| 1 | Distortion minimization for multimedia transmission in NOMA HAP-UAV integrated aerial access networks显示文摘Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform(HAP) and Unmanned Air Vehicles(UAVs) with the NonOrthogonal Multiple Access(NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm. | Guobin ZHANG Zhu HAN Hang XIN Xin WEI Boya DI | 2022 | Chinese Journal of Aeronautics2022，35，9： | 0 |
| 2 | Near-Far Field Beamforming for Holographic Multiple-Input Multiple-Output显示文摘Recently,holographic multiple-input multiple-output(HMIMO)has motivated its potential use to support high-capacity data transmission with spatially quasi-continuous apertures.As a practical instance of HMIMO,reconfigurable refractive surfaces(RRSs)equipped with numerous metamaterial elements are utilized as antennas by refracting incident signals from signal sources.In this paper,we investigate a multi-user communication system with an RRS deployed as the base station(BS)’s transmit antenna.To mitigate the high overhead of accurate channel state information(CSI)acquisition,the codebook design and beam training are employed to perform beamforming.Given the large scale of RRS,users are likely to be randomly distributed in both the near and far fields around the BS,which is unknown in advance.By considering radiation characteristics in both fields,a near-far field codebook is designed to be applicable to all users,regardless of their locations.To reduce overhead,a multi-user beam training is proposed to serve all users simultaneously by enhancing each codeword capable of covering multiple areas.Considering a general case that includes users in both fields,simulation results indicate that,without prior knowledge of user distribution,the proposed scheme outperforms state-of-the-art ones in terms of sum rate and overhead. | Yutong Zhang Boya Di Hongliang Zhang Lingyang Song | 2023 | Journal of Communications and Information Networks2023，8，2： | 0 |
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