An Implementation Of The Server Side And Terminal Device Driver In AGPS Hybrid Positioning System

After years of the large-scale construction of China's mobile communication networks, mobile terminals become very popular and operators focus on integrating existing networks, creating new business models, improving the quality of service and opening up new markets, so that the investors can achieve rapid return on investment. Accordingly, operators turn to huge potential data services, which are considered as a new revenue growing point of markets. Among them mobile positioning is the most potential one.AGPS (Assisted Global Positioning System) is a technology which integrates GPS satellite navigation and mobile communication networks. The basic idea of AGPS is to simplify the work of the terminal, which means the most complex work, such as scanning satellites and calculating position, will be moved from terminals to servers in mobile networks. As a result, the terminal's positioning accuracy, sensitivity and cold start speed (time to first fix) will be improved and terminal power consumption will be reduced. Moreover, when GPS signals can not be received, like indoor, terminals can switch to non-GPS positioning technologies, CELL_ID for example.To popularize positioning services and nurture positioning market, the variable needs of customers should be met as much as possible. The AGPS Hybrid Positioning System, combining high precision AGPS and low costs CELL_ID together, can provide flexible positioning options to customers. The paper will discuss the principles of AGPS and a concrete realization of AGPS system at different chapters. At the part of system realization, we focus on realization of the AGPS system server and AGPS terminal's device drivers.In cognitive radio (CR) system, secondary users (SU) must be able to sense and detect spectral holes dynamically and reliably. Multi-carrier modulation technique should be adopted as an effective realization method for SU spectrum sensing in CR. Therefore, to detect the spectrum effectively and quickly, a novel spectrum sensing method based on multi-taper spectrum estimation for CR nodes was proposed and implemented by filter banks. Multi-taper spectrum estimator (MTSE) designed by multi-band modulation of prolate filter has unique characteristics such as high spectral dynamic range (SDR), thus it can be more effective than periodogram spectrum estimator (PSE) in the aspect of estimating power spectrum density (PSD) of interference temperature. Simulation and analysis of PSD of interference temperature indicate that as the SU'former spectrum analyzer, the estimator can estimator PSD of interference temperature accurately, and realize interference restraint at primary user (PU)'s receiver.