For commercial availability reasons, most actual multi-hops ad-hoc simulations and test-beds are based on IEEE 802.11 standard [1] and its medium access method CSMA/CA. But this standard has not been designed for that kind of network and presents serious flaws in this context. In this paper, we shall try to highlight problems that can appear in the non-direct neighborhood of important data flows in ad-hoc networks. In some situations, the fairness of the medium access can indeed be very poor. Various techniques could be used to solve this problem. In this paper we present one solution, which only requires minor modifications to the standard.