Performance Analysis of Uplink NOMA-IoT Networks with Space-Time Line Code

In this paper, we investigate the performance of uplink non- orthogonal multiple access (NOMA) systems for internet- of-things (IoT) applications, which exploits a space-time line code (STLC) and a binary phase shift keying (BPSK) modulation at each sensor (transmitter). A single transmit antenna is assumed to be equipped at the sensor and two receive antennas are assumed to be equipped at a fusion center (FC). The STLC enables the FC to decode the transmitted symbols from multiple sensors without channel state information (CSI) of each sensor. In particular, we mathematically analyze the symbol error rate (SER) of the super-imposed symbol received at the FC and obtain the diversity order of the uplink NOMA-IoT network. We also propose a phase steering (PS)-based STLC technique to improve the SER performance, in which certain sensors rotate its constellation. The proposed PS-STLC technique significantly outperforms the conventional STLC scheme in the uplink NOMA-IoT network.