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- C. Tjhai, M. Tomlinson, R. Horan, M. Ahmed, M. Ambroze
- 2008

This paper presents a more efficient algorithm to count codewords of given weights in self-dual double-circulant and formally self-dual quadratic double-circulant codes over GF(2). A method of deducing the modular congruence of the weight distributions of the binary quadratic double-circulant codes is proposed. This method is based on that proposed by… (More)

- C. Tjhai, M. Tomlinson, R. Horan, M. Ahmed, M. Ambroze
- 2006 IEEE Information Theory Workshop - ITW '06…
- 2006

An efficient algorithm to count all codewords of given weight and a method to deduce the modular congruence of the weight distributions of the binary quadratic double-circulant codes are presented. Using this algorithm, we give the weight distribution of the quadratic double-circulant code of length 168 and that of the extended quadratic-residue code of the… (More)

- R. Horan, Cen Tjhai, Martin Tomlinson, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2005

We show how to construct an algorithm to search for binary idempotents which may be used to construct binary LDPC codes. The algorithm, which allows control of the key properties of sparseness, code rate and minimum distance, is constructed in the Mattson-Solomon domain. Some of the new codes, found by using this technique, are displayed.

- Cen Tjhai, Martin Tomlinson, R. Horan, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2005

Based on the ideas of cyclotomic cosets, idempotents and Mattson-Solomon polynomials, we present a new method to construct GF(2m ), where m > 0 cyclic low-density paritycheck codes. The construction method produces the dual code idempotent which is used to define the parity-check matrix of the low-density parity-check code. An interesting feature of this… (More)

In this paper we propose a new high capacity, low energy requirement, and robust spread spectrum watermark approach for still images. This approach uses an orthogonalisation scheme to generate a set of binary spread spectrum carriers that are able to minimize the interference of the original image on the watermark information detection, so that, more than… (More)

- Cen Tjhai, Martin Tomlinson, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2008

The Hamming weight enumerator function of the formally self-dual even, binary extended quadratic residue code of prime p = 8m + 1 is given by Gleason’s theorem for singly-even code. Using this theorem, the Hamming weight distribution of the extended quadratic residue is completely determined once the number of codewords of Hamming weight j Aj , for 0 ≤ j ≤… (More)

Patterned magnetic media promises areal densities in excess of 1 Tbit/in for data storage. However, current imperfect patterning techniques result in a variation in the dimensions and distribution of the fabricated islands. As a result, this variation introduces jitter in the replay waveform that makes data recovery difficult. In this paper, we investigate… (More)

- Ke Zhang, Martin Tomlinson, Mohammed Zaki Ahmed, Marcel Ambroze, Miguel R. D. Rodrigues
- IET Communications
- 2014

- P. Shah, M. Ahmed, M. Ambroze, C. Tjhai, P. J. Davey
- 2006

This paper investigates the use of multi-level modulation for magnetic recording using a novel Soft-Feedback Equalisation (SFE) approach. Different aspects of investigation are: 1) Multilevel Recording, 2) SFE and 3) Application of Turbo Codes. The SFE scheme is a model in which the partial response (PR) equaliser and Maximum A Posteriori (MAP) decoder are… (More)

- Jing Cai, Cen Tjhai, Martin Tomlinson, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2005

This paper investigates decoding of binary linear block codes over the binary erasure channel (BEC). Of the current iterative decoding algorithms on this channel, we review the Recovery Algorithm and the Guess Algorithm. We then present a Multi-Guess Algorithm extended from the Guess Algorithm and a new algorithm – the In-place Algorithm. The Multi-Guess… (More)