Research On Semi-persistent Scheduling And TTI-bundling About Key Technology Of VoLTE

Voice over LTE(VoLTE)is a mainstream voice communications solution in the 4G network,which is based on IP Multimedia Subsystem.VoLTE replaces circuit switch with packet switch to transmit voice information,which enables 4G network to be full IP network.VoLTE can improve user capacity and base station coverage in the cell,currently VoLTE is at the stage of experimental network and small-scale pilot with a lot delimma.VoLTE includes some key technologies,and this paper choose semi-persistent scheduling and transmission time interval bundling(TTI-bundling)as research objectives.Firstly,this paper states basic principle and evolution of VoLTE,of which both semi-persistent scheduling and TTI-bundling is the key point,meamwhile,analyzes related research progress at home and aboard.Secondly,this paper studies channel quality indicator(CQI)of semi-persistent scheduling,and puts forward adaptive modified CQI,which integrates the user's past and current state of the radio channels with consideration of user's move speed and direction to ensure more reasonable configuration by base station in the next cycle of semi-persistent scheduling.The simulation results show that adaptive modified CQI can improve user capacity and reduce the utilization rete of control channel at the price of air inter face resource small-scale increasement.Also studies the scenario of combining dynamic scheduling and semi-persistent scheduling,the simulation results show that the scheduling strategy of integrating the state of whole cell can improve the index such as cell throughput user satisfaction and fairness.Finally,this paper studies TTI bundle mode,and comes up with mix bundle mode,which divides all edge users to normal edge user and super edge users and configures matched TTI bundle mode depending on the degree of deterioration of radio channels,the former with 4 TTI bundle and the latter with 8 TTI bundle.The simulation results show that both time-delay decreasement and resistance of block error rate can be promoted.Meanwhile,this paper also analyzes the impact of differernt codec of Adaptive Multiple-Wide Band(AMR-WB)for TTI-bundling.The simulation results show that in the scenes of cell edge codec(12.65kbps)has more fault tolerance than codec(23.85kbps),as same as codec of AMR-WB.