Delta Modulation with a Switched Predictor and an Adaptive Three-Level Quantizer
An analysis of the influence of predictor coefficients on performances of the proposed delta modulation configurations with an adaptive three-level quantization is carried out in order to determine the optimal coefficients which maximize [SNR.
Comparing results to a delta modulation system with two-level and four-level Lloyd-Max quantization we see that the proposed scheme with fixed predictor attains almost the same SNRDM value as four-level delta modulation, with reduction in the bit rate of 0.
The results for a three-level delta modulation schemes when a three-level quantizer designed according to the simultaneous criterion of minimal distortion and minimal bit rate (criterion 2) is used are summarized in Table II.
We can observe that delta modulation with the switched predictor provides PESQ scores slightly better than the one of four-level delta modulation baseline, and it outperforms configurations with fixed predictor and two-level Lloyd-Max's quantization, at the same time satisfying the rate distortion lower bound.
Two configurations based on delta modulation with adaptive three-level scalar quantization are proposed in this paper, one with a simple fixed first-order predictor and one with a switched predictor utilizing correlation.
Tombras, "2-bit adaptive delta modulation system with improved performance," EURASIP Journal on Advances in Signal Processing, Article ID 16286, 2007.
Delta modulation scheme with a fixed predictor and adaptive three-level quantizer: a) encoder, b) decoder