Integration of a genetic optimisation algorithm in a simulation framework for optimising femtocell networks.

The developments in mobile communication systems from 1G to 4G have increased demands on the network due to the increased number of devices and increasing volume of data and 5G is expected to significantly increase demands further. Therefore, networks need to be more efficient to deliver the expected increase in volume. An energy and cost efficient way to cope with such an anticipated increase in the demand of voice and data is the dense deployment of small cells i.e. femtocells. Femtocells are identified as a crucial way to the delivery of the increased demands for heterogeneous networks in which macrocells work in combination with femtocells to provide coverage to offices, homes and enterprise. A survey of the literature is conducted to examine the mechanisms and approaches different authors have used to optimise the network. One of the major activities in this project before the transfer was the identification of the parameters. The literature was analysed and key performance parameters were identified. Based on the identified key performance parameters, a simulation framework is used to perform the experiments and to analyse the performance of a two-tier LTE-A system having femtocell overlays. A comprehensive and easy to use graphical user interface has been set up with the desired two- tier network topologies. It estimates the throughput and path loss of all the femto and macro users for all the supported bandwidths of an LTE-A system using different modulation schemes. A series of tests are carried out using the described simulation framework for a range of scenarios. The modulation scheme that yield highest throughput for a femtocell user is identified, and path loss is found to be independent from the modulation scheme but is dependent on the distance from its base station. In another series of experiments, the effects that walls inside buildings have on connectivity are examined and positioning of the femtocells is changed for each scenario inside buildings to analyse the performance. These results are used to find the optimised location of femtocells in different room layouts of the building. The simulation framework is further developed to be able to optimise the whole femtocell network by finding the optimised positioning of femtocells using the genetic optimisation algorithm. The end user can provide the inputs of the desired network topology to the simulation framework through a graphical user interface. The throughput and path loss of all the femto users are calculated before and after optimisation. The simulation results are generated in the form of tables before and after optimisation for comparison and analysis. The layouts depicting the indoor environment of the building before and after optimisation can be seen and analysed through the graphical user interface developed as a part of this simulation framework. Two case studies are defined and described to test the capacity and capability of the developed simulation framework and to show how the simulation framework can be used to identify the optimum positions of the femtocells under different configurations of room designs and number of users that represent contrasting loads on the network. Any desired network topology can be created and analysed on the basis of throughput and path loss by using this simulation framework to optimise the femtocell networks in an indoor environment of the building. The results of the experiments are compared against the claims in other published research

Channel Capacity Maximization using NQHN Approach at Heterogeneous Network

In present scenario, the high speed data transmission services has pushed limits for wireless communication network capacity, at same time multimedia transmission in real-time needs provision of QoS, therefore the network capacity and small cell coverage has comes with lots of challenges. Improving the channel capacity and coverage area within the available bandwidth is necessary to provide better QoS to users, and improved channel capacity for the FCUs and MCUs in network. In this paper, we are proposing an NQHN approach that incorporate with efficient power allocation, improving the channel capacity by optimized traffic scheduling process in a small cell HetNets scenario. This work efficiently handle the interference with maintaining the user QoS and the implemented power controller uses HeNB power as per the real time based approach for macro-cell and femto-cell. Moreover, we consider the real traffic scenario to check the performance of our proposed approach with respect to existing algorith

Interference mitigation in cognitive femtocell networks

“A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of Philosophy”.Femtocells have been introduced as a solution to poor indoor coverage in cellular communication which has hugely attracted network operators and stakeholders. However, femtocells are designed to co-exist alongside macrocells providing improved spatial frequency reuse and higher spectrum efficiency to name a few. Therefore, when deployed in the two-tier architecture with macrocells, it is necessary to mitigate the inherent co-tier and cross-tier interference. The integration of cognitive radio (CR) in femtocells introduces the ability of femtocells to dynamically adapt to varying network conditions through learning and reasoning. This research work focuses on the exploitation of cognitive radio in femtocells to mitigate the mutual interference caused in the two-tier architecture. The research work presents original contributions in mitigating interference in femtocells by introducing practical approaches which comprises a power control scheme where femtocells adaptively controls its transmit power levels to reduce the interference it causes in a network. This is especially useful since femtocells are user deployed as this seeks to mitigate interference based on their blind placement in an indoor environment. Hybrid interference mitigation schemes which combine power control and resource/scheduling are also implemented. In a joint threshold power based admittance and contention free resource allocation scheme, the mutual interference between a Femtocell Access Point (FAP) and close-by User Equipments (UE) is mitigated based on admittance. Also, a hybrid scheme where FAPs opportunistically use Resource Blocks (RB) of Macrocell User Equipments (MUE) based on its traffic load use is also employed. Simulation analysis present improvements when these schemes are applied with emphasis in Long Term Evolution (LTE) networks especially in terms of Signal to Interference plus Noise Ratio (SINR)

Heterogeneous network optimization using robust power-and-resource based algorithm

