Mobile devices in the IEEE 802.11 based multihop ad hoc networks support the transmission of data frames at various predefined transmission rates. To achieve high throughput performance, these multiple rates should be exploited and used in an adaptive manner depending on the channel condition. In this paper, we propose a data rate adaptation scheme with the use of Kalman Filter to determine the channel conditions (forthcoming interference). Upon receiving the RTS (request to send) packet, the receiver predicts the future interference and accordingly selects the appropriate transmission rate. Then, the receiver encapsulates the rate value in the CTS packet sent to the transmitter. Furthermore and to ensure correct convergence of the kalman Filter, we propose a fuzzy logic approach to tune the parameters of the Kalman Filter. The performance of the proposed scheme is tested and verified in a discrete event simulation environment.