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Simultaneous wireless information power transfer with power splitting is a new technology for energy harvesting that splits the received signal into two streams with adjustable power levels for information decoding and energy saving. Traditionally, decode and forward (DF) and amplify and forward (AF) schemes are used for energy harvesting in three‐step two‐way relay networks (TWRNs). In this paper, piece‐wise and forward (PF) scheme are applied with power splitting for energy harvesting in TWRNs. In PF, the received signal from each source at relay is compared to an adaptive threshold, if the signal strength is above the threshold, the relay functions similar to DF scheme, otherwise, the relay transmits a particular combination of its received signals from the sources. Next, the outage performance of PF protocol in a three‐step TWRN is studied and optimal lossless energy saving (OLES) method are presented to minimise the outage probability by computing the optimum power splitting ratio. The simulation and analytical results indicate that the outage probability of PF can be significantly improved using OLES technique in comparison with other related relaying schemes. The results show that the outage probability of PF‐OLES is 13, 3, and 5dB$5\nobreakspace \text{dB}$ lower than AF‐OLES, DF‐OLES, and DAPS [1], respectively. [ABSTRACT FROM AUTHOR]

The increasing proliferation of Internet-of-things (IoT) networks in a given space requires exploring various communication solutions (e.g., cooperative relaying, non-orthogonal multiple access, spectrum sharing) jointly to increase the performance of coexisting IoT systems. However, the design complexity of such a system increases, especially under the constraints of performance targets. In this respect, this paper studies multiple-access enabled relaying by a lower-priority secondary system, which cooperatively relays the incoming information to the primary users and simultaneously transmits its own data. We consider that the direct link between the primary transmitter–receiver pair uses orthogonal multiple access in the first phase. In the second phase, a secondary transmitter adopts a relaying strategy to support the direct link while it uses non-orthogonal multiple access (NOMA) to serve the secondary receiver. As a relaying scheme, we propose a piece-wise and forward (PF) relay protocol, which, depending on the absolute value of the received primary signal, acts similar to decode-and-forward (DF) and amplify-and-forward (AF) schemes in high and low signal-to-noise ratio (SNR), respectively. By doing so, PF achieves the best of these two relaying protocols using the adaptive threshold according to the transmitter-relay channel condition. Under PF-NOMA, first, we find the achievable rate region for primary and secondary receivers, and then we formulate an optimization problem to derive the optimal PF-NOMA time and power fraction that maximize the secondary rate subject to reliability constraints on both the primary and the secondary links. Our simulation results and analysis show that the PF-NOMA outperforms DF-NOMA and AF-NOMA-based relaying techniques in terms of achievable rate regions and rate-guaranteed relay locations. [ABSTRACT FROM AUTHOR]