A method for communication in a wireless device (24) includes establishing a first connection with a base station (BS-28) of a long-range wireless data network, and a second connection on a Wireless Local Area Network (WLAN). A time interval (96) is selected in the wireless device for communicating over the second connection. In preparation for the selected time interval, the BS is caused to refrain from scheduling data transmission from the wireless device to the BS over the first connection during the time interval, by reporting to the BS prior to the time interval that no data is pending for transmission from the wireless device. The wireless device communicates over the second connection on the WLAN during the time interval.