Adaptive echo cancellation/AGC structures for two-wire, full-duplex data transmission

Three different receiver arrangements are studied, all of which incorporate provision for joint adaptive echo cancellation and gain adjustment to provide two-wire full-duplex data communication. In each case, the canceler consists of a data-driven transversal filter, but the architectures differ in the way the gain adjustment is provided. For all architectures, we investigate the properties of a joint adaptive lms algorithm based on the receiver's decisions on far-end data symbols and present appropriate computer simulations. We show that an arrangement where the gain control adjusts the reference level after the decision detector output performs significantly better than agc schemes attempting to adjust the level of the analog signal.