"The topology of a network (such as a telecommunications, multiprocessor, or local area network, to name just a few) is usually modelled by a graph in which vertices represent 'nodes' (stations or processors) while undirected or directed edges stand for 'links' or other types of connections, physical or virtual. A cycle that contains every vertex of a graph is called a hamiltonian cycle and a graph which contains a hamiltonian cycle is called a hamiltonian graph. The problem of the existence of a hamiltonian cycle is closely related to the well known problem of a travelling salesman. These problems are NP-complete and NP-hard, respectively. While some necessary and sufficient conditions are known, to date, no practical characterization of hamiltonian graphs has been found. There are several ways to generalize the notion of a hamiltonian cycle. In this thesis we make original contributions in two of them, namely k-walks and r-trestles." --Abstract. / Doctor of Philosophy

Thesis (PhDTelecommunications)--University of South Australia, 2008.

Block codes are one of the most widely used codes to improve reliability of data transmissions. They are used both independently as well as with other codes such as convolutional codes and have found many applications in many areas, ranging from space communications to digital versatile discs (DVD). More recently, powerful codes derived from block and iteratively decoded codes have also been adopted in serveral standards (e.g. DVB-S2). The first part of this thesis deals with the design of computationally efficient soft-decision decoding algorithms for block codes. / A bandwidth-efficient modulation technique called orthogonal frequency division multiplexing (OFDM) has been adopted in many international standards to achieve high speed data transmissions over frequency selective fading channels. OFDM signals however, have high amplitude fluctuations. This is known as the peak-to-average power ratio (PAPR) problem. The second part of this thesis focuses on designing a coding scheme to simultaneously correct errors and reduce the PAPR of OFDM signals. / Soft-decision decoding of block codes provide significant performance gains over hard-decision decoding. However, optimal soft-decision decoding is an NP-hard problem, where the decoding complexity grows exponentially with the code length. This thesis develops two computationally efficient sub-optimal soft-decision decoding algorithms by formulating soft-decision decoding as an optimisation problem. The two algorithms are based on a compact genetic algorithm and a k shortest paths algorithm, respectively. The performance and complexity of these algorithms are investigated and compared with various other known decoding schemes. The results obtained show that the proposed decoding algorithm achieves large performance gains over the known decoding schemes. It is also observed that the proposed algorithms achieve near-optimal performance with manageable complexity. / In addition to these soft-decision decoding algorithms, this thesis also proposes a coding technique and an efficient encoding algorithm for joint error-correction and PAPR reduction of OFDM signals. The proposed coding technique is first expressed as an optimisation problem and a computationally efficient sub-optimal algorithm is then proposed to solve this problem. The PAPR reduction and error-correction performance of the proposed algorithm are studied. The results show that the proposed algorithm significantly improves the system performance and also gives PAPR reductions comparable with other known PAPR reduction techniques. / Thesis (PhDTelecommunications)--University of South Australia, 2007.

This thesis investigates the ability of dynamic algorithms to adequately share limited satellite channel resources between explicit user demands for bandwidth, anticipated bandwidth demands from users, and signalling traffic transmitted from user terminals. In particular it investigates the design of multiple access control protocols and the way their features affect the performance of higher layer protocols, and the efficiency of using the underlying resources. / Thesis (PhDTelecommunications)--University of South Australia, 2007.

Using the approach of Coloured Petri nets (CPNs) and automata theory, this thesis shows how to formalise the service provided by the Transmission Control Protocol (TCP) and verify TCP Connection Management, an essential part of TCP. Most of the previous work on modelling and analysing TCP Connection Management is based on early versions of TCP, which are different from the current TCP specification. Also the scope is mainly confined to the connection establishment procedure, while the release procedure is either simplified or omitted from investigation. This thesis extends prior work by verifying a detailed model of TCP Connection Management. In defining the TCP service, the set of service primitives and their sequencing constraints are specified at each service access point. / Thesis (PhDComputerSystemsEng)--University of South Australia, 2004.

Recent designs for low-density parity-check (LDPC) codes have exhibited capacity approaching performance for large block length, overtaking the performance of turbo codes. While theoretically impressive, LDPC codes present some challenges for practical implementation. In general, LDPC codes have higher encoding complexity than turbo codes both in terms of computational latency and architecture size. Decoder circuits for LDPC codes have a high routing complexity and thus demand large amounts of circuit area. / There has been recent interest in developing analog circuit architectures suitable for decoding. These circuits offer a fast, low-power alternative to the digital approach. Analog decoders also have the potential to be significantly smaller than digital decoders. / In this thesis we present a novel and efficient approach to LDPC encoder / decoder (codec) design. We propose a new algorithm which allows the parallel decoder architecture to be reused for iterative encoding. We present a new class of LDPC codes which are iteratively encodable, exhibit good empirical performance, and provide a flexible choice of code length and rate. / Combining the analog decoding approach with this new encoding technique, we design a novel time-multiplexed LDPC codec, which switches between analog decode and digital encode modes. In order to achieve this behaviour from a single circuit we have developed mode-switching gates. These logic gates are able to switch between analog (soft) and digital (hard) computation, and represent a fundamental circuit design contribution. Mode-switching gates may also be applied to built-in self-test circuits for analog decoders. Only a small overhead in circuit area is required to transform the analog decoder into a full codec. The encode operation can be performed two orders of magnitude faster than the decode operation, making the circuit suitable for full-duplex applications. Throughput of the codec scales linearly with block size, for both encode and decode operations. The low power and small area requirements of the circuit make it an attractive option for small portable devices. / Thesis (PhDTelecommunications)--University of South Australia, 2004.

Thesis (PhD)--University of South Australia, 1993.

"The topology of a network (such as a telecommunications, multiprocessor, or local area network, to name just a few) is usually modelled by a graph in which vertices represent 'nodes' (stations or processors) while undirected or directed edges stand for 'links' or other types of connections, physical or virtual. A cycle that contains every vertex of a graph is called a hamiltonian cycle and a graph which contains a hamiltonian cycle is called a hamiltonian graph. The problem of the existence of a hamiltonian cycle is closely related to the well known problem of a travelling salesman. These problems are NP-complete and NP-hard, respectively. While some necessary and sufficient conditions are known, to date, no practical characterization of hamiltonian graphs has been found. There are several ways to generalize the notion of a hamiltonian cycle. In this thesis we make original contributions in two of them, namely k-walks and r-trestles." --Abstract. / Doctor of Philosophy

Using the approach of Coloured Petri nets (CPNs) and automata theory, this thesis shows how to formalise the service provided by the Transmission Control Protocol (TCP) and verify TCP Connection Management, an essential part of TCP. Most of the previous work on modelling and analysing TCP Connection Management is based on early versions of TCP, which are different from the current TCP specification. Also the scope is mainly confined to the connection establishment procedure, while the release procedure is either simplified or omitted from investigation. This thesis extends prior work by verifying a detailed model of TCP Connection Management. In defining the TCP service, the set of service primitives and their sequencing constraints are specified at each service access point. / thesis (PhDComputerSystemsEng)--University of South Australia, 2004.

Thesis (M.S.)--Rochester Institute of Technology, (1989). / Includes bibliographical references (leaves 170-171).