Patent ID: 8279767

Claim:
A channel assignment method applied to a Base Station (BS) of a secondary user to which a frequency channel licensed to a primary user is assigned in a multiple Frequency Assignment (FA) system, the method comprising: a channel sensing process, wherein the BS classifies multiple frequency channels licensed to the primary user into a plurality of channel state sets according to usage states, periodically senses channel states by changing a sensing period according to types of the classified channel state sets, and manages the sensed channel states as frequency channel state set information; a channel state set broadcasting process, wherein the BS transmits the frequency channel state set information managed in the channel sensing process to secondary user terminals using a broadcast message; and a channel assigning process, wherein if the BS receives a channel assignment request message from a new secondary user terminal which has received the broadcast message, the BS assigns an unused frequency channel from among frequency channels licensed to the primary user to the new secondary user terminal using the frequency channel state set information, wherein in the channel state set classification process of the channel sensing process, frequency channels assigned to the secondary user belong to an active set, frequency channels unused by the primary user and not assigned to any secondary user belong to a candidate set, frequency channels used by primary users belong to an occupied set, and frequency channels allowed but not belonging to the active set, the candidate set, or the occupied set belong to a null set.