Miss Insah Bhurtah Main Supervisor: Prof. K.M.S. Soyjaudah Associate Supervisor: Dr C Catherine

Overview  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

 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. 3

 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 4

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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. 6

 (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. 7

 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.  Expanding the usage of LDPC codes in high generation wireless communication systems such as WiMax. 8

 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. 9

 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 G T 10

 Decoding involves getting the original message back.  It is done over the bipartite graph having two sets of vertices. 11

 Check vertices are connected to bit vertices by edges allowing flow of information. 12

 Performance curves of LDPC show the presence of an error floor during the decoding process. 13

Evolving Wireless Networks Outside The Internet 14

 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. 15

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 DTNs – Network of regional networks. Overlay on top of regional networks.  Accommodate long delays, intermittent connectivity (no end- to-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. 17

 Literature Review of past publications.  Designing of algorithms in C/C++ language to generate matrices for encoding.  Studying of decoding algorithms. 18

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