Method for the blind estimation of OFDM modulation parameters according to a maximum likelihood criterion
AssigneeCommissariat A L'energie Atomique Et Aux Energies Alternatives
InventorsAbdelaziz Bouzegzi, Pierre Jallon, Philippe Ciblat
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Abstract
The present invention relates to a method for blind estimation of at least one parameter of an OFDM signal according to a maximum likelihood (ML) criterion. In one embodiment, the estimation method uses a deterministic maximum likelihood criterion. In another embodiment, the estimation method assumes that the modulation symbols modulating the sub-carriers of the OFDM multiplex are i.i.d. and Gaussian random variables. The estimation of said parameter is carried out while minimizing a cost function depending on the chosen criterion.
Claims8
A method of blind estimation of at least one modulation parameter (θ) of an OFDM signal comprising a plurality of OFDM symbols, the method comprising:
- baseband sampling the OFDM signal for a given observation period (T0) to obtain a plurality of samples;
- calculating, for a plurality of values of the parameter and a block of modulation symbols (ak,n) of a modulation constellation, a cost function (Ω) depending on a distance between a vector y made up of the plurality of samples and a vector Hθa, wherein a comprises the symbols of the block and Hθ comprises a matrix representing the modulation of the sub-carriers of the OFDM multiplex by the modulation symbols, the matrix depending on the parameter to be estimated;
- and
- averaging the cost function for each value of the parameter on a set of blocks of possible symbols to obtain an averaged value (Ea(Ω(∥y−Hθa∥))) of the cost function, the estimation of the parameter being obtained as the value of the parameter ({circumflex over (θ)}) corresponding to the lowest averaged value
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A method of blind estimation of at least one modulation parameter (θ) of an OFDM signal comprising a plurality of OFDM symbols, the method comprising:
- baseband sampling the OFDM signal for a given observation period (T0) to obtain a plurality M of samples;
- calculating, for a plurality of values of the parameter, a cost function (Ω) depending on a distance between a vector y made up of the plurality of samples and a vector HθHθ†y wherein Hθ comprises a matrix representing the modulation of the sub-carriers of the OFDM multiplex by a block of modulation symbols, the matrix depending on the parameter to be estimated, and wherein Hθ† comprises the pseudo-inverse matrix of Hθ;
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- estimating the parameter being obtained as the value of the parameter ({circumflex over (θ)}) corresponding to the lowest value of the cost function of the plurality of values of the parameter
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A method for of blind estimation of at least one modulation parameter θ of an OFDM signal comprising a plurality of OFDM symbols, the method comprising:
- baseband sampling the OFDM signal for a given observation period (T0) to obtain a plurality of samples;
- calculating, for a plurality of values of the parameter, a cost function Ω, a decreasing function of the Gaussian conditional probability pg(y|θ), where y comprises a vector made up of the plurality of samples and pg(y|θ) is obtained from a Gaussian distribution of the modulation symbols modulating the various sub-carriers of the OFDM multiplex for the plurality of OFDM symbols;
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- estimating the parameter being obtained as the value of the parameter ({circumflex over (θ)}) corresponding to the lowest value of the cost function on the plurality of values of the parameter.
Dependencies are inferred from the claim text.