Exploring simultaneous transmission and reception at the same carrier frequency, in-band full duplex (IBFD) has great potential to double the spectral efficiency of wireless communications. However, IBFD also creates a major problem, that is, strong self-interference, which must be suppressed to the receiver noise floor to make it work. Thus, this paper first gives estimates of self-interference strength, then evaluates self-interference reduction techniques, and finally identify where enhancement can be made to those techniques.