TH21103B - Channel estimation circuits and related methods for digital communication systems. - Google Patents

Abstract

DC60 (11/06/40) Channel estimator circuits and related methods for digital receivers work to estimate the pulse response of a transmitting channel when inter-symbol interference is induced on a specific communication signal by the transmitter and receiver circuits. The channel estimation quality is improved even when inter-symbol interference is induced on the communication signal during its transmission. The channel estimation quality is improved by breaking down the components of inter-symbol interference into those that occur during transmission on the communication channel and those that are generated by the transmitter and receiver circuits. Channel estimator circuits and related methods for digital receivers work to estimate the pulse response of a transmitting channel when inter-symbol interference is induced on a specific communication signal by the transmitter and receiver circuits. The channel estimation quality is improved even when inter-symbol interference is induced on the communication signal during its transmission. The channel estimation quality is improved by breaking down the components of inter-symbol interference into those that occur during transmission on the communication channel and those that are generated by the transmitter and receiver circuits.

Claims (18)

1. A channel estimator evaluates the impulse response of a transmission channel where the communication symbol consists of the synchronization symbol transmitted by the transmitter (the communication signal is transmitted at the symbol rate of the communication signal to the receiver). This channel estimator consists of a symbol sampler connected to receive representative signals of the communication signal received by the receiver. This symbol sampler samples a portion of the corresponding signal (at least the synchronization symbol portion) at a sampling rate greater than the symbol rate of the communication signal. Therefore, it samples each synchronization signal at least at the first and second sampling points to produce at least the first and second sampled signals representing the synchronization signals sampled at the first and second sampling points, respectively. A matrix computation circuit is connected to receive at least the first and second sampled signals produced by the symbol sampler. This matrix computation circuit calculates the matrix between the parts of at least the first and second sampled signals and stores the stored data. The stored data word represents the values of synchronization symbols modified by the selected distortion levels occurring on the communication signals by the transmitter and receiver before transmitting and receiving the communication signals, respectively. Such matrix computation circuits are also used to select which of the at least two first-sampled and second-sampled signals most closely matches the stored data word in order to estimate the channel impulse response. 2. The channel estimator of claim 1, where the metric computation circuit consists of a correlation circuit for correlating parts of the sampled signal with the stored data word, and for selecting which of at least two of the first and second sampled signals most closely matches the stored data word in order to estimate the channel impulse response. 3. The channel estimator of claim 2, where the sampling rate at which the symbol sampler samples the value of at least the synchronization symbol consists of a sampling rate at least twice the symbol rate of the synchronization signal. 4. The channel estimator of claim 2, where the symbol sampler produces a number of sampled signals corresponding to the number of sampling points at which each synchronization symbol is sampled. 5. The fourth claim channel estimator, where the correlation circuit correlates the different parts of each sampled signal with the stored data and selects the sampled signal that most closely matches the stored data. 6. The second claim channel estimator, where the stored data word represents the synchronization symbol, is further modified by the selected distortion level occurring on the communication signal by the transmitting channel. 7. The second claim channel estimator still includes a memory circuit for storing the stored data so that the correlation circuit can correlate the various parts of the sampled signal. 8. The estimator of the second claim, where the symbolic sampler consists of an analog-to-digital converter. 9. Channel estimator: This device evaluates the impulse response of a transmission channel where the communication symbols consist of synchronization symbols transmitted by the transmitter (the communication signal is sent to the receiver at the same symbol rate as the communication signal). The channel estimator consists of a symbol sampler connected to receive a representative signal of the communication signal received by the receiver. This symbol sampler samples at least each synchronization symbol of the signal at least at a rate corresponding to the communication signal's symbol rate and produces a representative signal of that sampled signal. A matrix computation circuit is connected to receive the sampled signal produced by the symbol sampler. This matrix computation circuit calculates the matrix between the parts of the sampled signal and the stored data words. The stored data words of the representative synchronization symbol values are modified by the selected distortion levels occurring in the communication signals of the transmitter and receiver before transmission and reception, respectively. The matrix computation circuit is also used to select which of the resulting matrix data words most closely matches the sampled signal in order to estimate the channel impulse response. 10. The channel estimator of claim 9, where the metric calculation circuit consists of a correlation circuit for the correlation of different parts of the sampled signal with the stored data words, and for selecting which of the all stored data words has the best level of correlation. 11. The estimator of the claim 9 channel, where the stored data words consist of a number of stored data words, each with a different value. 12. The channel estimator of claim 9 still includes a memory circuit for storing the stored data so that the correlation circuit can correlate the various parts of the sampled signal. 13. The channel estimator of claim 9, in which the symbolic sampler consists of an analog-to-digital converter. 14. A method for estimating the impulse response of a transmission channel where the communication signal consists of a synchronization signal transmitted by the transmitter (such communication signal is transmitted at the symbol rate of the communication signal to the receiver). The method involves sampling at least the synchronization symbol values of the signal at a sampling rate greater than the symbol rate of the communication signal; thus, each synchronization symbol is sampled at least at the first and second sampling points. This is followed by the production of at least the first-sampled and second-sampled signals representing the synchronization symbol values sampled at at least the first and second sampling points, respectively. During this sampling process, a matrix is calculated between the parts of the first-sampled signal (stored data word) and the second-sampled signal (stored data word of the representative synchronization symbol values modified by the selected distortion levels occurring in the communication signals of the transmitter and receiver before transmission and reception, respectively), and the selection of which of the at least the first-sampled and second-sampled signals most closely approximates the stored data word. To estimate the impulse response of the channel. 15. The channel estimator of claim 14, where the metric calculation procedure involves correlating the various parts of the sampled signal and the stored data. 16. A method for estimating the impulse response of a transmission channel where the communication signal consists of a synchronization signal transmitted by the transmitter (such communication signal is transmitted at the symbol rate of the communication signal to the receiver). Such a method consists of the following steps: sampling at least the synchronization symbol representation of the communication signal at least at a rate corresponding to the symbol rate of the communication signal; generating a sampled signal representation of the sampled values during the sampling step; calculating the matrix between the parts of the sampled signal and the stored data words; storing the stored data words of the synchronization symbol representation values modified by the selected distortion levels occurring on the communication signals by the transmitter and receiver before transmission and reception, respectively; and selecting which of the stored data words most closely resembles the sampled signal in order to estimate the channel impulse response. 17. The channel estimator of claim 16, where the metric calculation procedure involves correlating the various parts of the sampled signal and the stored data. 18. The channel estimator of claim 17, where the selection procedure involves choosing which of the stored data terms has the closest correlation coefficient.