Local Broadcast Algorithms in Wireless Ad Hoc Networks:
Reducing the Number of Transmissions
Abstract:
There are two main approaches, static and dynamic, to broadcast algorithms
in wireless ad hoc networks. In the static approach, local algorithms determine the
status (forwarding/nonforwarding) of each node proactively based on local
topology information and a globally known priority function. In this paper, we first
show that local broadcast algorithms based on the static approach cannot achieve a
good approximation factor to the optimum solution (an NP-hard problem).
However, we show that a constant approximation factor is achievable if (relative)
position information is available. In the dynamic approach, local algorithms
determine the status of each node “on-the-fly” based on local topology information
and broadcast state information. Using the dynamic approach, it was recently
shown that local broadcast algorithms can achieve a constant approximation factor
to the optimum solution when (approximate) position information is available.
However, using position information can simplify the problem. Also, in some
applications it may not be practical to have position information. Therefore, we
wish to know whether local broadcast algorithms based on the dynamic approach
can achieve a constant approximation factor without using position information.
We answer this question in the positive—we design a local broadcast algorithm in
which the status of each node is decided “on-the-fly” and prove that the algorithm
can achieve both full delivery and a constant approximation to the optimum
solution.
Architecture:
Algorithm:
Hybrid Algorithm:
The proposed broadcast algorithm is a hybrid algorithm, hence every node that
broadcasts the message may select some of its neighbors to forward the message.
In our proposed broadcast algorithm, every broadcasting node selects at most one
of its neighbors. A node has to broadcast the message if it is selected to forward.
Other nodes that are not selected have to decide whether or not to broadcast on
their own. This decision is made based on a self-pruning condition called the
coverage condition.
Existing System:
The existing local broadcast algorithms can be classified based on
whether the forwarding nodes are determined statically (based on only local
topology information) or dynamically (based on both local topology and broadcast
state information). In the static approach, the distinguishing feature of local
algorithms over other broadcast algorithms is that using local algorithms any local
topology changes can affect only the status of those nodes in the vicinity.
Therefore, local algorithms can provide scalability as the constructed CDS can be
updated, effciently. The existing local algorithms in this category typically use a
priority function known by all nodes in order to determine the status of each node.
In this paper we show that, using only local topology information and a globally
known priority function, the local broadcast algorithms based on the static
approach are not able to guarantee a good approximation factor to the optimum
solution (i.e., MCDS). On the other hand, we show that local algorithms based on
the static approach can achieve interesting results such as a constant approximation
factor and shortest path preservation if the nodes are provided with position
information.
Disadvantages:
1. Minimum number of transmission will be Possible.
2. All the Nodes have been static.
3. Data loss problem occurred.
Proposed System:
In the dynamic approach, the status of each node (hence the CDS) is
determined “on-the-fly” during the broadcast progress. Using this approach, the
constructed CDS may vary from one broadcast instance to another even when the
whole network topology and the source node remain unchanged. Consequently, the
broadcast algorithms based on the dynamic approach typically have small
maintenance cost and are expected to be robust against node failures and network
topology changes. Many local broadcast algorithms in this category use local
neighbor information to reduce the total number of transmissions and to guarantee
full delivery (assuming no loss at the MAC/PHY layer). If only selected node will
be forward the message.
Advantages:
1. Local broadcast algorithms in reducing the total number of
transmissions.
2. Full delivery and constant approximation to the optimum solution.
3. Avoid forwarding/rebroadcasting a message.
4. Hybrid algorithm.
5. Node’s are dynamic.
6. Calculate Maximum and Minimum transmission range of the nodes
in the network.
Modules:
1) Node.java : This module contains node information such as nodeid,position in
the network and messages list received
from the sender.
2) CanvasScreen : This module is a graphical user interface which display all
movable nodes. Colors of nodes will be changed while
sending and receiving data. This module contains refrences of nodes. Upon reset
this module removes all nodes information and can
be ready to create new nodes topology.
3) Broadcast : This module continuously receive data from all sender nodes and
transmit to receiver nodes. This module receive all working nodes
information from CanvasScreen. This module is responsible to extract ids from
braodcasting nodes and the ids of reciving nodes from the message list
and this module determine the sender has already broadcast this message earlier
then it will remove that message from list. If not broadcast then it will
update message list to transmit to all receiver nodes.
4) sender Node : This module is responsible to broadcast messages to receiver
nodes. Before broadcasting it will add it id and receiver id to message list and
the broadcast message. All messages will be accepted by Broadcast module for
further processing.
5) Receiver Node : This node receiver message from sender node and update itself
with new message and its arrival time,packet size and sender id.
6) MoveThread : This module place all nodes at random position and every second
it will chnage node position and update same informatiuon to node refrences and
other
modules to determine position of nodes.
7) ViewRouting : This module helps us to view and trace all transmission happens
between receiver and sender nodes. Using this module we can identify at which
time transmission happen packet size,receiver id and sender id.
8)Login : This module allows only authorize users to access this application.
System Requirement:
Hardware requirements:
 Processor
: Any Processor above 500 MHz.
 Ram
: 128Mb.
 Hard Disk
: 10 Gb.
 Compact Disk
: 650 Mb.
 Input device
: Standard Keyboard and Mouse.
 Output device
: VGA and High Resolution Monitor
Software requirements:
 Operating System
: Windows Family.
 Language
: JDK 1.5
 Data Bases
: my sql
 Front End
: Java Swing