Modem equalizer training using previously stored parameters
First Claim
1. A method of equalized modem training between at least two modems comprising the steps of:
- receiving a long train sequence of training signals having strong spectral components at the band edges of the transmission spectrum and a subsequent pseudorandom sequence;
acquiring a first set of modem parameters including a timing difference parameter for the difference between the optimum timing of said strong spectral components and said pseudorandom sequencestoring at least one of said modem parameters in a memory;
transferring a block of data between said modems;
terminating the transmissions;
reinitiating the transmissions;
receiving a short sequence of training signals;
acquiring subsequent receiver parameters including a short train timing parameter;
reloading at least one of said stored modem parameters from said memory;
adding said timing difference parameter to said short train timing parameter; and
transferring a subsequent block of data.
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Accused Products
Abstract
A high-speed modem which acquires receiver operating parameters and equalizer coefficients, stores the parameters and coefficients after an initial modem communication having an initial training sequence, and reinitializes the modem equalizer and receiver at the beginning of subsequent modem transmissions with the previously stored coefficients and parameters to be followed by a shortened training sequence. The modem according to the present invention acquires the above-mentioned parameters and coefficients with improved accuracy by extending the initial training period before the transmission of data. The particular stored receiver parameters include carrier frequency offset and data timing frequency offset parameters. According to the present invention, an additional Δ parameter is determined and stored which optimizes the receiver timing according to a difference between parameters acquired at different portions of the initial training sequence. During subsequent modem transmissions and after restoration of several of the previously used equalizer coefficients and receiver parameters, the modem further acquires the remaining receiver parameters during a very brief training period. The parameters acquired during the brief training period are adjusted by the previously determined Δ parameter to achieve a high data accuracy with a minimum (brief) training period, which maximizes data transfer during the subsequent transmissions.
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Citations
11 Claims
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1. A method of equalized modem training between at least two modems comprising the steps of:
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receiving a long train sequence of training signals having strong spectral components at the band edges of the transmission spectrum and a subsequent pseudorandom sequence; acquiring a first set of modem parameters including a timing difference parameter for the difference between the optimum timing of said strong spectral components and said pseudorandom sequence storing at least one of said modem parameters in a memory; transferring a block of data between said modems; terminating the transmissions; reinitiating the transmissions; receiving a short sequence of training signals; acquiring subsequent receiver parameters including a short train timing parameter; reloading at least one of said stored modem parameters from said memory; adding said timing difference parameter to said short train timing parameter; and transferring a subsequent block of data.
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2. In a modem receiving a training sequence, a method of modem adjustment comprising the steps of:
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receiving a first segment having strong spectral components at the band edges of the transmission spectrum; acquiring a preliminary data timing parameter therefrom; receiving a second segment having a pseudorandom sequence; adjusting the preliminary data timing to provide a final data timing parameter according to the received pseudorandom sequence; detecting a data timing difference parameter according to the difference between said preliminary and final data timing parameter; transferring data; storing the data timing difference parameter; terminating the data transfer; providing a training sequence to reorganize said preliminary data timing parameter; combining the stored data timing difference parameter and said preliminary data timing parameter to restore said final timing parameter; and transferring subsequent data. - View Dependent Claims (3)
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4. A communications system including a communication channel and a plurality of corresponding modems wherein one of said modem includes;
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means for selectively transmitting a long training sequence, a short training sequence, and data signals on said communication channel;
whereinthe corresponding modem includes; means for receiving said transmitted signals from said communication channel, including; means for equalizing the received signal from said communication channel, having selectable equalizer coefficients; means for detecting a long train sequence from the received signal; means for detecting the timing from the received signal; means for acquiring modem parameter values during said long train sequence from said means for equalizing and said means for detecting the timing, including a revised timing epoch value acquired at the end of said long train sequence; means for storing said parameter values from said means for acquiring, including the equalizer coefficients selected according to said timing epoch; means for receiving a block of data thereafter from the received signal; means for detecting a short train sequence from the received signal; means for restoring said revised timing epoch from the received signal and said means for storing; means for restoring said equalizer coefficients from said means for storing; and means for receiving data from the received signal after the parameters are restored.
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5. For use in a data communication system having a training signal sequence preceding the transmission of data, a modem comprising:
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means for establishing a channel and receiving a signal; means for detecting a training sequence on said channel, said training sequence having predetermined training signals of at least two distinct segments; means for acquiring receiver parameters on said channel according to said detected training sequence including a timing signal derived from at least two of said distinct segments; means for storing said receiver parameters from said means for acquiring receiver parameters; means for restoring said receiver equalizer and timing parameters from said means for storing after said means for detecting indicates a subsequent training sequence, wherein a subsequent training sequence is shorter than the initial timing sequence, and said receiver parameters being fully restored after said subsequent training sequence; means for measuring an initial timing parameter; means for measuring a revised timing parameter; and means for determining the difference between said timing and revised parameter, wherein said difference parameter is stored in said means for storing. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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Specification