A wireless access node serves wireless User Equipment (UEs) and wireless Integrated Access and Backhaul Mobile Terminations (IAB MTs). A radio exchanges access communications with the UEs over a frequency channel. The radio receives an IAB request from one of the IAB MTs, and in response, a controller allocates the frequency channel into a UE subchannel and an MT subchannel. The radio now exchanges access communications with the UEs over the UE subchannel and exchanges backhaul communications with the wireless IAB MT over the MT subchannel. The controller reallocates the frequency channel when an IAB MT is added to give the new IAB MT its own MT subchannel. The controller reallocates the frequency channel when an IAB MT is removed to increase the size of the UE subchannel.