Miniaturized DGS and EBG structures for decoupling multiple antennas on compact wireless terminals

MIMO (Multiple Input Multiple Output) technology has been presented to significantly increase the wireless channel capacity and reliability without requiring additional radio spectrum or power. In MIMO systems, multiple antennas are mounted at both the transmitter and the receiver. When this technology is employed for a compact wireless terminal, one of the most challenging tasks is to reduce the high mutual coupling between closely placed antenna array elements. The high mutual coupling produces high correlation between antenna elements and affects the channel capacity of MIMO system. The objectives of this thesis are to design practical miniaturized structures to reduce high mutual coupling for small wireless terminals. The research is conducted in the following areas. Initially, a PIFA design and two-element PIFA array are proposed and optimized to operate at 1.9GHz. A pair of two coupled quarter-wavelength linear slits is inserted in a compact ground plane, resulting in significant reduction of the mutual coupling across antenna operating frequency band. In order to take up less space on the ground plane, instead of the linear slits, miniaturized convoluted slits are implemented between the two closely placed PIFAs. Although the convoluted slits have small area and are positioned close to the edges of the ground plane, the miniaturized convoluted slit structures achieve a reduction of mutual coupling between antenna elements and succeed in reducing the effect of the human body (head and hand) to the antennas. In order to further reduce the size of the slits etched on the compact ground plane, a novel double-layer slit-patch EBG structure is proposed. It consists of a two-layer structure including conducting patches and aperture slits placed on either side of a very thin dielectric layer. They are placed in very close proximity to each other (55μm). A two-element printed CPW-fed monopole array operating around 2.46GHz and a two-element UWB planar monopole array operating from 3GHz to 6GHz have been employed to investigate the proposed slit-patch EBG structures. The optimized double-layer slit-patch EBG structure yields a significant reduction of the mutual coupling and produces the maximum miniaturization of antenna array. Another novel convoluted slit-patch EBG structure has been presented to reduce the mutual coupling between two PIFAs operating at 1.9GHz. These results demonstrate that the slit-patch EBG structure is a feasible technology to reduce the mutual coupling between multiple antennas for compact wireless terminals

Performance characterisation of MIMO-UWB systems for indoor environments

Although recent advances in wireless system technologies have provided ever increasing throughputs, end user demand continues to increase unabated. The research investigates the performance of a system harnessing two relatively new but powerful technologies, Multiple-Input and Multiple-Output (MIMO) and Ultra Wideband (UWB) transmission as a possible solution to meet the growing demand for capacity. Each of these technologies in its own right has been subject to a large volume of research and has been proven to bring an increase in throughput. Nevertheless the predicted future demand will outstrip what each strategy can provide individually. MIMO-UWB systems are thus an emerging wireless solution with, in particular, the potential to satisfy short distance, high speed transmission requirements within indoor environments. Before any system is deployed it is important to characterise performance within representative operating environments. The study therefore emulates appropriate indoor environments, defines an experimental protocol to execute a range of measurements that provide robust evidence of the behaviour of the combined system within indoor scenarios. The application scenario dictates that the transmitter represents a gateway device attached to the ceiling and the receiver, a user device set on a table. The sequence of measurements relate to different positioning of the user device, with different angles and ranges to the gateway device, the layout of antenna placements being important. The output of the study is an accurate model for engineers and, the foundation for the design of MIMO-UWB systems for indoor services.Although recent advances in wireless system technologies have provided ever increasing throughputs, end user demand continues to increase unabated. The research investigates the performance of a system harnessing two relatively new but powerful technologies, Multiple-Input and Multiple-Output (MIMO) and Ultra Wideband (UWB) transmission as a possible solution to meet the growing demand for capacity. Each of these technologies in its own right has been subject to a large volume of research and has been proven to bring an increase in throughput. Nevertheless the predicted future demand will outstrip what each strategy can provide individually. MIMO-UWB systems are thus an emerging wireless solution with, in particular, the potential to satisfy short distance, high speed transmission requirements within indoor environments. Before any system is deployed it is important to characterise performance within representative operating environments. The study therefore emulates appropriate indoor environments, defines an experimental protocol to execute a range of measurements that provide robust evidence of the behaviour of the combined system within indoor scenarios. The application scenario dictates that the transmitter represents a gateway device attached to the ceiling and the receiver, a user device set on a table. The sequence of measurements relate to different positioning of the user device, with different angles and ranges to the gateway device, the layout of antenna placements being important. The output of the study is an accurate model for engineers and, the foundation for the design of MIMO-UWB systems for indoor services

Mutual coupling suppression in multiple microstrip antennas for wireless applications

