The present invention relates to a communication system having a main station and at least one subsidiary station, and a communication apparatus and method used in the system.
Recently, a great deal of attention has been paid to radio communication systems for personal areas, e.g., IrDA, Bluetooth, HomeRF systems. The Bluetooth and HomeRF systems, in particular, use RF signals, and hence have merits, e.g., no directivity and high transparency, as compared with infrared communication schemes such as the IrDA system. Therefore, further development and popularization of the Bluetooth and HomeRF systems are greatly expected.
Such a radio communication system allows simultaneous connection of a plurality of devices. In addition, one of the noticeable characteristic features of this system is that the transmission distance is relatively long (10 to 100 m). For this reason, in the Bluetooth or HomeRF system, when devices are to be actually connected to each other, there is no need to face them each other, unlike a communication system with a high directivity, e.g., the IrDA system, in which devices must be faced each other to specify the partner devices. In the case of Bluetooth, HomeRF, or the like, a station finding message is transmitted as a broadcast message from the main station, and response messages from subsidiary stations which have received the station finding message are received by the main station, thereby searching for a device that can communicate.
When Bluetooth, HomeRF, or the like is used, although the lack of directivity facilitates handling, since the station finding message is transmitted to all devices in a search range, response messages from devices other than target devices are received. As a consequence, a long time is spent to find a station. In addition, in general, all pieces of information received from devices in the search range must be displayed on a display means such as a display to notify a user of the information. Consequently, many pieces of information from stations other than stations that need to communicate are displayed. This makes it difficult for the user to perform a subsequent procedure for designating a destination station on the basis of the displayed information.
The present invention has been made in consideration of the above situation, and has as its object to provide a communication system and communication apparatus and method which can efficiently perform a station finding procedure in a short period of time by changing the reachable range of a station finding message in searching for a station as a connection target, efficiently perform designation of a station thereafter, and are easy for a user to use.