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With the increasing trend of unmanned aerial vehi-cles (UAVs) applications, UAV-based base station (BS) has gained significant popularity for rapid deployable networks. Compared with the fixed infrastructure that could be severally disrupted in the case of natural disasters, the UAV-based BSs are easily for deployment and can provide the emergency communication in the target areas. In addition, for the limited power supply in UAV, energy-efficient transmission is also essential in the wireless coverage. Accordingly, in this paper we focus our attention on

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The problem of network multiple-input multiple-output precoding under distributed channel state information is a notoriously challenging question, for which optimal solutions with reasonable complexity remain elusive. In this context, we assess the value of hierarchical information exchange, whereby an order is established among the transmitters (TXs) in such a way that~a given TX has access not only to its local channel estimate but also to the estimates available at the less informed TXs.

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Nowadays, a significant goal of technology is to prolong the lifetime of the wireless communication devices. To this end, this paper studies and optimizes the performance of simultaneous wireless information and power transfer with an integrated energy and information receiver, which has the advantage of low complexity and energy cost. Specifically, a tractable expression for the achievable rate is provided, which is then used to describe the achievable harvested energy-rate region.

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Consider an ambient modulated backscatter communication (AmBC) system adopting binary phase shift keying modulation that the receiver is to decode the backscatter device induced message without knowledge of the channel state information, the statistical channel covariance matrices, and the noise variance at the receiver antennas. In this paper, we apply the fact that the ambient orthogonal frequency-division multiplexing (OFDM) signals with a large number of subcarriers contain repetitive elements inducing time correlation.

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In this paper, we consider a simple downlink channel with a multi-antenna base station and two single-antenna receivers. We assume that the channel is deterministic and known to all the nodes. Our contribution is two-fold. First, we show that linear precoding with private streams can have unbounded gap to the capacity of the channel. Second, we show that using rate-splitting with a simple power allocation one can achieve the sum capacity to within a constant gap for any channel realization.

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Massive MIMO relies on nearly orthogonal user channels to achieve unprecedented spectral efficiency. But in LoS (line-of-sight) environment, some users can be subjected to similar channel vectors. Serving users with similar channel vectors simultaneously can severely compromise the throughput performance to all users. We propose a scheduler that identifies users with similar channels and serves them in separate time slots with properly assigned data rates, while aiming to provide fair service to all users and maximize the system spectral efficiency at the same time.

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