Location-based services are using information about where a mobile device is located. Such services bring convenience to mobile user but also provide criminals with powerful weapons to compromise the privacy of mobile user. To address the location privacy issue, much architecture for location privacy control was presented and experimented. Qi He proposed a special and feasible architecture, using blind signature to generate an authorized anonymous ID that replaces the real ID of a legitimate mobile device. The original purpose of Qi's architecture is that eliminating the relationship of authorized anonymous ID and real ID. Unfortunately we prove that Qi's registration protocol did not indeed delete the linkability of authorized anonymous ID and real ID. Furthermore we propose an improved registration protocol adapted the same cryptographic technique based on bilinear pairings. Moreover we demonstrate that the administrator can learn no information on the legitimate user's authorized anonymous ID and real ID