Likelihood corrector and likelihood correction method
AssigneeOki Semiconductor Co., Ltd.
InventorHiroji Akahori
Life of this patent
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Abstract
In an orthogonal frequency division multiplexing system using a scattered pilot signal, after equalization and Fourier transformation of the received signal, the pilot signals are extracted and further processed to generate likelihood values. In one process, the transformed signal is multiplied by the reciprocal of a variance. In another process, the transformed signal is multiplied by the reciprocal of a mean amplitude and by a weighted signal-to-interference ratio. These processes enable appropriate likelihoods to be obtained despite fast fading, shadowing, and automatic gain control.
Claims16
A likelihood corrector comprising:
- a pilot symbol extractor for extracting pilot symbols included in an orthogonal frequency division multiplexing (OFDM) signal, performing a complex-valued operation thereon, and generating complex-valued results;
- a variance calculator for determining a variance of the complex-valued results;
- a reciprocal calculator for determining a reciprocal value of the variance;
- and
- a multiplier for multiplying the OFDM signal by the reciprocal value.
A likelihood corrector comprising:
- a pilot symbol extractor for extracting pilot symbols included in an OFDM signal, performing a complex-valued operation thereon, and generating complex-valued results;
- a first mean calculator for determining a mean amplitude of the complex-valued results;
- a reciprocal calculator for determining a reciprocal value of the mean amplitude;
- a signal-to-interference ratio estimator for estimating a signal-to-interference ratio (SIR) from the complex-valued results;
- a quantizing circuit for quantizing the estimated SIR;
- a weighting circuit for weighting the quantized estimated SIR to generate a weighted SIR;
- and
- a multiplier for multiplying the OFDM signal by said reciprocal value and the weighted SIR.
A likelihood correcting method comprising:
- extracting pilot symbols included in an OFDM signal;
- performing a complex-valued operation on the extracted pilot symbols to obtain complex-valued results;
- determining a variance of the complex-valued results;
- determining a reciprocal value of the variance;
- and
- multiplying the OFDM signal by the reciprocal value.
A likelihood correcting method comprising:
- extracting pilot symbols included in an OFDM signal;
- performing a complex-valued operation on the extracted pilot symbols, thereby obtaining complex-valued results;
- determining a mean amplitude of the complex-valued results;
- determining a reciprocal value of the mean amplitude;
- estimating an SIR from the complex-valued results;
- quantizing the estimated SIR;
- weighting the quantized estimated SIR to obtain a weighted SIR;
- and
- multiplying the OFDM signal by the reciprocal value and the weighted SIR.
Dependencies are inferred from the claim text.