Renovate Cognitive Networks under Spectrum Unavailability

Spectrum availability is a decisive factor for the continuity of Cognitive Network (CN) broadcast. Cognitive networks lease the spectrum temporarily whenever the primary users went off. Thus, localized wireless changes within CN cells rapidly affect the transmissions of the cognitive radios. This situation becomes more complicated for cognitive mesh networks when establishing a link over many cells. Therefore, link formation failure may cause complete disruption at certain sites of the network. A mathematical model is first introduced to study the delay impacts of the spectrum unavailability on the CN's which has been analyzed as the most severe cause for the CN failures. In this paper, a new subnet called Cognitive Radio over Fibre (CRoF) is proposed as an alternative for the wireless links between cognitive base stations every time there is no free spectrum to communicate. In this proposed solution, the CRoF subnet splits the CN into zones according to the number of expected users and free spectrum available. Then, CRoF base stations are placed at the edges of the structured zones to act as seniors for other cognitive cells. Consequently, a new management for secondary networks is achieved for local spectrum access. Initial Opnet simulations show 11% time savings during packet delivery for the CRoF designed scenarios in comparison with traditional CN's. The proposed CRoF subnet provides a permanent solution to restore service delivery for the CN's affected by wireless changes.