| In recent years,the rapid development of the Internet of Things(IoT),Industrial Internet,Internet of Vehicles,and other industries,while rapidly changing the way of human life and production,also put forward higher requirements on the existing communication systems,especially in the indoor environment where mobile data traffic is exploding.For this reason,Visible Light Communication(VLC)has attracted widespread attention as an emerging communication technology.Compared to Radio Frequency(RF)communication,VLC has the advantages of low interference,extensive spectrum resources,rapid installation due to multiplexing with existing lighting systems,etc.It has broad perspectives on high-speed communication,secure communication,and indoor localization.It also suffers from the disadvantages of being susceptible to blocking interference,the difficulty of establishing uplinks,and the limited coverage area.At present,research on VLC systems mostly assumes that the channel is interference-free,and VLC is not effectively combined with other communication approaches to form a comprehensive system,making it challenging to embody VLC’s strengths.Therefore,how to scientifically analyze the performance of VLC systems,how to optimize the resource allocation of VLC systems or VLC/RF hybrid systems,or even heterogeneous networks including VLC are crucial to the further development of VLC,to improve resource utilization and user service quality,and to serve as a powerful supplement to RF.This paper focuses on the study of indoor VLC systems,commencing with the analysis of VLC channels and the resource allocation strategy design for energy efficiency optimization,then extending the study to the design and resource allocation of hybrid VLC/RF systems,finally investigating the network selection for heterogeneous networks.The main contributions of this thesis are listed as follows:(1)Considering the susceptibility of VLC to blocking that can lead to dramatic degradation in communication performance.Indoor environments are ubiquitous in terms of shadows from obstructions,and existing models tend to characterize link unavailability in terms of occlusion probabilities.In this paper,an indoor scenario with multiple randomly distributed obstructions is constructed,and the location and size of the shadows generated by the obstructions are calculated using an approximate method with low complexity and an accurate method with high complexity,and the effects of overlap between shadows,room sizes,and the boundaries of rooms are also taken into account.It is demonstrated through simulation that the increase in the number of obstructions results in an increase in the probability of outage and has a negative impact on system throughput.(2)The issue of energy consumption due to the proliferation of devices accessing the network is one of the challenges in the development of communication networks.For VLC,it is practical to improve energy efficiency by scientifically allocating the AC/DC power of light sources and access resources.For this purpose,this paper investigates an indoor VLC system employing Simultaneous Lightwave Information and Power Transfer(SLIPT)for energy efficiency optimization,considering the deployment of multiple Light Emitting Diode(LED)arrays as access points,utilizing the AC component of the optical power to provide communication to IoT devices and the DC component for wireless energy harvesting.First,the energy efficiency optimization is represented as a mixed integer fractional nonlinear programming problem which is difficult to solve quickly;then,the transmission scheme is divided into two stages: sub-channel assignment and power allocation;on the one hand,a virtual cell formation and sub-channel assignment strategy is proposed based on the joint transmission considering device location,quality of service(Qo S)demand,and working state;On the other hand,based on the sub-channel assignment results,a power allocation strategy is designed using parametric simplification and quadratic transformation to convert the original problem into a series of convex problems that can be solved iteratively.Ultimately,it is proved that the proposed scheme is significantly more energy efficient than the two benchmark schemes.(3)The system is extended to a hybrid VLC/RF system and the Sustainability-Driven resource allocation problem for multiple IoT devices is investigated.First,VLC is used to construct the downlink and RF communication is used for uplink transmission.In this case,IoT devices can collect DC energy based on SLIPT and then use the collected energy to send uplink data without relying on any external energy supply.Next,given the sustainability-driven objective,the performance of the system is enhanced by maximizing the minimum data collection rate of all devices.For the non-convex problem obtained,an algorithm is designed to transform it into an iteratively solvable convex problem,and the feasibility and effectiveness of the algorithm are verified through numerical simulations.(4)To further broaden the application scenario,indoor scenarios with multiple network coverage are considered.Usually,different users have different service requirements and different communication performance demands.A network selection method with the objective of improving the quality of experience(Qo E)of users is proposed.The user requirements for different network parameters and the actual performance differences of each candidate network metric are fully considered.Firstly,the analytical hierarchy process and standard deviation method are introduced to quantify the subjective requirements of users and the objective performance of the network respectively.Secondly,in order to improve the quality of service,a metric ”Benefit and Cost Ratio(BCR)” is defined to represent the user requirements under different services,helping to rank the alternative networks in real-time.Finally,simulations demonstrate that the proposed selection scheme can effectively rank and adjust the candidates according to user requirements. |
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