In this paper, physical layer security (PLS) in a non-orthogonal multiple access (NOMA)-based mobile edge computing (MEC) system is investigated, where hybrid successive interference cancellation (SIC) decoding is considered. Specifically, users intend to complete confidential tasks with the help of the MEC server, while an eavesdropper attempts to intercept the offloaded tasks. By jointly designing computational resource allocation, task assignment, and power allocation, a latency minimization problem is formulated. Based on the interactions between local computing time and MEC processing time, the closed-from solutions of computational resource allocation and task assignment are derived. After that, a strategy selection mechanism is established to select offloading strategies based on the corresponding conditions. Moreover, according to the analysis of hybrid SIC decoding, the conditions of different decoding orders in secure NOMA networks are derived. Furthermore, a reinforcement learning based algorithm is proposed to solve the power allocation problems for NOMA and OMA offloading strategies. This work is extended to a multi-user scenario, in which a matching-based algorithm is proposed to solve the formulated sub-channel assignment problem. Simulation results indicate that: i) the proposed solution can significantly reduce the latency and provide dynamic strategy selection for various scenarios; ii) the NOMA offloading strategy with hybrid SIC decoding can outperform other strategies in the considered system.Index Terms-Mobile edge computing (MEC), Non-orthogonal multiple access (NOMA), physical layer security (PLS), reinforcement learning, sub-channel assignment.

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In this paper, the harmony between non-orthogonal multiple access (NOMA) and rate-splitting (RS) is explored in a multi-antenna scenario, where a RS-NOMA system is proposed to implement dynamically transformation between these two transmission schemes. Specifically, a common signal is generated at the base station (BS) and transmitted with the users' private signals. By utilizing successive interference cancellation (SIC), the common signal is decoded and removed at each user, and then the private signals can be decoded based on NOMA schemes. By jointly design power allocation and user pairing, a weighted sum rate maximization problem is formulated with quality of service (QoS) constraints, where the priority of different signals is presented. By analyzing the monotonicity, the optimal power allocation is expressed in several cases, and then the strategy of each user to achieve the QoS threshold is obtained in all cases. To solve the user pairing problem, a matching based algorithm is developed, where the property is analyzed. Simulation results indicate that: i) the proposed RS-NOMA system outperforms the conventional RS and NOMA systems in general; ii) the developed power allocation strategy and user pairing algorithm can improve the RS-NOMA system in terms of the weighted sum rate and outage probability.