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Unmanned aerial vehicle (UAV) systems undergo a period of rapid development in both civil and military scenarios. A major challenge in the malicious jamming environment is to guarantee the reliability of UAV communications links. Frequency hopping (FH) is one of the most commonly used means of combatting the influence brought about by jamming. In this paper, we integrate low-rate codes into an anti-jamming FH communications system, and propose an efficient and low-complexity turbo-Hadamard code scheme. Tail-biting is applied to design the component convolutional-Hadamard codes, and a corresponding decode algorithm is used for implementation in the UAV hardware platform. Numerical simulation results demonstrate that the anti-jamming performance of this method is improved as compared with conventional concatenated codes. Finally, we compare the complexity and transmission efficiency of the proposed algorithm with the algorithms implemented on the field programmable gate array (FPGA) platform in detail. [ABSTRACT FROM AUTHOR]

Combining noncoherent detection (NCD) with polar codes is a promising way to improve the performance of polar-coded systems in presence of imperfect channel state information. This letter proposes a novel NCD architecture for polar-coded systems by exploiting information feedback and reconstruction. Specifically, extra low-complexity signal processing steps are merged into the conventional polar-coded scheme with NCD, yielding low detection complexity that is crucial for resource-limited systems. Moreover, a polar-coded NCD algorithm is proposed via the information feedback and reconstruction. Simulation results prove that our proposed algorithm outperforms conventional NCD algorithms in terms of bit error rate and block error rate. Finally, the complexity of the proposed NCD algorithm is analyzed in detail. [ABSTRACT FROM AUTHOR]

Smart City Internet of Things will become a fundamental infrastructure to support massive machine-type communications between the widely deployed sensors serving big cities. Since there exists many location constraints for the existing terrestrial Internet of Things, the non-terrestrial Internet of Things sheds light on breaking these limits. Therefore, this article conducts a comprehensive survey on non-terrestrial Internet of Things technologies for Smart City, which is an important complement to terrestrial Internet of Things. We first present the application scenarios of Internet of Things and point out where the existing terrestrial Internet of Things cannot work perfectly. Two non-terrestrial Internet of Things technical proposals are then introduced, namely satellite Internet of Things and unmanned aerial vehicle Internet of Things. However, the focuses of these non-terrestrial Internet of Things are distinct, that is, the major problems of satellite and unmanned aerial vehicle Internet of Things are the high dynamic nature of channel and high maneuverability of unmanned aerial vehicles, respectively. The key technologies for satellite and unmanned aerial vehicle Internet of Things are then reviewed separately. Both physical and non-physical layer technologies are surveyed for satellite Internet of Things, and the route planning is mainly investigated for the unmanned aerial vehicle Internet of Things. Finally, we draw a conclusion and give some potential research directions of non-terrestrial Internet of Things. [ABSTRACT FROM AUTHOR]