Research On Cognitive Radio-Based TD-LTE Uplink Power Control Algorithm

Spectrum resources will be in increasingly severe lack along with the rapid development of wireless communication service. The deployment of TD-LTE (Time Division Long Term Evolution) system in the wide area coverage also faces the problem of spectrum scarcity, especially low frequency. As a result of the transition from analogue TV to digital TV, some vacant spectra become available in DTV spectrum which is called TV White Space (TVWS) and the utilization of TVWS in mobile communications has been a research hotspot. As an advanced technology of spectrum sharing, cognitive radio (CR) enables TD-LTE users to make use of TVWS. However, the introduction of TD-LTE to TVWS can cause vertical interference to DTV receivers. When TVWS is shared among heterogeneous secondary networks, there may be horizontal interference between these systems. How to eliminate interference is also very important for researchers.In this work, the measure to cope with the interference is power control. But the existing algorithms of TD-LTE uplink power control always focus on the improvement of TD-LTE’s performance. They are not proper for this scene because interference between these two systems is not considered. In this work, novel TD-LTE uplink power control algorithms are proposed based on the analysis of coexistence scenario of TD-LTE, FD-LTE (Frequency Division Long Term Evolution) and TV system.The research in this paper comes from "A new generation of broadband wireless mobile communication network" national science and technology major project-"Research and test of cognitive radio technology in TD-LTE system". This research focuses on the availability of TVWS and the coexistence scenario of TD-LTE and DTV systems and will offer theoretical analysis and simulation support for application of cognitive radio in TD-LTE system.The research in this work includes:development history and system architecture of TD-LTE, TD-LTE uplink power control, description and basic performance of DTTB (Digital Television Terrestrial Broadcasting) system, cognitive radio network and spectrum sharing technology. Then two system models are studied, including coexistence model of TD-LTE and DTTB and coexistence model of TD-LTE, FD-LTE and DTTB when TVWS is shared by TD-LTE and FD-LTE.In order to eliminate the vertical interference caused by TD-LTE to DTTB, an Isolation-based TD-LTE Uplink Power Control Algorithm (IPCA) is proposed. This algorithm sets target SINR for each UE based on its isolation in Open Loop Power Control (OLPC). The ratio of pass loss and ACIR (Adjacent Channel Interference Ratio) is decided by ratio parameter. Then the optimization model is proposed. In this model, interference must be lower than the threshold and. And the goal is the maximum the rate of TD-LTE and DTTB. After solution of the model by Lagrangian multiplier method, we can get the value of UE’s power. Simulation results show that this algorithm can not only reduce the interference of TD-LTE to DTV, but also improve the overall spectrum efficiency of the two systems.In order to eliminate the vertical and horizontal interference, a Game Theory-based TD-LTE Uplink Power Control Algorithm (GPCA) is proposed. In this algorithm, a novel power control game model is proposed which considers both vertical and horizontal interference. Then the existence and uniqueness of Nash Equilibrium are proved and the process of this algorithm is proposed. Furthermore, simulation results show that the proposed algorithm outperforms the OLPC in eliminating interference to DTTB and FD-LTE.