US Patent 8391129 Time alignment in multicarrier systems

Transmission timing of a random access preamble in an uplink carrier of a carrier group being determined employing a synchronization signal transmitted on a downlink carrier of the carrier group. The wireless device receives a time alignment command from the base station. The time alignment command comprises a time adjustment value and an index identifying the carrier group. The wireless device apply the time adjustment value to uplink signals transmitted on all activated uplink carriers in the carrier group.