Research On Downlink Channel And Resource Scheduling For Indoor Visible Light Communication

With the growing awareness of the energy saving and environmental protection,lightemitting diodes(LED)have gradually become the main lighting sources in the market by virtue of the advantages of low power consumption and long life.At the same time,with the popularization of intelligent equipment terminals and the increase of mobile user equipments,the current radio frequency band gradually fails to meet human demands for the security and transmission rate of wireless communication networks.As a result,visible light communication(VLC)based on LED,which has both lighting and communication functions,has become a powerful alternative technology for the next-generation wireless communication networks with its advantages of high security and abundant unregulated bandwidth resources.How to optimize the communication performance of the VLC system has become a research focus when it applied into the practical environment.Therefore,this thesis focuses on the downlink channel estimation and resource scheduling for indoor VLC systems.Aiming at the problem that the transmitted signals can not be accurately estimated at the receiving end of indoor VLC systems due to the signals are already distorted,an improved compressed sensing channel estimation method based on the transmitter pilots is proposed.The pilots are placed orthogonally on the transmitter.Besides,an improved compressed sensing channel estimation method is proposed which is called as sparsity adaptive threshold backtracking orthogonal matching pursuit reconstruction algorithm.In the algorithm,an adaptive threshold based on the logistic regression function is designed to select the atoms adaptively and a backtracking strategy is increased to improve the accuracy of atomic selection.In addition,the termination conditions are also redefining to reduce the effect of noises.The simulation results indicate that the proposed algorithm can effectively improve the channel estimation accuracy under the premise of ensuring the system bit error rate.To solve the inter-cell interference and inter-user interference caused by the overlapping areas and the resources competition,a resource scheduling method based on dynamic frequency reuse is proposed.In the method,a user equipment interference graph is constructed to analyze the interference relationships among all user equipments.And every user equipments are access to a LED according to the optimal channel strategy.After that,a bidirectional double tabu list tabu search(BDTLTS)algorithm is designed to seek the optimal frequency reuse scheme.The dynamic frequency reuse is achieved according to the solution found by the BDTLTS algorithm and the results of all LEDs allocation.Simulation results show that our proposed scheme improves effectively the data rate and average spectral efficiency of the system without lowering the fairness performance.