The Study Of Scheduling Algorithm In Downlink LTE-A System

LTE-A is the further evolution of LTE. It requires more cell average throughput and higher data rate of users in cell edge. Relay Node (RN) is introduced into the LTE-A system as a low-power and low-cost node. It aims at providing higher system capacity, greater coverage and lower cost of network construction. The introduction of RN increases the number of nodes in the cell, which makes radio resource scheduling as a new research topic.First, this paper introduces the LTE-A system and its key technologies in general. Then the resource scheduling of wireless systems is introduced. With some existing classical scheduling algorithms available lucubrated, their performances and shortages are analyzed.To aim at the technical characteristics of LTE-A downlink OFDMA system, the paper outlines transmission program and structure of physical resource. Simultaneously it also analyzes resource scheduling mode, optimized algorithm, sub-optimal scheduling algorithm and resource scheduling algorithm which based on Time Division Multiplexing scheduling criteria, from a theoretical point of view.Then this paper mainly analyzes the relay technology in LTE-A system and its impact on system resource scheduling. After the relay technology is used, the resource scheduling problem is transformed into the problem including relay selection and resource allocation. As a prelude to research on scheduling of relay based OFDMA systems, the paper analyzes several scheduling algorithm which based the relay selection.Joint optimization of relay selection and resource allocation can fully exploit multi-user diversity, so good performance is obtained. After analyzing the adaptive joint routing and scheduling, an improved scheduling criterion in eNB is proposed, considering queue and quality of service. A low-complexity iterative resource allocation algorithm is proposed to solve the complex optimized problem applying the Hungarian algorithm. Further, the paper propose a distribute algorithm including the resource scheduling in eNB and RN. Finally, this paper analyzes the performance of scheduling algorithms mentioned above through the system simulation. The results prove that the proposed algorithms get better performance in throughput, fairness and QoS.