AbstractSpectrum sharing in Open Spectrum systems is a challenging problem, particularly since users experience dynamic spectrum availabilities that vary over time and location. In the absence of any centralized infrastructure, users coordinate their spectrum usage to support fair access of spectrum and avoid interference. One critical challenge is to construct an efficient signaling path in the presence of spectrum dynamics, where users exchange control and negotiation information reliably. In this paper, we propose a distributed coordination protocol (HD‐MAC) to construct an in‐band control path, without relying on the existence of a pre‐assigned out‐of‐band control channel. In particular, we propose a distributed group formation to construct coordination path using local common channels, and a heterogeneity‐aware ranking scheme to select channels for data transmissions. Extensive experimental results demonstrate the efficiency and reliability of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.