In this paper, we investigate robust resource allocation algorithm design for multiuser downlink multiple-input single-output (MISO) unmanned aerial vehicle (UAV) communication systems, where we ...account for the various uncertainties that are unavoidable in such systems and, if left unattended, may severely degrade system performance. We jointly optimize the two-dimensional (2-D) trajectory and the transmit beamforming vector of the UAV for minimization of the total power consumption. The algorithm design is formulated as a non-convex optimization problem taking into account the imperfect knowledge of the angle of departure (AoD) caused by UAV jittering, user location uncertainty, wind speed uncertainty, and polygonal no-fly zones (NFZs). Despite the non-convexity of the optimization problem, we solve it optimally by employing monotonic optimization theory and semidefinite programming relaxation which yields the optimal 2-D trajectory and beamforming policy. Since the developed optimal resource allocation algorithm entails a high computational complexity, we also propose a suboptimal iterative low-complexity scheme based on successive convex approximation to strike a balance between optimality and computational complexity. Our simulation results reveal not only the significant power savings enabled by the proposed algorithms compared to two baseline schemes, but also confirm their robustness with respect to UAV jittering, wind speed uncertainty, and user location uncertainty. Moreover, our results unveil that the joint presence of wind speed uncertainty and NFZs has a considerable impact on the UAV trajectory. Nevertheless, by counteracting the wind speed uncertainty with the proposed robust design, we can simultaneously minimize the total UAV power consumption and ensure a secure trajectory that does not trespass any NFZ.
Increasing demands for spectrum have necessitated the coexistence of communications and radar systems within the same band. This paper investigates how an unaltered radar system affects the ...performance of a communications receiver. For a single-carrier communications system, it is shown that a low power radar signal can be treated as Gaussian noise while a strong radar signal can be subtracted off the received signal, but in doing so one of the two signal dimensions is lost. Complex-valued constellation design problems are next proposed, with the goal of either minimizing the error rate under a power constraint, or maximizing the transmission rate under both error rate and power constraints. Numerically, the designed constellation is shaped as a concentric hexagon for weak radar interference while it morphs into an uneven pulse amplitude modulation for strong interference. A multi-carrier orthogonal frequency division multiplexing communications system is lastly considered. Due to the radar interference, the received signal becomes correlated over time and across carriers. To reduce the complexity of the optimal receiver, several suboptimal decoders are analyzed, among which the one that discards the correlations between subcarriers is numerically found to perform close to the optimal one.
3G Evolution Erik Dahlman, Stefan Parkvall, Johan Skold, Per Beming
2010, 2007, 2007-12-31, c2007
eBook
This very up-to-date and practical book, written by engineers working closely in 3GPP, gives insight into the newest technologies and standards adopted by 3GPP, with detailed explanations of the ...specific solutions chosen and their implementation in HSPA and LTE. The key technologies presented include multi- carrier transmission, advanced single-carrier transmission, advanced receivers, OFDM, MIMO and adaptive antenna solutions, advanced radio resource management and protocols, and different radio network architectures. Their role and use in the context of mobile broadband access in general is explained. Both a high-level overview and more detailed step-by-step explanations of HSPA and LTE implementation are given. An overview of other related systems such as TD SCDMA, CDMA2000, and WIMAX is also provided.This is a 'must-have' resource for engineers and other professionals working with cellular or wireless broadband technologies who need to know how to utilize the new technology to stay ahead of the competition.The authors of the book all work at Ericsson Research and are deeply involved in 3G development and standardisation since the early days of 3G research. They are leading experts in the field and are today still actively contributing to the standardisation of both HSPA and LTE within 3GPP.* Gives the first explanation of the radio access technologies and key international standards for moving to the next stage of 3G evolution: fully operational mobile broadband * Describes the new technologies selected by the 3GPP to realise High Speed Packet Access (HSPA) and Long Term Evolution (LTE) for mobile broadband * Gives both higher-level overviews and detailed explanations of HSPA and LTE as specified by 3GPP
Recently, deep learned enabled end-to-end communication systems have been developed to merge all physical layer blocks in the traditional communication systems, which make joint transceiver ...optimization possible. Powered by deep learning, natural language processing has achieved great success in analyzing and understanding a large amount of language texts. Inspired by research results in both areas, we aim to provide a new view on communication systems from the semantic level. Particularly, we propose a deep learning based semantic communication system, named DeepSC, for text transmission. Based on the Transformer, the DeepSC aims at maximizing the system capacity and minimizing the semantic errors by recovering the meaning of sentences, rather than bit- or symbol-errors in traditional communications. Moreover, transfer learning is used to ensure the DeepSC applicable to different communication environments and to accelerate the model training process. To justify the performance of semantic communications accurately, we also initialize a new metric, named sentence similarity. Compared with the traditional communication system without considering semantic information exchange, the proposed DeepSC is more robust to channel variation and is able to achieve better performance, especially in the low signal-to-noise (SNR) regime, as demonstrated by the extensive simulation results.
