Communication terminal device, base station device and radio communication system in which a random access channel is accessed by employing an initial access code randomly selected from a selected group of initial access codes

Abstract

There is disclosed a communication terminal device capable of eliminating collision of access request signals simultaneously transmitted from communication terminal devices in a local cell, preventing generation of interference signal in another cell adjacent to the local cell, and improving the throughput in the local cell. There is also disclosed a base station device for controlling the transmission power of the access permission signal so as to prevent generation of an interference signal in another cell adjacent to the local cell. In this device, a use sub-channel selection unit () has a correspondence table between the reception quality of the pilot signals divided into classes and the sub-channel allocated to the classes. According to the correspondence table, the use sub-channel selection unit () selects a sub-channel group of RACH correlated to the measurement result of the reception quality of the pilot signals reported from the reception quality measurement unit (). One sub-channel to be used for transmission of the access request signal is selected at random from the sub-channel group selected.