Underlay versus interweaved cognitive radio networks: A performance comparison study

In this paper, an analytical performance study is carried out for cognitive radio (CR) systems with the intent of comparing the two most popular CR designs, namely the interweaved and underlay setups. The comparison is carried out on an equal footing, by measuring the achievable ergodic capacity for secondary communication, under a common constraint on primary user´s (PU) communication disturbance. Closed form expressions for the outage probability at the PU as well as expressions for the ergodic capacity of the secondary user (SU) are derived, as a function of key system parameters, under a rate-optimal sensing protocol for the interweaved scenario, and a standard power control policy for the underlay setting. The analysis reveals the regimes (in terms of primary activity, interference tolerance levels at the PU) where the interweaved design outperforms the underlay one and reciprocally.