Managing Imperfect Spectrum Sensing in the Secondary Service: Increasing Sensing Time or Adopting Channel Coding?

Imperfect spectrum sensing in overlay spectrum sharing may cause collision between primary and secondary transmission resulting in performance degradation for primary users. To satisfy the quality of service requirement imposed by the primary service, the maximum probability of collision has to be kept below a given threshold. The collision, if occurs, also results in increasing error rate in the secondary system. What can be done if the secondary service needs better error rate than the value imposed by the collision constraint in the primary network? From secondary user perspective, this can be taken care of by employing channel coding techniques at the expense of effective rate reduction. Alternatively, one can increase the sensing time to reduce the collision probability at the expense of reducing the data transmission time. This also reduces the effective data rate for secondary users. In this letter, we compare these two approaches and demonstrate a situation where using rate-compatible Low-Density Parity-Check codes, the effective data rate for the coded case can be significantly more than that of the case without channel coding while exhibiting a considerably better performance. We then discuss necessary condition for such an advantage and come up with cases where increasing sensing time is preferred over adopting channel coding.