Embodiments herein relate to a method performed by a network node for enabling channel estimation in a wireless communications network. The wireless communications network includes at least a first and a second Access Point, AP, having overlapping cells using contention-based transmission resources of the same frequency. The first network node controls the first AP to transmit information indicating that wireless devices served by the first AP are not to contend for the contention-based transmission resources when the second AP is transmitting a Null Data Packet, NDP. Then, the first network node controls the second AP to transmit a NDP. Embodiments of the first network node are also described. Embodiments herein also relate to a method performed by a wireless device for enabling channel estimation in a wireless communications network, and embodiments of the wireless device.