On Performance Of Packet Scheduling For LTE Downlink

LTE system is the main trend of wireless communication system after 3G. Compared with the former wireless communication systems, the physical layer multiple access technologies have some changes. It uses orthogonal frequency division multiple access (OFDMA) based on cyclic prefix (CP) in the downlink, while in the uplink, single carrier frequency division multiple access (SC-FDMA) is adopted. Together with MIMO, LTE can provide us higher rate, more extensive frequency spectrum utilization and more services. LTE system supports a variable bandwidth from 1.25MHz to 20MHz. How to take full advantage of the bandwidth improve the system throughput and enhance the quality of service, the radio resource scheduling plays an important role.This thesis is presented to research the radio resource scheduling of 3GPP LTE system by MATLAB-based simulation in system level. And the mainly contributions are as follows.Firstly, LTE system simulation platform is constructed in accordance with the simulation parameters which 3GPP requires. Main function modules including network topology generation, UE generation, location update, wireless link generation, SINR computing and data collections are introduced.Secondly, the advantages and disadvantages of the three classic packet scheduling algorithms (RR, MAX C/I and PF) are analysized and validated in the simulation platform.Then, the packet scheduling algorithms how to improve the edge UE performance are studied, and focus on the PF algorithm based on CQI. Simulation results show that the the algorithm can not only effectively improve the edge UE's average throughput, but also guarantee the system's spectrum efficiency.And finally, consider that, initial allocation result obtained from the packet scheduling algorithm, can only ensure that the highest priority UE on each RB, but can not guarantee system throughput as much as possible. A resource block adjustment strategy based on CQI is presented. Simulation results show that, compared with the allocation scheme in order, the optimized scheme can improve the system throughput to some extent.