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A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications

Wireless channels are characterized by multipath and fading that can often cause long burst of errors. Even though, to date, many very sophisticated error correcting codes have been designed, yet none can handle long burst of errors efficiently. An interleaver, a device that distributes a burst o...

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Main Author: Khan, Muhammad Asif
Format: Final Year Project
Language:English
Published: Universiti Teknologi Petronas 2009
Subjects:
TK Electrical engineering. Electronics Nuclear engineering
Online Access:http://utpedia.utp.edu.my/8959/1/2009%20Master%20-%20A%20Novel%20Seed%20Based%20Random%20Interleaving%20for%20OFDM%20System%20and%20Its%20PHY%20Layer%20Security%20I.pdf
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spelling my-utp-utpedia.89592017-01-25T09:44:01Z http://utpedia.utp.edu.my/8959/ A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications Khan, Muhammad Asif TK Electrical engineering. Electronics Nuclear engineering Wireless channels are characterized by multipath and fading that can often cause long burst of errors. Even though, to date, many very sophisticated error correcting codes have been designed, yet none can handle long burst of errors efficiently. An interleaver, a device that distributes a burst of errors, possibly caused by a deep fade, and makes them appear as simple random errors, therefore, proves to a very useful technique when used in conjunction with an efficient error correcting code. In this work, a novel near optimal seed based random interleaver is designed. An optimal interleaver scatters a given burst of errors uniformly over a fixed block of data - a property that is measured by so called 'spread'. The design makes use of a unique seed based pseudo-random sequence generator or logistic map based chaotic sequence generator to scramble the given block of data. Since the proposed design is based on a seed based scrambler, the nature of input is irrelevant. Therefore, the proposed interleaver can interleave either the bits or the symbols or the packets or even the frames. Accordingly, in this work, we analyze the suitability of interleaver when introduced before or after the modulation in single carrier communication systems and show that interleaving the bits before modulation or interleaving the symbols after modulation has same advantage. We further show that, in an orthogonal frequency division multiplexing (OFDM) systems, the position of interleaver, whether before or after constellation mapper, has no significance, and is interchangeable. However, scrambling symbols is computationally less expensive than scrambling bits. For the purpose of analyzing the performance of the proposed seed based random interleaver, simulations are carried out in MA TLAB®. Results show that our proposed seed based random interleaver has near optimal properties of 'spread' and 'dispersion'. Furthermore, the proposed interleaver is evaluated in terms of bit error rate (BER) versus length of burst error in a single carrier system both before and after modulation. The proposed interleaver out-performs the built in RANDINTLV in MA TLAB® when used in the same system. It shows that proposed inter Ieaver can convert greater amount of burst errors into simple random errors than that of MA TLAB® interleaver. The proposed interleaver is also tested in IEEE 802.16e based WiMAX system with Stanford University Interim (SUI) channels to compare the performance of average BER versus SNR for both pre modulation and post modulation interleaver. Results show that pre modulation interleaver and post modulation has same performance. There is also a side advantage of this seed based interleaver, in that it generates a variety of unique random-looking interleaving sequences. Only a receiver that has the knowledge of the input seed can generate this sequence and no one else. If the interleaving patterns are kept secure then it can possibly be used to introduce an extra layer of security at physical (PHY) layer. In that way, at PHY layer, one builds an additional entry barrier to break through and it comes with no extra cost. This property has been investigated by carrying out key sensitivity analysis to show that the attacks to guess key can be very futile, as difference at 41 h decimal place in the initial condition can lead to entirely different scrambling. Universiti Teknologi Petronas 2009-07 Final Year Project NonPeerReviewed application/pdf en http://utpedia.utp.edu.my/8959/1/2009%20Master%20-%20A%20Novel%20Seed%20Based%20Random%20Interleaving%20for%20OFDM%20System%20and%20Its%20PHY%20Layer%20Security%20I.pdf Khan, Muhammad Asif (2009) A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications. Universiti Teknologi Petronas. (Unpublished)
