Lets be clear here, the Walkera DOES NOT use a 22.2v battery. Someone else asked when you would need a separate bec and I answered.

The walkera probably uses a 7.2V or 11.1 volt battery, all servos will accept 4.8v but some can also function on 6v.

What you need is a 6ch tx/rx, find out whether your motor is brushed or brushless, buy the appropriate esc w/ integrated bec, if you need a gyro then get one of those as well (not sure if the walkera has it in the 3in1 or not).