Title :
An adaptive QAM linearizer using data postdistortion
Author :
Moffatt, J.P. ; MacEachern, J.P.
Author_Institution :
AT&T Bell Lab., North Andover, MA, USA
Abstract :
An adaptive Volterra linearizer for reducing channel nonlinearities in QAM (quadrature amplitude modulation) data transmission systems is described, and its performance is evaluated. The linearizer is implemented as a modern receiver digital circuit which employs two read-only memories that are programmed to cancel either third- or fifth-order nonlinearities. The memory outputs are scaled by adaptive coefficients which minimize the channel nonlinearity. The linearizer has been shown to be effective for input nonlinear bit error rates up to 10-3. At input error rates up to 10-6, the linearizer reduces the nonlinear error rate by five orders of magnitude in a 64-QAM digital radio system, and the linearized system has a selective fading performance approximately equal to that of a linear system. The circuit is entirely digital and can be manufactured with automated processes
Keywords :
adaptive systems; amplitude modulation; data communication systems; digital radio systems; error statistics; radio receivers; 64-QAM; BER; ROM; adaptive QAM linearizer; adaptive Volterra linearizer; adaptive coefficients; channel nonlinearities reduction; data postdistortion; data transmission systems; digital radio system; nonlinear bit error rates; quadrature amplitude modulation; read-only memories; receiver digital circuit; selective fading performance; Bit error rate; Data communication; Digital circuits; Digital communication; Error analysis; Fading; Linear systems; Manufacturing automation; Manufacturing processes; Quadrature amplitude modulation;
Conference_Titel :
Global Telecommunications Conference and Exhibition 'Communications Technology for the 1990s and Beyond' (GLOBECOM), 1989. IEEE
Conference_Location :
Dallas, TX
DOI :
10.1109/GLOCOM.1989.64004