Bluetooth Low Energy (BLE) is a short range, low power wireless networking technology that is increasingly used in various applications of the Internet of Things (IoT). Whereas the performance of classical Bluetooth has already been intensively studied using analytical models and simulative methods. These studies are not directly applicable to BLE since BLE is based on a fundamentally different design targeting extremely low power consumption rather than high data rates. In particular, there are no sufficient models to simulate the performance of BLE in multi-device environments where several BLE peripheral devices are connected to a master device in a piconet (star topology). This lack of comprehensive models for the simulative analysis hinders the development and evaluation of IoT systems based on BLE. Keeping them in mind, the goals of this thesis is to design, implement, and evaluate simulation models for BLE focusing on multi device environments. Relevant performance metrics include the delay and energy consumption. Suitable abstraction of the different protocol layers has been defined to allow for implementing relevant aspects for the simulator. The simulation results are compared with real world hardware to measure the difference and to find the reasons for the differences.