부산대학교 도서관

As Internet of Things (IoT) develops, new radio access techniques that can effectively accommodate a massive number of devices are required to improve spectrum efficiency. Moreover, low latency communications are recently required for automation systems in IoT communications. For this reason, we have researched and developed a system which realizes both massive connection and low latency simultaneously by using both non-orthogonal multiple access (NOMA) and configured grant (CG). In our system, successive interference cancellation (SIC) is applied as a signal separation method for NOMA because of less amount of calculation. However, when signal to interference power ratio (SIR) of the superimposed signals is not sufficiently high, the probability that the SIC can correctly separate them decreases. To prevent this, we propose that repetition is combined with SIC named repetition-SIC that can improve block error probability (BLER). Although the repetition makes the probability of the collision increase, SIC can mitigate this disadvantage by removing replica from the collision signals. Moreover, in our study, the repetition signal is configured by changing redundancy version (RV). Thanks only to the RV changes in repetition signals, the gNodeB (gNB) can deal with the repetition signals as retransmission signal of hybrid automatic repeat request (HARQ). To evaluate the repetition-SIC, we conduct the computer simulation. From the results of the simulations, we confirm that the proposed method is effective to reduce BLER from $1.50\times 10^{-2}$ to $1.31\times 10^{-3}$ when 5 UEs randomly transmit signals every 833.3 μs in average.