken over the function. Hence, it will drop that packet from its

packet list. Besides maintaining the packet list, check the interface queue. When the packet

arrives at the routing layer, the same packet might have already been sent down to the lower

layers by the current node. With additional inspection of the interface queue, it further

decreases the duplicate packets appearing in the wireless channel.

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3.1.4 Analysis

In this section, theoretical analysis on the robustness of POR will be conducted. The

overhead inclusive of memory consumption and duplicate relaying will also be discussed.

Since the focus lies on the effect of node mobility, an ideal wireless channel is assumed in the

following part and the unit disc graph model will be used by default: a link between two

nodes exists if and only if the distance between them is less than a certain threshold. When

two nodes are located inside each others’ coverage range (R), bidirectional data transmission

between them can be achieved without failure.

Fig. 3.1.4. (a) Network model. (b) Out of range caused by node’s movement.

Owing to node mobility, it is impossible that the location information of a node’s neighbors

which is maintained through beacon exchange is always up to date. Therefore, an error disc

b(x, re) corresponding to each neighbor exists from the current node’s perspective, with x as

the latest obtained coordinate of the neighbor. The radius of the error disc re is the maximum

deviation from x and the value of re varies with the elapsed time, t, since the last update and

is defined as follows

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re (t) = vr^m· t, 0 ≤ t < δt (1)

Where vr^m represents the maximum relative speed and δt is the neighbor update interval..

Assume there are N forwarding candidates. Let us denote C0 as the next hop and Ci, i∈ [1,

N] as the forwarding candidates, so Ci, i∈ [0, N] is generally referred to as a forwarder. At a

specific elapsed time t since the last update, given the values of the nodes’ relative speeds Vr

= v, the deviation from the latest updated location of Ci can be expressed as follows:

ri (t, v) = v · t, 0 ≤ t < δt (2)

Further, given the distance between Ci and S, Li = l (0 <l ≤ R), that only if ri (t, v) +l >R,

then Ci may move out of S’s transmission range, and the corresponding probability is given

by

pi (t, v, l) = P {Ci is out | t, Vr = v, Li = l} = {βi (t, v, l)/π, vt + l > R,

{0 otherwise. (3)

where 2βi (t, v, l) represents the range of direction towards which the movement of Ci will

cause it to be out of S’s transmission range in βi (t, v, l) can be expressed as

βi (t, v, l) = arc cos (R^2-l^2-(vt) ^2) (2l.vt) (4)

Where βi grows as the value of vt increases, leading to a higher probability of Ci

moving out of S’s range.

Without loss of generality, packet forwarding time from S to Ci is uniformly distributed in [0,

δt). Thus give the average probability that Ci has moved out of S’s transmission range when a

packet from S is being sent to Ci as

R 2vmax δt

Pi = ∫ ∫ ∫ pi (t, v, l) 1 dt ƒ Vr (v) dv ƒLi (l) dl (5) 0 0 0 δt

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where ƒVr (v) and ƒLi (l) are the probability distribution function of Vr and Li, respectively. ƒVr (v) = 1 ∫ ∫ ƒ Vr (v| V1=v1; V2=v2) dv1 dv2 ln^2(v max) v1v2 v min

After the formulation of pi, we can give the probability (for one hop) that when a packet is

being sent from S, at least one of the N +1 potential forwarders4 succeeds in receiving the

packet (i.e. is still within the transmission range of S) as follows

Psucc = {P {NF > 1} (1-p0), N=0

P {NF > 1} Phop^N, N > 1.

Where NF is the number of nodes that make positive progress towards the destination. N = 0

corresponds to the traditional ad hoc routing protocols where no forwarding candidates

participates. Phop^N represents the probability that a packet can be successfully delivered

when at most N (N ≥ 1) forwarding candidates are involved and it is expressed as follows

N-1 i N

Phop^N = ∑ P {NC=i} (1-∏ pj) + P {NC > N} (1-∏ pj)

i=0 j=0 j=0

Where NC is the number of potential candidates located in the forwarding area

3.2 Virtual Destination based Void Handling Mechanism (VDVH)

3.2.1 Trigger node

In many existing geographic routing protocols, the mode change

happens at the void node. Then Path 1 (A-B-E-· · ·) and/or Path 2 (A-BC-F-· · ·) (in some

cases only Path 1 is available if Node C is outside Node B’s transmission range) can be used

