Secure Transmission in NOMA-based mMTC Networks under Statistical Delay QoS Guarantees

Abstract

Non-orthogonal multiple access (NOMA) has been proposed to improve the capacity, enhance Quality of Service (QoS) and support massive connectivity in the era of Internet of Things (IoT). A variety of services in current massive machine-type communications (mMTC) scenario need to meet specific security and delay requirements. In this paper, we propose a NOMA-based mMTC secure communication model, where MTC devices (MTCDs) transmit confidential information to the destination base station (BS) in presence of a passive malicious eavesdropper. Considering both security and delay requirements, we define the effective secrecy capacity (ESC) as the user’s maximum secrecy transmission rate in presence of an eaves-dropper under statistical delay QoS guarantees. Moreover, the optimization problem of maximizing ESC is formulated, which is constrained by the maximum number of MTCDs sharing the same subchannel and maximum transmission power of each MTCD. A subchannel allocation algorithm based on delay QoS exponent and channel gain difference is proposed. Furthermore, to maximize the ESC of every subchannel, we propose a power allocation algorithm. The effectiveness of proposed algorithms is evaluated through simulations.