<div>This paper presents the design and bit error rate (BER) analysis of a
phase-independent non-orthogonal</div>


<div>multiple access (NOMA) system. The proposed NOMA system can utilize
amplitude-coherent detection</div>


<div>(ACD) which requires only the channel amplitude for equalization
purposes. In what follows, three</div>


<div>different designs for realizing the detection of the proposed NOMA are
investigated. One is based on the</div>


<div>maximum likelihood (ML) principle, while the other two are based on
successive interference cancellation</div>


<div>(SIC). Closed-form expressions for the BER of all detectors are derived
and compared with the BER of</div>


<div>the coherent ML detector. The obtained results, which are corroborated
by simulations, demonstrate that,</div>


<div>in most scenarios, the BER is dominated by multiuser interference rather
than the absence of the channel</div>


<div>phase information. Consequently, the BER using ML and ACD are comparable
for various cases of</div>


<div>interest. The paper also shows that the SIC detector is just an
alternative approach to realize the ML</div>


<div>detector, and hence, both detectors provide the same BER performance.</div>