Indoor positioning systems are becoming a required sub-system in many ambient assisted living scenarios. Another area that would greatly benefit from the enriched context of localization is the IoT (Internet of Things) device interaction. However, at this moment there aren't any satisfying technologies or approaches for precise indoor positioning. This paper proposes an indoor positioning method based on trilateration using Wi-Fi RSSI measurements with corrections to eliminate the noise and the bias. The proposed method is tested in a laboratory environment and results are described.