Cross-Layer Optimization for Power-Efficient and Robust Digital Circuits and Systems

With the increasing digital services demand, performance and power-efficiency become vital requirements for digital circuits and systems. However, the enabling CMOS technology scaling has been facing significant challenges of device uncertainties, such as process, voltage, and temperature variations. To ensure system reliability, worst-case corner assumptions are usually made in each design level. However, the over-pessimistic worst-case margin leads to unnecessary power waste and performance loss as high as 2.2x. Since optimizations are traditionally confined to each specific level, those safe margins can hardly be properly exploited. To tackle the challenge, it is therefore advised in this Ph.D. thesis to perform a cross-layer optimization for digital signal processing circuits and systems, to achieve a global balance of power consumption and output quality. To conclude, the traditional over-pessimistic worst-case approach leads to huge power waste. In contrast, the adaptive voltage scaling approach saves power (25% for the CORDIC application) by providing a just-needed supply voltage. The power saving is maximized (46% for CORDIC) when a more aggressive voltage over-scaling scheme is applied. These sparsely occurred circuit errors produced by aggressive voltage over-scaling are mitigated by higher level error resilient designs. For functions like FFT and CORDIC, smart error mitigation schemes were proposed to enhance reliability (soft-errors and timing-errors, respectively). Applications like Massive MIMO systems are robust against lower level errors, thanks to the intrinsically redundant antennas. This property makes it applicable to embrace digital hardware that trades quality for power savings.Comment: 190 page

Novel Models and Algorithms Paving the Road towards RF Convergence

After decades of rapid evolution in electronics and signal processing, the technologies in communications, positioning, and sensing have achieved considerable progress. Our daily lives are fundamentally changed and substantially defined by the advancement in these technologies. However, the trend is challenged by a well-established fact that the spectrum resources, like other natural resources, are gradually becoming scarce. This thesis carries out research in the field of RF convergence, which is regarded as a mean to intelligently exploit spectrum resources, e.g., by finding novel methods of optimising and sharing tasks between communication, positioning, and sensing. The work has been done to closely explore opportunities for supporting the RF convergence. As a supplement for the electromagnetic waves propagation near the ground, ground-to-air channel models are first proposed and analysed, by incorporating the atmospheric effects when the altitude of aerial users is higher than 300 m. The status quos of techniques in communications, positioning, and sensing are separately reviewed, and our newly developments in each field are briefly introduced. For instance, we study the MIMO techniques for interference mitigation on aerial users; we construct the reflected echoes, i.e., the radar receiving, for the joint sensing and communications system. The availability of GNSS signals is of vital importance to the GNSS-enabled services, particularly the life-critical applications. To enhance the resilience of GNSS receivers, the RF fingerprinting based anti-spoofing techniques are also proposed and discussed. Such a guarantee on GNSS and ubiquitous GNSS services drive the utilisation of location information, also needed for communications, hence the proposal of a location-based beamforming algorithm. The superposition coding scheme, as an attempt of the waveform design, is also brought up for the joint sensing and communications. The RF convergence will come with many facets: the joint sensing and communications promotes an efficient use of frequency spectrum; the positioning-aided communications encourage the cooperation between systems; the availability of robust global positioning systems benefits the applications relying on the GNSS service

A bibliography experiment on research within the scope of industry 4.0 application areas in sports: Sporda endüstri 4.0 uygulama alanları kapsamında yapılan araştırmalar üzerine bir bibliyografya denemesi

Developed countries develop their production sites within the scope of industry 4.0 technology components and experience constant change and transformation to establish economic superiority. This situation allows them to produce more in various fields and thus to rise to a more advantageous position economically. Industry 4.0 technology affects areas within the scope of the sports industry such as sports tourism, athlete performance, athlete health, sports publishing, sports textile products, sports education and training, sports management and human resources, and creates an international competition environment in terms of production and performance. In this study, it is aimed to examine the researches about the usage areas of industry 4.0 in sports. From this point on, researches in the context of the subject have been presented with bibliographic method. In the conclusion section, the weaknesses and possibilities of youth sociology were discussed, and efforts were made to present a projection on what to do about the field. In this respect, a youth sociology evaluation has been tried to be made on the prominent topics, forgotten aspects and themes left incomplete in youth sociology studies. ​Extended English summary is in the end of Full Text PDF (TURKISH) file.   Özet Gelişmiş ülkeler endüstri 4.0 teknolojisi bileşenleri kapsamında üretim sahalarını geliştirmekte ve ekonomik üstünlük kurmak amacıyla sürekli değişim ve dönüşüm yaşamaktadır. Bu durum onların çeşitli alanlarda daha fazla üretmelerine dolayısıyla ekonomik yönden daha avantajlı konuma yükselmelerine olanak sağlamaktadır. Endüstri 4.0 teknolojisi spor turizmi, sporcu performansı, sporcu sağlığı, spor yayıncılığı, spor tekstil ürünleri, spor eğitimi ve öğretimi, spor yönetimi ve insan kaynakları gibi spor endüstrisi kapsamındaki alanları etkilemekte üretim ve performans yönünden ülkeler arası bir rekabet ortamı oluşturmaktadır. Bu çalışmada endüstri 4.0’ın sporda kullanım alanları ile ilgili araştırmaların incelenmesi hedeflenmektedir. Bu noktadan hareketle konu bağlamındaki araştırmalar bibliyografik metodla ortaya konmuştur. Sonuç bölümünde ise sporda endüstri 4.0 kullanım alanları tartışılmış, alana olan katkıları ve olumuz etkilerinin değerlendirilmesi yapılmıştır. &nbsp

Recent Trends in Communication Networks

In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges

Coexistence of directional and non-directional technologies in 6G wireless dense networks

Dense networks are characterized by the prevalence of wireless access points (APs) in close proximity to a population of user devices on a similar scale. By increasing AP density, the aggregate data consumption of a system can be dramatically increased. In this dissertation we consider dense deployment of directional visible light APs. Firstly, we analyze the performance of a visible light communication (VLC) link and propose algorithmic methods as well as novel receiver structures to enhance its quality. Secondly, we study handover algorithms and investigate an AP placement strategy that ties to the system outage probability. Thirdly, we use a geometric model for an indoor space and a reference optical channel model to formulate an optimization problem that proposes a dynamic field of view (FOV) receiver with a goal of optimizing receiver FOV for maximum signal to noise ratio (SNR). From the promising results we get, we then propose the dynamic FOV technique with receiver tracking capability. Its results show an average SNR increase of up to 40% when compared to a fixed FOV receiver. These results motivate the adoption of dynamic pointing and adaptive FOV at the receiver in order to realize improved performance for mobile devices in an optical wireless dense network. This opts us to study interference in VLC systems and how to mitigate it using our proposed receivers. In the context of multi-user networks, we formulate two main novel optimization problems i) a joint optimization of transmit emission pattern and transmit power while satisfying illumination requirements and ii) an optimization to allocate users, balance the network load and optimize device FOV for best performance. We then evaluate the effect of self-blockage as well as random human blockers on our proposed receivers. Finally, we propose to deploy the VLC system in a hybrid setting of other technologies to evaluate the overall system performance for future 6G networks.2022-01-17T00:00:00