Research And Realization On Wireless Packet Scheduling Algorithm And Resource Allocation Strategy In TD-LTE Downlink System

In the LTE system, scheduling is accomplished by scheduler located at eNodeB, which includes downlink scheduler and uplink scheduler. They are responsible for managing the downlink and uplink resource packet scheduling respectively. Compared to the WCDMA systems, in which packet scheduling is controlled by the RNC, packet scheduling in the LTE system can choose proper MCS and code rate in a timely manner according to channel conditions and fading characteristics with adaptive modulation and rate change, while reducing system latency.Meanwhile, TD-LTE system has unique TDD frame structure and employs Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink. LTE adopts Orthogonal Frequency Division Multiplexing (OFDM), Multiple Input Multiple Output (MIMO), Adaption Modulation Coding (AMC), Hybrid Automatic Repeat Quest (HARQ) and many other techniques. In downlink resource packet scheduling, the impact of these TD-LTE system characteristics should be fully considered.In addition, there are various kinds of traffic in the LTE system. It not only includes real-time services, such as VoIP, VideoStream and a variety of non-real time services, such as e-mail, FTP, P2P and so on, which made services’ requirements on QoS different from each other and it requires scheduling algorithm to consider different QoS requirements fully. LTE QoS includes the following parameters:QoS Class identifier, guaranteed bit rate, transfer delay and so on.How to reasonably allocate resources for a variety of service with different QCI classification, different rate requirement and different time delay requirement, and do its best to access users as many as possible and provide service for them and improve the overall network throughput in the downlink, are the final tasks of the downlink packet scheduling algorithm.This paper focuses on the downklink packet scheduling algorithm based on TD-LTE system level simulation platform. Firstly, the whole TD-LTE system simulation platform is introduced, including the main simulation flow. Secondly, the classical packet scheduling algorithm(RR algorithm, MAX C/I algorithm and PF algorithm) and its evaluation standard is discussed and then provides a new QoS-oriented packet scheduling algorithm—RAD algorithm, and validates it on the simulation platform. The main purpose of the new scheme is to give priority to the data transmission of the users with high QCI level according to the actual needs of various kinds of users in the network and to minimize the number of retransmission, while taking the fairness into account. At the same time, the basic flow of downlink packet scheduling in the LTE system is introduced and semi-persistent scheduling, downlink transmission mode adaption and MU-MIMO are researched and implemented based on it. Finally the performance of scheduling algorithms and resource allocating strategy in the downlink is analyzed by simulation.