A New Cross-Layer FPGA-Based Security Scheme for Wireless Networks

This chapter presents a new cross-layer security scheme which deploys efficient coding techniques in the physical layer in an upper layer classical cryptographic protocol system. The rationale in designing the new scheme is to enhance security-throughput trade-off in wireless networks which is in contrast to existing schemes which either enhances security at the detriment of data throughput or vice versa. The new scheme is implemented using the residue number system (RNS), non-linear convolutional coding and subband coding at the physical layer and RSA cryptography at the upper layers. The RNS reduces the huge data obtained from RSA cryptography into small parallel data. To increase the security level, iterated wavelet-based subband coding splits the ciphertext into different levels of decomposition. At subsequent levels of decomposition, the ciphertext from the preceding level serves as data for encryption using convolutional codes. In addition, throughput is enhanced by transmitting small parallel data and the bit error correction capability of non-linear convolutional code. It is shown that, various passive and active attacks common to wireless networks could be circumvented. An FPGA implementation applied to CDMA could fit into a single Virtex-4 FPGA due to small parallel data sizes employed

Use of RNS Based Pseudo Noise Sequence in DS-CDMA and 3G WCDMA

Code Division Multiple Access (CDMA) based on Spread Signal (SS) has emerged as one of the most important multiple access technologies for Second Generation (2G) and Third Generation (3G) wireless communication systems by its wide applications in many important mobile cellular standards. CDMA technique relies on spreading codes to separate dierent users or channels and its properties will govern the performance of the system. So many of the problems of communication systems based on CDMA technology stem from the spreading codes/sequences, which includes two sub-categories, one being the orthogonal codes, such as Walsh Hadamard (WH) codes and Orthogonal Variable Spreading Factor (OVSF) codes, and the other being pseudo-noise or Pseudo Random (PN) sequences, such as Gold sequences, Kasami sequences, m-sequences, etc. In this thesis a PN sequence generation based on Residue Arithmetic is investigated with an eort to improve the performance of existing interference-limited CDMA technology for mobile cellular systems. This interference-limited performance is due to the fact that all the existing CDMA codes used in mobile cellular standards does not consider external interferences, multipath propagation, Doppler eect etc. So the non-ideal correlation properties of the pseudo-random CDMA codes results in MAI when used in a multi-user system. The PN codes appear random yet they are completely deterministic in nature with a small set of initial conditions. Consequently this work focuses on CDMA code design approach based on Residue Number System (RNS) which should take into account as many real operational conditions as possible and to maintain a suciently large code set size.First, the thesis reviews RNS, DS-CDMA and CDMA codes that are already implemented in various mobile cellular standards. Then the new PN Sequencegenerator design based on RNS is discussed. Comparison of the generated PN sequence with respect to other standard sequence is done in terms of number of codes and correlation properties. Monte-Carlo simulations with the generated sequence are carried out for performance analysis under multi-path environment. The system has been evaluated in AWGN, Rayleigh Fading channel and dierent Stationary Multipath Channels for dierent cross-correlation threshold. It is known that orthogonal Codes are used to multiplex more than one signal for downlink transmission over cellular networks. This downlink transmission is prone to self interference caused by the loss of orthogonality between spreading codes due to multipath propagation. This issue is investigated in detail with respect to WCDMA standards, which is very good representative for CDMA based 3G mobile cellular systems where the channelization code is OVSF code. The code assignment blocking (CAB) (If a particular code in the tree is used in a cell, then all its parent codes and child codes should not be used in the same cell to maintain orthogonality among the users) problem of OVSF codes restricts the number of available codes for a given cell. Since the 3rd generation WCDMA mobile communication systems apply the same multiple access technique, the generated sequence can also be the channelization code for downlink WCDMA system to mitigate the the same. The performance of the system is compared with Walsh Hadamard code over multipath AWGN and dierent Fading channels. This thesis work shows that RNS based PN sequence has enhanced performance to that of other CDMA codes by comparing the bit error probability in multi- user and multipath environment thus contributing a little towards the evolution of next generation CDMA technology

Design of tch-type sequences for communications

This thesis deals with the design of a class of cyclic codes inspired by TCH codewords. Since TCH codes are linked to finite fields the fundamental concepts and facts about abstract algebra, namely group theory and number theory, constitute the first part of the thesis. By exploring group geometric properties and identifying an equivalence between some operations on codes and the symmetries of the dihedral group we were able to simplify the generation of codewords thus saving on the necessary number of computations. Moreover, we also presented an algebraic method to obtain binary generalized TCH codewords of length N = 2k, k = 1,2, . . . , 16. By exploring Zech logarithm’s properties as well as a group theoretic isomorphism we developed a method that is both faster and less complex than what was proposed before. In addition, it is valid for all relevant cases relating the codeword length N and not only those resulting from N = p

Performance and energy efficiency in wireless self-organized networks

fi=vertaisarvioitu|en=peerReviewed

On architecture and scalability of optical multi-protocol label switching networks using optical-orthogonal-code label.

