International Journal of Engineering Trends and Technology- July to Aug Issue 2011
QUALITY OF SERVICE METRICS FOR
DATA TRANSMISSION IN MESH
TOPOLOGIES
SWATHI NANDURI*
ZAHOOR-UL-HUQ*
Master of Technology,
G. Pulla Reddy Engineering College,
Kurnool, Andhra Pradesh,
India,
Associate Professor,
G. Pulla Reddy Engineering College,
Kurnool, Andhra Pradesh,
India,
ABSTRACT
Mesh topologies are important for large-scale highly engineered systems. The Quality of
Service (QoS) in such systems is known to decrease as the number of nodes and messages
increases. We present a scalable approach for dissemination that exploits all the shortest paths
between a pair of nodes and improves the QoS. Despite the presence of multiple shortest
paths in a system, we show that these paths cannot be exploited by spreading the messages
over the paths in a simple round-robin manner; nodes along one of these paths will always
handle more messages than the nodes along the other paths. We characterize the set of
shortest paths between a pair of nodes in regular mesh topologies and derive rules, using this
characterization, to effectively spread the messages over all the available paths. These rules
ensure that all the nodes that are at the same distance from the source handle roughly the
same number of messages. By using multipath propagation and demonstrating the
transmission results in case of propagation irregularities and link failures the QoS improved
with this approach.
Keywords: Mesh Topology, Dissemination, Contour, Contour Guided Dissemination
I. INTRODUCTION
The use of novel devices for communication
in highly engineered and network embedded
systems are presenting new challenges for
monitoring and diagnosing them. These
systems contain large number of nodes
which will interact in peer-peer manner to
achieve the application objectives [1]. To
increase the number of simultaneous
interactions between these nodes the
transmission range of each node is restricted
so that it can only communicate with its
immediate set of neighbors. This
arrangement is called Mesh Topology [2].
Multihop communications are necessary in
such systems to send messages from any
source to any destination. For example,
intermediate nodes must forward messages
to a monitoring station from nodes that
cannot communicate directly with the
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International Journal of Engineering Trends and Technology- July to Aug Issue 2011
monitoring station. Routing protocols are
used extensively in wired and wireless
networks
to
support
multihop
communication [6]. Such protocols construct
and maintain routing tables at each node by
relying on system wide unique node
identifiers. When the number of nodes is
very large, such as in sensor networks, it is
not feasible to use such identifiers. Several
techniques, called dissemination methods,
were developed at the network layer to
regulate the flow of messages between
nonadjacent nodes without relying on unique
node identifiers or constructing routing
tables using these identifiers[3][4][5].In this
paper we consider all the nodes arranged in a
mesh topology and try to effectively utilize
all the shortest paths present between the
nodes and thus ensure that this effective
utilization improves QOS. Because each
node communicates directly with its
immediate set of neighbors, there are
multiple shortest paths between many pairs
of nodes in a mesh topology. The number of
such paths is limited by the relative locations
of the nodes. For example, the number of
shortest paths between certain pairs of nodes
is one, despite the mesh topology. We define
a Contour as the union of all the shortest
paths between a pair of nodes and present
some results to precisely characterize the
structure of contours. Using this structure,
we show that when messages are spread in a
round-robin manner, nodes along one path in
the contour will always handle more
messages than the nodes along other paths in
the contour. Consequently, the benefits of
the multiple paths cannot be fully realized.
We then present a strategy for spreading
messages to neighboring nodes that
effectively exploits the available shortest
paths and show that our rules for spreading
the messages result in a balanced loading of
all the available shortest paths. We refer to
this approach as
Dissemination (CGD).
Contour
Guided
II. RELATED WORK
Routing protocols used in traditional wired
and wireless networks are based on
shortest path algorithms such as the
Bellman-Ford algorithm [6] and Dijkstra’s
algorithm [7].Similar protocols have been
reported for ad hoc, wireless, and mobile
networks The QoS achieved in these
systems has also been studied . The
dissemination method we describe in this
paper is somewhat similar to a gradient
dissemination scheme with the cost metric
being the deviation from evenness of load
distribution on all available shortest paths.
In the current methods, the motivating
factors for considering multipath routing
include fault tolerance, higher aggregate
bandwidth, and load balancing. The QoS
aspects of multipath routing have also
been addressed. The split multipath
routing protocol maintains maximally
edge-disjoint paths. All such method
essentially focus on the discovery and
maintenance of multiple paths that are
useful under various constraints on the
node distribution. In contrast, we assume
regular mesh topologies and then precisely
characterize the set of all shortest paths
between any pair of nodes. We then use
this geometric structure to propose rules
for dissemination that result in all
available shortest paths being utilized
effectively so that QoS improves.
III. OTHER DATA DISSEMINATING
ALGORITHSMS
In this section we describe other data
disseminating methods and compare its
performance with CGD.
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International Journal of Engineering Trends and Technology- July to Aug Issue 2011
A. Classical Flooding
In this approach a node wishes to
disseminate a piece of data across the
network by sending the data across all its
neighbors. Whenever a node receives a data
it makes copies of the data and sends that
data across all its neighbors except to the
node from which it received the data. The
amount of time that all the nodes receives
the data and makes copies of it and forwards
that to all its neighbors is called a “Round”.
The disadvantage with this approach is it
will cause the nodes to handle many
messages.
B. Gossiping
Gossiping is an alternative to classical
flooding that uses randomization to conserve
energy. Instead of forwarding data to all
neighbors gossiping node only forwards data
on to one randomly selected neighbors. If
gossiping node receives data from a given
neighbor it can forward data back to that
neighbor provided if it randomly selects that
neighbor. This approach requires less
communication traffic but average end-end
delivery rate is poor.
C. Reverse-path forwarding
It is a general approach that is used in
several dissemination protocols. In this
approach, a sink node (such as a Monitoring
Station) generates a “query” that indicates an
interest in data items from one or more
nodes. Such a query is forwarded along one
or more paths from the sink to all the nodes.
The nodes forward data along these paths;
since the data propagates in a direction that
is reverse of the query direction, this method
is referred to as reverse-path forwarding.
The major flaw with this approach is if the
underlying dynamic routing mechanism
changes the routing tables used by the nodes
during the course of broadcast, then that
packet may not be delivered to the node
even if the path to it exists.
D. Cost field approach
This is another choice for routing. Every
node maintains a scalar that represents the
cost of sending data back to the sink and
the data is propagating along the cost
gradients. Protocols based in cost-field
require less memory space compared to
reverse-path forwarding since there is no
need to maintain a routing table. Routing
decisions are based in the cost at each
node. Since nodes are resource constrained
in both communication and computation
capabilities, cost field based approach is a
good choice.
E. Virtual Hierarchy approach
As shown in the fig.. nodes form local
clusters and a cluster head will be elected
from the cluster. Nodes in the cluster may
rotate their roles as the cluster head in order
to achieve the energy consumption balance
in the cluster. Since the radio transmission
strength is adjustable, the cluster head node
can be set to a more powerful transmission
range to reach the monitoring station.
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International Journal of Engineering Trends and Technology- July to Aug Issue 2011
In this analysis, we present a
dissemination method that will ensure that
all the nodes that are equidistant from the
source node, of a contour handle
approximately same number of messages.
While in a uniform spreading this load
balancing is not achieved.The shapes of
the contours varies depending upon the
node parameters.
F. Geographical forwarding
By utilizing the GPS or the location on a
grid, the network uses location information
to achieve a more efficient routing in the
network. Geographic adaptive fidelity sets
up a virtual grid depending on the GPS
providing location and saves energy in the
network by propagating messages in
different nodes in the same region. The
disadvantage with this approach is that GPS
receivers are too expensive in terms of
energy consumption ,size or cost.
Structure of a Contour in E8
Concrete Challenges with the above
Methods:



