Demand for ad-hoc networks is increasing so it is expected ad-hoc networks will exist in close proximity in the future. A contention window control method, ACWA, which improves throughput of ad-hoc network against radio interference has been recently proposed. However unfairness of throughput between ACWA and DCF might be caused. We propose a modified ACWA method (GSAR scheme) which drastically improves the unfairness and keeps throughput as high as ACWA. GSAR just uses DCF at the sending node and uses ACWA in the rest. Jain's fairness index resulted in 1.0 from 0.56 in two ad-hoc networks with DCF and GSAR.