Effective Capacity of Cognitive Radio Systems with GSC Diversity under Imperfect Channel Knowledge

In this paper, we investigate the effective capacity of opportunistic spectrum sharing with generalized selection combining (GSC) diversity at the secondary receiver in fading environments. In particular, we study the impact of outdated channel information between the secondary transmitter and the primary receiver on the performance of the secondary user. An exact closed-form expression for the effective capacity of the secondary user with GSC diversity is derived under the peak interference constraint at the primary receiver. Comparisons done using simulations show the effect of the uncertainty of channel information on the effective capacity. Specially, the performance gap due to imperfect channel information becomes smaller with the increase of the number of selected antennas {k}. Theoretic analysis and simulations show that the system performance is robust against imperfect channel information and selection combining (SC) should be adopted under strict delay quality of service (QoS) requirements.