Abstract
Radio frequency (RF) signals can be relied upon for conventional wireless information transfer (WIT) and for challenging wireless power transfer (WPT), which triggers the significant research interest in the topic of simultaneous wireless information and power transfer (SWIPT). By further exploiting the advanced non-orthogonal-multiple-access (NOMA) technique, we are capable of improving the spectrum efficiency of the resource-limited SWIPT system. In our SWIPT system, a hybrid access point (H-AP) superimposes the modulated symbols destined to multiple WIT users by exploiting the power-domain NOMA, while WPT users are capable of harvesting the energy carried by the superposition symbols. In order to maximise the amount of energy transferred to the WPT users, we propose a joint design of the energy interleaver and the constellation rotation based modulator in the symbol-block level by constructively superimposing the symbols destined to the WIT users in the power domain. Furthermore, a transmit power allocation scheme is proposed to guarantee the symbol-error-ratio (SER) of all the WIT users. By considering the sensitivity of practical energy harvesters, the simulation results demonstrate that our scheme is capable of substantially increasing the WPT performance without any remarkable degradation of the WIT performance.
Highlights
We proposed a constellation rotation modulation scheme in [33] for a threeuser NOMA-simultaneous wireless information and power transfer (SWIPT) system, which includes a pair of wireless information transfer (WIT) users and a single wireless power transfer (WPT) user
Our NOMA aided SWIPT system consists of KI WIT users denoted as {uI1, · · ·, uIKI }, KE WPT users denoted as {uE1, · · ·, uEKE } and a single hybrid access-point (H-AP), which is capable of simultaneously delivering information to the WIT users and transferring energy to the WPT users
We firstly investigate the convergence of Algorithm 1 in Fig. 6, where we maximise the energy carried by a specific subcarrier by solving the optimisation problem (P3)
Summary
In the upcoming era of 5G and Internet of Things (IoT), massive machine-type communications are enabled by the deployment of low-power IoT devices, which triggers more difficulties on the spectrum efficiency [1], energy efficiency [2], or security [3]. By allowing the downlink and uplink transmissions in the same time-frequency resource block, the full-duplex technique may further double the spectrum efficiency of the NOMA [8], if the self-interference can be appropriately mitigated. In order to alleviate their energy shortage, radio frequency (RF) signal based wireless power transfer (WPT) can be relied upon for remotely charging these batterypowered IoT devices [9]. By exploiting the broadcast nature of the wireless channels, the transmitter is capable of simultaneously transferring RF signals to both the WIT users and the WPT users [14]. The WIT users recover the requested information from the received RF signals, while the WPT users harvest energy from their received RF signals.
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