Evaluation of Sigma-Delta-over-Fiber for High-Speed Wireless Applications

Future mobile communication networks aim to increase the communication speed,\ua0provide better reliability and improve the coverage. It needs to achieve all of these enhancements, while the number of users are increasing drastically. As a result, new base-station (BS) architectures where the signal processing is centralized and wireless access is provided through multiple, carefully coordinated remote radio heads are needed. Sigma-delta-over-fiber (SDoF) is a communication technique that can address both requirements and enable very low-complexity, phase coherent remote radio transmission, while transmitting wide-band communication signals with high quality. This thesis investigates the potential and limitations of SDoF communication links as an enabler for future mobile networks.In the first part of the thesis, an ultra-high-speed SDoF link is realized by using state-of-the-art vertical-cavity surface-emitting-lasers (VCSEL). The effects of VCSEL characteristics on such links in terms of signal quality, energy efficiency and potential lifespan is investigated. Furthermore, the potential and limitations of UHS-SDoF are evaluated with signals having various parameters. The results show that, low-cost, reliable, energy efficient, high signal quality SDoF links can be formed by using emerging VCSEL technology. Therefore, ultra-high-speed SDoF is a very promising technique for beyond 10~GHz communication systems.In the second part of the thesis, a multiple-input-multiple-output (MIMO) communication testbed with physically separated antenna elements, distributed-MIMO, is formed by multiple SDoF links. It is shown that the digital up-conversion, performed with a shared local-oscillator/clock at the central unit, provides excellent phase coherency between the physically distributed antenna elements. The proposed testbed demonstrates the advantages of SDoF for realizing distributed MIMO systems and is a powerful tool to perform various communication experiments in real environments.In general, SDoF is a solution for the downlink of a communication system, i.e. from central unit to remote radio head, however, the low complexity and low cost requirement of the remote radio heads makes it difficult to realize the uplinks of such systems. The third part of this thesis proposes an all-digital solution for realizing complementary uplinks for SDoF systems. The proposed structure is extensively investigated through simulations and measurements and the results demonstrate that it is possible realize all-digital, duplex, optical communication links between central units and remote radio heads.In summary, the results in this thesis demonstrate the potential of SDoF for wideband, distributed MIMO communication systems and proposes a new architecture for all-digital duplex communication links. Overall, the thesis shows that SDoF technique is powerful technique for emerging and future mobile communication networks, since it enables a centralized structure with low complexity remote radio heads and provides high signal quality

Sigma-Delta-over-Fiber for High-Speed Wireless Communication Systems

Future mobile communication networks aim to increase the communicationspeed, provide better reliability and improve the coverage. It needs to achieveall of these enhancements, while the number of users are increasing drastically.As a result, new base-station (BS) architectures where the signal processingis centralized and wireless access is provided through multiple, carefullycoordinated remote radio units are needed.The sigma-delta-over-fiber (SDoF) is a communication technique that canaddress both requirements and enable very low-complexity, phase coherentremote radio transmission, while transmitting wide-band communication signalswith high quality. This thesis investigates the potential and limitations of SDoFcommunication links as an enabler of future mobile networks.In the first part of the thesis, a multiple-input-multiple-output (MIMO)communication testbed with physically separated antenna elements, distributed-MIMO, is formed by multiple SDoF links. It is shown that the digital upconversion,performed with a shared local-oscillator/clock at the central unit,provides excellent phase coherency between the physically distributed antennaelements. Moreover, the same approach decreases the complexity and thepackage size of the antenna units\ua0significantly by moving the complexity of theBSs to a central unit. The implemented testbed is evaluated through variouscommunication experiments. The results show that distributing the antennaunits of a MIMO communication system can increase the coverage and signalquality.In the second part of the thesis, an ultra-high-speed SDoF (UHS-SDoF) linkis realized by using the state-of-the-art vertical-cavity surface-emitting-lasers(VCSEL). The effects of VCSEL characteristics on such links in terms of signalquality, energy efficiency and potential lifespan is investigated. Furthermore, thepotential and limitations of UHS-SDoF are evaluated with signals having variousparameters. The results show that, low-cost, reliable, energy efficient, highsignal quality SDoF links can be formed by using emerging VCSELs. Therefore,UHS-SDoF is a very promising technique for beyond 10 GHz communicationsystems.In conclusion, this thesis has showed that low-complexity, low-cost, andenergy efficient ultra-high speed communication links and distributed MIMOsystems can be implemented by employing SDoF

Behaviour of Magnetized Strange Quark Matter in f(R,T) Theory for General Kantowski-Sachs Model

In this study, we have investigated the behavior of magnetized strange quark matter (MSQM) in f(R,T) gravity for LRS Bianchi I, Bianchi III and Kantowski-Sachs (GKS) universe models with cosmological term. For the solutions of modified field equations, we have used linearly varying deceleration parameter (LVDP), anisotropy parameter and equation of state for strange quark matter. When the models goes to the isotropy magnetic field only occurs in Bianchi III and Kantowski-Sachs universe models. When trarr%253Binfin%253B, strange quark matter distribution behaves like dark energy. The K(theta%253B) parameter, which allows us to obtain different universe models, is effective on the magnetic field, cosmological term and f(R,T) function. In addition, the graphics of the obtained results were examined in detail

