Adaptive despreader
AssigneeQUALCOMM Incorporated
InventorArthur Ross
Life of this patent
Estimating the term…
Abstract
A method and apparatus for adaptively despreading a direct sequence spread spectrum signal. The direct sequence spread spectrum signal is provided to a transversal filter. The output of the filter is demodulated to provide a soft symbol. The soft symbol is provided to an error corrector which generates an error corrected version of the soft symbol, referred to as a hard symbol. The value of the hard symbol is subtracted from the soft symbol to generate an error symbol. The error symbol is then used to compute tap values of the transversal filter by an LMS algorithm.
Claims23
An adaptive despreader comprising:
- transversal filter means for receiving input samples and for filtering said input samples in accordance with a set of adaptive filter tap values to provide filtered chip values wherein said adaptive tap values are updated in accordance with a re-spread error signal;
- de-spreading means for receiving said filtered chip values and de-spreading said filtered chip values in accordance with a direct sequence spread spectrum format to provide a first estimated symbol and for generating a second estimated symbol in accordance with a predetermined decision format;
- error calculator means for receiving said first estimated signal and said second estimated signal and for generating an error signal in accordance with said first estimated signal and said second estimated signal;
- spreading means for receiving said error signal and for spread spectrum spreading said error signal in accordance with a predetermined spread spectrum format to provide said re-spread error signal.
A method for adaptively despreading a spread spectrum signal comprising the steps of:
- receiving input samples;
- filtering said input samples in accordance with a set of adaptive filter tap values to provide filtered chip values wherein said adaptive tap values are updated in accordance with a re-spread error signal;
- de-spreading said filtered chip values in accordance with a direct sequence spread spectrum format to provide a first estimated symbol;
- generating a second estimated symbol in accordance with a predetermined decision format;
- generating an error signal in accordance with said first estimated signal and said second estimated signal;
- and
- spreading said error signal in accordance with a predetermined spread spectrum format to provide said re-spread error signal.
An adaptive despreader comprising:
- transversal filter having a first input for receiving input samples and having a second input for receiving tap update values and having an output;
- error calculator having an input coupled to said transversal filter output and having an output for providing a spread spectrum calculated error signal;
- and
- tap update calculator having a first input coupled to said error calculator output and having an output coupled to said second transversal filter input.
Dependencies are inferred from the claim text.