Multicode transmission using Walsh Hadamard transform
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorShiau-He Shawn Tsai
Life of this patent
Estimating the term…
Abstract
A symbol sequence contained in a received signal comprising a cyclic convolution of a Walsh code multiplexed signal and a channel impulse response of a multipath channel is detected using Walsh Hadamard domain equalization techniques. The method comprises converting the received signal and the channel impulse response of the multipath channel from the time domain to the WHT domain, and determining the symbol sequence based on equalizing the received signal in the WHT domain using WHT spectra of the channel impulse response to remove inter-symbol interference from the received signal due to cross-correlation between Walsh codes.
Claims14
A method of detecting a symbol sequence contained in a received signal comprising a cyclic convolution of a Walsh code multiplexed signal and a channel impulse response of a multipath channel, the method comprising:
- calculating a transformation matrix that relates the Walsh Hadamard Transform (WHT) domain spectra of the data signal and the WHT domain spectra of the channel impulse response to the received signal;
- and
- estimating the symbol sequence as a function of the transformation matrix and the received signal, by inverting the transformation matrix and multiplying the received signal by the inverse of the transformation matrix;
- wherein calculating the transformation matrix is based on applying similarity transforms to the WHT domain spectra of the channel impulse response, wherein the similarity transforms relate the time domain cyclic convolution of the data signal and the channel impulse response to a dyadic convolution of the data signal and the channel impulse response;
- and
- wherein applying similarity transforms to the WHT domain spectra of the channel impulse response comprises computing Hadamard products of the similarity transforms and one-dimensional expansions of the WHT domain spectra of the channel impulse response.
A receiver configured to detect a symbol sequence contained in a received signal comprising a cyclic convolution of a Walsh code multiplexed signal and a channel impulse response of a multipath channel, the receiver comprising one or more processing circuits configured to:
- calculate a transformation matrix that relates the Walsh Hadamard Transform (WHT) domain spectra of the data signal and the WHT domain spectra of the channel impulse response to the received signal;
- and
- estimate the symbol sequence as a function of the transformation matrix and the received signal, by inverting the transformation matrix and multiplying the received signal by the inverse of the transformation matrix;
- wherein the one or more processing circuits are configured to calculate the transformation matrix by applying similarity transforms to the WHT domain spectra of the channel impulse response, wherein the similarity transforms relate the time domain cyclic convolution of the data signal and the channel impulse response to-a dyadic convolution of the data signal and the channel impulse response;
- and
- wherein the one or more processing circuits are configured to apply similarity transforms to the WHT domain spectra of the channel impulse response by computing Hadamard products of the similarity transforms and one-dimensional expansions of the WHT domain spectra of the channel impulse response.
Dependencies are inferred from the claim text.