Allocation algorithms in IEEE 802.11-based WLAN, that consist to associate to each AP a channel, are mainly based on a conflict graph that represents the conflicts (interference, CCA detection, etc.) between APs. In this paper, we propose to use an enriched version of the conflict graph, namely a weighted conflict graph. This latter models the CCA detection that can be total (all transmissions are detected) or partial. Beside, a model is given to compute the throughput of each AP for a given allocation. This model is combined to a greedy algorithm that aims to find the allocation that maximizes the proportional fairness. Simulations based on the recent IEEE 802.11ax amendment are carried out for small WLANs with a few APs and very dense networks. Results show that when the network is dense or constrained, there is a gain to consider partial detection.