Radio access for LTE-advanced femtocells
Creators: name: Arafat, Abdullah Omar
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400608
subject: Wireless communication systems and technologies (incl. microwave and millimetrewave)

description: The evolution of wireless communication technology has entered a new era where the vision of vendors and researchers to move beyond connecting people to connecting everything is becoming reality. Pioneers have been working for decades to enhance the network coverage and capacity to cope with the ever-increasing demand by wireless users. Challenges remain and the race to better utilise the radio spectrum is still occurring. The race primarily aims to enhance the allocation of radio resources and to optimise coverage, thus providing more bandwidth for the rapidly increasing number of data-hungry applications. The opportunity for novel channel scheduling and spectrum sharing techniques to improve performance has arisen with the introduction of advanced wireless communication systems including the Long Term Evolution-Advanced (LTE-A) system, which supports resilient and efficient spectrum utilisation.<br><br>One of the main features of LTE-A is the ability to efficiently utilise femtocells both for home and enterprise broadband users. Femtocells are central to the next iteration of mobile cellular network development based on LTE-A. Typical femtocells are expected to include a low power and low cost mobile cellular base station, known as a home evolved node base station, that connects to the Internet over a service provider broadband network connection. Locally networked femtocell arrays are used to enhance mobile network coverage and capacity in crowded urban and indoor locations.<br><br>Traditional resource management, channel scheduling and spectrum access techniques are either not applicable for LTE-A femtocells or operate inefficiently; therefore, innovative techniques are required to manage interference and intelligently maintain the quality of service. The research carried out presents a number of original contributions to fulfil these objectives.<br><br>In this thesis, a performance analysis of LTE-A based femtocells is carried out and three different radio access and optimisation techniques are proposed. When considering low-cost solutions for urban indoor coverage and data rate, femtocells come to the fore. Due to potentially dense self-deployment of femtocells that are incorrectly configured, considerable inter-femtocell interference might occur, thereby resulting in severe performance degradation. To mitigate the inter-femtocell interference and to utilise the available transmission channels more efficiently, at first, a new cognitive co-channel cluster-based femtocell configuration that uses a priority-based users' spectrum sharing model was proposed. This proposal builds upon an existing fractional frequency reuse technique to ensure that interference is minimised and the utilisation of bandwidth between the femtocell users is maximised.<br><br>Second, a femtocell coverage optimisation algorithm is presented that reduces coverage gaps and cell interference while increasing the signal-to-noise ratio of the femtocell users. The proposed coverage optimisation algorithm utilises two power allocation techniques that continuously update the femtocell network transmission power levels by including a weighted value that is based on performance. The proposed algorithm enhances coverage and cell edge throughput of the overall network.<br><br>And finally, an uplink channel scheduling algorithm for LTE-A single-carrier frequency division multiple access (SC-FDMA) in a frequency division multiple access femtocell network is proposed. In LTE-A the allocation of the uplink channel is mandated by the contiguity paradigm, which requires computational complexity and intricacy. With changing consumer expectations, the user experience is now affected by both uplink and downlink speeds, reliability and latency. SC-FDMA is utilised in LTE-A to maintain a low peak-to-average power ratio, which is an obligatory feature that allows low power consumption and contiguous resource allocation; therefore, an uplink channel scheduling algorithm is the best choice for optimised operation. In previous studies, different algorithms have been proposed to achieve optimal spectrum utilisation. However, a more effective and compact channel scheduling algorithm is yet to be proposed that improves performance. In this research, a normalised weight-based channel scheduling algorithm has been proposed to improve spectrum utilisation in the LTE-A uplink femtocell network.<br><br>In this research, three different radio access and optimisation techniques are presented, with a hybrid access femtocell network utilised for the performance analysis. The proposed algorithms were compared and analysed with the existing research found in the literature. A game theory model for dynamic spectrum access in LTE-A femtocells is also adopted. Throughout this research, the analytical results and formula were modelled using computer simulations developed using Wireless InSite and MATLAB. Numerical examples are presented to reflect the practicality of the proposed methodologies. Most of the work presented in this dissertation has been published in-part or as-a-whole in peer-reviewed journals and conference proceedings or is otherwise currently undergoing a review process.