Fading channel simulator
First Claim
1. A fading channel simulator for affecting a transmitted radio signal with a selected channel scattering function for use in testing fading channel transmission characteristics of a receiver and transmitter in a communications system, comprising:
- first transform means for receiving an analog output from said transmitter and outputting a plurality of Fast Fourier Transform (FFT) signal coefficient matrices, each said FFT matrix corresponding to one of a series of segments in a data string representing said analog output;
second transform means for receiving said selected scattering function and outputting a plurality of inverse-FFT channel realization coefficient matrices, each matrix representing successive delay-spread and Doppler-spread characteristics;
multiplication means for multiplying one of said signal coefficient matrices with one of said channel realization coefficient matrices to form an output matrix; and
output signal means for forming the inverse FFT of said output matrix and outputting a faded channel signal string representing said received radio signal for input to said receiver.
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Accused Products
Abstract
Fading channel effects on a transmitted communication signal are simulated with both frequency and time variations using a channel scattering function to affect the transmitted signal. A conventional channel scattering function is converted to a series of channel realizations by multiplying the square root of the channel scattering function by a complex number of which the real and imaginary parts are each independent variables. The two-dimensional inverse-FFT of this complex-valued channel realization yields a matrix of channel coefficients that provide a complete frequency-time description of the channel. The transmitted radio signal is segmented to provide a series of transmitted signal and each segment is subject to FFT to generate a series of signal coefficient matrices. The channel coefficient matrices and signal coefficient matrices are then multiplied and subjected to inverse-FFT to output a signal representing the received affected radio signal. A variety of channel scattering functions can be used to characterize the response of a transmitter-receiver system to such atmospheric effects.
31 Citations
8 Claims
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1. A fading channel simulator for affecting a transmitted radio signal with a selected channel scattering function for use in testing fading channel transmission characteristics of a receiver and transmitter in a communications system, comprising:
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first transform means for receiving an analog output from said transmitter and outputting a plurality of Fast Fourier Transform (FFT) signal coefficient matrices, each said FFT matrix corresponding to one of a series of segments in a data string representing said analog output; second transform means for receiving said selected scattering function and outputting a plurality of inverse-FFT channel realization coefficient matrices, each matrix representing successive delay-spread and Doppler-spread characteristics; multiplication means for multiplying one of said signal coefficient matrices with one of said channel realization coefficient matrices to form an output matrix; and output signal means for forming the inverse FFT of said output matrix and outputting a faded channel signal string representing said received radio signal for input to said receiver. - View Dependent Claims (2, 3, 4)
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5. A method for simulating fading channel effects on a transmitted high frequency radio signal, comprising the steps of:
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generating a series of complex realizations of said fading channel from a channel scattering function including both a delay-spread function and a Doppler-spread function; segmenting said transmitted radio signal into time length segments each having a preselected duration; forming a digital representation of said signal in each segment; performing a FFT on each digital representation to obtain a matrix of signal coefficients; affecting each one of said segments with a one of said realizations of said fading channel to generate a received signal; and combining said received signal segments to recreate a received radio signal with amplitude and phase fading effects for input to a receiver. - View Dependent Claims (6, 7, 8)
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Specification