Receiving spread spectrum signals with narrowband interference
AssigneeBritish Telecommunications public limited company
InventorTerence Widdowson
Life of this patent
Estimating the term…
Abstract
A receiver receives spread spectrum signals which include unwanted narrowband signals, for example, radio signals which comprise a mixture of signals from signal sources using the Group Special Mobile (GSM) ETSI standard coding and from signal sources using Code Division Multiple Access (CDMA) coding. Both despreading of the spread spectrum signal and attenuating of predetermined frequencies (corresponding to the narrowband signal) of the spread spectrum signal are performed prior to downconverting. In another approach to decoding a spread spectrum signal in which an unwanted narrowband signal has been coded using a coding scheme with error correction capabilities, the narrowband signal is decoded, regenerated and subtracted prior to despreading of the spread spectrum signal.
Claims18
An apparatus for decoding a spread spectrum signal comprising:
- means for generating a despreading signal for despreading the spectrum signal;
- a notch filter arranged to attenuate predetermined frequencies of the despreading signal to produce a notched despreading signal;
- means for despreading the spectrum signal using said notched despreading signal so as to simultaneously despread the spread spectrum signal and attenuate the predetermined frequencies of the spread spectrum signal;
- means for downconverting a signal to produce a lower frequency signal;
- wherein no downconversion of the spread spectrum signal occurs prior to said despreading and attenuation.
An apparatus for decoding a spread spectrum signal which has been transmitted via a transmission channel, said spread spectrum signal comprising a wanted spread spectrum signal component and an unwanted narrowband signal component, a narrowband signal having been coded using a coding scheme with error correction capabilities, said apparatus comprising a narrowband signal subtractor containing:
- means for decoding and correcting a composite signal according to the narrowband signal coding scheme to provide a decoded version of the narrowband signal;
- means to estimate amplitude and phase characteristics of the transmission channel;
- means to encode the decoded corrected narrowband signal according to the narrowband signal coding scheme to produce an estimated narrowband signal;
- means to adjust phase and amplitude of the estimated narrowband signal according to the estimated amplitude and phase characteristics;
- and
- means to subtract the adjusted estimated narrowband signal from the received composite signal to provide an estimate of the spread spectrum signal component.
An apparatus for decoding a spread spectrum signal which has been transmitted via a transmission channel, said spread spectrum signal comprising a wanted spread spectrum signal component and an unwanted narrowband signal component, a narrowband signal having been coded using a coding scheme with error correction capabilities, said apparatus comprising a narrowband signal subtractor containing:
- means for decoding and correcting a composite signal according to the narrowband signal coding scheme to provide a decoded version of the narrowband signal;
- means to estimate amplitude and phase characteristics of the transmission channel;
- means to encode the decoded corrected narrowband signal according to the narrowband signal coding scheme to produce an estimated narrowband signal;
- means to adjust phase and amplitude of the estimated narrowband signal according to the estimated amplitude and phase characteristics of the transmission channel;
- and
- means to subtract the adjusted estimated narrowband signal from the received composite signal to provide an estimate of the spread spectrum signal component;
- wherein the narrowband coding scheme can also detect uncorrectable errors and in which the decoding means is arranged upon detection of an uncorrectable error to suppress the subtraction.
A method for decoding a spread spectrum signal comprising:
- generating a despreading signal for despreading the spread spectrum of a signal;
- attenuating predetermined frequencies of the despreading signal to produce a resulting notched despreading signal;
- despreading the spread spectrum signal of the spread spectrum signal using the notched despreading signal so as to simultaneously despread the spread spectrum signal and attenuate the predetermined frequencies of the spread spectrum signal;
- downconverting a signal to produce a lower frequency signal;
- and
- attenuating predetermined frequencies of the spread spectrum signal;
- wherein no downconversion of the spread spectrum signal is performed prior to said despreading and attenuation.
A method for decoding a spread spectrum signal which has been transmitted via a transmission channel, said spread spectrum signal comprising a wanted spread spectrum signal component and an unwanted narrowband signal component, a narrowband signal having been coded using a coding scheme with error correction capabilities, said method including narrowband signal subtraction comprising:
- decoding and correcting a composite signal according to the narrowband signal coding scheme to provide a decoded version of the narrowband signal;
- estimating amplitude and phase characteristics of the transmission channel;
- encoding the decoded corrected narrowband signal according to the narrowband signal coding scheme to produce an estimated narrowband signal;
- adjusting phase and amplitude of the estimated narrowband signal according to the estimated amplitude and phase characteristics of the transmission channel;
- and
- subtracting the adjusted estimated narrowband signal from the received composite signal to provide an estimate of the spread spectrum signal component.
A method for decoding a spread spectrum signal which has been transmitted via a transmission channel, said spread spectrum signal comprising a wanted spread spectrum signal component and an unwanted narrowband signal component, a narrowband signal having been coded using a coding scheme with error correction capabilities, said method including narrowband signal subtraction comprising:
- decoding and correcting a composite signal according to the narrowband signal coding scheme to provide a decoded version of the narrowband signal;
- estimating amplitude and phase characteristics of the transmission channel;
- encoding the decoded corrected narrowband signal according to the narrowband signal coding scheme to produce an estimated narrowband signal;
- adjusting phase and amplitude of the estimated narrowband signal according to the estimated amplitude and phase characteristics of the transmission channel;
- and
- subtracting the adjusted estimated narrowband signal from the received composite signal to provide an estimate of the spread spectrum signal component;
- wherein the narrowband coding scheme can also detect uncorrectable errors and in which upon detection of an uncorrectable error, subtracting the narrowband signal is omitted.
An apparatus for decoding a spread spectrum signal comprising:
- means for generating a despreading signal for despreading the spread spectrum of a signal;
- means for despreading the spread spectrum of a signal using the despreading signal;
- means for downconverting a signal to produce a lower frequency signal;
- and
- means for attenuating predetermined frequencies of a signal;
- wherein the despreading means is connected to despread the spread spectrum signal prior to downconverting and the attenuating means is connected to attenuate predetermined frequencies of the spread spectrum signal prior to downconverting;
- and
- the attenuating means is connected to attenuate predetermined frequencies of the despreading signal and a resulting notched despreading signal is connected to simultaneously despread the spread spectrum signal and attenuate the predetermined frequencies of the spread spectrum signal.
A method for decoding a spread spectrum signal comprising:
- generating a despreading signal for despreading the spread spectrum signal;
- despreading the spread spectrum signal using the despreading signal;
- downconverting a signal to produce a lower frequency signal;
- and
- attenuating predetermined frequencies of a signal;
- wherein despreading of the spread spectrum signal is performed prior to downconverting and attenuating of predetermined frequencies of the spread spectrum signal is performed prior to downconverting;
- and
- the predetermined frequencies of the despreading signal are attenuated and a resulting notched despreading signal is used to simultaneously despread the spread spectrum signal and attenuate the predetermined frequencies of the spread spectrum signal.
Dependencies are inferred from the claim text.