Central management server for special communication and access method of the central management server

A central management server for special communication, the central management server forming a part of a communication system comprising the central management server and a plurality of spectrum sensing servers, the central management server comprising:

• a spectrum sensing information acquisition unit configured to acquire spectrum sensing information from the plurality of spectrum sensing servers;
• an Opportunistic Probability (OP) map generation unit configured to generate an OP value for each channel if there is an access request from a second layer, the OP value being a probability of successful communication, the second layer being an access layer for special communication;
• and
• a channel allocation unit configured to allocate a channel based on the OP value to a user terminal of the second layer requesting access if there is an access request from the second layer,
• wherein the channel allocation unit allocates the channel corresponding to a highest OP value from among available channels if there are available channels unused by both a first layer and a lower-level layer, and the channel allocation unit selects and allocates a particular channel unused by the first layer but used by the lower-level layer if there are no available channels unused by both the first layer and the lower-level layer.