A plurality of radio communication systems such as a cell-phone system and a radio MAN (Metropolitan Area Network) are currently used. For attaining a further speeding up and large capacity of radio communication, lively discussion is continuously performed about a next generation radio communication technology.
For example, in a 3GPP (3rd Generation Partnership Project) being a standardization organization, there is proposed a communication standard referred to as an LTE (Long Term Evolution) enabling communication using a frequency band of 20 MHz at a maximum. Further, as a next generation communication standard of LTE, there is proposed a communication standard referred to as an LTE-A (LTE-Advanced) enabling communication using five frequency bands (namely, a frequency band of 100 MHz) of 20 MHz at a maximum (see, for example, Non-Patent Literatures 1 and 2). In the LTE-A, the number of frequency bands to be used is proposed to be dynamically changed according to traffic (see, for example, Non-Patent Literature 3).
Further, in a radio communication system, from one radio communication device (e.g., a mobile station) to another radio communication device (e.g., a base station) which performs allocation control of radio resources, a random access may be performed. The random access from the mobile station to the base station is performed, for example, at the time when (1) the mobile station first accesses the base station, (2) an allocation of radio resources used for data transmission is requested to the base station, and (3) synchronization is established during reception of data from the base station, and (4) synchronization is achieved with a mobile target base station during a handover.
The random access includes a contention based random access and a non-contention based random access (see, for example, 10. 1. 5 section of Non-Patent Literature 4, and 5. 1 section of Non-Patent Literature 5). In the case of the random access from the mobile station to the base station, in the contention based random access, the mobile station arbitrarily selects a signal sequence from among a plurality of signal sequences and transmits it to the base station as a random access preamble. In the non-contention based random access, the base station notifies the mobile station of information in which a signal sequence is specified and the mobile station transmits a signal sequence according to the notification from the base station as the random access preamble.
NPTL1: 3GPP (3rd Generation Partnership Project), “Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced)”, 3GPP TR 36.913 V8.0.1, 2009-03.
NPTL2: 3GPP (3rd Generation Partnership Project), “Feasibility study for Further Advancements for E-UTRA (LTE-Advanced)”, 3GPP TR 36.912 V9.0.0, 2009-09.
NPTL3: 3GPP (3rd Generation Partnership Project), “The need for additional activation procedure in carrier aggregation”, 3GPP TSG-RAN WG2 #67bis R2-095874, 2009-10.
NPTL4: 3GPP (3rd Generation Partnership Project), “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description”, 3GPP TS 36.300 V9.0.0, 2009-06.
NPTL5: 3GPP (3rd Generation Partnership Project), “Evolved Universal Terrestrial Radio Access (E-UTRA) Medium Access Control (MAC) protocol specification”, 3GPP TS 36.321 V9.1.0, 2009-12.
Incidentally, in a radio communication system capable of performing communication by using a plurality of frequency bands, the number of frequency bands to be used according to traffic as described above is considered to be changed. However, in a method as described in the Non-Patent Literature 3, after communication is started between radio communication devices (after completing a random access procedure), a procedure is freshly performed so as to use other frequency bands except the frequency band in which communication is started. In this method, in the case where it is proved that the other frequency bands are desired to be used before starting communication (for example, in the case where a transmission data amount is proved to be large), the procedure becomes inefficient.