The number of Internet-of-Things (IoT) devices will increase rapidly. In next-generation mobile communication systems, a base station (BS) must effectively accommodate massive numbers of IoT devices. To address this problem, we have proposed a novel up-link non-orthogonal multiple access (NOMA) system that can also be utilized for low latency communication. We have developed and evaluated the system through computer simulation. This paper describes experiments conducted on a prototype system in actual environments. The paper shows results of the experiments when 3 fixed user equipments (UEs) and 2 mobile UEs transmitted signals simultaneously to a BS and then the BS separated superimposed signals using successive interference cancellation (SIC). We also evaluated repetition transmission (RT) and space receive diversity (SD) techniques employed to enhance the signal separation performance for NOMA systems. The results of the experiments confirm that the system using neither SD nor RT could separate 3.5 UEs' signals on average while employing either SD or RT could make the number increase to 4.1 and 4.0, respectively. When both SD and RT were employed, the number rose to 4.4.