NOMA-Based Spectrum Sensing for Satellite-Terrestrial Communication

With the continuous development of wireless communication technology,the number of access devices continues to soar,which poses a grate challenge to the already scarce spectrum resources.Meanwhile,6G will be an era of air-space-terrestrial-sea integration,and satellite spectrum resources are also very tight in the context of giant constellations.In this paper,we propose a Non-Orthogonal Multiple Access(NOMA)based spectrum sensing scheme for the future satellite-terrestrial communication scenarios,and design the transceiver from uplink and downlink scenarios,respectively.In order to better identify the user's transmission status,we obtain the feature values of each user through feature detection to make decision.We combine these two technologies to design the transceiver architecture and deduce the threshold value of feature detection in the satellite-terrestrial communication scenario.Simulations are performed in each scenario,and the results illustrate that the proposed scheme combining NOMA and spectrum sensing can greatly improve the throughput with a similar detection probability as Orthogonal Multiple Access(OMA).

Environmental Information-Aided Electromagnetic Propagation Testbed for Maritime Communication

Maritime channel modeling can be affected by some key time-varying environmental factors.The ducting effect is one of the thorniest factors since it causes anomalous propagation enhancement and severe co-channel interference.Moreover,the atmospheric attenuation is much more severe in the ocean environment,resulting in shorter coverage distance and more link outage.In this paper,we propose an environmental information-aided electromagnetic propagation testbed.It is based on complex refractivity estimation and improved parabolic equation propagation model,taking into account both ducting effect and atmospheric attenuation.A large-scale temporal and spatial propagation measurement was conducted with meteorological acquisition.We consider practical path loss and ducting conditions to verify the testbed feasibility in these long-distance radio links.The simulation results are in good agreement with the measured data,which further reveal the basic temporal and spatial distribution of ducting effect at 3.5 GHz band.

Weight Based Channel Selection Towards 5G in the Unlicensed Spectrum

The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommunication systems. To meet the ever-increasing mobile traffic demand in the next 5 th generation(5 G) communication systems, deploying 5 G in the unlicensed spectrum(5 G-U), has been regarded as a promising technology. The Third Generation Partnership Project(3 GPP) has specified the standardization of the Licensed Assisted Access(LAA) and its extension enhanced LAA(e LAA), to opportunistically transmit in the unlicensed spectrum. The LAA/e LAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the e LAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the e LAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the e LAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.

Flexible Uplink MU-MIMO Scheduling in UnlicensedSpectrum

Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In this paper,we investigate the uplink multi-user multiple-input multiple-output(UL MU-MIMO) technique to achieve multiplexing gain in unlicensed spectrum.We first define a new parameter called channel busy radio(CBR) which is related to the probability of occupying the unlicensed channel,and find that the failure to occupy the unlicensed channel leads to the performance degradation in unlicensed spectrum.Then,according to the user-specific CBR of the unlicensed channel,we propose a flexible scheduling scheme for UL MU-MIMO in unlicensed spectrum,and formulate an optimization problem for the optimal scheduled user number.Furthermore,an adaptive scheduling algorithm is proposed to decide the optimal number of the scheduled users efficiently.The simulation results show that,based on statistical channel condition in unlicensed spectrum,adjusting the number of the scheduled user flexibly can offset the degraded throughput and form an optimal MU-MIMO transmission.

Brain-Computer-Interface Inspired Communications

Following the massive commercialization of 5G mobile communication systems,both academia and industry are initiating research activities to shape the next-generation communication systems,namely,6G.Although the detailed killer-applications and key technologies of 6G have not been clearly defined yet,it is commonly expected that 6G will provide hypercoverage and hyper-connectivity.Enabled by these capabilities,the 6G communication systems are especially aiming at improving the user’s experi-ence greatly,or more ambitiously,to change the way of human’s everyday life.So far,many new services with more stringent requirements,such as truly immersive extended reali¬ty(XR),high-fidelity mobile hologram,and digital replica,are expected to be satisfied by the 6G communication systems.

Fragmental Weight-Conservation Combining Scheme for Statistical Signal Transmissions under Fast Time-Varying Channels

Statistical Signal Transmission(SST)is a technique based on orthogonal frequency-division multiplexing(OFDM)and adopts cyclostationary features,which can transmit extra information without additional bandwidth.However,the more complicated environment in 5G communication systems,especially the fast time-varying scenarios,will dramatically degrade the performance of the SST.In this paper,we propose a fragmental weight-conservation combining(FWCC)scheme for SST,to overcome its performance degradation under fast time-varying channels.The proposed FWCC scheme consists of three phases:1、incise the received OFDM stream into pieces;2、endue different weights for fine and contaminated pieces,respectively;3、combine cyclic autocorrelation function energies of all the pieces;and 4、compute the final feature and demodulate data of SST.Through these procedures above,the detection accuracy of SST will be theoretically refined under fast time-varying channels.Such an inference is confirmed through numerical results in this paper.It is demonstrated that the BER performance of proposed scheme outperforms that of the original scheme both in ideal channel estimation conditions and in imperfect channel estimation conditions.In addition,we also find the experiential optimal weight distribution strategy for the proposed FWCC scheme,which facilitates practical applications.

Simulation on Pyrolysis Products of Thermoset Phenolic Resin with Different Chemical Structure and Experimental Validation

The simulation on pyrolysis products of pure PF resin with different chemical structure was investigated and validated by pyrolysis gas-chromatography mass spectrometry(Py-GC/MS).The simulation of pyrolysis products of phenolic resin with different chemical structure was investigated by AMBER(Assisted Model Building with Energy Refinement)force field.The content of pyrolysis products phenol and cresol decreases with the increase of F/P(formaldehyde/phenol)value.The content of pyrolysis products dimethylphenol and trimethylphenol increases with the enhancement of F/P value.The crosslink density of phenolic mixture can be measured by the content of pyrolysis products dimethylphenol and trimethylphenol.Consequently,the results of simulation were validated by the Py-GC/MS experiment.

Analysis and prediction of 100 km-scale atmo-spheric duct interference in TD-LTE networks

Atmospheric ducts are horizontal layers that occur under certain weather conditions in the lower atmosphere.Radio signals guided in atmospheric ducts tend to experience less attenuation and spread much farther,i.e,hundreds of kilometers.In a large-scale deployed TD-LTE(Time Division Long Term Evolution)network,atmospheric ducts cause faraway downlink wireless signals to propagate beyond the designed protection distance and interfere with local uplink signals,thus resulting in a large outage probability.In this paper,we analyze the characteristics of ADI atmospheric duct interference(Atmospheric Duct Interference)by the use of real network-side big data from the current operated TD-LTE network owned by China Mobile.The analysis results yield the time varying and directional characteristics of ADI.In addition,we proposed an SVM(Support Vector Machine)-classi er based spacial prediction method of ADI by machine learning over combination of real network-side big data and real meteorological data.Furthermore,an implementation of ADMM(Alternating Direction Methods of Multipliers)framework is proposed to implement a distributed SVM prediction scheme,which reduces data exchange among di erent regions/cities,maintains similar prediction accuracy and is thus of a more practical use to operators.