Wen Yonggang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references.Abstracts in English and Chinese.Chapter 1 --- IntroductionChapter 1.1 --- Multi-Protocol Label Switching (MPLS) Technology --- p.1Chapter 1.2 --- Objective of this Thesis --- p.4Chapter 1.3 --- Reference --- p.5Chapter 2 --- Optical MPLS Network and Optical Label SchemesChapter 2.1 --- Optical MPLS Network --- p.7Chapter 2.2 --- Optical Label Schemes --- p.10Chapter 2.2.1 --- Time-division OMPLS scheme --- p.12Chapter 2.2.2 --- Wavelength-division OMPLS scheme --- p.16Chapter 2.2.3 --- Frequency-division OMPLS scheme --- p.22Chapter 2.2.3.1 --- UCSB Testbed --- p.23Chapter 2.2.3.2 --- UC-Davis Testbed --- p.26Chapter 2.2.3.3 --- NCTU-Telecordia Testbed --- p.28Chapter 2.2.4 --- Code-division OMPLS scheme --- p.30Chapter 2.2.4.1 --- Coherent Code-Division Label Scheme --- p.30Chapter 2.2.4.2 --- Noncoherent Code-Division Label Scheme --- p.32Chapter 2.3 --- Reference --- p.35Chapter 3 --- Architecture of OOC-based OMPLS networkChapter 3.1 --- Infrastructure of OOC-label switch router (code converter) --- p.37Chapter 3.1.1 --- Architecture of the Proposed Code Converter --- p.38Chapter 3.1.2 --- Enhancement of the Code Converter --- p.41Chapter 3.2 --- Implementation of the OOC code converter --- p.43Chapter 3.2.1 --- Encoders/Decoders --- p.43Chapter 3.2.1.1 --- All-parallel encoders/decoders --- p.43Chapter 3.2.1.2 --- All-serial encoders/decoders --- p.45Chapter 3.2.1.3 --- Serial-to-parallel encoder/decoders --- p.47Chapter 3.2.1.4 --- Comparison of the three kinds of encoders/decoders --- p.49Chapter 3.2.2 --- Time-Gate-Intensity-Threshold (TGIT) Device --- p.50Chapter 3.2.3 --- Optical Space Switch Array --- p.54Chapter 3.2.3.1 --- All-optical Space Switch --- p.54Chapter 3.2.3.2 --- Optical switching technologies --- p.56Chapter 3.2.3.2.1 --- Scalability --- p.56Chapter 3.2.3.2.2 --- Switching Speed --- p.57Chapter 3.2.3.2.3 --- Reliability --- p.57Chapter 3.2.3.2.4 --- Losses --- p.58Chapter 3.2.3.2.5 --- Port-to-Port repeatability --- p.58Chapter 3.2.3.2.6 --- Cost --- p.59Chapter 3.2.3.2.7 --- Power Consumption --- p.60Chapter 3.3 --- Reference --- p.61Chapter 4 --- Scalability of OOC-based MPLS networkChapter 4.1 --- Limitation on Label Switching Capacity --- p.63Chapter 4.1.1 --- Upper Bound --- p.65Chapter 4.1.2 --- Lower Bound --- p.66Chapter 4.2 --- Limitation on Switching Cascadability --- p.70Chapter 4.2.1. --- Limit Induced by the Inter-channel Crosstalk --- p.70Chapter 4.2.2 --- Limits Induced by the Residue Intensity of Sidelobes --- p.74Chapter 4.3 --- Appendix --- p.78Chapter 4.3.1 --- Derivation of Chip Intensity --- p.78Chapter 4.3.2 --- The 5% residue power criterion --- p.81Chapter 4.4 --- Reference --- p.83Chapter 5 --- ConclusionChapter 5.1 --- Summary of the Thesis --- p.85Chapter 5.2 --- Future work --- p.8