Apparatus and method for improved performance in radio telecommunication systems that use pulse-shaping filters
First Claim
1. An apparatus comprising:
- a transmitter for transmitting a time domain signal, wherein the transmitter comprises;
an orthogonal frequency division multiplexing (OFDM) modulator that divides a modulated information-bearing signal into a plurality of streams, spreads each of the plurality of streams with a spreading code, sums the spread streams into an input vector X of length Nb, divides the input vector X of length Nb into two parts, inserts Nx zeros between the two parts, and takes an inverse fast Fourier transform (IFFT) of size NbNx to obtain a time-domain signal; and
a pulse-shaping filter coupled to the OFDM modulator for processing the time-domain signal prior to transmission; and
a receiver for receiving the transmitted time-domain signal, wherein the receiver comprises an OFDM demodulator for taking a fast Fourier transform (FFT) of size NbNx of the received signal and removes the zeros inserted in the transmitter from the resulting frequency-domain signal.
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Accused Products
Abstract
A apparatus and method for improved performance in radio telecommunications systems, and in particular multi-carrier code division multiple access (MC-CDMA) networks that employ pulse-shaping filters on the transmit side of a radio link. In order to more accurately transmit a radio signal bearing a symbol sequence, the modulated and spread information stream is upsampled using a technique that involves inserting zeros in the frequency domain. A corresponding downsampling procedure on the receive side permits reconstruction of the transmitted symbols. A new channel estimation algorithm may also be used, and the improved channel estimation advantageously employed to obtain more faithful symbol detection.
11 Citations
21 Claims
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1. An apparatus comprising:
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a transmitter for transmitting a time domain signal, wherein the transmitter comprises; an orthogonal frequency division multiplexing (OFDM) modulator that divides a modulated information-bearing signal into a plurality of streams, spreads each of the plurality of streams with a spreading code, sums the spread streams into an input vector X of length Nb, divides the input vector X of length Nb into two parts, inserts Nx zeros between the two parts, and takes an inverse fast Fourier transform (IFFT) of size NbNx to obtain a time-domain signal; and a pulse-shaping filter coupled to the OFDM modulator for processing the time-domain signal prior to transmission; and a receiver for receiving the transmitted time-domain signal, wherein the receiver comprises an OFDM demodulator for taking a fast Fourier transform (FFT) of size NbNx of the received signal and removes the zeros inserted in the transmitter from the resulting frequency-domain signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus comprising:
a receiver configured to receive a time domain signal, wherein the time domain signal is generated by dividing a modulated information-bearing signal into a plurality of streams, spreading each of the plurality of streams with a spreading code, summing the spread streams into an input vector X of length Nb, dividing the input vector X of length Nb into two parts, inserting Nx zeros between the two parts, and taking an inverse fast Fourier transform (IFFT) of size NbNx to obtain the time-domain signal, said receiver comprising; an orthogonal frequency division multiplexing (OFDM) demodulator for taking an FFT of the received time-domain signal and removing the inserted zeros. - View Dependent Claims (14)
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15. A method comprising:
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dividing a modulated information-bearing signal into a plurality of streams; spreading each of the plurality of streams with a spreading code; summing the spread streams into a symbol sequence of length Nb; dividing the symbol sequence into two portions; inserting zeros between the two portions to generate a resulting stream; taking an inverse fast Fourier transform (IFFT) of the resulting stream to obtain a time-domain signal; providing the time-domain signal to a pulse-shaping filter; and transmitting the time-domain signal over a transmission channel. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A transmitter comprising:
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an orthogonal frequency division multiplexing (OFDM) modulator that divides a modulated information-bearing signal into a plurality of streams, spreads each of the plurality of streams with a spreading code, sums the spread streams into an input vector X of length Nb, divides the an input vector X of length Nb into two parts, inserts Nx zeros between the two parts, and takes an inverse fast Fourier transform (IFFT) of size NbNx to obtain a time-domain signal; and a pulse-shaping filter coupled to the OFDM modulator for processing the time-domain signal prior to transmission.
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Specification