Spreading and precoding in OFDM

摘要

An OFDM transmitter spreads original data symbols with a complex-valued spreading matrix derived from a discrete Fourier transform. Spread data symbols are mapped to OFDM subcarriers. Spreading and mapping are configured to produce a transmitted spread-OFDM signal with a low peak-to-average power ratio (PAPR) and orthogonal code spaces. In MIMO systems, the complex-valued spreading matrix can comprise a MIMO precoding matrix, and the code spaces can comprise MIMO subspaces. In Cooperative-MIMO, a combination of low code-space cross correlation and low PAPR can be achieved.

主权项

1. A transmitter configured to reside in a User Equipment (UE), comprising
a discrete Fourier transform (DFT) spreader configured to spread a block of original data symbols with a DFT-based spreading matrix comprising a plurality of orthogonal spreading codes to produce a plurality of spread data symbols; a subcarrier mapper responsive to channel-dependent scheduling that assigns a set of uplink orthogonal frequency division multiplex (OFDM) subcarriers to the UE, the subcarrier mapper configured to map each of a plurality of non-zero data symbols to one of the set of uplink OFDM subcarriers, the plurality of non-zero data symbols comprising the plurality of spread data symbols; and an inverse-DFT configured to modulate the plurality of non-zero data symbols onto the set of uplink OFDM subcarriers to generate an OFDM signal for transmission into a wireless wide area network (WWAN); wherein at least one of the DFT spreader and the subcarrier mapper configures the plurality of non-zero data symbols to reduce the OFDM signal's peak-to-average-power ratio (PAPR).