Enhanced power choice barring scheme for massive MTCs with grant-free NOMA

Massive machine-type communication (mMTC) is a typical application scenario of the fifth generation (5G) mobile communications. To keep the mMTC reliable and minimize the energy consumption of the mMTC devices, this paper proposes an enhanced power choice barring (EPCB) scheme based on the distributed layered grant-free non-orthogonal multiple access (NOMA) framework, where the cell is divided into different layers according to a predetermined power levels. The proposed EPCB scheme not only combines the grant-free strategy with the sleep mode to reduce the energy consumption, but also designs a power level choosing strategy to increase the access success probability. Simulation results show that when compared with existing schemes, the proposed EPCB scheme has better performance in the aspects of the access success probability and energy efficiency.