In order to meet the increasing mobile data-traffic, spatial densification of network with several low-power nodes, the high-power macro BS and HetNet are the major key enabling solution. However, the HetNet is unplanned in nature, causes irregularities and interferences that without any user association rules. The appropriate deployment of the femto-cell in HetNet can provide effective traffic offloading, where the alleviate mobbing in the macro-cells can decrease the power consumption therefore it optimizes the user experience. Moreover, the protection is also important for the macro and femto cell users in a network through maintaining the min-max level of interferences. In this paper, we proposed RPRA that comprises two robust approach such as robust power-controller and the robust channel-allocation approach, which can improve the spectral efficiency and user experiences at lower network coverage areas via eliminating the week coverage zones. Also provide high user rate connection by effective interference in an efficient spectrum, lowering in transmission power and cost-effectiveness via less time delay. To show the effectiveness of our proposed model we have compared with several existing techniques and we got significant improvement in throughput, also reduction in time delay and transmission power

Analysis of Reconfigurability, Control and Resource Management in Heterogeneous Wireless Networks

Modern communications networks integrate different access technologies that require interoperability for seamless and user-transparent transfer of multimedia-reach content. Latest standardization activities in this area pinpoint the IEEE 802.21 standard as an enabler of media independent handovers in various scenarios. Additionally, the implementation of the heterogeneous network paradigm yields optimized and efficient resource management techniques emphasizing the need for reconfiguration and interoperability capabilities within future wireless networks. This paper analyzes a combination of reconfigurability, interoperability and resource management aspects in heterogeneous wireless networks based on the IEEE 802.21 standard. It introduces a novel platform for wireless heterogeneous communication systems and a prototype of a reconfigurable mobile terminal that rely on the IEEE 802.21 standard. The introduced platforms are extensively validated through simulations and laboratory experiments showcasing that the IEEE 802.21-backed interoperability is able to support uninterrupted content delivery across multiple communication technologies with high performance

Modeling and design for future wireless cellular networks: coverage, rate, and security

Accompanied by the wide penetration of smartphones and other personal mobile devices in recent years, the foremost demand for cellular communications has been transformed from offering subscribers a way to communicate through low data rate voice call connections initially, into providing connectivity with good coverage, high data rate, as well as strong security for sensitive data transmission. To satisfy the demands for improved coverage and data rate, the cellular network is undergoing a significant transition from conventional macrocell-only deployment to heterogeneous network (HetNet), in which a multitude of radio access technologies can be co-deployed intelligently and flexibly. However, the small cells newly introduced in HetNet, such as picocells and femtocells, have complicated the network topology and the interference environment, thus presenting new challenges in network modeling and design. In recent studies, performance analyses were carried out accurately and tractably with the help of Poisson point process (PPP)-based base station (BS) model. This PPP-based model is extended in this work with the impact of directional antennas taken into account. The significance of this extension is emphasized by the wide usage of directional antennas in sectorized macrocell cells. Moreover, studies showed that little coverage improvement can be achieved if small cells are randomly deployed in a uniform-distributed way. This fact inspires us to explore the effect of the non-uniform BS deployment. We propose a non-uniform femtocell deployment scheme, in which femtocell BSs are not utilized if they are located close to any macrocell BSs. Based upon our analytical framework, this scheme can provide remarkable improvements on both coverage and data rate, thus stressing the importance of selectively deploying femtocell BSs by considering their relative locations with macrocell BSs. To alleviate the severe interference problem, the uplink attenuation technique is frequently employed in femtocell receivers to reduce the impact of interference from unattached terminals such that femtocell communication can take place. In order to analyze and optimize the femtocell system performance with this technique, we propose an analytical framework and demonstrate the performance tradeoff resulted from higher and lower uplink attenuation levels. Furthermore, we provide two improved uplink attenuation algorithms, which adaptively adjust to the information of the scheduled traffic, data rate requirement, and interference condition. Apart from the cellular coverage and data rate, communication security has been an important issue to be addressed due to the increasing demand for transmitting private and sensitive information over wireless networks. In the last part of the thesis, physical layer security, as a new way to improve wireless secrecy, is studied for cellular networks. By highlighting the unique cellular features offered by the carrier-operated high-speed backhaul, we investigate the probabilistic characterization of the secrecy rate, and identify the performance impacts of cell association and location information exchange between BSs. These results provide necessary network design guidelines for selecting the appropriate cell association method and information exchange range

Energy Efficiency Metrics in Cognitive Radio Networks: A Hollistic Overview

Due to the explosive progression in the number of users for new generation wireless communication networks which includes cognitive radio networks, energy efficiency has been a fundamental factor affecting its development and performance.  In order to adeptly access and analyze the energy efficiency of a cognitive radio network, a standardized metric for this purpose is required. As a starting point, in this article we provided an analysis for energy efficiency metrics of a cognitive radio network in respect to its design and operation. The performance metrics and metrics developed at the different levels of a cognitive radio network are also studied. Establishing a comprehensive metric for evaluating, measuring and reporting the energy efficiency of cognitive radio networks is a crucial step in achieving an energy-efficient cognitive radio network