Multi-tone transmissions over two-user cognitive radio channel with weak interference

A transmitter with cognitive capability can sense talk between the other transmitter-receiver pairs. When this transmitter knows full or partial message of the others, it can choose an efficient strategy to access the transmission medium. This is referred to as cognitive radio channel. This work aims to investigate multi-tone transmission over two-user cognitive radio channels where cross-talk interference is weak. Cognitive transmitter (Ttimes1) is assumed to have full knowledge of message that is sent by the other transmitter (Ttimes2) to its corresponding receiver (Rtimes2). Channel capacity is carefully analyzed for frequency-selective scenarios. Efficient power-allocation strategies at Ttimes1 are investigated for various wireless environments. It is shown that Ttimes1 can find an efficient resource-accessing strategy if the channel gain of Ttimes1-Rtimes1 (the corresponding receiver) link is larger than the channel gain of Ttimes2-Rtimes2 link. In this case, the cognitive transmitter Ttimes1 can offer better performance by employing equal power allocation approach. Otherwise, it is not worthy for Ttimes1 to access transmission medium of Ttimes2-Rtimes2 link.