Differential BPSK vs BPSK what are the advantages and disadvantages?
Differential BPSK

As the information is encoded in the phase difference of two consecutive symbols, phase estimation can be omitted in systems where the carrier phase can be assumed to be constant during two symbols. Specifically, it can be used in a self-coherent receiver which mixes one symbol with its predecessor in order to reconstruct the phase difference between the two symbols. In such a scheme, no local oscillator is required which simplifies the system (e.g. frequency synchronization is not needed).

Non-differential (coherent) BPSK

In differential BSPK, two symbols are "added" and as a consequence the noise of the two symbols adds up. This results in a 3 dB sensitivity gain of coherent BPSK. In other words, coherent BPSK is more robust against noise.