Orthogonal Frequency Division Multiplexing (OFDM) is a digital transmission
method developed to meet the increasing demand for higher data rates in
communications which can be used in both wired and wireless environments. This
thesis describes the issue of the Peak to Average Power Ratio (PAPR) in OFDM
which is a major drawback, and presents new and variations to existing algorithms to
reduce it.

Peak power reduction in orthogonal frequency division multiplexing transmitters

Bit-error rate based Doppler estimation for shallow water acoustic OFDM communication

https://eprints.ncl.ac.uk/file_store/production/197541/DD7BC629-F2AA-4E17-938E-44293A4706C1.pdf

Efficient algorithms for computing the new Mersenne number transform

This thesis explores three distinct philosophies for improving the efficiency of multi-carrier communication on the digital subscriber loop. The first topic discussed is impulse response shortening for discrete multitone transceivers. The minimum mean-squared error impulse response shortener is reformulated to allow near-optimal rate performance. It is demonstrated that the best existing eigen-filter designed channel shortener is a particular case of the proposed reformulation. An adaptive time-domain LMS algorithm is provided as an alternative to eigen-decomposition. The next part of the thesis examines bitand powerloading algorithms for multitone systems. The problem of rate-optimal loading has already been solved. It is shown, however, that the rate-optimal solution does not give best value for complexity, and that near optimal schemes can perform very well at a fraction of the computational cost. The final section of the thesis is a brief exposition of the use of wavelet packets to achieve multi-carrier communication. It is proposed that the non-uniform spectral decomposition afforded by wavelet packet modulation allows reduced inter-symbol interference effects in a dispersive channel. Associated Publications D. Daly , C. Heneghan and A.D. Fagan, “Minimum mean-squared error impulse response shortening for discrete multitone transceivers”, accepted for publication, IEEE Trans. Signal Process.. D. Daly , C. Heneghan and A.D. Fagan, “Powerand bitloading algorithms for multitone communications”, accepted for IEEE Int. Symp. Image, Signal Process., Analysis, Rome, Italy, Sep. 2003. D. Daly , C. Heneghan and A.D. Fagan, “Optimal wavelet packet modulation”, in Proc. Irish Signals, Syst. Conf., Cork, pp. 47-52, June 2002. D. Daly , C. Heneghan, A.D. Fagan and M.Vetterli, “Optimal wavelet packet modulation under finite complexity constraint”, in Proc. IEEE Int. Conf. Acoust., Speech, Signal Process., Orlando FLA, Vol III, pp. 2789-2792, May 2002. D. Daly , C. Heneghan, and A.D. Fagan, “A minimum mean-squared error interpretation of residual ISI channel shortening for discrete multitone transceivers” in Proc. IEEE Int. Conf. Acoust., Speech, Signal Process., Salt Lake City, UT, May 2001.

Efficient Multi-Carrier Communication on the Digital Subscriber Loop

Peak Power Reduction in

We propose an efficient FFT (fast Fourier transform) algorithm for OFDM (orthogonal frequency division multiplexing) modulation, named "radix-4/2". This algorithm, based on the radix-4 butterfly operator reduces the number of non-trivial multiplications compared to the radix-2/sup 3/ FFT algorithm, and it has twice the processing rate as the radix-2/sup 3/ FFT algorithm. With 64-point and pipeline architecture, the proposed radix-4/2 algorithm reduces the number of non-trivial multiplications to the ratio of 3 to 2 compared with the radix-4 algorithm, and it has twice the processing rate as the radix-2/sup 3/ algorithm.

Yonji Tak

Papers

Efficient FFT algorithm for OFDM modulation