Aspects of capacity enhancement techniques in cellular networks

Frequency spectrum is the scarce resource. From mobile operator’s point of view, efficient utilization of the radio resources is needed while providing maximum coverage, and ensuring good quality of service with minimal infrastructure. In high capacity demanding areas, multilayer networks with multiband and multi radio access technologies are deployed, in order to meet the capacity requirements. In his doctoral thesis, Usman Sheikh has proposed a “Smart Traffic Handling” strategy, which is based on user’s required service type and location. Smart traffic handling scheme efficiently utilizes the different layers of the network, balances the load among them, and improves the system capacity. Power resources at base station are also limited. Usman Sheikh’s proposed “Power Control Scheme for High Speed Downlink Packet Access (HSDPA) network” improves the cell edge user experience, while maintaining the fairness among the other users in a cell. With the help of a proposed power control scheme, a user far from the base station can also enjoy the better quality of service. Generally, mobile operators use macro cells with wide beam antennas for wider coverage in the cell, but future capacity demands cannot be achieved by using only them. “Higher Order Sectorization” is one possible way to increase the system capacity. Usman Sheikh proposed new network layouts called “Snowflake” and “Flower” tessellations, for 6-sector and 12-sector sites, respectively. These tessellations can be used as a basis for making a nominal network plan for sites with higher order sectorization. These tessellations would be helpful for simulation purposes. Through his work, he has also tried to highlight the importance of deploying “Adaptive MIMO Switching” in Long Term Evolution (LTE) system, the fourth generation of wireless networks. In future, the fifth generation of wireless networks is expected to offer thousand times more capacity compared to LTE. The novel concept of “Single Path Multiple Access (SPMA)” given by Usman Sheikh is a revolutionary idea, and gives a possibility to increase the system capacity by a giant margin. SPMA can be considered as a right step towards 5G technology. Usman Sheikh’s work is of high importance not only from mobile operator’s point of view; rather his contributions to the scientific community will also lead to better user (customer) experience. His work will definitely benefit the mankind in utilizing the limited resources in an optimum and efficient way

Impact of Femtocell backhaul limitation on performance of Macro-Femto HetNet

This thesis is a techno-economical study which focuses on addressing the exponentially rising data capacity demand through network densification. The study is based on the two popular deployment strategies; Macrocellular networks and Macro-Femto heterogeneous networks, deployed in a suburban type environment with modern houses. The main aim of the dissertation is to investigate the impact of network densification on capacity, energy- and cost-efficiency of the network, while considering different femtocell backhaul connectivity limitations. The network performance is evaluated for both indoor and outdoor scenarios. A comparative analysis between the macrocellular and macro-femto network is done by increasing the density of the macrocells, femtocells and the operating frequency spectrum. The capacity is enhanced by increasing the density of the cell sites in the network but operators want to generate profit and want to adopt a cost effective solution to cater the problems. The results show that increasing the density of low-cost, low-powered femtocell access points (FAPs) in the network can solve the problem of 1000x future data capacity demand while keeping the CAPEX and OPEX of the network relatively lower than legacy pure macrocellular deployments. The deployment of the FAPs both in indoor and outdoor environments enhances the network capacity. This study helped in providing results, understanding and insight of both technical and techno-economical aspects of different mobile network deployment and densification solutions. Furthermore, the outcome of the thesis will give some guidelines for network vendors and mobile operators in evolving their network in future

Mobile network design : Orange UK 2G to 3G mobile backhaul evolution

The research presented in this thesis is focused on the evolution of a GSM/GPRS (2G) cellular mobile network to UMTS (3G) and then subsequently, HSDPA. The particular technical area of research relates to the mobile backhaul network which provides the connectivity between radio cell sites which support the wide area radio coverage, and the mobile network operator’s core network. Due to the evolution of UMTS with HSDPA, the research covers the initial UMTS network rollout and then addresses the evolution of this infrastructure to support mobile broadband communications, through the introduction of HSDPA as a network upgrade. The two research questions being addressed are therefore: •How is it possible to evolve a GSM/GPRS mobile backhaul network to support a converged GSM/GPRS and UMTS cellular mobile service? •How is it possible to ensure scalability of the converged backhaul network given the introduction of HSDPA and associated mobile broadband data growth? The starting point of the research is an established GSM and GPRS commercial network in the UK and the study is based on the design of the Orange network and focused on the period 2000 to 2010. During this period the author was working as Principal Network Designer within Orange and had overall responsibility for the strategy, architecture and design of the UK mobile backhaul network. The thesis provides a detailed explanation of the novel network design that was adopted and how it was evolved throughout the ten year period covered by the research. The research proves that the original static TDM approach was not suitable for UMTS and therefore the outcome was the introduction of an ATM network with optimisation based on traffic class rt-VBR over protected STM-1 transmission links. HSDPA drove further traffic growth and resulted in an evolution of the solution to ensure massive scalability was supported through the migration to Carrier Ethernet and implementation of pseudo-wires. In addition, to providing a technical description of the network design, the thesis also aims to provide a historical record of the technologies and equipment used during this period of rapid change within the UKs mobile networks

Investigations on some compact wideband fractal antennas

Today’s small handheld and other portable devices challenge antenna designers for ultrathin, and high performances that have the ability to meet multi standards. In the context, fractal geometries have significant role for antenna applications with varying degree of success in improving antenna characteristics. In this thesis, we have investigated several wideband fractal monopole antennas. This work starts with design and implementation of Koch fractal, hybrid fractal, sectoral fractal, semi-circle fractal monopole antennas with discussion, covering their operations, electrical behavior and performances. The performances of these designs have been studied using standard simulation tools used in industry/academia and are experimentally verified. Frequency reconfigurable Koch snowflake fractal monopole antenna is also introduced. The present antenna can be used as an array element and has a wideband frequency of operation. A square Sierpinski monopole antenna has been designed, which is suitable for use in indoor UWB radio system and outdoor base station communication systems. Technique for obtaining a band stop function in the 5-6 GHz frequency band is numerically and experimentally presented. In addition to examining the performance of UWB system, the transfer function and waveform distortion are discussed. Finally, fractal antenna for array with MIMO environment is developed for mobile communication devices. Aim of this work is to achieve the acceptable performances in terms of isolation, envelope correlation coefficient, capacity loss, radiation patterns and efficiency. Furthermore, a wideband feed network prototype based on a modified Wilkinson power divider is designed. The designed feed network has been used in constructing 2-element and 4-element linear antenna arrays for high gain. This research work has addressed the effectiveness of fractal geometries in antenna and to bring-out the true advantages of their in antenna engineering

Research and technology highlights, 1993

This report contains highlights of the major accomplishments and applications that have been made by Langley researchers and by our university and industry colleagues during the past year. The highlights illustrate both the broad range of the research and technology activities supported by NASA Langley Research Center and the contributions of this work toward maintaining United States leadership in aeronautics and space research. This report also describes some of the Center's most important research and testing facilities