The　subcarrier　allocation　problem　in　cognitive　radio　(CR)　networks　with　multi-user　orthogonal　frequency-division　multiplexing　(OFDM)　and　distributed　antenna　is　analyzed　and　modeled　for　the　flat　fading　channel　and　the　frequency　selective　channel,　where　the　constraint　on　the　secondary　user　(SU)　to　protect　the　primary　user　(PU)　is　that　the　total　throughput　of　each　PU　must　be　above　the　given　threshold　instead　of　the　＇interference　temperature＇.　According　to　the　features　of　different　types　of　channels,　the　optimal　subcarrier　allocation　schemes　are　proposed　to　pursue　efficiency　(or　maximal　throughput),　using　the　branch　and　bound　algorithm　and　the　0-1　implicit　enumeration　algorithm.　Furthermore,　considering　the　tradeoff　between　efficiency　and　fairness,　the　optimal　subcarrier　allocation　schemes　with　fairness　are　proposed　in　different　fading　channels,　using　the　pegging　algorithm.　Extensive　simulation　results　illustrate　the　significant　performance　improvement　of　the　proposed　subcarrier　allocation　schemes　compared　with　the　existing　ones　in　different　scenarios.　©　Copyright.