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to route around the communication hole. It is obvious that Path 3 (A-C-F-· · ·) is better than

Path 2. If the mode switch is done at Node A, Path 3 will be tried instead of Path 2 while Path

1 still gets the chance to be used. A message called void warning, which is actually the data

packet returned from Node B to Node A with some flag set in the packet header, is

introduced to trigger the void handling mode. As soon as the void warning is received, Node

A (referred to as trigger node) will switch the packet delivery from greedy mode to void

handling mode and re-choose better next hops to forward the packet. Of course if the void

node happens to be the source node, packet forwarding mode will be set as void handling at

that node without other choice

Fig 3. 2.1 Potential paths around the void

3.2.2 Virtual Destination

In the case of communication hole, we propose a Virtual Destination based

Void Handling (VDVH) scheme in which the advantages of greedy forwarding and

opportunistic routing can still be achieved while handling communication voids. To handle

communication voids, almost all existing mechanisms try to find a route around. During the

void handling process, the advantage of greedy forwarding cannot be achieved as the path

that is used to go around the hole is usually not optimal (e.g. with more hops compared to the

possible optimal path). More importantly, the robustness of multicast-style routing cannot be

exploited. In order to enable opportunistic forwarding in void handling, which means even in

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dealing with voids, we can still transmit the packet in an opportunistic routing like fashion;

virtual destination is introduced, as the temporary target that the packets are forwarded to.

Fig. 3.2

The fig 3.2 shows an example in which VDVH achieves the optimal path of 7 hops while

GPSR undergoes a much longer route of 15 hops. Thus, by using VDVH protocol the time is

consumed.

3.2.3 Path Acknowledgement and Disrupt Message

In VDVH, if a trigger node finds that there are forwarding candidates in both

directions, the data flow will be split into two where the two directions will be tried

simultaneously for a possible route around the communication void. In order to reduce

unnecessary duplication, two control messages are introduced, namely, path

acknowledgement and reverse suppression. If a forwarding candidate receives a packet that is

being delivered or has been delivered in void handling mode, it will record a reverse entry.

Once the packet reaches the destination, a path acknowledgement will be sent along the

reverse path to inform the trigger node. Then the trigger node will give up trying the other

direction. For the same flow, the path acknowledgement will be periodically sent. If a packet

that is forwarded in void handling mode cannot go any further or the number of hops

traversed exceeds a certain threshold but it is still being delivered in void handling mode, a

DISRUPT control packet will be sent back to the trigger node as reverse suppression. Once

the trigger node receives the message, it will stop trying that direction.

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Advantage:

No end-to-end routes need to be maintained, leading to high efficiency and

scalability in transfer

The additional latency incurred by local route recovery is greatly reduced

and the duplicate relaying caused by packet reroute is also decreased.

No data loss

Data can be forward through neighbor node to the destination node.

4. MODULES:

Implementing Dynamic Mobile Ad-hoc Networks

Implementing POR Protocol

o Candidate Selection Algorithm

o Processing the POR

o Performance Analysis GPSR Vs POR

Implementing VDVH Scheme

o Effect of communication hole

5. MODULE DESCRIPTION:

5.1 Implementing Dynamic Mobile Ad-hoc Networks:

For implementing Dynamic networks, initialize the simulation parameters such as

MAC Protocol

Propagation Model

Transmission Range

Mobility Model

Traffic type

Packet Size

Number of Nodes

Simulation Time

Parameter Value

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MAC Protocol

Propagation Model

Transmission Range

Mobility Model

Traffic Type

Packet Size

Number of Nodes

Simulation Time

IEEE 802.11

Two-ray Ground

250m

Random Way Point(RWP)

Constant Bit Rate(CBR)

256 Bytes

80

900 sec

Fig 5.1.1 Simulation Parameters

The improved random way point (RWP) without pausing is used to model nodes mobility.

The minimum node speed is set to 1m/s and we vary the maximum speed to change the

mobility degree of the network. The transmission range is around 250m. The Packet Size is

up to 256 Bytes and the simulation is around 900sec.

5.2 Implementing POR Protocol:

5.2.1 Candidate Selection Algorithm

First, initialize the candidate selection by selecting and prioritizing the forwarding

candidates.

Choosing the correct neighbor list from the candidate list.

