The wireless device selects a first licensed assisted access (LAA) cell uniformly randomly from a plurality of LAA cells. The wireless device performs a first listen before talk (LBT) procedure for the first LAA cell employing a long monitoring period. The wireless device performs a second LBT procedure for a second LAA cell in the plurality of LAA cells employing a short monitoring period. The wireless device transmits to a base station one or more first transport blocks (TBs) on the first LAA cell and one or more second TBs on the second LAA cell.