Performance analysis of some timing offset equalizers for FBMC/OQAM systems

The requirements of future wireless networks lead to reconsidering the physical layer and, particularly the respective merits of the major multicarrier transmission techniques, OFDM and FBMC. In comparison, equalization has been a sticking issue for filter bank multicarrier systems, because of performance and implementation aspects. In contrast, equalization is straightforward to implement in OFDM systems and it is easy to figure out the performance achieved, thanks to the presence of the cyclic prefix. Here, OFDM and FBMC/OQAM systems are compared for timing offset equalization, which is representative of global channel equalization and appears as such in some use cases, e.g. asynchronous access. The single tap equalizer and the multitap time-domain equalizer are analyzed for a specific, yet representative, FBMC scheme. It is shown that multitap time-domain timing-offset sub-channel equalization brings improvements over single-tap equalization but its discrete time nature limits its performance. There is no such limitation in the frequency domain and a recently proposed implementation of the FBMC concept, named frequency spreading, is analyzed. Equipped with this receiver, an FBMC system can withstand any timing offset and, then, unlike OFDM, it is able, in a multicarrier context, to support asynchronous users while keeping spectral efficiency.