Multi-mode orthogonal frequency division multiplexing transmitter for highly-spectrally-efficient communications

摘要

A transmitter may comprise a symbol mapper circuit and operate in at least two modes. In a first mode, the number of symbols output by the mapper circuit per orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter may be greater than the number of data-carrying subcarriers used to transmit the OFDM symbol. In a second mode, the number of symbols output by said mapper circuit per orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter is less than or equal to the number of data-carrying subcarriers used to transmit said OFDM symbol. The symbols output by the symbol mapper circuit may be N-QAM symbols. While the circuitry operates in the first mode, the symbols output by the mapper may be converted to physical subcarrier values via filtering and decimation prior to being input to an IFFT circuit.

主权项

1. A transmitter comprising:
circuitry comprising a symbol mapper circuit and being operable in at least two modes, wherein: while said circuitry operates in a first of said modes, the number of symbols output by said symbol mapper circuit for a first-mode orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter is greater than the number of data-carrying subcarriers used to transmit said first-mode OFDM symbol; while said circuitry operates in a second of said modes, the number of symbols output by said symbol mapper circuit for a second-mode orthogonal frequency division multiplexing (OFDM) symbol transmitted by said transmitter is less than or equal to the number of data-carrying subcarriers used to transmit said second-mode OFDM symbol; said transmitter comprises a decimator and is operable to generate said first-mode OFDM symbol via a decimation performed by said decimator; said decimation introduces an amount of aliasing such that the ratio of P1 to P2 is equal to or less than a threshold signal-to-noise ratio of a receiver to which said OFDM subcarriers are transmitted; P1 is total signal power of C′ virtual subcarrier values prior to said decimating; and P2 is the signal power of a portion of said C′ virtual subcarrier values residing at a frequency above a folding frequency determined by a decimation factor.