As the rapid development of wireless communication technologies and the widespread popularity of smart terminals, traffic and demands of the mobile network grow exponentially, moreover the deployment of small cells in current heterogeneous networks becomes denser and denser. These bring lots of signaling overhead and too much energy consumption, in addition these challenge the robustness of mobile performance. In order to cope with these problems, we have already proposed a macro-assisted Data-only Carrier (DoC) system for small cell enhancement in [1]. In this article, we focus on the performance analysis of DoC system, especially for signaling overheads, mobility enhancement and small cell on/off schemes. Meanwhile, performance evaluation is intended to prove the benefits of the Data-only Carrier architecture by a complete system and link level simulation platform according to current 3GPP LTE standard.