CONSTELLATION DESIGN FOR A PCM MODEM

• Main Authors: YURI OKUNEV, QIN WANG, VITALY DRUCKER, YURI GOLDSTEIN
• Format: Patent
• Language: Chinese; English
• Published: 04.10.2002
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

Modem constellations are designed by independently optimizing for each slot of a frame, the distances between constellation points used for that slot. A maximum number of points N(0) are chosen having at least the minimum distance d0 without exceeding a power limitation Plim. Using N(0), an attempt is made to increase the d0 in the constellation without exceeding Plim. Constellations may be further optimized by, where possible, decreasing N(0) in a particular constellation without affecting the total data rate of the frame. Thus, a maximum potentially achievable data rate Rmax is calculated given the number of points which are in each of the six constellations, and comparing Rmax to a standards-permitted data rate DR; and then, if Rmax exceeds DR, by decreasing N(0) in one or more constellations, provided the decrease in the number of points does not cause a recalculated Rmax to drop below DR. Further optimization is obtained by attempting to increase d0 in one or more slots by permitting that slot(s) to exce