Research And Performance Evaluation Of Spectrum-sharing Access For Typical Millimeter-wave Unlicensed Spectrum

With the exponential increase in mobile communication network data traffic,wireless networks are facing unprecedented challenges in terms of capacity.To address the spectrum bottleneck issue and improve network capacity,3GPP has proposed the New Radio-based access to Unlicensed spectrum(NR-U)technology,which uses millimeter-wave bands to extend the licensed spectrum.However,this technology faces the challenge of fairly coexisting with other wireless access technologies in the millimeterwave unlicensed spectrum and competing for resources.This article focuses on coexistence scenarios in the millimeter-wave unlicensed spectrum,aiming to improve the spectrum efficiency of unlicensed spectrum and ensure fair coexistence.The main contributions of this article are as follows:(1)A new non-authorized access method based on a threedimensional Markov chain model is proposed to address channel quality and channel access conflict in the time-frequency domain of millimeterwave unlicensed spectrum.A competition window(C W)backoff algorithm based on channel quality indicator feedback information is used to represent the collision probability of the spectrum sharing access process.The article comprehensively analyzes the key reasons for time-frequency domain packet transmission failures by considering different RAT conflicts and channel quality degradation conditions.A fairness-based spectrum sharing access algorithm is proposed,which assigns the optimal CW to minimize the collision probability for the LBT system and ensures fairness between the LBT and the wireless fidelity coexistence system.Simulation evaluation results show that the proposed algorithm can improve the throughput of the coexistence system by 16.7%and ensure fairness between different systems in the unlicensed spectrum band.(2)In response to the issue of hidden nodes and link obstruction caused by the directional Listen Before Talk(LBT)mechanism’s single detection direction in unlicensed millimeter-wave airspace,this study presents an adaptive LBT access and fast reconnection algorithm designed for airspace.The algorithm is capable of adaptively switching between omnidirectional LBT and directional LBT modes based on transmitter and receiver channel energy detection results,thereby maximizing channel spatial reuse.The LBT failure identification mechanism is implemented in the airspace to solve communication issues resulting from obstructions.In cases where communication interruption is determined to be caused by obstructions,the LBT competition window is reduced to increase node likelihood of winning the next competition.This ensures that relevant links can rapidly re-establish connections following the disappearance of obstructions,minimizing negative impacts on network performance.Simulation results indicate that the proposed algorithm enhances system throughput by 9.6%and 2.7%,and average node speed by 45.7%and 15.9%relative to traditional directional LBT and omnidirectional LBT,respectively.The algorithm further decreases delay under obstruction conditions by 19.6%and 15.7%.