The Fifth Generation (5G) of Wireless Communication is a collection of reviewed and relevant research chapters, offering a comprehensive overview of recent developments in the field of Electrical and ...Electronic Engineering. The book comprises single chapters authored by various researchers and edited by an expert active in the Electrical and Electronic Engineering research area. All chapters are complete in itself but united under a common research study topic. This publication aims at providing a thorough overview of the latest research efforts by international authors on the fifth generation (5G) of wireless communication, and open new possible research paths for further novel developments.
Magnetoelectric (ME) antennas have offered significant advantages in the design of very-low-frequency (VLF) communication systems operating in challenging environments such as underground, ...underwater, and inside metallic enclosures. However, state of the art ME-based communication systems either depend on bulky commercial signal processing instruments or have limited reports on digital signal transmissions. In this work, we demonstrate a compact design of an ME VLF communication system based on self-designed modulator and demodulator circuits, working at the electromechanical resonance frequency of the ME antenna and having a remarkably reduced size for greater applicability in realistic industrial scenarios. The concept of sending Morse code through amplitude-shift-keying modulation was confirmed in the proposed ME VLF communication system. Our findings revealed that the maximum communication distance can be considered as 5.7 m when the bit-error-rate is limited to 10 -2 . Furthermore, VLF wireless signal transfer through a harsh environment (metal box) was verified with our communication system. An effective communication distance of 0.85 m could be realized when placing the ME receiver in a 5 mm iron box, demonstrating the ability of the wireless signal to penetrate conductive media. The proposed fully packed ME VLF communication system provides advantageous alternative for underground, underwater, and inside-metal-containers communications.
A Review on Terahertz Communications Research Kleine-Ostmann, Thomas; Nagatsuma, Tadao
Journal of infrared, millimeter and terahertz waves,
02/2011, Letnik:
32, Številka:
2
Journal Article
Recenzirano
The increasing demand of unoccupied and unregulated bandwidth for wireless communication systems will inevitably lead to the extension of operation frequencies toward the lower THz frequency range. ...Higher carrier frequencies will allow for fast transmission of huge amounts of data as needed for new emerging applications. Despite the tremendous hurdles that have to be overcome with regard to sources and detectors, circuit and antenna technology and system architecture to realize ultrafast data transmission in a scenario with extensive transmission loss, a new area of research is beginning to form. In this article we give an overview of emerging technologies and system research that might lead to ubiquitous THz communication systems in the future.
Channel estimation is challenging for the reconfigurable intelligent surface (RIS)-aided wireless communications. Since the number of coefficients of the cascaded channel among the base station (BS), ...the RIS, and the user equipment (UE), is the product of the number of BS antennas, the number of RIS elements, and the number of UEs, the pilot overhead can be prohibitively high. In this paper, we propose a two-timescale channel estimation framework to exploit the property that the BS-RIS channel is high-dimensional but quasi-static, while the RIS-UE channel is mobile but low-dimensional. Specifically, to estimate the quasi-static BS-RIS channel, we propose a dual-link pilot transmission scheme, where the BS transmits downlink pilots and receives uplink pilots reflected by the RIS. Then, we propose a coordinate descent-based algorithm to recover the BS-RIS channel. Since the quasi-static BS-RIS channel is estimated less frequently than the mobile channel is, the average pilot overhead can be reduced from a long-term perspective. Although the mobile RIS-UE channel has to be frequently estimated in a small timescale, the associated pilot overhead is low thanks to its low dimension. Simulation results show that the proposed two-timescale channel estimation framework can achieve accurate channel estimation with low pilot overhead.
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