On optimal operating characteristics of sensing and training for cognitive radios
Heejung Yu, Youngchul Sung, Yong Hoon Lee · IEEE International Conference on Acoustics Speech and Signal Processing · 2008
The problem of optimal sensing and training in a cognitive radio system is considered when the training signal of the primary transmitter is used for both channel estimation at the primary receiver and sensing for the secondary transmitter. First, the optimal operating characteristics of sensing that maximizes the overall system rate for given training is investigated. It is shown that the optimal false alarm probability at the secondary sensor is monotone increasing as the activity of the primary user increases if the sensing ROC curve is concave. When the primary activity factor is unknown, the max-min criterion is applied to optimal sensing strategy and the resulting max-min optimal solution is given by an equalizer rule for any type of sensing ROC curve. The joint optimization of sensing and training has a unique solution and it can be easily found numerically using a gradient ascent algorithm. By optimal design of sensing and training in such a way, the overall system rate can be improved.