Location system
First Claim
1. A system for transmitting information comprising:
- a transmitter unit configured to transmit an ultrasound signal comprising (i) a signature comprising a first pattern which is PSK-encoded on a first carrier and a second pattern which is PSK-encoded on a second carrier, wherein the first and second carriers have the same frequency but wherein the second carrier is out of phase with first carrier, and wherein the second pattern is offset from the first pattern in time by a transmitter-specific offset, and (ii) a PSK-encoded message-bearing portion;
a receiver unit configured to receive the ultrasound signal from the transmitter unit; and
a processing subsystem configured;
to use the first and second patterns in the received signal to characterise a motion-induced phase distortion in the received signal;
to use said characterisation to compensate for motion-induced phase distortion in the message-bearing portion of the received signal, thereby generating a compensated signal; and
to decode the message from the compensated signal.
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Accused Products
Abstract
Static transmitter stations are used to determine the position of a mobile receiver unit. Each transmitter station transmits an ultrasonic signal including a transmitter-specific phase-shifting signature. The receiver unit receives a signal and identifies a transmitter station by its signature. It uses the received signal and the identity of the source transmitter station to determine the position of the mobile receiver unit. The signature may include two patterns phase-shift-key (PSK)-encoded on respective carrier signals of the same frequency but different phase, with the patterns being offset from each other by a transmitter-specific offset. The signal from the transmitter station may also include a PSK-encoded message.
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Citations
12 Claims
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1. A system for transmitting information comprising:
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a transmitter unit configured to transmit an ultrasound signal comprising (i) a signature comprising a first pattern which is PSK-encoded on a first carrier and a second pattern which is PSK-encoded on a second carrier, wherein the first and second carriers have the same frequency but wherein the second carrier is out of phase with first carrier, and wherein the second pattern is offset from the first pattern in time by a transmitter-specific offset, and (ii) a PSK-encoded message-bearing portion; a receiver unit configured to receive the ultrasound signal from the transmitter unit; and a processing subsystem configured; to use the first and second patterns in the received signal to characterise a motion-induced phase distortion in the received signal; to use said characterisation to compensate for motion-induced phase distortion in the message-bearing portion of the received signal, thereby generating a compensated signal; and to decode the message from the compensated signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of transmitting information comprising:
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transmitting an ultrasound signal from a transmitter unit, the signal comprising (i) a signature comprising a first pattern which is PSK-encoded on a first carrier and a second pattern which is PSK-encoded on a second carrier, wherein the first and second carriers have the same frequency but wherein the second carrier is out of phase with first carrier, and wherein the second pattern is offset from the first pattern in time by a transmitter-specific offset, and (ii) a PSK-encoded message-bearing portion; receiving the signal at a receiver unit; using the first and second patterns in the received signal to characterise a motion-induced phase distortion in the received signal; using said characterisation to compensate for motion-induced phase distortion in the message-bearing portion of the received signal; and decoding the message from the compensated signal.
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- 11. A receiver unit configured to receive from a transmitter unit an ultrasound signal comprising (i) a signature comprising a first pattern which is PSK-encoded on a first carrier and a second pattern which is PSK-encoded on a second carrier, wherein the first and second carriers have the same frequency but wherein the second carrier is out of phase with first carrier, and wherein the second pattern is offset from the first pattern in time by a transmitter-specific offset, and (ii) a PSK-encoded message-bearing portion, the receiver unit comprising a processing system configured to use the first and second patterns in the received signal to characterise a motion-induced phase distortion in the received signal, wherein the processing system is further configured to use said characterisation to compensate for motion-induced phase distortion in the message-bearing portion of the received signal.
Specification