Cross-layer techniques for enhancing the performance of heterogeneous OFDMA based cellular systems

• Main Author: Pramudito, Wahyu Agung
• Other Authors: Alsusa, Emad
• Published: University of Manchester 2013
• Subjects: 621.384
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607389

Increasing licensed spectrum utilisation can be achieved through physical (PHY) and/or medium access control (MAC) layer approaches. In the PHY layer, resource utilisation can be increased by implementing multiple input multiple output (MIMO) transmission. On the other hand, a low-cost solution of the MAC layer approach is the resource utilisation improvement by implementing femtocells based heterogeneous network (HetNet) that allows end-users to deploy small-size basestations (BSs) in their own premises. While this also reduces the installation and maintenance cost of the operators, it results in higher interference levels in the network. This research proposes solutions in both, PHY and MAC layers, to improve the licensed spectrum efficiency. In the case of the PHY layer approach, this thesis proposes a new pairing cooperative technique in the uplink transmission that can provide spatial diversity and constructive interference exploitation in uplink orthogonal frequency division multiple access (OFDMA) systems. Both synchronous and asynchronous transmission scenarios are considered. The performance of this technique is evaluated through Monte Carlo simulations and accurate mathematical analysis. It is shown that the proposed scheme provides significant BER reductions, especially at low SNR, as well as, throughput improvements relative to existing cooperative transmission techniques. In the case of the MAC layer approach, this research proposes a novel interference mapping based RRM that combines network routing protocols and cooperation between BSs and the cellular management system to produce an effective way of utilising the spectrum. It will be shown through mathematical analysis and computer simulations that this proposal improves the overall bit rate and quality of service (QoS), enhances the energy efficiency and provides a good platform to manage femtocell accessibility.