Previously, we proposed the active access-point (AP) configuration algorithm for elastic Wireless Local-Area Network (WLAN) systems using heterogeneous APs. This algorithm activates or deactivates APs depending on traffic demands, assuming that any active AP can use a different channel to avoid interferences among APs. However, the number of non-interfered channels in IEEE 802.11 protocols is limited. In this paper, we propose an extension of this algorithm to consider the channel assignment to the active APs under this limitation. After the channel assignment to the active APs, AP associations of hosts are improved to further minimize interferences by averaging loads among different channels. The effectiveness of our proposal is evaluated using the WIMNET simulator.