US Patent 8699317 Transmission timing in a carrier group

A base station configures a first carrier group and a second carrier group in a wireless device. The wireless device transmits first uplink signals in the second carrier group employing a first secondary carrier in the second carrier group as a timing reference carrier. The wireless device autonomously changes the timing reference carrier to a second secondary carrier in the second carrier group. The second secondary carrier is an active carrier different from the first secondary carrier. The wireless device transmits second uplink signals in the second carrier group employing the second secondary carrier as the timing reference carrier.