Embedded delta modulation

In an embedded delta modulation (EDM) encoder, a supplemental pulse-code-modulation (PCM) encoder processes the error signal of a delta modulator. The PCM and DM bit streams are multiplexed and then transmitted. The decoder adds and then filters the analog versions of the separately decoded PCM and DM signals. To enhance the efficiency of EDM, it is desirable to filter and decimate the DM error signal prior to PCM encoding. Corresponding filtering and decimation of the decoded DM signal is then required. The theory of both full-rate and reduced-rate EDM, which include filtering and decimation, is presented. The performance of these codes are those of compared to PCM, DM, and two embedded codes, embedded-differential PCM and multistage DM. It is found that reduced-rate EDM has a higher signal-to-noise ratio than DM and PCM. It is comparable in performance to multistage DM but simpler to implement. The signal-to-noise ratio of EDM is lower than that of embedded DPCM. However, EDM is simpler to implement, and the signal-to-noise ratio penalty is less than 2.6 dB over a range of transmission rates of practical interest