In this paper, we propose a framework for performing distributed admission control in a collaborative wireless environment. In particular, a wireless device will not inject a new flow into a wireless network if it determines that by doing so, there is not enough resources to support all the existing flows. Our contributions are three-fold. First, we propose a slight modification to 802.11x based network to improve the bandwidth efficiency. Specifically, doubling the contention window size after a collision is no longer necessary in the modified 802.11x based network. Second, we provide a performance analysis for the modified 802.11x based wireless networks with multiple flows having different throughput requirements. Third, using the theoretical analysis, we propose two distributed admission control algorithms based on the transmission opportunity (TXOP) and the contention window size. Simulation results confirm our theoretical predictions on the performance of the proposed admission control algorithms.