Message loss rate is more
Path link failures are more
Difficult to re-transmit the messages
IV. Contour Guided Dissemination
V. SYSTEM EVALUATION
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International Journal of Engineering Trends and Technology- July to Aug Issue 2011
In this section, we investigate the impact
on the performance of Contour Guided
Dissemination system resulting from the
adopted strategy to deploy it in the
network.. We consider the following
schemes to implement our CGD:

Here in order to realize the benefits
of all the shortest paths we consider that
every node receives a packet from its
upstream neighbor and forwards it to its
downstream neighbor.

To utilize this practically we
consider that every node will have the
address of its sender and receiver.

As the message propagate through
the network, every intermediate node
could easily compute (using, e.g., the
distance criterion) which of its immediate
neighbors are on a shortest path to the
destination.
For our analysis purpose we have used
Java technology to show the results of our
CGD approach by exploiting all the
available shortest paths and observed the
efficiency in the transmission of messages
even incase of link failures. The number of
messages handled by each node, average
end-end latency, jitter , message loss rate
were the primary QOS metrics considered.
It was observed after practical analysis that
CGD has comparatively low message loss
rate and less jitter and delay were
experienced.
We used the above mentioned metrics as a
basis to compare the performance of CGD
with the unipath routing which is based on
distance vector routing algorithm and
shortest path
tree that will be precomputed using structure of all shortest
paths.
In the following graphs we have taken
probability of link failures on X-axis and
various QoS parameters like Message loss
rate Jitter and average delayon Y-axis and
obtained the following results:
Message Loss Rate
VI. IMPLEMENTATION
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International Journal of Engineering Trends and Technology- July to Aug Issue 2011
Average Delay
with general topologies. In such networks,
some nodes must spread the messages,
while other nodes must utilize one of the
available paths without spreading the
messages further. Identifying the structure
of contours, for networks with general
topologies are interesting problems and the
method presented here provides a
systematic framework in which to carry
out future investigation.
IX . REFERENCES
Jitter
VII. FUTURE SCOPE
Contour Guided Dissemination for
propagating messages in networked
embedded systems that exploits the
location of each node and the multiple
paths available between a source and a
sink. The union of all of the shortest paths
between a source and a sink was defined to
be a contour. Focus will be laid in
developing such Dissemination protocols
to achieve efficient data transmissions.
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VIII. CONCLUSION
Although the results were based on a
regular topology, these results suggest new
methods for dissemination in networks
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