In this book we present a new approach to cancelling echoes, mostly occurrence in todays telecommunication system due to acoustic coupling between loudspeaker and a microphone. The proposed algorithm is a Modified VSS-NLMS-UM algorithm the popularity of this algorithm due to the solve a conflicting requirement of fast convergence and low misadjustment. Most of the algorithm was design under-modeling scenario the proposed algorithm doesnt require any prior information about acoustic environment. Due to the specific characteristic of this algorithm are equipped with good robustness feature...