Research On Resource Allocation Mechanisms And Algorithms For Symbiotic Communication

Wireless communication is the essential engine driving the future intelligent society in China.With the emergence of these new intelligent application scenarios,such as smart healthcare,intelligent manufacturing,intelligent transportation,and so on,wireless com-munication needs various communication systems to support a wide range of services and improve core technical indicators,and thus it is showing the trend where various commu-nication systems coexist.With limited communication resources such as spectrum and energy,these communication systems need to share their resources to prompt resource efficiency.Therefore,wireless communication research focuses on realizing the efficient coexistence among these communication systems.Symbiotic communication(SC)pro-vides a novel wireless communication paradigm that realizes the efficient coexistence between the active and the passive communication systems.In the SC,the backscatter device(BD)in the passive communication system leverages the radio frequency signal generated by the active communication system to perform the backscatter transmission.The active communication system can also benefit from the additional multipath compo-nents introduced by the passive communication system.Thus,the active and the passive communication systems share spectrum,energy,and infrastructure resources and are thus expected to yield mutual benefits and achieve an efficient coexistence.To further improve the performance of the SC system,it is imperative to figure out the effects of some key transmission parameters on the performance and the relation between the active and the passive communication systems,to enhance the transmissions with some new BD designs,and also to study these SC systems' resource allocation mechanisms and algorithms.Therefore,this dissertation is motivated to investigate the resource allocation mech-anisms and algorithms for SC systems.It starts from the study on the transmission per-formance and the relation between the active and the passive communication systems un-der different SC system transmission setups and then introduces the full-duplex and the reflection-enhanced BD into the SC system designs.The dissertation is mainly composed of four research contents,including(1)SC system design principles and rate analysis?(2)Full-duplex SC system design and resource allocation algorithm?(3)Single-antenna reflection-enhanced SC system design and resource allocation algorithm?(4)Multiple-antenna reflection-enhanced SC system design and resource allocation algorithm.The specific research contents and main contributions are summarized as follows.This dissertation first investigates the transmission performance and the relation be-tween the active and the passive communication systems under different symbol period setups,providing the basic design principles to the succeeding research.According to the analysis on the achievable rates of the active and the passive communication systems,the kinds of typical symbiosis modes are categorized,namely the parasitic SC and the mutual-istic SC.Then,the resource allocation mechanisms and algorithms are studied under these two kinds of symbiosis modes.By optimizing the transmit beamforming of the transmit-ter(Tx),either the weighted sum rate of the active and the passive communication system is maximized,or the transmit power of the active communication system is minimized.Meanwhile,the low-complexity resource allocation algorithm is proposed after investi-gating the relation between the transmit beamforming and the relevant channels in the SC system.Simulation results compare the performances of the two typical SC systems and show that the mutualistic SC system outperforms the other one in the spectrum efficiency.Considering the transmission of control information between the SC system's active and passive communication systems,this dissertation proceeds to research the design and resource allocation algorithm of the full-duplex SC system.Specifically,the BD can si-multaneously perform information reception and backscatter transmission by introducing the full-duplex BD design.The achievable rates are analyzed with the parasitic SC system design,including the broadcast transmissions from the Tx to the BD and the receiver(Rx)and the backscatter transmission from the BD to the Rx.Then,the transmit power mini-mization problem is proposed under the achievable rate constraints.The problem is then solved with the semi-definite relaxation(SDR)based exhaustive-search algorithm or the closed-form based low-complexity algorithm by optimizing the Tx transmit beamforming and the BD power receiving coefficient.Simulation results show that the full-duplex BD design can enable efficient transmission for the SC system when the Tx sends the control information.Further,considering the requirement to increase the mutualistic benefits of the active and the passive communication systems,this dissertation investigates the single-antenna reflection-enhanced SC system design and resource allocation algorithm.In particular,by exploiting the negative resistance,the reflection-enhanced BD can amplify the incident signal via the reflection and thus enhance the backscatter link strength.The active trans-mission rate maximization problem is proposed with the mutualistic SC system,which additionally considers an interference temperature constraint to protect the non-SC incum-bent users(IU)from the excessive interference generated by the SC system.This problem is then solved with the alternating optimization algorithm,which iteratively solves two sub-problems: the Tx transmit beamforming design and the BD power reflection coeffi-cient design.The transmit beamforming can be optimized with the SDR technique,while the power reflection coefficient can be optimized with fractional programming.Simula-tion results show that the reflection-enhanced BD can effectively improve the transmission performance of both the active and the passive communication systems.Finally,this dissertation considers an extended scenario of the previous research and studies the multi-antenna reflection-enhanced SC system design and resource allocation algorithm to increase the mutualistic benefits.Specifically,the enhanced reconfigurable intelligent surface(RIS)is introduced to the mutualistic SC system design.The enhanced RIS can realize reflection amplification and reflect beamforming by consuming small amounts of power,whose power consumption model is investigated later.The active transmission rate maximization problem is proposed under the RIS power overhead con-straint and the interference temperature constraints,which can be solved with the alter-nating optimization algorithm.The transmit beamforming can be optimized by solving a series of mean-square error minimization problems,while the reflect beamforming can be optimized by fractional programming.Besides,the trade-off between the number of the reflecting antenna elements and the reflection amplification is specially investigated when the enhanced RIS maximizes the backscatter link's signal-to-noise ratio(SNR).Simula-tion results show that under the same power budget,the enhanced RIS outperforms the traditional RIS with better transmission gain but less reflecting antenna elements,which significantly increases the performance of the proposed SC system.