| 摘要 |
<p>A frequency to be used in a cognitive wireless system can be appropriately determined. A DB apparatus, which manages white spaces (WS) for each of a plurality of frequencies, calculates and informs, to a mobile terminal, WS vectors (distances from a mobile terminal position to interference areas in the four directions of north, south, east and west) for each frequency. The mobile terminal refers to the WS vectors to use a frequency that provides the longest available distance in a traveling direction. The available-distance calculation uses various methods to perform interpolations (triangular interpolation, elliptical interpolation and rectangular interpolation), thereby determining WS boundaries. Preferably, the mobile terminal informs a traveling direction to the DB apparatus, and the DB apparatus informs a distance to an interference area only in the two directions that are near the traveling direction. Also preferably, information indicating whether interference areas in two directions are the same or different ones is added to the WS vectors, and according to this information, the mobile terminal apparatus may cause interpolation methods, which are to be employed, to be changed.</p> |
