Methods and apparatus for signal conditioning in OFDMA systems

摘要

Methods and systems for conditioning an orthogonal frequency division multiplex (OFDM) signal are disclosed. The OFDM signal may be conditioned prior to transmission by a transmitter in an orthogonal frequency division multiple access (OFDMA) system operating on a channel with a plurality of subcarriers grouped into subchannels. The OFDM signal may be clipped based on a desired peak-to-average-power ratio (PAPR) to produce a clipped-off portion of the OFDM signal. The clipped-off portion of the OFDM signal may be transformed into the frequency domain to produce a frequency-domain signal. An in-band spectral shaping mask may be applied to subcarriers or subchannels of the frequency-domain signal within the channel to control the levels of distortion on the individual subcarriers or subchannels. The shaped frequency-domain signal is transformed into the time domain to produce a time-domain signal. A conditioned signal is produced for transmission by subtracting the time-domain signal from the OFDM signal.

主权项

1. A method for conditioning an orthogonal frequency division multiplex (OFDM) signal prior to transmission by a transmitter in an orthogonal frequency division multiple access (OFDMA) system operating on a channel with a plurality of subcarriers grouped into subchannels, the method comprising:
clipping said OFDM signal in the time domain to produce a clipped-off portion of said OFDM signal, wherein a time sample of the clipped-off portion of the said OFDM signal is set to zero if a corresponding time sample of the OFDM signal is not greater than a threshold that is based on a desired peak-to-average-power ratio (PAPR); transforming said clipped-off portion of said OFDM signal to produce a frequency-domain signal; applying an in-band spectral shaping mask to individual subcarriers or subchannels of the frequency-domain signal within the channel to control levels of in-band distortion on the individual subcarriers or subchannels, wherein a different in-band distortion level is allowed for a different subcarrier or subchannel; transforming the shaped frequency-domain signal to produce a time-domain signal; and producing a conditioned signal for transmission by subtracting the time-domain signal from said OFDM signal.