Flexible Multi-Group Single-Carrier Modulation: Optimal Subcarrier Grouping and Rate Maximization

摘要

Orthogonal frequency division multiplexing (OFDM) and single-carrierfrequency domain equalization (SC-FDE) are two commonly adopted modulationschemes for frequency-selective channels. Compared to SC-FDE, OFDM generallyachieves higher data rate, but at the cost of higher transmit signalpeak-to-average power ratio (PAPR) that leads to lower power amplifierefficiency. This paper proposes a new modulation scheme, called flexiblemulti-group single-carrier (FMG-SC), which encapsulates both OFDM and SC-FDE asspecial cases, thus achieving more flexible rate-PAPR trade-offs between them.Specifically, a set of frequency subcarriers are flexibly divided intoorthogonal groups based on their channel gains, and SC-FDE is applied over eachof the groups to send different data streams in parallel. We aim to maximizethe achievable sum-rate of all groups by optimizing the subcarrier-groupmapping. We propose two low-complexity subcarrier grouping methods and show viasimulation that they perform very close to the optimal grouping by exhaustivesearch. Simulation results also show the effectiveness of the proposed FMG-SCmodulation scheme with optimized subcarrier grouping in improving the rate-PAPRtrade-off over conventional OFDM and SC-FDE.