Reliable Transmission of Short Packets in Cognitive Radio Inspired NOMA Network

Aiming at the high-performance requirements of Internet of Things (IoT) scenarios, a cognitive radio-inspired nonorthogonal multiple access (CR-NOMA) scheme in short packet communication is investigated. Primary and secondary users share the same nonorthogonal communication resource block to achieve high spectral efficiency. A priority selection combination method is designed and employed by the primary user considering the nonnegligible decoding error rate in short packet communication. We focus on the transmission performance of the secondary users while ensuring the reliable communication of the primary user as a priority. To characterize the performance of the CR-NOMA network, approximate closed-form expressions of the average block error rate (BLER) for primary and secondary users are derived and analyzed. The results show that the communication reliability and throughput of the primary user with the CR-NOMA scheme are enhanced compared with the no-CR scheme. Meanwhile, the secondary users can also achieve reliable communication on the premise of improving the performance of the primary user through spectrum sharing. A performance tradeoff between primary and secondary users can be achieved through power allocation. Furthermore, there is a tradeoff between BLER and throughput, and the maximum throughput can be achieved by choosing an optimal blocklength.