What is important in location-aware services is how to track moving objects efficiently. To this end, an efficient protocol which updates location information in a location server is highly needed. In fact, the performance of a location update strategy highly depends on the assumed mobility pattern. In most existing works, however, the mobility issue has been disregarded and too simplified as linear function of time. In this paper, we propose a new mobility model, namely state-based mobility model (SMM) to provide more generalized framework for both describing the mobility and updating location information of moving objects. We also introduce the state-based location update protocol (SLUP) based on this mobility model.