Terahertz (THz) communications have been widely envisioned as a promising enabler to provide adequate bandwidth and achieve ultra-high data rates for sixth generation (6G) wireless networks. In order ...to mitigate blockage vulnerability caused by serious propagation attenuation and poor diffraction of THz waves, an intelligent reflecting surface (IRS), which manipulates the propagation of incident electromagnetic waves in a programmable manner by adjusting the phase shifts of passive reflecting elements, is proposed to create smart radio environments, improve spectrum efficiency and enhance coverage capability. Firstly, some prospective application scenarios driven by the IRS empowered THz communications are introduced, including wireless mobile communications, secure communications, unmanned aerial vehicle (UAV) scenario, mobile edge computing (MEC) scenario and THz localization scenario. Then, we discuss the enabling technologies employed by the IRS empowered THz system, involving hardware design, channel estimation, capacity optimization, beam control, resource allocation and robustness design. Moreover, the arising challenges and open problems encountered in the future IRS empowered THz communications are also highlighted. Concretely, these emerging problems possibly originate from channel modeling, new material exploration, experimental IRS testbeds and intensive deployment. Ultimately, the combination of THz communications and IRS is capable of accelerating the development of 6G wireless networks.
With the exponential growth of the data traffic in wireless communication systems, terahertz (THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond ...fifth generation (5G), bridging the gap between millimeter wave (mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency (IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.
Sparse code multiple access (SCMA) has been proposed to obtain high capacity and support massive connections. Due to the sparse feature of codewords, SCMA achieves low complexity multiuser detection ...by utilizing message passing algorithm (MPA). However, the complexity reduction of MPA is still a significant issue. In this letter, a novel MPA based on sphere decoding, called SD-MPA, is proposed, which narrows down the range of believable superposed constellation points. Furthermore, simulation results show that SD-MPA detector can reach low complexity detection and maintain negligible bit error ratio performance decline compared with conventional MPA.
The fifth generation (5G) wireless communication networks are being deployed worldwide from 2020 and more capabilities are in the process of being standardized, such as mass connectivity, ...ultra-reliability, and guaranteed low latency. However, 5G will not meet all requirements of the future in 2030 and beyond, and sixth generation (6G) wireless communication networks are expected to provide global coverage, enhanced spectral/energy/cost efficiency, better intelligence level and security, etc. To meet these requirements, 6G networks will rely on new enabling technologies, i.e., air interface and transmission technologies and novel network architecture, such as waveform design, multiple access, channel coding schemes, multi-antenna technologies, network slicing, cell-free architecture, and cloud/fog/edge computing. Our vision on 6G is that it will have four new paradigm shifts. First, to satisfy the requirement of global coverage, 6G will not be limited to terrestrial communication networks, which will need to be complemented with non-terrestrial networks such as satellite and unmanned aerial vehicle (UAV) communication networks, thus achieving a space-air-ground-sea integrated communication network. Second, all spectra will be fully explored to further increase data rates and connection density, including the sub-6 GHz, millimeter wave (mmWave), terahertz (THz), and optical frequency bands. Third, facing the big datasets generated by the use of extremely heterogeneous networks, diverse communication scenarios, large numbers of antennas, wide bandwidths, and new service requirements, 6G networks will enable a new range of smart applications with the aid of artificial intelligence (AI) and big data technologies. Fourth, network security will have to be strengthened when developing 6G networks. This article provides a comprehensive survey of recent advances and future trends in these four aspects. Clearly, 6G with additional technical requirements beyond those of 5G will enable faster and further communications to the extent that the boundary between physical and cyber worlds disappears.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Terahertz (THz) communications recently attract significant attention and become an emerging technology pillar for sixth generation (6G) wireless systems. Due to the serious path attenuation of THz ...signals, THz communication is applicable for the short-distance indoor scenarios. However, the THz waves are easily blocked by obstacles, leading to a communication interruption. To this end, an intelligent reflecting surface (IRS), which interacts with incident THz waves in a controlled manner by adjusting the discrete phase shifts of the IRS elements, is considered as a promising technology to mitigate blockage vulnerability and enhance coverage capability for indoor scenarios. In light of graphene-enabled hardware structure of an IRS, the IRS-assisted THz multiple-input multiple-output (MIMO) system model is developed. Moreover, an iterative atom pruning based subspace pursuit (IAP-SP) scheme is developed for channel estimation. Compared to the classical subspace pursuit (SP) scheme, the proposed IAP-SP algorithm can substantially reduce the computational complexity while maintaining accurate channel recovery. With the estimated channel, a data rate maximization problem is formulated, which can be converted to a discrete phase shift search problem. The exhaustive search method is firstly proposed to obtain the optimal transmission rate but endure extremely high computational burden. Then, a local search method is proposed to decrease the number of possible discrete phase candidates of IRS while undergoes obvious performance loss. Interestingly, a novel feedforward fully connected structure based deep neural network (DNN) scheme is put forward, which has the ability to learn how to output the optimal phase shift configurations by inputting the features of estimated channel. Simulation results demonstrate that, in contrast with the exhaustive search scheme and the local search scheme, the proposed DNN-based scheme achieves a near-optimal communication rate performance. Meanwhile, the DNN-based scheme enormously alleviates the computational complexity and allows for dynamic parameter adaption in rapid-varying channel conditions.