Localization With Distributed MIMO Using a High-Speed Sigma-Delta-Over-Fiber Testbed

Distributed MIMO (D-MIMO) with synchronized access points (APs) is a promising architecture for both communications and localization in 5G and beyond systems. In this letter, we develop a time-difference-of-arrival (TDOA)-based indoor localization system using a 2.35-GHz high-speed sigma-delta-over-fiber (SDoF) D-MIMO testbed with 40-MHz bandwidth, exploiting the fully synchronized nature of the APs. Experimental results over an area of size 100 m\ub2 demonstrate accuracies below 0.2 m and agree with the theoretical Cram\ue9r-Rao bounds (CRBs) at most measurement locations, indicating the localization capability of high-speed SDoF D-MIMO

Automatic Distributed MIMO Testbed for beyond 5G Communication Experiments

This paper demonstrates an automated testbed suitable for beyond-5G distributed MIMO experiments, where bandwidth, number of transmitters and precoding methods are flexible and configured through a central unit. This is based on an all-digital radio-over-fiber approach to communication through 12 fully coherent, low-complexity remote radio transmitters. An automated robot receiver is implemented to facilitate efficient communication data collection in realistic environments. Using the proposed system, co-located and distributed MIMO communication antenna configurations are compared in a real in-door environment. The results show that distributed MIMO provides more significantly more uniform power distribution and better overall MIMO capacity compared to co-located MIMO

Distributed Massive MIMO via all-Digital Radio Over Fiber

A crucial challenge in the implementation of distributed massive multiple-input multiple-output (MIMO) architectures is to provide phase coherence while, at the same time, limit the complexity of the remote-radio heads (RRHs), which is important for cost-efficient scalability. To address this challenge, we present in this paper a phase-coherent distributed MIMO architecture, based on off-the-shelf, low-cost components. In the proposed architecture, up- and down-conversion are carried out at the central unit (CU). The RRHs are connected to the CU by means of optical fibers carrying oversampled radio-frequency (RF) 1-bit signals. In the downlink, the 1-bit signal is generated via sigma-delta modulation. At the RRH, the RF signal is recovered from the 1-bit signal through a bandpass filter and a power amplifier, and then fed to an antenna. In the uplink, the 1-bit signal is generated by a comparator whose inputs are the low-noise-amplified received RF signal and a suitably designed dither signal. The performance of the proposed architecture is evaluated with satisfactory results both via simulation and measurements from a testbed

Semantic Sketch-Based Video Retrieval with Autocompletion

The IMOTION system is a content-based video search engine that provides fast and intuitive known item search in large video collections. User interaction consists mainly of sketching, which the system recognizes in real-time and makes suggestions based on both visual appearance of the sketch (what does the sketch look like in terms of colors, edge distribution, etc.) and semantic content (what object is the user sketching). The latter is enabled by a predictive sketch-based UI that identifies likely candidates for the sketched object via state-of-the-art sketch recognition techniques and offers on-screen completion suggestions. In this demo, we show how the sketch-based video retrieval of the IMOTION system is used in a collection of roughly 30,000 video shots. The system indexes collection data with over 30 visual features describing color, edge, motion, and semantic information. Resulting feature data is stored in ADAM, an efficient database system optimized for fast retrieval

Evaluation of the Electronic Resource Usage of Ankara University Faculty Members

Günümüzde üniversiteler, eğitim-öğretim, araştırma ve uygulama faaliyetleri içerisinde bulunabilmek için bilimsel bilgiye en doğru ve en hızlı biçimde ulaşmayı hedeflemektedir. Bundan dolayı, Ankara Üniversitesi akademik personelinin bilimsel bilgiye erişim için çağdaş bilgi ve iletişim teknolojilerini kullanması kaçınılmazdır. Bilimsel her veri tabanının standart taşıması gereken belirli özellikleri bulunmaktadır. Bu özellikler veri tabanında yer alan verilere erişimin doğru ve hızlı olması bakımından önem kazanmaktadır. Ankara Üniversitesi mensuplarına gereksinim duyacakları bilimsel bilgi kaynakları elektronik ortamda en çağdaş bilgi ve iletişim teknolojilerini kullanarak sunulmaktadır. Bu araştırmada, Ankara Üniversitesi akademik personelinin bilgi gereksinimleri doğrultusunda oluşturulan ve elektronik kütüphanede yer alan veri tabanlarının kullanılıp kullanılmadığının belirlenmesi amaçlanmış; bu amaca yönelik bilgi modeli ve içeriği belirlenerek uygulamaların gerçekleştirilmesi hedeflenmiştir.Education, research, and implementation activities of universities necessitate access to information in the most accurate and fastest manner in today's conditions. In this regard; Members of Ankara University have to access scientific information through the most contemporary information and communication technology in the electronic environment, primarily through the global internet system. Each scientific database has specific standard characteristics. These properties gain importance in terms of the correctness and speed of access to the data contained in the database. The sources of scientific information that the members of Ankara University will need are presented in the electronic environment using the most contemporary information and communication technologies. This article aims to determine the information needs of the members of Ankara University and to determine the information access and the use of information by identifying the information access model for researching the educational facilities and the necessary infrastructure and technical support so that the maximum benefit can be obtained from the electronic library. Aims at realizing their application by determining the information model and content for this purpose