Abstract
This paper presents an enhanced overlay spectrum sharing scheme in a cognitive radio network, which consists of two pairs; a primary transmitter-primary receiver pair and a secondary base station-secondary receiver pair. The developed scheme is based on a three time slots overlay spectrum sharing, which exploits the maximum diversity gain for both the primary and secondary users. The performance of the developed scheme is assessed through the derivation of new closed form expressions for the bit error rate for arbitrary signal-to-noise ratio (SNR). In addition, we carry out an asymptotic analysis in the high SNR regime, which proves that the proposed scheme achieves a full diversity order for the PU and SU. Results of analytical expressions and numerical simulations both verify that the proposed scheme achieves significant gains for error performance, for both the PU and SU, in comparison to other baseline schemes.