The paper proposes a Waiting-time Dependent Increasing rate Adapted Backoff (WDIA) algorithm to improve the contention efficiency in the IEEE 802.16e. A contention model is first proposed to analyze the frame-based behavior of contention resolution in 802.16e network. We introduce the concept of reduced overlapping between back-off windows of contending stations and we adopt an adaptable increasing rate. An initial ranging scenario is constructed to evaluate the effectiveness of WDIA. The simulation results show that the WDIA algorithm achieves better performance than Truncated Binary Exponential Backoff (TBEB) algorithm in terms of number of retransmissions, access delay and resource utilization.