2.3.2 Spectrum Database Implementation

The spectrum database is implemented to store the information of available channel bands for the CRCN users. Essentially, these channel bands are classified into several categories according to the standard IEEE802.22. For simplicity, this simulator defines two classes for the channel bands. The channel bands belong to the first class (i.e., Level1) can be occupied by the CRCN users immediately, once these channel bands are detected as unoccupied by the primary users. On the contrary, those channel bands which are vacated by the CRCN users because of the presence of primary users are classified as the second class (i.e., Level2). These channel bands also need to be sensed by the CRCN users periodically. After claimed as vacant by the CRCN for a determined number of times, the channel bands in the second class are upgraded into the first class. These channel band information are saved in a table called “Available Channel Bands for CRCN”.

There is another table in the database which is called “Channel Sensing Report”. This table records the sensing reports from the secondary users for each channel band. There are only two items in this table, i.e., the channel index and the channel utilization status. The channel utilization status indicates if this channel band is occupied by the primary user (represented by “1”) or not (represented by “0”).

The two tables and their relationship are shown below:

Available Channel Bands for CRCN
Channel Index *	Channel Status	Channel Bandwidth (MHz)
0	Level 1	5
1	Level 2	5
2	Lever 1	5
3	Lever 1	5
4	Lever 1	5
5	Lever 2	5

Channel Sensing Report
Channel Index *	Channel Utilization Status
0	1
1	0
2	0
3	0
4	1
5	1

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