9.1.1 Echo Cancelation in Communications Two Possible Ways 1.Design a compromise fired echo canceler based on some “average'”echo path(平均的抵消回声). 2.Design an adaptive echo canceler that can "learn"the echo path when it is first turned on and afterward "tracks"its variations without any intervention from the designer 应的抵消回声)·Two Possible Ways 1. Design a compromise fixed echo canceler based on some “average” echo path（平均的抵消回声）. 2. Design an adaptive echo canceler that can “learn” the echo path when it is first turned on and afterward “tracks” its variations without any intervention from the designer（自适 应的抵消回声）. 9.1.1 Echo Cancelation in Communications