Secondary usage of a frequency channel is discussed as a method for alleviating future depletion of frequency resources. The secondary usage of a frequency channel is that part of or all the frequency channels preferentially allocated to a system is secondarily used by the other system. Typically, a system which is preferentially allocated with a frequency channel is called primary system and a system which secondarily uses the frequency channel is called secondary system.
A TV white space is an exemplary frequency channel whose secondary usage is discussed (see Non-Patent Literatures 1 and 2). The TV white space is a channel which is not used by a TV broadcast system depending on an area among frequency channels allocated to the TV broadcast system as a primary system. The TV white space is opened to a secondary system so that the frequency resource can be efficiently utilized. A standard for a physical layer (PHY) and a MAC layer for enabling the secondary usage of the TV white space can employ IEEE802.22, IEEE802.11af and ECMA (European Computer Manufacturer Association)-392 (CogNea, see Non-Patent Literature 3 described later).
The secondary system is generally required to operate so as not to give an excessive interference to the primary system during the secondary usage of the frequency channel. An important technique therefor is transmission power control. For example, Patent Literature 1 described later proposes therein a method for calculating a path loss from a base station as a master node of a secondary system to a reception device as a primary system and a discrete frequency width between frequency channels and determining maximum transmission power of the secondary system based on the calculation result.
USPTO Backgrounds
USPTO Backgrounds