Loss and recapture of orthogonality in the modified Gram-Schmidt algorithm
SIAM Journal on Matrix Analysis and Applications
On the sphere-decoding algorithm I. Expected complexity
IEEE Transactions on Signal Processing - Part I
A universal lattice code decoder for fading channels
IEEE Transactions on Information Theory
On maximum-likelihood detection and the search for the closest lattice point
IEEE Transactions on Information Theory
Performance increase through the use of multiple sub-carriers in WSN
Proceedings of the 7th ACM international symposium on Mobility management and wireless access
A new quasi-optimal detection algorithm for a non orthogonal spectrally efficient FDM
ISCIT'09 Proceedings of the 9th international conference on Communications and information technologies
A fast constrained sphere decoder for ill conditioned communication systems
IEEE Communications Letters
Spectrally efficient OFDMA lattice structure via toroidal waveforms on the time-frequency plane
EURASIP Journal on Advances in Signal Processing - Special issue on applications of time-frequency signal processing in wireless communications and bioengineering
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This paper investigates the transmission of Frequency Division Multiplexed (FDM) signals, where carrier orthogonality is intentionally violated in order to increase bandwidth efficiency. In analogy to conventional OFDM, signal generation relies on an Inverse Fractional Fourier Transform (IFRFT) that can be implemented with O(N log2 N) algorithmic complexity. Optimal Maximum Likelihood (ML) detection is overly complex due to the presence of substantial Intercarrier Interference (ICI). Consequently, we investigate an alternative detection mechanism based on the Generalized Sphere Decoding (GSD) algorithm. We examine the bandwidth efficiency and the error performance in Additive White Gaussian Noise (AWGN), for various FDM signal parameters. In particular, we show that it is possible to detect optimally and efficiently FDM signals, with 25% bandwidth gain with respect to analogous OFDM signals. This indicates that the transmission of spectrally efficient non orthogonal FDM signals is tangible.