This paper investigates an integrated wireless communication system including non-orthogonal multiple access, full-duplex relaying, and energy harvesting techniques (named as EH-FD-NOMA). In this scheme, an energy-limited full-duplex relay harvests energy from a source at the first stage. Then, the relay detects the superimposed signal from the source and transmits the decoded signal to destination. Closed-form outage probabilities and ergodic rates at the relay and destination are derived. Numerical results verify the analytical results and show the superior performance of the EH-FD-NOMA if compared to its counterparts.

In this paper, we propose a novel semantic digital analog converter (sDAC) for the compatibility between semantic and digital communications. Most of the current semantic communication systems rely primarily on analog modulation, limiting their integration with digital communication systems, which are more common in practice. In fact, traditional quantization methods are unsuitable for semantic communication because they do not account for semantic information within symbols. These factors block the wide application of the semantic communication. To address these challenges, sDAC is proposed. It is a simple yet efficient and generative module used to realize digital and analog bi-directional conversion. The entire process is independent of any specific semantic model, modulation methods, or channel conditions. In the experiment section, the performance of sDAC is tested across different semantic models, semantic tasks, modulation methods, channel conditions and quantization orders. Test results show that the proposed sDAC has great generative properties and channel robustness.

This paper studies the physical layer security for a cooperative non-orthogonal multiple access system with energy harvesting (EH) and full-duplex (FD) relaying. In particular, the base station transmits a superposed message to a dedicated EH-FD relay according to NOMA principle. Then, the relay forwards the decoded message to users. At the same time, the message transmitted by the relay can be wiretapped by an passive eavesdropper. The lower bound on the ergodic secrecy rates and the approximated secrecy outage probabilities of users are analyzed with closed-form solutions considering imperfect SIC. Finally, simulation results demonstrate the correctness of theoretical analysis, reflect the influence of the key parameters on the system performance and verify the better secrecy performance of the proposed scheme than its counterpart.

This paper designs and characterizes an adaptive relaying protocol in a short-packet cooperative non-orthogonal multiple access (NOMA) network. Particularly, a base station broadcasts a superposed signal to a strong user and a weak user with the help of a dedicated relay. Compared with the conventional fixed decode-and-forward relaying protocol (DFRP) and amplified-and-forward relaying protocol (AFRP), we propose a novel adaptive hybrid relaying protocol (AHRP) for a short-packet cooperative NOMA network, in which the dedicated relay chooses the transmission modes adaptively to help the information transmission of the weak user according to the comparison between the achievable data rates and the target data rates. Moveover, the ergodic rates of the two users are approximated with closed-form expressions and an asymptotic performance comparison among the DFRP, AFRP, and AHRP is also provided. Simulation results indicate that the proposed AHRP outperforms the DFRP and AFRP in terms of users' ergodic rates. Furthermore, the AHRP can achieve higher user rate and robustness than the DFRP, AFRP, and cooperative orthogonal multiple access under various network settings.

This paper studies the performance of unmanned aerial vehicle (UAV)-enabled NOMA networks with selective incremental relaying and imperfect channel state information (CSI). In particular, an access point transmits a superposed signal based on NOMA principle to an UAV terminal (UT) which can act as a relay to assist the information transmission for a ground terminal (GT). Different from the conventional relaying protocol requiring UT to relay the message all the time no matter how the received signal quality of two terminals are, we propose a novel NOMA-based selective incremental relaying protocol that allows relay to forward messages on the condition of the received signal with satisfied quality at UT and the unsatisfied quality signal at GT. The closed-form solutions of outage probabilities for the two terminals are characterized with the elevation angle-based path loss exponent and small-scale fading. Moreover, the benchmark schemes are provided to exhibit the superiority of the proposed protocol. Finally, simulation and theoretical results validate the correctness of the outage analysis, demonstrate the advantage of the proposed relaying protocol over its counterparts, and show that the stronger impact of channel estimation error on GT than UT in terms of outage probability.

Successive Interference Cancellation (SIC) has been regarded as the de facto decoding method in the Non-Orthogonal Multiple Access (NOMA) system. However, SIC often requires the paired users to have significantly different received power levels for the uplink scenario. This is problematic in terms of fairness and outage probabilities when the paired users are close to each other. To address this challenge, we propose a new decoding method for uplink NOMA based on compute-and-forward. In particular, we show that our method achieves better fairness and smaller average outage probabilities while enjoying essentially the same complexity as SIC decoding.