Rapid economic development and accelerated urbanization have seriously affected the development of traditional ethnic villages in China. We used the minimum cumulative resistance (MCR) model based on ...land use, landscape pattern, and ecosystem service value (ESV) to evaluate the spatio-temporal dynamics of sustainable development in Hani traditional ethnic villages from 1995 to 2020. By analyzing changes in sustainability indicators in the Hani area and different buffer zones, this paper aims to assess the impact of ethnic villages in the Hani Area on sustainable development and provide recommendations for the sustainable development of traditional ethnic Hani villages. The results indicated that: (1) The area of construction land and landscape fragmentation in the Hani area significantly increased and the value of ecosystem services and levels of sustainable development decreased each year during the study period; (2) The area of cropland in the 2 km buffer zone of the traditional ethnic villages increased, the degree of landscape fragmentation, the value of ecosystem services, and the level of sustainable development were lower than in the 4 km buffer zone during the study period. This is due to population increases in traditional ethnic Hani villages, as well as the intensive reclamation of cropland, increased construction land, and landscape fragmentation. We suggest that the Hani should implement scientific land planning and management policies to protect the local ecosystem and realize the sustainable development of traditional ethnic Hani villages.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
► Sudan I in food samples is determined using an electrochemical method. ► Graphene exhibits excellent catalytic activity towards the electrochemical oxidation of Sudan I. ► Sodium dodecyl sulphonate ...can remarkably increase the oxidation peak current of Sudan I. ► The mechanism relies on the special structure of graphene and sodium dodecyl sulphonate.
This paper describes a novel electrochemical method for the determination of Sudan I in food samples based on the electrochemical catalytic activity of graphene modified glassy carbon electrode (GMGCE) and the enhancement effect of an anionic surfactant: sodium dodecyl sulphonate (SDS). Using pH 6.0 phosphate buffer solution (PBS) as supporting electrolyte and in the presence of 1.5×10−4molL−1 SDS, Sudan I yielded a well-defined and sensitive oxidation peak at a GMGCE. The oxidation peak current of Sudan I remarkably increased in the presence of SDS. The experimental parameters, such as supporting electrolyte, concentration of SDS, and accumulation time, were optimised for Sudan I determination. The oxidation peak current showed a linear relationship with the concentrations of Sudan I in the range of 7.50×10−8–7.50×10−6molL−1, with the detection limit of 4.0×10−8molL−1. This new voltammetric method was successfully used to determine Sudan I in food products such as ketchup and chili sauce with satisfactory results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Sparse code multiple access (SCMA) has been proposed to support massive connections, and becomes a promising non-orthogonal multiple access in future fifth generation wireless communication systems. ...In SCMA, message passing algorithm (MPA) is utilized to achieve nearly optimal multiuser detection, but the high complexity of MPA detector still makes it hard to implement in practice. To tackle this issue, we present a low complexity MPA detector based on the dynamic factor graph, named DFG-MPA, in which the branches with large belief values in the factor graph model do not participate in the message propagation in current and later iterations. Moreover, choosing the number of partial branches with large belief values for each iteration adaptively depends on practical application scenarios. Numerical results show that the proposed detection scheme provides a commendable tradeoff between bit-error-rate (BER) performance and computational complexity compared with some existing MPA schemes.
Accurate and reliable determination of synthetic dyes in foodstuff is very important to underpin their regulation so as to prevent harm to consumers. Herein, a poly(L-phenylalanine)-modified glassy ...carbon electrode (PLPA/GCE) for the determination of sunset yellow (SY) and tartrazine (Tz) was fabricated through electrochemical immobilization. The electrochemical behavior of SY and Tz at the PLPA/GCE was studied by cyclic voltammetry in phosphate-citrate buffer, and the results showed that the reaction of SY and Tz at the PLPA/GCE was greatly facilitated. This was further used to determine the two species by differential pulse voltammetry. Under optimized analytical conditions, the reduction peak current of SY showed a linear relationship with its concentration in a range of 181–6,333 μg L⁻¹and the oxidation peak current of Tz showed a linear relationship with its concentration in a range of 214–88,169 μg L⁻¹. The limits of detection for SY and Tz were 18.1 and 10.7 μg L⁻¹, respectively. The proposed method shows excellent sensitivity, selectivity, and accuracy and has been satisfactorily applied for the determination of SY and Tz in a variety of real food and drug samples.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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