Cognitive Radio with Partial Channel State Information at the Transmitter

Cognitive radio (CR) has been proposed as an efficient method to reuse the licensed spectrum. It recognizes the primary (licensed) users´ signals and adapts its own to minimize the interference it generates. When perfect channel state information is known at the transmitters, the capacity of CR system can be achieved by utilizing the dirty paper coding (DPC). In this paper, we consider the performance of the CR system under both fast and slow fading channels with only channel statistics known at the transmitters. Due to the limited channel state information, the original DPC fails and is replaced by the so-called linear-assignment Gel´fand-Pinsker coding. By carefully designing the parameters based on this preceding, this system has significant rate gains over naively treating primary users´ signals as interference for fast and slow fading scenarios.