Transmit power adaptation for enhancing the performance of wireless multi hop half or full duplex underlay cognitive relay networks

Abstract

The rise in popularity of high-speed wireless multimedia communications has necessitated the design of spectral efficient technologies for the fifth generation (5G) wireless networks. Cognitive radio allows unlicensed or secondary users (SUs) to share the spectrum originally allotted to the licensed or primary users (PUs). When cognitive radio operates in the underlay spectrum sharing mode, SUs are allowed to have concurrent transmissions with PUs by sharing the licensed spectrum, provided the interference induced by SUs on PU receiver remains below the acceptable thresh-old level. This imposes constraints on the instantaneous transmit powers of SUs, which affects the radio coverage of the secondary network. In a multi-hop cognitive relay network (MH-CRN), multiple cooperative relay nodes are employed in the secondary network to improve the coverage. In-band full duplex relaying (FDR) has recently been proposed for improving the spectral efficiency (SE) of the 5G wireless networks. The multi-hop full duplex CRN (MH-FDCRN), which combines multi-hop full duplex relaying with cognitive radio, is currently being investigated as one of the key architectures for the 5G wireless networks. Even though FDR improves the SE, when compared to its half-duplex (HD) counterpart, it generates residual self-interference (RSI), which proportionally grows with the transmit power used at the relay nodes. Further, the secondary network in MH-FDCRN suffers from inter-relay interference (IRI), when frequency reuse is employed. The major objectives of the thesis are: (i) to analyze the transmission rate, outage and energy efficiency (EE) performance of MH-FDCRN in the presence of co-channel interference and/or RSI over fading channels and (ii) to develop computationally efficient algorithms for transmit power optimization to improve the performance. newline