QoS Oriented Packet Scheduling Algorithms For The Downlink Of LTE/LTE-A

With the development of wireless technologies and application services are switching to multimedia-oriented data communications from voice-oriented ones, the next generation mobile communication system is supposed to provide better Quality of Service and satisfy more users based on higher transmission rate. As effective packet scheduling algorithm is critical to achieve this goal, this thesis concentrates on offering better packet scheduling algorithm, which will provide QoS guarantees, for downlink of LTE/LTE-Advanced system.LTE/LTE-Advanced system, including downlink and uplink, are introduced briefly in the beginning of this thesis. And then a conclusion for the current packet scheduling algorithm was drawn. The last but not the least, the discussion about packet scheduling algorithms for downlink of LTE and LTE-Advanced system are referred distinctly. The major contributions of the thesis are as follows:First, for the downlink of LTE system, in order to guarantee the QoS requirements of users, two cross-layer packet scheduling algorithms are proposed which takes channel and queue state information into account. The first algorithm, which aims at the real-time service scenario, the scheduling priority for each user is distinct based on the channel conditions and delay constraint. The given QoS requirements can be guaranteed with this kind of algorithm which can be approved by the simulation results. The second algorithm based on the first one and for the multi-class services, imports the channel quality variance, the delay adjust indicator and the effective transmission rate. Simulation results present that the system throughput is increased and fairness is improved with respect to the achieved data rate per user.Secondly, as relay function is imported for LTE-A system, In order to improve the system throughput, a centralized packet scheduling scheme by adjusting transmission rates dynamically in response to the variation of channel quality and packet delay is proposed. Then demonstrate that the proposed scheme can utilize the capacity of network more efficiently, and achieve proportional fairness and traffic balance to users by simulation.