yes it is necessary to use 6 channels; 4 direction (left.right.backword.forword ) and the 5th channel to make robot turn with angle , the last channel to stop the robot
I think you can accomplish it by just using encoder and decoder at transmitting and receiving side respectively.In fact i dont know that how to use it thats why u have to search in google about it......but according to me encoder and decoder is must......