Research On Resource Allocation Algorithm Of Downlink For Indoor Cascaded PLC-VLC System

The rapid development of Internet of Things,Cloud Computing and other technologies has brought great challenges to the traditional wireless communication spectrum with spectrum deficit.Visible light communication(VLC)has become a potential high-speed wireless access scheme because of its high transmission power,no electromagnetic interference,security and no need for spectrum authentication.However,visible light cannot be used directly as an information source,and must be combined with other communication technologies to avoid becoming an information island.Among the candidates for all backbone networks,power line communication(PLC)is a better choice because it can utilize the existing infrastructure of each light emitting diode(LED).Therefore,more and more researchers tried to integrate VLC with PLC to form a cascaded PLC-VLC system.Hitherto,key technologies such as networks integration technology,channel modeling technology,multi-user access technology,power allocation scheme and subcarrier allocation scheme are required to make breakthroughs in cascaded PLC-VLC systems.Therefore,in order to improve the throughput of indoor cascaded PLC-VLC systems,this thesis studies power allocation scheme and subcarrier allocation scheme of cascaded PLC-VLC systems.Firstly,the main reason limiting the communication rate and capacity in a cascaded PLC-VLC system is that the modulation bandwidth of the LED is limited.Multiple users could share the same time and frequency resources to provide higher spectral efficiency by using non-orthogonal multiple access(NOMA)method than traditional multiple access method.Therefore,we investigate the power allocation strategy for a downlink cascaded PLC-VLC system based on NOMA in chapter three.In the power allocation scheme,our goal is to maximize the throughput of the cascaded PLC-VLC system while considering user fairness.To solve this optimization problem,we present an optimal power allocation(OPA)algorithm that finds optimal solution by transforming the non-convexity of the original formulated model into the convex programming.Numerical results show that the proposed OPA algorithm significantly outperforms the gain ratio power allocation(GRPA)and the fixed power allocation(FPA)algorithm in terms of the system throughput,and improves the fairness among users.Secondly,NOMA technology is introduced in chapter three,but allocating all users to a resource block will lead to higher computational complexity and decoding delay.In order to achieve a good compromise between system performance and computational complexity,we propose an improved genetic algorithm-joint user pairing and subcarrier allocation(IGA-JUPSA)scheme in chapter four.In this scheme,we use the optimal user pairing algorithm for user pairing,which can maximize the throughput of the cascaded PLC-VLC system;all paired users use an improved genetic algorithm for subcarrier allocation,which improves the algorithm's performance through improved crossover and mutation operations,and can also take into account the fairness and user satisfaction of the cascaded PLC-VLC system.Simulation results show that the proposed IGA-JUPSA scheme can reduce the computational complexity while ensuring the performance of the cascaded PLC-VLC system,and can also take into account the fairness and user satisfaction of the cascaded PLC-VLC system.