Tail Shortening Of OQAM/FBMC Signals

In the past, orthogonal frequency division multiplexing(OFDM) has enjoyed its dominance as the most popular signaling method for broadband communications. OFDM offers minimum complexity, and achieves fair bandwidth efficiency, and possibly it is the best compromise choice for point-to-point communication. However, it has been noted that OFDM has to face many challenges when considered for adoption in the more complex networks. For instance, the use of OFDM in the uplink of multiuser networks, known as orthogonal frequency division multiple access(OFDMA), requires accurate synchronization of the users' signals at the base station input. Such synchronization is not straightforward and demands a lot of resources.Filter bank multicarrier with offset quadrature amplitude modulation(OQAM/FBMC) is considered as a promising alternative to the conventional OFDM technique. Different from OFDM systems, the basic concept of OQAM/FBMC is based on a well-designed pulse shaping filter with good time frequency localization features. However, because of the ramp-up and ramp-down of the waveform at the beginning and the end of each packet, its spectral efficiency can drop significantly in short packets/data bursts.In this paper, we propose a novel method that shortens the ramp-up and ramp-down of OQAM/FBMC signals by appending a few virtual symbols(i.e., none data carrying) at the beginning and the end of each packet. We show that the ramp-up and ramp-down tails in FMBC/OQAM can be suppressed to an extent that they deem as negligible and thus may be ignored. This shortens the length of signal burst in each OQAM/FBMC packet, hence, improves on its bandwidth efficiency. Simulation results show that the proposed method has a much improved error vector magnitude(EVM) and similar out-of-band(OOB) emission performance, when compared with a truncation method through a similar window, but without transmitting virtual symbols.We develop an optimization method that allows computation of virtual symbols, for each data packet. We present extensive simulations in residual tail and cancelation signal energy, EVM, bit error rate(BER), peak-to-average power ratio(PAPR) and power spectral density(PSD) with a tail overhead of T/4 on each side. The results showed that while the proposed method retains the excellent OOB emission performance of the conventional OQAM/FBMC method, a very low EVM, and a very minimal change in PAPR, it results in a tail overhead that remains comparable to or lower than those of the universal filtered multicarrier(UFMC), generalize frequency division multiplexing(GFDM) and cyclic filter bank multicarrier(C-FBMC), which in recent literature have been introduced as its competitors.