Research On Packet Scheduling In Downlink Of LTE System

In the UMTS system before introducing HSDPA, packet scheduling is controlled by the RNC which can not reflect the transmit information of time-varying channel, making it impossible to conduct quick link adaptive and fast packet scheduling. The introduction of R5 later, packet scheduling is transplanted to the Node B, which makes that packet scheduling can adapt mudilation and code scheme according to channel condition and fading charactistics, and reduce the UE memory requirements and system propagation delay. The status of packet scheduling for packet-switched datas services is equivalent to the status of the channel resource allocation for circuit-switched services. It can be seen that packedt scheduling is at the core of the dominant position in radio resource management, determines the quality and efficiency of services provided by radio packet servicds system and has an important impact on the decision-making and implementation of another techniques and algorithms.The types of services provided by LTE system include a variety of real-time services, such ad streaming media, but also include avariety of non-real-time services, such as WWW browsing. How to allocation resources to the services with different bandwidth requirement, different time delay requirement and different QoS level based on services requirements to improve overall throughput and spectrum efficiency is the task of packet scheduling.In contrast to UMTS, the multiple access technology is not CDMA but OFDMA/SC-FDMA. Resources can be allocated in time domain,frequency domain and code domain in the OFDMA/SC-FDMA system which is not implementation in CDMA system. This makes that packet scheduling in LTE system is different from 3G systems. The flexibility and efficiency of frequency scheduling in LTE system should be considered which is of importance for LTE system performance.This thesis focuses on packet scheduling algorithms and packetscheduling schemes in LTE mobile communication system. First, some typical packet scheduling algorithms applicable are classified and analyzed; and PF algorithm implementation scheme is introcuced and analyzed in OFDM system. Meanwhile, a novel scheduling scheme of frequency scheduling is proposed and verified through computer simulation. The simulation results demonstrate that the system throughput can be improved in the new scheme.