Design And Simulation Of Adaptive Coding And Modulation In Multi-mode Access System

In the multi-standard,multi-layer heterogeneous wireless networks,the traditional multi-standard network access equipment are fused to form a multi-mode configurable access equipment,in order to improve efficiency,reduce costs and provide the convenience for clients to access the network.This thesis studied the base band processing unit of the multi-mode base station.Adaptive coding and modulation scheme based on the fixed threshold algorithm is designed for the LTE system of the base band processing unit of the multi-mode base station.The Signal Noise Ratio(SNR)of the system is divided into many non overlapping continuous interval where the threshold is the interval boundary value.In each interval,the system selects different coding and modulation scheme according to the requirements of the target BER to increase the throughput of the system.Based on the fixed threshold algorithm,it introduces several ways to determine the sub-band SNR adaptive coded modulation scheme.Simulation results show that the system throughput is significantly improved when using the optimal threshold search adaptive modulation and coding scheme when the condition of the target FER is satisfied.Adaptive decision algorithm is designed for the wireless local area network adaptive coding and modulation of the base band processing unit of the multi-mode base station.Estimate and predict the next frame or a next transmission cycle which MCS should be adopted according to the factors of amplitude and noise interference of the received signal,by using an adaptive decision algorithm and achieving adaptive process,ensure the reliability of the transmission system and improving system throughput.Simulation results show that the throughput of the AMC scheme is significantly improved compared to the throughput of fixed MCS in the case of low SNR or high SNR.