Only the node specified in the candidate list will act as forwarding candidates.

The lower index of the node in the candidate list, has highest priority

A node located in the forwarding area, satisfies the following conditions:

o It makes positive progress towards the destination.

o Its distance to the next hop node should not exceed half of their transmission

range of a wireless node (i.e. R/2}

Every node maintains a forwarding table for the packets of each flow that it has sent

or forwarded.

Before calculating a new forwarder list, it looks up the forwarding table, to check if a

valid item for that destination is still available.

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(src_ip,dst_ip) Next_hop Candidate_list

(N1,N11)(N2,N12)

…..

N4N7…..

N5,N6N8,N5

…..

Fig 5.2.1

The fig 5.2.1 shows that N1 is IP address of source node and N11 is the IP address of

Destination node. Here, N4 is choosed as next hop node. N5, N6 are acting as the forwarding

candidates. Like wise the process continues.

5.2.2 Processing the POR:

In POR, the similar scheme as the MAC multicast mode that the packet is transmitted

as unicast in IP layer and multiple reception is achieved using MAC interception

The use of RTS/CTS/DATA/ACK significantly reduces the collision and all the nodes

within the transmission range of the sender can eavesdrop on the packet successfully

with higher probability due to medium reservation.

As the data packets are transmitted in a multicast like form, each of them is identified

with a unique tuple (src_ip, seq_no) where src_ip is the IP address of the source node

and seq_no is the corresponding sequence number.

Every node maintains a monotonically increasing sequence number, and an ID_Cache

to record the ID (src_ip, seq_no) of the packets that have been recently received.

If a packet with a same ID is received again, it will be discarded.

Otherwise, it will be forwarded at once if the receiver is the next hop, or cached in a

Packet List if it is received by a forwarding candidate, or dropped if the receiver is not

specified.

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Fig. 1. (a) The operation of POR in normal situation.(b)The operation of POR when the next hop fails to receive the packet.

5.2.3 Performance Analysis GPSR Vs POR:

Performance will be analyzed for POR and GPSR based on following attributes:

Packet delivery ratio: The ratio of the number of data packets received at the

destination to the number of data packets sent by the source.

End-to-end delay: The average and the median end-to-end delay are

evaluated, together with the cumulative distribution function (CDF) of the delay.

Path length: The average end-to-end path length (number of hops) for

successful packet delivery.

Packet forwarding times per hop (FTH): The average number of times a

packet is being forwarded from the perspective of routing layer to deliver a data

packet over each hop.

Packet forwarding times per packet (FTP): The average number of

times a packet is being forwarded from the perspective of routing layer to deliver

a data packet from the source to the destination.

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5.3 Implementing VDVH Scheme:

5.3.1 Effect of Communication Hole:

To test the effectiveness of VDVH, we further evaluate the routing performance in

mobile networks with communication hole.

The source and destination nodes are fixed at the two ends of the rectangle while

the remaining 78 nodes move in the annular region according to the RWP model.

The central gray area is simulated as the communication hole with no mobile node

distributed.

Figure 5.3.1 Network topology: with communication hole

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6. System Architecture

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Establishing AdHocNetwork

Locating nodes for Routing

Selecting Neighbor from Candidates

Establishing Network

Implementation of POR

Candidate Listing

7. FLOW DIAGRAM:

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Establishing AdHoc

Network

Locating nodes for Routing

Candidate Listing

Selecting Neighbor from Candidates

Establishing Network

Successful implementation of POR

SOFTWARE REQUIREMENTS

OS – Linux Ubuntu 10.04 Simulator - NS2.34

REFERENCE

J. Broch, D. A. Maltz, D. B. Johnson, Y.-C. Hu, and J. Jetcheva, “A performance comparison of multi-hop wireless ad hoc network routing protocols,” in MobiCom ’98..

M. Mauve, A. Widmer, and H. Hartenstein, “A survey on position-based routing in mobile ad hoc networks,” Network, IEEE, vol. 15, no. 6.

B. Karp and H. T. Kung, “Gpsr: greedy perimeter stateless routing for wireless networks,” in MobiCom ’00, 2000, pp. 243–254.

D. Chen and P. Varshney, “A survey of void handling techniques for geographic routing in wireless networks,” Communications Surveys & Tutorials, IEEE, vol. 9, no. 1, pp. 50–67, Quarter 2007.

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