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonMutual Coupling (MC) is the exchange of energy between multiple antennas when placed on the same PCB, it being one of the critical parameters and a significant issue to be considered when designing MIMO antennas. It appears significantly where multiple antennas are placed very close to each other, with a high coupling affecting the performance of the array, in terms radiation patterns, the reflection coefficient, and influencing the input impedance. Moreover; it degrades the designed efficiency and gain since part of the power that could have been radiated becomes absorbed by other adjacent antennas’ elements. The coupling mechanism between multiple antenna elements is identified as being mainly through three different paths or channels: surface wave propagation, space (direct) radiation and reactive near-field coupling. In this thesis, various coupling reduction approaches that are commonly employed in the literature are categorised based on these mechanisms. Furthermore, a new comparative study involving four different array types (PIFA, patch, monopole, and slot), is explained in detail. This thesis primarily focuses on three interconnected research topics for mutual coupling reduction based on new isolation approaches for different wireless applications (i.e. Narrowband, Ultra-wide-band and Multi-band). First, a new Fractal based Electromagnetic Band Gap (FEBG) decoupling structure between PIFAs is proposed and investigated for a narrowband application. Excellent isolation of more than 27 dB (Z-X plane) and 40 dB (Z-Y plane) is obtained without much degradation of the radiation characteristics. It is found that the fractal structures can provide a band-stop effect, because of their self-similarity features for a particular frequency band. Second, new UWB-MIMO antennas are presented with high isolation characteristics. Wideband isolation (≥ 31 dB) is achieved through the entire UWB band (3.1-10.6 GHz) by etching a novel compact planar decoupling structure inserted between these multiple UWB antennas. Finally, new planar MIMO antennas are presented for multi-band (quad bands) applications. A significant isolation improvement over the reference (≥ 17 dB) is achieved in each band by etching a hybrid solution. All the designs reported in this thesis have been fabricated and measured, with the simulated and measured results agreeing well in most cases

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin

IEEE Access Special Section: Antenna and Propagation for 5G and Beyond

5G is not just the next evolution of 4G technology; it is a paradigm shift. “5G and beyond” will enable bandwidth in excess of 100s of Mb/s with a latency of less than 1 ms, in addition to providing connectivity to billions of devices. The verticals of 5G and beyond are not limited to smart transportation, industrial IoT, eHealth, smart cities, and entertainment services, transforming the way humanity lives, works, and engages with its environment

Contextually and identity aware 5G services

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University LondonThe fifth generation (5G) mobile networks aim to be ten times faster than the existing 4G connection, whilst providing low latency, and flexibility. Hence, various alterations are planned to the existing network infrastructure to be able to reach the 5G expected performance levels. The main technologies that were used, to ensure high performance, flexible network, and efficient resource allocation, are Software Defined Network and Network Function Virtualization. As these technologies are replacing the device-based architecture with, a service-based architecture. This thesis provides a design of location database interactive web interface and interactive mobile application. The implementation of real time video streaming location server, the streaming system's performance parameters demonstrated a high level of QoS (0.07ms jitter and 9.53ms delay). In regard to experimental examination, it measured the localisation coverage, accuracy measurements and a highly scalable security solution. The localisation coverage and accuracy measurements were achieved through the mmWave and VLC link transmitters. The proposed simulated annealing algorithm aimed at data optimisation for location measurements accuracy showed results of the average location error of x and y which showed significant improvement from x= 22.5 and y=21.6 to x=11.09 and y= 11.63. The proposed indoor location security solution showed significant results, as it provides a high scalability solution using the VNF. The solution showed that it was not 100% effective, as some of the fake discover packets still reached the DHCP server. This was due to the high load of traffic passing through the network. Nonetheless, 90% of the fake DHCP discover packets never reached the DHCP server because the scripts began blocking all fake discover packets after realising it was an attack. This conveys that the proposed system was able to run successfully without crashing or overloading the controller. Overall, the main challenges facing 5G have been addressed with their proposed solutions, which showed promising results. Conclusively showing that there is a lot more space for technological advancements to support the future of mobile networks.European Union’s Horizon 2020 research program - the Internet of Radio-Light (IoRL) project H2020-ICT 761992

Optimisation of adaptive localisation techniques for cognitive radio

Spectrum, environment and location awareness are key characteristics of cognitive radio (CR). Knowledge of a user’s location as well as the surrounding environment type may enhance various CR tasks, such as spectrum sensing, dynamic channel allocation and interference management. This dissertation deals with the optimisation of adaptive localisation techniques for CR. The first part entails the development and evaluation of an efficient bandwidth determination (BD) model, which is a key component of the cognitive positioning system. This bandwidth efficiency is achieved using the Cramer-Rao lower bound derivations for a single-input-multiple-output (SIMO) antenna scheme. The performances of the single-input-single-output (SISO) and SIMO BD models are compared using three different generalised environmental models, viz. rural, urban and suburban areas. In the case of all three scenarios, the results reveal a marked improvement in the bandwidth efficiency for a SIMO antenna positioning scheme, especially for the 1×3 urban case, where a 62% root mean square error (RMSE) improvement over the SISO system is observed. The second part of the dissertation involves the presentation of a multiband time-of arrival (TOA) positioning technique for CR. The RMSE positional accuracy is evaluated using a fixed and dynamic bandwidth availability model. In the case of the fixed bandwidth availability model, the multiband TOA positioning model is initially evaluated using the two-step maximum-likelihood (TSML) location estimation algorithm for a scenario where line-of-sight represents the dominant signal path. Thereafter, a more realistic dynamic bandwidth availability model has been proposed, which is based on data obtained from an ultra-high frequency spectrum occupancy measurement campaign. The RMSE performance is then verified using the non-linear least squares, linear least squares and TSML location estimation techniques, using five different bandwidths. The proposed multiband positioning model performs well in poor signal-to-noise ratio conditions (-10 dB to 0 dB) when compared to a single band TOA system. These results indicate the advantage of opportunistic TOA location estimation in a CR environment.Dissertation (MEng)--University of Pretoria, 2012.Electrical, Electronic and Computer Engineeringunrestricte