| 摘要 |
A method of estimating signal quality includes taking complex samples 110 of a decoded signal, mapping 130 each of the samples by expressing its phase modulo f /n where n is an integer equal to the number of points in the constellation divided by 2 (where all the constellation points have the same amplitude) and rotating 140 each of the modulo f /n samples by - f /2n. For example, for quadrature phase shift keying (QPSK) where n=2, each of the samples is mapped to the upper right QPSK quadrant. The ratio 150 of the imaginary part of each of the rotated samples to its real part is then taken to provide an instantaneous square root of an interference to signal (I/C) ratio. A variance associated with several I/C ratios is calculated 170 to provide an estimate of the signal quality. Application is to TETRA radio communication systems. |
