INTERFERENCE MANAGEMENT FOR CR NETWORKS
A major issue in interference-tolerant CR networks in 5G is how to reliably and practically manage the mutual interference of CR and primary systems.
Regulating the transmit power is essential for the CR system to coexist with other licensed systems.
An interference temperature model is introduced for this purpose to characterize the interference from the CR to the
licensed networks.
Interference cancellation techniques should also be applied to mitigate the interference at CR receivers.
Another issue in interference-tolerant CR networks is that a feedback mechanism is important to periodically inform the CR network about the current interference status at the licensed system.
A practical solution is that the interference state information can be sent from licensed systems and collected by a central unit (or a third party system).
Any CR network should first register to the central unit in order to be updated regarding the allowed spectrum and interference.
Alternatively, the CR transmitters can listen to beacon signals transmitted from the primary receivers and rely on the channel reciprocity to estimate the channel coefficient.
In this case, the CR transmitters can cooperate among themselves to regulate the transmit power and prevent the interference at the primary receivers being above the threshold.