The mobile communication system has been developed for the user to communicate on the move. With the rapid advance of technologies, the mobile communication system has evolved to the level capable of providing high speed data communication service as well as voice telephony service.
Recently, as one of the next generation mobile communication system, Long Term Evolution (LTE) is on the standardization by the 3rd Generation Partnership Project (3GPP). LTE is a technology designed to provide high speed packet-based communication of up to 100 Mbps and has been ratified almost.
Recent studies are focused on the LTE-Advanced (LTE-A) for improving data rate with the adaptation of several new techniques to legacy LTE system. Carrier Aggregation (CA) is one of the most important techniques for such a leap in technology. Unlike the conventional data communication using single downlink carrier and single uplink carrier, CA uses multiple downlink and multiple uplink carriers. In order for a terminal to transmit data using multiple uplink carriers, many new requirements such as per-carrier uplink transmission timing management and multi-carrier random access have to be fulfilled. The present invention relates to a method and apparatus for transmitting data on the uplink carriers while fulfilling such requirements.