According to a WiMAX method, a cellular system is constructed by establishing individual communication area having a cell radius of several hundreds meters. According to IEEE standard 802.16-2004, a WiMAX-based system employs a modulation method of orthogonal frequency division multiplexing (OFDM), which provides frequencies divided in terms of time to be usable for each data communication.
According to IEEE standard 802.16e, which is related to a mobile broadband system, a WiMAX-based system employs an orthogonal frequency division multiple access (OFDMA) method, which allows data division using subcarriers, in addition to data division by time according to the OFDM method. Base stations and terminal devices are in a master-and-slave relation, where the base stations carry out line allocation, etc.
A system employing the OFDM method is disclosed, for example, in Published Japanese Translation of PCT International Publication for Patent Application 2006-507753. The disclosed system is such a mobile communication system that a down-link subframe contains a synchronization preamble and a search preamble to enable synchronization in time and frequency and more efficient cell searching.
FIG. 1 is a structural example of a communication system using the WiMAX method.
A cellular system is constructed by establishing a communication area of a cell 100 having a cell radius of several km or more with a base station 101 at the center, according to the WiMAX method. Mobile terminal devices #0 to #n come in and out of such a communication area as the cell 100. A number of sequence processes, which includes power supply sequence, initial setting sequence, and call sequence, are executed on the mobile terminal devices #0 to #n located within the communication area.