A new study on VCMA-based blind equalization for underwater acoustic communications

In underwater acoustic digital communications, the decline of communication quality caused by multi-path effects, was considered the biggest obstacle at underwater acoustic. The most effective way is to use the equalizer. Compared with the conventional adaptive equalization, blind equalization without resorting to a training sequence, can improve the efficiency of the communication system. In order to solve the contradiction between convergence speed and steady-state error in constant modulus algorithm (CMA), we studied variable step-size constant modulus algorithm (VCMA). Theory and simulation, especially tracking constellation figure, indicate that, compared with the traditional constant module blind equalization algorithm, VCMA algorithm has the quicker convergence rate and smaller stable remainder error, and achieve the purposes of equalization.