institution Universiti Teknologi Petronas
building UTP Resource Centre
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Petronas
content_source UTP Electronic and Digitized Intellectual Asset
url_provider http://utpedia.utp.edu.my/
language English
topic TK Electrical engineering. Electronics Nuclear engineering
spellingShingle TK Electrical engineering. Electronics Nuclear engineering
Khan, Muhammad Asif
A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
description Wireless channels are characterized by multipath and fading that can often cause long burst of errors. Even though, to date, many very sophisticated error correcting codes have been designed, yet none can handle long burst of errors efficiently. An interleaver, a device that distributes a burst of errors, possibly caused by a deep fade, and makes them appear as simple random errors, therefore, proves to a very useful technique when used in conjunction with an efficient error correcting code. In this work, a novel near optimal seed based random interleaver is designed. An optimal interleaver scatters a given burst of errors uniformly over a fixed block of data - a property that is measured by so called 'spread'. The design makes use of a unique seed based pseudo-random sequence generator or logistic map based chaotic sequence generator to scramble the given block of data. Since the proposed design is based on a seed based scrambler, the nature of input is irrelevant. Therefore, the proposed interleaver can interleave either the bits or the symbols or the packets or even the frames. Accordingly, in this work, we analyze the suitability of interleaver when introduced before or after the modulation in single carrier communication systems and show that interleaving the bits before modulation or interleaving the symbols after modulation has same advantage. We further show that, in an orthogonal frequency division multiplexing (OFDM) systems, the position of interleaver, whether before or after constellation mapper, has no significance, and is interchangeable. However, scrambling symbols is computationally less expensive than scrambling bits. For the purpose of analyzing the performance of the proposed seed based random interleaver, simulations are carried out in MA TLAB®. Results show that our proposed seed based random interleaver has near optimal properties of 'spread' and 'dispersion'. Furthermore, the proposed interleaver is evaluated in terms of bit error rate (BER) versus length of burst error in a single carrier system both before and after modulation. The proposed interleaver out-performs the built in RANDINTLV in MA TLAB® when used in the same system. It shows that proposed inter Ieaver can convert greater amount of burst errors into simple random errors than that of MA TLAB® interleaver. The proposed interleaver is also tested in IEEE 802.16e based WiMAX system with Stanford University Interim (SUI) channels to compare the performance of average BER versus SNR for both pre modulation and post modulation interleaver. Results show that pre modulation interleaver and post modulation has same performance. There is also a side advantage of this seed based interleaver, in that it generates a variety of unique random-looking interleaving sequences. Only a receiver that has the knowledge of the input seed can generate this sequence and no one else. If the interleaving patterns are kept secure then it can possibly be used to introduce an extra layer of security at physical (PHY) layer. In that way, at PHY layer, one builds an additional entry barrier to break through and it comes with no extra cost. This property has been investigated by carrying out key sensitivity analysis to show that the attacks to guess key can be very futile, as difference at 41 h decimal place in the initial condition can lead to entirely different scrambling.
format Final Year Project
author Khan, Muhammad Asif
author_facet Khan, Muhammad Asif
author_sort Khan, Muhammad Asif
title A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
title_short A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
title_full A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
title_fullStr A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
title_full_unstemmed A Novel Seed Based Random Interleaving for OFDM System and Its PHY Layer Security Implications
title_sort novel seed based random interleaving for ofdm system and its phy layer security implications
publisher Universiti Teknologi Petronas
publishDate 2009
url http://utpedia.utp.edu.my/8959/1/2009%20Master%20-%20A%20Novel%20Seed%20Based%20Random%20Interleaving%20for%20OFDM%20System%20and%20Its%20PHY%20Layer%20Security%20I.pdf
http://utpedia.utp.edu.my/8959/
_version_ 1739831619860037632
score 13.211869

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