Environment-aware Wireless Network Access

In recent years,the rapid development of the Internet of things and the mobile Internet has placed higher demands on the network speed,connection density,link delay and user experience of wireless networks.With the development of communication technology and the improvement of hardware performance,concepts such as cognitive radio,software-defined network,cognitive network,and software-defined air interface have been proposed.Due to the environmental awareness ability,the environment-aware wireless network has attracted widespread attention from academia and industry.Compared with traditional wireless networks,such wireless network can perceive,analyze and understand the network environment.Then,network parameters are adapted to the varying network environment.It is a brand-new development direction of future wireless networks.Based on the practical environment and actual scenarios of wireless networks,this thesis carries out research on channel perception in the non-stationary fast-varying environment and proposes wireless network access schemes for two scenarios,i.e.,the massive connectivity and disaster communication scenarios.The contents and contributions of this thesis are listed as follows.1.A channel perception scheme is proposed for non-stationary fast-varying network environment.With the emergence of applications such as high-speed trains and Internet of vehicles,together with the technologies such as massive multiple-input multiple-output,millimeter waves,and ultra-dense networks,the far-field transmission and wide-sense channel stationary assumptions of wireless networks are no longer valid in time-spacial dimension.Therefore,a scattering cluster time-spacial distribution channel modeling method,an edge detection assisted statistical channel state acquisition method as well as joint symbol detection instantaneous channel state prediction method are proposed.The author first conducts an in-depth study on channel characteristics in time-spacial non-stationary fast-varying network environment,then proposes a channel model based on the scattering cluster timespacial distribution.Based on this model,an edge detection assisted statistical channel state acquisition method is proposed.By collecting and processing the channel data in the cell,the edge detection technology is used to divide the non-stationary cell into several stationary sub-regions,and traditional channel estimation is then used to obtain statistical channel state in sub-regions.At the same time,a joint symbol detection instantaneous channel state prediction is proposed.By channel state estimation from original pilot and prediction from the result of symbol detection,the channel changes are tracked to achieve instantaneous channel state prediction.The proposed methods can effectively improve the channel perception in non-stationary fast-varying network environment,and provide prerequisites for access schemes design.2.For wireless network access in massive connectivity scenario,a channel domain non-orthogonal multiple access(CFMA)scheme is proposed.In the applications such as the Internet of things and smart cities,various users with different requirements will bring great challenges to wireless network access.Therefore,a CFMA scheme with corresponding resource scheduling method is proposed.To achieve better performance,the CFMA scheme utilizes the differences of the channel states.It divides the available spectrum into several sub-bands,and allocates the users into the sub-bands according to the user's requirements and channel states.User signals on different sub-bands are independent from each other,and user signals on the same sub-band overlap with each other.Spectrum mapping and interference suppression are used to receive signals.At the same time,the resource scheduling method dynamically adjusts the mapping relationship between users and sub-bands according to the channel states of users.Compared with the orthogonal multiple access scheme,the proposed CFMA scheme with corresponding resource scheduling method can improve the spectral efficiency by 278% and access efficiency by 273%.As for the power-domain non-orthogonal multiple access scheme,these numbers are 273% and 53%,respectively.3.For the wireless network access in disaster communication scenario,a channel perception and battery feedback based access scheme is proposed.Disaster communication is a scenario that comprehensively utilizes emergency communication vehicle,low orbit satellite and unmanned aerial vehicle(UAV)to guarantee disaster communication in an emergency event with the damaged infrastructure,which is related to the safety of victims.Therefore,based on channel perception and battery feedback,a wireless network access scheme and corresponding resource scheduling method is proposed to maximize the rescue ratio of victims.Due to the characteristics of disaster communications,a disaster network architecture composed of a low orbit satellite,UAVs and victims has been proposed.Under the network architecture,an accessing scheme based on channel perception and battery feedback is proposed.The UAV relay with a better channel preferentially access the low-orbit satellite due to the limitation of low-orbit satellite capacity,while the victims with lower battery and better channel state have priority to access because of the limitation of UAV relay capacity.These measures ensure the successful access of low battery victims.Compared with the random access scheme,the proposed access scheme based on channel perception with corresponding resource scheduling method can improve the rescue ratio by 28%.In summary,this dissertation focuses on environmental-aware wireless network access issues.A channel perception scheme is proposed,and then based on channel perception,two wireless network access schemes in different scenarios are proposed.It provides reference for design of wireless network access schemes.