Transcript Improving the encoding and the decoding process of low

Miss Insah Bhurtah
Main Supervisor: Prof. K.M.S. Soyjaudah
Associate Supervisor: Dr C Catherine
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Introduction
Digital Communications
Digital Communication Block
Low-Density Parity-Check Codes (LDPC Codes)
Objectives Of The Research
Methodology
Encoding of LDPC Codes
Decoding of LDPC Codes
Evolving Wireless Networks Outside The Internet
Delay Tolerant Networks (DTNs)
Ongoing Research
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In the field of digital communications,
coding is used to transmit data correctly.
It ensures that a sent original
message is obtained at a receiver.
Planning to do coding in Delay
Tolerant Networks (DTNs) and
Interplanetary Networks (IPNs)
Aim is to improve the performance of
low-density parity-check codes for application in DTNs
and IPNs.
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It involves the transmission of information from source
to a sink.
It works by the physical transmission of data over a
point-to-point or point-to-multipoint medium
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Data from the source passes into a noisy channel.
Channel coding: Redundancy added to the data before
transmission and the same redundancy used to correct
errors introduced by the channel to get the original data
at the receiver.
Many types of error-correcting codes used such as
turbo codes and low-density parity-check codes being
among the best.
In this research, channel encoding and decoding, and
low-density parity-check codes are dealt.
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(LDPC) codes are the second generation of “modern”
codes, following turbo codes.
They were first defined by Gallager in 1962, but were not
practical at that time.
Rediscovered after the turbo code revolution in 1994
Many improvements have been made in the last few years
through extensive research.
Advances in LDPC coding enabled better performance than
turbo codes to be achieved. In 2003, an LDPC code beat six
turbo codes to turn into the new DVB-S2 standard for the
satellite transmission of digital television.
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Adapting LDPC codes for novel applications such as
Delay Tolerant Networks (DTNs) and Interplanetary
Networks (IPNs).
◦ DTN : overlay of regional networks that accommodates long
delays between and within them.
◦ IPN : interplanetary internet currently being developed for
space communication.
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Expanding the usage of LDPC codes in high generation
wireless communication systems such as WiMax.
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Development of matrix creation techniques for
creation of high rate LDPC codes
Improving performance by improving specific-edge
connections and local topologies of the bipartite graph
Designing of very low error rates LDPCs to their
effective use in satellite transmission, IPNs and DTNs.
Devising of algorithms to enhance wireless
transmission.
Use of C/C++ programming language to design
algorithms to reduce the error floor in bipartite
graphs.
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Encoding is to transform the data into a format so that
it can be transmitted into the channel.
It is carried out by the equation, where t is the
transmitted codeword, s the source sequence and the
generator-transpose matrix of the code GT
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Decoding involves getting the original message back.
It is done over the bipartite graph having two sets of
vertices.
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Check vertices are connected to bit vertices by edges
allowing flow of information.
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Performance curves of LDPC show the presence of an
error floor during the decoding process.
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Today’s internet connectivity relies primarily on wired
links.
Communication outside of the internet – power-limited
mobile wireless, satellite, interplanetary
communications are developing.
Future space missions crewed by people motivate
interest in interplanetary internet.
Long and variable delays, arbitrarily long periods of
disconnection and high error rates.
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DTNs – Network of regional networks. Overlay on top of
regional networks.
Accommodate long delays, intermittent connectivity (no endto-end path between source and destination), long or variable
delays from node to node
Moving communicating bodies (interplanetary space, earth
mobile wireless communication), links shut down by
intervening bodies to conserve energy or preserve secrecy.
DTNs solve these problems by store-and-forward message
switching.
Design of error correction codes can provide large reductions
in delay.
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Literature Review of past publications.
Designing of algorithms in C/C++ language to generate
matrices for encoding.
Studying of decoding algorithms.
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