Data recovery using gradients
AssigneeJohn W. Bogdan
InventorJohn W Bogdan
Life of this patent
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Abstract
The data recovery from gradients (DRG) of sub-carriers of a received OFDM signal affected by deterministic and random distortions introduced by a transmission link, contributes a method and a system for utilizing gradients characterizing shapes of OFDM sub-carriers comprised in such OFDM signal for recovering data symbols transmitted originally.
Claims8
A method using inverse transformation of subranges of subcarriers gradients (ITSSG) for transmitted data recovery from an orthogonal frequency division multiplexing (OFDM) signal, applied to subcarriers produced by a transmission channel including a data coding circuit, encoding said transmitted data into OFDM frames defining the subcarriers, a transmission link supplying the OFDM frames and a preprocessor of received OFDM frames transforming received OFDM frames into recovered the subcarriers characterized with the subcarriers gradients;
- wherein the ITSSSG method comprises the steps of:
- deriving the inverse transformation reversing a transfer function of the transmission channel, by processing parts of such received OFDM frame corresponding to known parts of a transmitted OFDM frame;
- wherein the inverse transformation is defining recovery of the transmitted data from the subranges of the subcarriers gradients identifying subcarriers subspaces comprising the recovered subcarriers;
- recovering the subcarriers maintaining a known phase relation to such received OFDM frame by applying frequency domain and time domain signal processing to such received OFDM frame;
- deriving the gradients of the recovered subcarriers by calculating integrals of samples of the recovered sub-carriers surrounding a middle one of the samples;
- wherein amplitudes of previous the samples are subtracted from amplitudes of following the samples shifted forward by the same number of sampling periods as the previous samples are trailing such middle sample;
- wherein any one of the integrals of the samples is derived by adding all results of such subtractions made over a proper part of a sub-carrier cycle surrounding the middle sample;
- comparing the subcarriers gradients with references defining plurality of the subranges of the subcarriers gradients;
- using results of such comparisons for identifying the subranges of the subcarriers gradients identifying the subcarriers subspaces comprising the recovered subcarriers;
- applying, by using an adaptive data decoder, the inverse transformation to the identified subranges of the subcarriers gradients in order to recover the transmitted data corresponding to the received subcariers.
A method using inverse transformation of subcarriers subspaces using subcarriers gradients (ITSSSG) for transmitted data recovery from an orthogonal frequency division multiplexing (OFDM) signal, applied to subcarriers produced by a transmission channel including a data coding circuit, encoding said transmitted data into OFDM frames defining the subcarriers, a transmission link supplying the OFDM frames and a preprocessor of received OFDM frames transforming received OFDM frames into recovered the subcarriers characterized with the subcarriers gradients;
- wherein the ITSSSG method comprises the steps of:
- deriving the inverse transformation reversing a transfer function of the transmission channel, by processing parts of such received OFDM frame corresponding to known parts of a transmitted OFDM frame;
- wherein the inverse transformation is defining recovery of the transmitted data from the subcarriers subspaces identified with reference frames as comprising the recovered subcarriers;
- recovering the subcarriers maintaining a known phase relation to such received OFDM frame by applying frequency domain and time domain signal processing to such received OFDM frame;
- deriving the gradients of the recovered subcarriers, needed for selecting reference frames expected to be close to the subcarriers, by calculating integrals of samples of the recovered sub-carriers surrounding a middle one of the samples;
- wherein amplitudes of previous the samples are subtracted from amplitudes of following the samples shifted forward by the same number of sampling periods as the previous samples are trailing such middle sample;
- wherein any one of the integrals of the samples is derived by adding all results of such subtractions made over a proper part of a sub-carrier cycle surrounding the middle sample;
- using the derived gradients for the selection of the reference frames expected to be close to the subcarriers;
- comparing sets of samples of the recovered subcarriers with corresponding sets of elements of the selected reference frames;
- using results of such comparisons for identifying the subcarriers subspaces which the received subcarriers belong to;
- applying, by using a content addressed memory, the inverse transformation to the identified subcarriers subspaces in order to recover the transmitted data from the received subcarriers.
Dependencies are inferred from the claim text.