Energy-efficient implementation of a wideband transceiver system with per-band equalisation and synchronisation

For emission in the TV white space spectrum, the regulators are imposing strict spectral masks, which can be fulfilled using a DFT-modulated filter-bank multi-carrier system to extract one or several TVWS channels in the 470–790MHz range. Such a system reduces the channel dispersion, but even with near-perfectly reconstructing filter banks, an equaliser is required to at least perform some form of timing synchronisation. In this work, we propose a per-band equalisation and synchronisation approach, performed by a constant modulus (CM) algorithm running concurrently with a decision-directed adaptation process for faster convergence and reduced phase ambiguity. We compare symbol- and fractionally-spaced versions, and investigate their fixed-point implementation on a field programmable gate array. We elaborate on advantages that this fractionally spaced concurrent system offers over a symbol-spaced equaliser and compare it to equalisers that are updated purely by a CM algorithm.