Compensation for multi-path interference using pilot symbols
First Claim
1. Circuitry for compensating a receiver for fading of signals propagating as frames of data from at least one transmitter that includes pilot symbol generation circuitry that provides a predefined plurality of pilot symbols in each frame of data transmitted to the receiver, said circuitry comprising:
- (a) separating means, coupled to the receiver for input of a received signal, for separating the plurality of pilot symbols from a plurality of data symbols in each frame of data, producing a pilot symbol signal comprising said plurality of pilot symbols and a data signal comprising said plurality of data symbols, said pilot signal and said data signal being separate from each other;
(b) delay means, coupled to receive the data signal, for delaying the data signal from a current frame until after the pilot symbol signal from at least one subsequent frame is received, said delay means thereby producing a delayed data signal;
(c) pilot signal processing means, coupled to receive the pilot symbol signal, for determining an estimated channel impulse response for the plurality of pilot symbols in each frame of received signals;
(d) interpolation filter means, coupled to receive the estimated channel impulse response for each frame of data and including storage means for storing an estimated channel impulse response from at least one prior frame, said interpolation filter means interpolating values of the estimated channel impulse response between the current and prior frames to determine, as a function of channel characteristics, an interpolated channel impulse response for each data symbol in a frame; and
(e) decoder means, coupled to receive the interpolated channel impulse response and the delayed data signal, for recovering the data transmitted to the receiver as a function of the interpolated channel impulse response and the delayed data signal, thereby substantially compensating for fading and interference in the received signals.
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Accused Products
Abstract
A method and apparatus for compensating fading and interference in a radio signal. A plurality of pilot symbols are appended to a plurality of data symbols to form successive frames that are modulated at a transmitter. The transmitted modulated signal is subject to loss of data due to simple fading and multi-path and simulcast interference. The received signals are demodulated by a receiver and processed to provide a data signal comprising the data symbols and a pilot signal comprising the pilot symbols. The data signal is delayed for sufficient time to enable channel impulse response estimates to be made of successive blocks of pilot symbols, preferably using pilot symbol blocks that both precede and follow the data symbols in the frame being processed. The channel impulse response estimates for blocks of pilot symbols are buffered and used by an interpolator to determine an interpolated channel impulse response estimate for each data symbol as a function of both the pilot symbols and of predefined channel characteristics. The interpolated channel impulse response estimates are applied to successive data symbols in the delayed data signal, enabling the data to be decoded, compensating for fading and interference. Interpolation using predefined channel characteristics based on worst case conditions substantially improves the bit error rate (BER) for the data recovered, compared to the prior art.
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Citations
22 Claims
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1. Circuitry for compensating a receiver for fading of signals propagating as frames of data from at least one transmitter that includes pilot symbol generation circuitry that provides a predefined plurality of pilot symbols in each frame of data transmitted to the receiver, said circuitry comprising:
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(a) separating means, coupled to the receiver for input of a received signal, for separating the plurality of pilot symbols from a plurality of data symbols in each frame of data, producing a pilot symbol signal comprising said plurality of pilot symbols and a data signal comprising said plurality of data symbols, said pilot signal and said data signal being separate from each other; (b) delay means, coupled to receive the data signal, for delaying the data signal from a current frame until after the pilot symbol signal from at least one subsequent frame is received, said delay means thereby producing a delayed data signal; (c) pilot signal processing means, coupled to receive the pilot symbol signal, for determining an estimated channel impulse response for the plurality of pilot symbols in each frame of received signals; (d) interpolation filter means, coupled to receive the estimated channel impulse response for each frame of data and including storage means for storing an estimated channel impulse response from at least one prior frame, said interpolation filter means interpolating values of the estimated channel impulse response between the current and prior frames to determine, as a function of channel characteristics, an interpolated channel impulse response for each data symbol in a frame; and (e) decoder means, coupled to receive the interpolated channel impulse response and the delayed data signal, for recovering the data transmitted to the receiver as a function of the interpolated channel impulse response and the delayed data signal, thereby substantially compensating for fading and interference in the received signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for compensating a receiver for fading of signals propagating as frames of data from at least one transmitter that provides a predefined plurality of pilot symbols in each frame of data transmitted to the receiver, said method comprising the steps of:
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(a) separating the plurality of pilot symbols from a plurality of data symbols in each frame of data, producing a pilot symbol signal and a data signal that are separate from each other; (b) delaying the data signal from a current frame until after the pilot symbol signal from at least one subsequent frame is received, thereby producing a delayed data signal; (c) determining an estimated channel impulse response from the plurality of pilot symbols in each frame of the received signal; (d) storing the estimated channel impulse response from at least one prior frame; (e) interpolating values of the estimated channel impulse response between the current and prior frames to determine, as a function of channel characteristics, an interpolated channel impulse response for each data symbol in a frame; and (f) recovering the data transmitted to the receiver as a function of the interpolated channel impulse response and the delayed data signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification