On the filter design for generalized frequency division multiplexing

Abstract

Generalized frequency division multiplexing (GFDM) is a multicarrier system based on digital filterbank. GFDM is a generalized version of orthogonal frequency division multiplexing (OFDM) and single-carrier frequency division multiplexing (SC-FDM) by filtering the upsampled symbols in the frequency domain per each subcarrier. GFDM symbol carries more than one subsymbols in one subcarrier, so it can reduce the cyclic prefix (CP) which is needed for OFDM-based system when the number of subcarriers is the same as OFDM systems. A GFDM system is flexible because it can control the number of subcarriers and the number of subsymbols which is suitable for demanding scenarios. So, GFDM is suitable for scenarios of the fifth generation (5G) networks. Since GFDM uses filtering in the frequency domain, the analysis of optimal filter which is suitable for the scenario of 5G networks is needed and PAPR analysis is important since uplink system cannot use high power amplifiers. In this paper, we analyze the optimal information rate filter for GFDM systems and the trade-off of information rate and the peak-to-average power ratio (PAPR) of the transmit signal of GFDM which are important to design the tranceiver system. This paper contributes to the following : 1) Optimal information rate filter for GFDM with suitable equalizer and analysis of the rate of optimal filter when the channel is ideal and the channel gain is varying. 2) Trade-off between the information rate and the PAPR of the system when the filter is a root-raised cosine (RRC) filter. In summary, SC-FDM is optimal in information-rate among GFDM systems if the channel is ideal, but there is another optimal filter when the channel gain is varying. Also, there is a PAPR optimal roll-off factor of RRC filter of GFDM system.