| 摘要 |
A method for constellation design in a telecommunications network (10) using pulse code modulation to transmit data signals upstream (30) between client and server voice-band modems (12,26). The invention selects a constellation for transmission over an analog channel of an equivalence class of data points using pulse code modulation based on the presence or absence of robbed bit signaling and interference from echo levels. The constellation is designed by determining noise in a PCM channel using a cumulative distribution function for echo (90), determining the extent of said noise for an array of possible constellation points (92), and selecting constellation points such that the largest negative noise of a first point remains above the largest positive noise level of a neighboring second point (94). Constellations are created off-line and stored (96) for retrieval during modulation depending on the level of the echo. <IMAGE> |
