Research On Subcarrier And Power Allocation Optimization Algorithm In High-speed Railway Communication System Based On Relay

The communication network of railway in current communication system can not meet the communication traffic demands of the public network already. In addition, high-speed railway scene is full of complexity because the channel has a significant time-varying characteristic, the wireless signal through the body of train experiences severe attenuation and the trains moving at a high speed cause cell handover frequently and Doppler shift. These characteristics of high speed railway have forced the railway communication system needs improvement and take use of more advanced broadband mobile communications technology. The universal mobile telecommunications system based on long-term evolution has better network architecture, higher data transfer rates, better spectral efficiency, seamless mobility and other advantages. The relay technology as one of key technologies in LTE-Advanced (LTE-A) has been studied extensively by a lot of domestic and foreign research institutions. Relay-based wireless mobile communications network technology is very suitable for high-speed railway public network communication system.This thesis sets the scene to high-speed railway public communication scenario, establishes transmission model of relay to half-duplex transmission model with two slots and focuses on radio resource allocation optimization problem in high-speed railway public communication system based on relay network. Research includes radio resource allocation algorithm, subcarrier pairing, and power allocation study.In LTE-A system, the introduction of relay nodes increases the complex of subcarrier resource optimization, power allocation and the coordination of resource between the backhaul link and the access link. Firstly, this thesis proposes scheduling algorithms that suitable for high-speed railway communication system that based on relay. Secondly, subcarrier pairing scheme is proposed. Finally, power distribution scheme is proposed. These steps can improve the whole system performance while reducing resource allocation complexity. Compared with traditional optimization that completes scheduling, subcarriers and power resources allocation at same time, the schemes that proposed has lower complexity, higher system capacity and better system performance.Based on the relay technology and resource scheduling algorithms that exists in public network, this thesis proposes Priority Weighted Proportional Fairness (PWPF) algorithm that is non-real time scheduling algorithm and Weighted Delay Proportional Fairness (WDPF) algorithm that is real time scheduling algorithm. PWPF algorithm that takes the system capacity and user fairness factor into account has better system performance. WDPF algorithm considers the system capacity and fairness, while adding the delay factor. In addition, WDPF algorithm also considers the characteristics of the two-hop relay link, so this algorithm is more suitable for high-speed railway public communication system scene based on relay network.Subcarrier pairing algorithm is a resource allocation optimization scheme that combines backhaul and access link characteristics in relay network. This thesis proposes Smallest Gap Priority Subcarrier Pairing (SGPSP) algorithm channel principle, and then analyzes and describes the pairing algorithm performance and implementation process. By analyzing the system performance compared to other pairing algorithm, SGPSP algorithm can improve system capacity effectively.Under the premise of completion of the subcarrier pairing, power allocation optimization become easier that compared with traditional optimization scheme because it can reduce the complexity of the entire process of allocation of resources and better system performance. Aiming at high-speed railway communication systems with relay, this thesis establishes power allocation mathematical model and verifies the proposed scheme has a good performance through theoretical analysis and simulation.