Nonuniform Subband Superposed OFDM with Variable Granularity Spectrum Allocation for 5G

Orthogonal frequency division multiplexing (OFDM) can not meet the diverse scenarios of the future fifth generation (5G) networks due to its high out-of-band emission (OOBE), relatively low spectrum efficiency, and poor flexibility. In this paper, a nonuniform subband superposed OFDM (NSS-OFDM) scheme, based on a variable granularity (VG) spectrum allocation technique, is proposed as a candidate waveform for 5G. The VG method is exploited to divide the transmission band into a certain amount of subbands, each of which is applied to a specified application scenario through configuring the signaling parameters. To reduce the computational complexity, a multistage polyphase subfiltering architecture is utilized. Additionally, with subtly designed filters, the OOBE is significantly suppressed, which can minimize the frequency guard intervals between subbands. At the receiver, bit-error- rate is investigated for the additive white Gaussian noise and frequency selective channel. Simulation results show that the spectral efficiency, in terms of spectrum utilization rate, is increased up to 98.85% when ignoring the BER performance loss.