Dynamic Control of
Coding for Progressive Packet Arrivals in DTNs
ABSTRACT:
In Delay Tolerant Networks
(DTNs) the core challenge is to cope with lack of persistent connectivity and
yet be able to deliver messages from source to destination. In particular,
routing schemes that leverage relays’ memory and mobility are a customary
solution in order to improve message delivery delay. When large files need to
be transferred from source to destination, not all packets may be available at
the source prior to the first transmission. This motivates us to study general
packet arrivals at the source, derive performance analysis of replication based
routing policies and study their optimization under two hop routing. In
particular, we determine the conditions for optimality in terms of probability
of successful delivery and mean delay and we devise optimal policies, so-called
piecewise-threshold
policies. We account for linear
block-codes and rate less random linear coding to efficiently generate
redundancy, as well as for an energy constraint in the optimization. We
numerically assess the higher efficiency of piecewise-threshold policies
compared with other policies by developing heuristic optimization of the
thresholds for all flavors of coding considered.
EXISTING SYSTEM:
Delay
Tolerant Networks (DTNs) leverage contacts between mobile nodes and sustain
end-to-end communication even between nodes that do not have end-to-end
connectivity at any given instant. In this context, contacts between DTN nodes
may be rare, for instance due to low densities of active nodes, so that the
design of routing strategies is a core step to permit timely delivery of
information to a certain destination with high probability. When mobility is
random, i.e., cannot be known beforehand, this is obtained at the cost of many
replicas of the original information, a process which consumes energy and
memory resources. Since many relay nodes (and thus network resources) may be
involved in ensuring successful delivery, it becomes crucial to design
efficient resource allocation and data storage protocols.
DISADVANTAGES
OF EXISTING SYSTEM:
ü The core challenge is to cope with lack of
persistent connectivity and yet be able to deliver messages from source to
destination.
ü The routing schemes that leverage relays’ memory and
mobility are a customary solution in order to improve message delivery delay.
ü When large files need to be transferred from source
to destination, not all packets may be available at the source prior to the
first transmission.
PROPOSED SYSTEM
This paper focuses on general packet
arrivals at the source and two-hop routing. We distinguish two cases: when the
source can overwrite its own packets in the relay nodes, and when it cannot.
The contributions are fourfold:
v For
work-conserving policies (i.e., the source sends systematically before stopping
completely), we derive the conditions for optimality in terms of probability of
successful delivery and mean delay.
v In
the case of non-overwriting, we prove that the best policies, in terms of
delivery probability, are piecewisethreshold. For the overwriting case,
work-conserving policies are the best without energy constraint, but are
outperformed by piecewise-threshold policies when there is an energy constraint.
v We
extend the above analysis to the case where copies are coded packets, generated
both with linear blockcodes and rateless coding. We also account for an energy
constraint in the optimization.
v We
illustrate numerically, in the non-overwriting case, the higher efficiency of
piecewise-threshold policies compared with work-conserving policies by
developing a heuristic optimization of the thresholds for all flavors of coding
considered. As well, in the overwriting case, we show that work-conserving
policies are the best without any energy constraint.
ADVANTAGES
OF PROPOSED SYSTEM:
ü In
DTNs the framework is different since the challenge is to overcome frequent
disconnections. Papers propose a technique to erasure code a file and
distribute the generated code-blocks over a large number of relays in DTNs, so
as to increase the efficiency of DTNs under uncertain mobility patterns.
ü The
performance gain of the coding scheme is compared with simple replication. The
benefit of coding is assessed by extensive simulations and for different
routing protocols, including two hop routing.
ü The
paper addresses the design of stateless routing protocols based on network
coding, under intermittent end-to end connectivity, and the advantage over
plain probabilistic routing is proven.
SYSTEM CONFIGURATION:-
HARDWARE CONFIGURATION:-
ü Processor - Pentium –IV
ü Speed - 1.1
Ghz
ü RAM - 256
MB(min)
ü Hard
Disk - 20
GB
ü Key
Board - Standard
Windows Keyboard
ü Mouse - Two
or Three Button Mouse
ü Monitor - SVGA
SOFTWARE CONFIGURATION:-
ü Operating System :
Windows XP
ü Programming Language : JAVA
ü Java Version : JDK 1.6 & above.
REFERENCE:
Eitan Altman, Lucile Sassatelli, and
Francesco De Pellegrini –“Dynamic Control of Coding for Progressive Packet Arrivals
in DTNs”- IEEE TRANSACTIONS ON WIRELESS
COMMUNICATIONS, VOL. 12, NO. 2, FEBRUARY 2013.
