Spread-response precoding system having signature sequences longer than the inter-symbol time interval
AssigneeLucent Technologies Inc.
InventorGregory W. Wornell
Life of this patent
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Abstract
Method and apparatus for preparing a message stream of symbols for wireless transmission by pre-coding it through convolution with a characteristic "signature" of predetermined symbols identifying a particular user of the message system. The time duration of the signature should exceed the inter-symbol interval of the message stream in order to reduce the likelihood of error caused by fading in the transmission channel.
Claims25
A method of preparing for transmission at least one stream of symbols characterized by a regular inter-symbol time interval, said method comprising the steps of:
- (a) supplying a train of signature sequences each of which has a controllable duration longer than said inter-symbol time interval,
- (b) delaying signature sequences of said train to form a train of delayed signature sequences in which adjacent signature sequences overlap in time, and
- (c) modulating said stream of symbols onto said train of delayed signature sequences, said modulating step including periodically determining instantaneous products of said symbols with corresponding values of said train of overlapping delayed signature sequences and summing said instantaneous products to develop a modulated signal in discrete form.
A method of preparing for transmission at least one stream of symbols characterized by a regular inter-symbol time interval, said method comprising the steps of:
- (a) expanding said stream of symbols in the time domain to produce a time-expanded symbol stream characterized by an expanded inter-symbol time interval,
- (b) supplying a train of signature sequences each of which has a controllable duration longer than said expanded inter-symbol time interval,
- (c) delaying signature sequences of said train to form a train of delayed signature sequences in which adjacent signature sequences overlap in time, and
- (d) modulating said time-expanded symbol stream onto said train of delayed signature sequences, said modulating step including periodically determining instantaneous products of said symbols with corresponding values of said train of overlapping delayed signature sequences and summing said instantaneous products to develop a modulated signal in discrete form.
A method of coding and preparing for transmission over a fading channel a series of data bits, said method comprising the steps of:
- (a) coding said series of data bits against errors introducible by said fading channel to provide a coded stream of symbols characterized by a regular inter-symbol time interval,
- (b) expanding said coded stream of symbols in the time domain to produce a time-expanded symbol stream in which adjacent symbols of said stream are separated by an expanded inter-symbol time interval,
- (c) supplying a train of signature sequences each of which has a duration longer than said expanded inter-symbol time interval,
- (d) delaying signature sequences of said train to form a train of delayed signature sequences in which adjacent signature sequences overlap in time, and
- (e) modulating said time-expanded symbol stream onto said train of delayed signature sequences, said modulating step including periodically determining instantaneous products of said symbols with corresponding values of said train of overlapping delayed signature sequences and summing said instantaneous products to develop a modulated signal in discrete form.
A method of coding and preparing for transmission over a fading channel a series of data bits, said method comprising the steps of:
- (a) coding said series of data bits against errors introducible by said fading channel to provide a coded stream of symbols characterized by a regular inter-symbol time interval,
- (b) supplying a train of signature sequences each of which has a duration longer than said inter-symbol time interval,
- (c) delaying signature sequences of said train to form a train of delayed signature sequences in which adjacent signature sequences overlap in time, and
- (d) modulating said coded stream of symbols onto said train of delayed signature sequences, said modulating step including periodically determining instantaneous products of said symbols with corresponding values of said train of overlapping delayed signature sequences and summing said instantaneous products to develop a modulated signal in discrete form.
Apparatus for preparing for transmission at least one stream of symbols characterized by a regular inter-symbol time interval, said apparatus comprising:
- (a) means for supplying a train of signature sequences each of which has a controllable duration longer than said inter-symbol time interval,
- (b) means for delaying signature sequences of said train to form a train of delayed signature sequences in which adjacent signature sequences overlap in time, and
- (c) a modulation device for identifying specific values of said train of delayed signature sequences corresponding to respective symbols of said stream, forming instantaneous products of said specific values of said train with respective corresponding symbols of said stream, and summing said instantaneous products to develop a modulated signal in discrete form.
Dependencies are inferred from the claim text.