METHOD AND SYSTEM FOR SYNCHRONIZING AND SELECTIVELY ADDRESSING MULTIPLE RECEIVERS IN A WIRELESS, SPREAD SPECTRUM COMMUNICATION SYSTEM
First Claim
1. A method for wireless communication, comprising the steps of:
- transmitting a series of transmissions at a predetermined frequency, said transmissions separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register;
receiving said series of transmissions at a receiver;
at said receiver, measuring relative times of arrival between consecutive ones of said transmissions;
determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions;
matching a receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions; and
using said receiver feedback shift register to carry out synchronized communication with the transmitter.
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Accused Products
Abstract
A system and method for synchronizing and selectively addressing multiple receivers in a wireless communication system includes a spread spectrum transmitter and one or more spread spectrum receivers. The transmitter transmits a signal having an observable parameter which is pseudo-randomly varied. The receiver measures the relative times between recurrences of a selected value of the observable parameter being pseudo-randomly varied, and determines an initial state of the transmitter based upon the measured relative times. The receiver then synchronizes itself to the estimated current state of the transmitter using the determined initial state as a starting reference. In a frequency hopping embodiment, the spread spectrum transmitter comprises a feedback shift register, and transmits a sequence of pseudo-randomly hopped frequencies determined by the shift register. A receiver is tuned to one of the hopping frequencies, measures the relative times of arrival between consecutive transmissions, and determines the initial code word in the transmitter feedback shift register from the measured relative times of arrival by constructing and solving a set of linear equations. The receiver then matches comprises its feedback shift register to the initial code word, adjusted by an amount of time elapsed during the synchronization process. Similar techniques may also be applied both to direct sequence spread spectrum communication systems.
53 Citations
43 Claims
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1. A method for wireless communication, comprising the steps of:
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transmitting a series of transmissions at a predetermined frequency, said transmissions separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register; receiving said series of transmissions at a receiver; at said receiver, measuring relative times of arrival between consecutive ones of said transmissions; determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions; matching a receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions; and using said receiver feedback shift register to carry out synchronized communication with the transmitter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In a frequency hopping spread spectrum communication system, wherein a frequency hopping transmitter transmits in a pseudo-random manner across a plurality of frequencies including a key frequency, the transmissions over said key frequency being separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register, a method of reception comprising the steps of:
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monitoring the key frequency for a series of transmissions by said frequency hopping transmitter; measuring relative times of arrival between consecutive ones of said transmissions; determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions; matching a receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions, thereby synchronizing said receiver feedback shift register to the transmitter feedback shift register; and using said receiver feedback shift register to despread the transmissions of the frequency hopping transmitter over said plurality of frequencies. - View Dependent Claims (11, 12, 13, 14)
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15. In a direct sequence spread spectrum communication system, wherein a direct sequence spread spectrum transmitter transmits in a pseudo-random manner over a predetermined frequency, the transmissions over said predetermined frequency being separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register, a method of reception comprising the steps of:
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monitoring the predetermined frequency for a series of transmissions by said direct sequence spread spectrum transmitter; measuring relative times of arrival between consecutive ones of said transmissions; determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions; matching a receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions, thereby synchronizing said receiver feedback shift register to the transmitter feedback shift register; and using said receiver feedback shift register to despread the transmissions of the direct sequence spread spectrum transmitter over said plurality of frequencies. - View Dependent Claims (16, 17, 18, 19)
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20. A method for broadcasting wireless signals to selected receivers, the method comprising the steps of:
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transmitting a series of frequency-hopped transmissions over a plurality of frequencies including one or more key frequencies, the transmissions on a key frequency separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register; and separately at each of a plurality of receivers; monitoring a designated one of said key frequencies; measuring relative times of arrival between consecutive ones of said transmissions on the receiver'"'"'s designated key frequency; determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions on the receiver'"'"'s designated key frequency; matching a receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions on the receiver'"'"'s designated key frequency; and using said receiver feedback shift register to carry out synchronized communication with the transmitter. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 38)
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28. A wireless communication system, comprising:
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a spread spectrum transmitter configured to transmit a series of transmissions at a predetermined frequency, said transmissions separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register; and a receiver comprising circuitry for receiving and synchronizing to said series of transmissions, said receiver comprising a receiver feedback shift register; means for measuring relative times of arrival between consecutive ones of said transmissions; a synchronizing circuit for determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions, and matching said receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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37. In a frequency hopping spread spectrum communication system, wherein a frequency hopping transmitter transmits in a pseudo-random manner across a plurality of frequencies including a key frequency, the transmissions over said key frequency being separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register, a receiver, comprising:
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a receiver feedback shift register; a receiving circuit tuned to said key frequency for detecting the transmissions over said key frequency; a clocking circuit for measuring relative times of arrival between consecutive ones of said transmissions detected by said receiving circuit; and a synchronizing circuit for determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions, and matching said receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions. - View Dependent Claims (39)
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40. A wireless communication system, comprising:
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a spread spectrum transmitter configured to transmit a series of frequency-hopped transmissions over a plurality of frequencies including one or more key frequencies, the transmissions on a key frequency separated by one or more clock intervals pseudo-randomly determined according to an initial code word loaded into a transmitter feedback shift register; and a plurality of receivers each attuned to a designated key frequency, each of said receivers comprising a receiver feedback shift register; means for measuring relative times of arrival between consecutive ones of said transmissions on the receiver'"'"'s designated key frequency; a synchronizing circuit for determining said initial code word in the transmitter feedback shift register from the measured relative times of arrival between the consecutive transmissions on the receiver'"'"'s designated key frequency, and matching said receiver feedback shift register to the initial code word, adjusted by an amount of time since receiving the first one of said consecutive transmissions on the receiver'"'"'s designated key frequency. - View Dependent Claims (41, 42)
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43. A method for synchronizing communication, comprising the steps of:
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transmitting, from a transmitter, a signal having an observable parameter which is pseudo-randomly varied; receiving said signal at a receiver; measuring relative times between recurrences of a selected value of said observable parameter being pseudo-randomly varied; determining an initial state of said transmitter based upon said measured relative times; and synchronizing said receiver to an estimated current state of said transmitter using said determined initial state as a starting reference.
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Specification