Pulse Shaping Filter Design for Filtered OFDM Transceivers

Abstract

CP-OFDM waveforms have been used successfully in the physical layer of 4G systems to overcome the channel selectivity and to provide good spectrum efficiency and high transmission data rates. 5G technology aims to support more communication services than its predecessor and considers many other scenarios such as the use of fragmented spectrum. However, this diversity of services cannot be supported by CP-OFDM since it applies a single set of parameters to the entire band to meet a particular service and it has large out-of-band spectral emission, which can affect transmissions in adjacent bands. Thus, in order to improve the spectrum containment, new waveforms more flexible than CP-OFDM have been proposed which make use of pulse shape filters. UFMC is a waveform that splits the bandwidth into several subbands which can be allocated to services with a particular set of parameters each. However, since the maximum length of UFMC filters is limited to size of CP, their stopband attenuation level can be not enough to meet spectrum emission mask requirements. This work presents a filter called semi-equiripple which has variable stopband decay rate, better frequency response than equiripple, and windowed sinc filters and good impulse response characteristics for reduction of ISI. The performance of the proposed filter is assessed in terms of the power spectrum density, spectrum mask compliance, MER, and operation in a multiservice asynchronous scenario.