Spectrum sensing and non-orthogonal multiple access based massive grant-free random access scheme
A massive grant-free random access scheme based on spectrum sensing MCT provided by cognitive radio (CR) and non-orthogonal multiple access (NOMA) was proposed for massive machine type communication scenarios.Firstly, a three-step grant-free random access protocol based on CR-NOMA was put up, which could support end users to obtain uplink channel s