Multi-hop Cellular Network (MCN) is an emerging wireless communication architecture, which combines the benefits of conventional Single-Hop Cellular Networks (SCN) and Multi-hop Ad-hoc Relaying Networks. In MCN, communication can be either between a mobile station (MS) and the base station (BS) through intermediate relay stations (RS) over multiple hops or the MS can communicate directly with other MS through intermediate RSs over multiple hops without the involvement of a BS. Since all these stations are mobile, multi-hop routing in MCN is a major issue. The route selection depends on the availability of intermediate nodes, their neighbourhood connectivity and the channel availability.

Cognitive Radio (CR) is an emerging communication paradigm which exploits the available radio frequencies opportunistically for the effective utilisation of the radio frequency spectrum. Currently, CR is an enabling technology for users of non-licensed spectrum (e.g. ISM band) to sense and utilise unused radio frequencies in the licensed spectrum (e.g. TV white space) in a dynamic and non-interfering way.

The incorporation of CR and Mobile Ad-Hoc Network (MANET) routing protocols in MCN could potentially improve the spectrum utilisation and the routing performance of MCN. This research deals with the development and investigation of a multi-interface CR mobile node model in Optimized Network Engineering Tool (OPNET) to enhance the routing performance in MCN. The interfaces used in this CR mobile node are IEEE 802.11a (Wi-Fi), IEEE 802.11af (White-Fi) and IEEE 802.16 (WiMax). The 802.11a and 802.11af interfaces are used for multi-hop communication while WiMax interface is used for single-hop communication with BS when multi-hop communication is not possible with 802.11a and 802.11af interfaces. The 802.11af interface uses the CR feature to perform a channel selection. The multi-hop routing protocol used in this research is a modified version of AODV (Ad-hoc On-demand Distance Vector). The route selection by this routing protocol is not based on the minimum hops as in conventional AODV but based on the output interface available (802.11a or 802.11af) when multi-hop communication is possible. This research firstly develops the OPNET model for the multi-interface CR mobile and then investigates their opportunistic spectrum utilisation and routing performance in MCN.