The extensive use of IEEE 802.11 WLAN networks have taken a tremendous leap in the area of wireless communication. Its increasing PHY data rate is at par with the wired Ethernet. However, at Medium Access Control (MAC) layer, the protocol lacks to utilize its full efficiency. The IEEE 802.11 Distributed Coordination channel access Function (DCF), is still based on contention-based random channel access for medium sharing. This results in a considerable amount of resource wastage due to idle wait time and increased collision as the network gets fairly loaded. In this paper, we propose a novel mechanism : Improved DCF (I-DCF) for IEEE 802.11 which regulates the sharing of the radio channel. It assigns differentiated and unique initial backoff values to each station. The backoff values are then dynamically adapted according to the network load. The proposed I-DCF is formulated and evaluated through simulations. Results show that it outperforms the IEEE 802.11 DCF scheme in terms of increased throughput, reduced delay and minimized collisions with minimum protocol modifications