System and method of signal wave shaping for spectrum control of an OFDM signal
View Patent ↗A system and method of controlling the spectrum of an orthogonal frequency division multiplexing (OFDM) signal. The method comprises receiving an input frame of data samples to be modulated onto orthogonal multi-carrier signals, performing frequency domain filtering and spectrum masking on the input frame of data samples, and modulating the respective frequency modified data samples onto a plurality of carriers. Such a system may include an over sampling logic to over sample the input data to increase the frequency resolution of the output spectrum, a wave shaping filter to perform frequency domain filtering of the input data, a spectrum mask to further modify the spectrum of the output signal, and an inverse fast Fourier transform (IFFT) to generate the modulated orthogonal multi-carrier signal. Another embodiment entails controlling the spectrum of the output OFDM signal by performing time-domain filtering.
1. An orthogonal frequency division multiplexing (OFDM) system for generating a modulated orthogonal multi-carrier signal, comprising:
an over sampling logic to generate an MN over sampled data frame from an N sample data frame, wherein said MN over sampled data frame comprises M-1 zeros between consecutive samples;
a wave shaping filter to perform convolution of said over sampled data frame with MN filter coefficients to produce an MN complex filtered sample frame in order to modify the frequency response of said modulated orthogonal multi-carrier signal in the frequency domain;
a spectrum mask to modify said MN complex filtered sample frame respectively by MN elements to produce an MN complex filtered and masked sample frame in order to further modify the frequency response of said modulated orthogonal multi-carrier signal; and
an inverse fast Fourier transform (IFFT) to generate said modulated orthogonal multi-carrier signal from said MN complex filtered and masked sample frame.
2. The OFDM system of claim 1 , further comprising a modulation and framing logic to generate said N sample data frame by modulating a binary data frame.
3. The OFDM system of claim 2 , wherein said modulation and framing logic performs phase shift keying (PSK) type modulation, coherent or differential.
4. The OFDM system of claim 2 , wherein said modulation and framing logic performs amplitude shift keying (ASK) type modulation.
5. The OFDM system of claim 2 , wherein said modulation and framing logic performs quadrature amplitude modulation (QAM).
6. The OFDM system of claim 1 , further comprising a framing and overlapping logic to frame in time said modulated orthogonal multi-carrier signal and overlap in time consecutive frames of said modulated orthogonal multi-carrier signal.
7. The OFDM system of claim 1 , further comprising a spectrum control input to receive information relating to a desired spectrum for said modulated orthogonal multi-carrier signal and to control said spectrum mask to produce said desired spectrum for said modulated orthogonal multi-carrier signal.
8. The OFDM system of claim 1 , wherein the first value M and the second value N are integer values.