Capacity versus interference in OFDM-based cognitive radio systems with beacon

We consider an OFDM-based cognitive radio network where a secondary user chooses parallel sub-channels from different primary users' bands to form its transmission link. It transmits one OFDM subcarrier per each sub-channel. Before starting its transmission, a primary user sends a beacon to inform the secondary user. If the secondary user receives this message, it does not use any sub-channel from that primary user band for its transmission in order to limit the interference to the primary receiver. However, it is possible that the secondary user misses the beacon of a primary user because of the channel fading and hence, considers the sub-channels of that primary user for its transmission. We are interested in the total interference caused by the secondary user to primary users' receivers and the total capacity of the secondary user. In particular, we provide the average of total interference as well as an analytical lower bound on the mean of the capacity. The trade-off between the capacity and the interference is useful in the design of an OFDM-based cognitive network with beacon.