Receiver Side Signal Processing for Nonlinear Distortion Compensation in 5G AND Beyond

Trading between transmit waveform quality and power efficiency is one of the most challenging issues in radio transmitter implementation. To this end, digital predistortion is the de-facto solution for mitigating power amplifier (PA) nonlinear distortion in cellular base-stations due to its high flexibility and good linearization performance. Theoretically, it is convenient to describe predistorter (PD) transfer function as the mathematical inverse of the PA transfer function, and PD modeling is often performed through parametric methods. Thus, an additional feedback loop is required in the system for PD model parameter estimation. PA is an analog device and DPD is a part of digital front-end, implying that PA output signal is needed to be downconverted to baseband and sampled in the parameter estimation path. Consequently, it is required to employ additional components in the feedback loop such as attenuator, downconverter, and analog-to-digital converter (ADC). In order to be able to capture higher order nonlinearities, it is necessary to perform upsampling operation, which implies that in addition to digital-to-analog converters (DACs) in the forward loop, the components in the feedback loop should support higher bandwidths than the original transmission bandwidth. Additionally, to have a good linearization performance, a high resolution ADC is required. Having an ADC/DAC that supports wide bandwidth and has high resolution is directly increasing the material cost and power consumption. When future millimeter-wave (mmWave) systems are considered, adopting DPD becomes even more complex and costly due to wider waveform bandwidths and employing active antenna arrays. Alternative to DPD, receiver based approaches, referred to as digital post-distortion (DPoD), can be utilized to mitigate the nonlinear effects of transmitter PA. Naturally, receiver side techniques do not provide any improvement in terms of out-of-band (OOB) emission issues, rather they aim to improve received signal error vector magnitude (EVM). As the radiated power at mmWave is typically EVM limited and OOB emission requirements are relaxed compared to sub-6 GHz band, DPoD can offer means for improved network energy-efficiency. Several iterative DPoD methods are proposed in the literature such as power amplifier nonlinearity cancellation (PANC), and reconstruction of distorted signals (RODS). In this thesis, we present a non-iterative computationally efficient receiver side nonlinearity mitigation technique, referred to as digital post-inverse (DPoI), along with the parameter estimation approach targeting existing 5G NR standard-compliant reference signal. The receiver EVM performance of presented approach is analyzed by using computer simulations. It is seen that DPoI can reach similar or improved performance compared to the iterative PANC method, which is chosen as a reference DPoD method. Moreover, it is shown that both DPoD methods overperform ideally linearized transmitter PA under strong nonlinear conditions, which allows higher power efficiency when receiver side techniques are employed

Cellular Digital Post-Distortion : Signal Processing Methods and RF Measurements

In this paper, we study the feasibility of digital post-distortion (DPoD) based mitigation of transmitter nonlinear distortion in cellular networks. With specific emphasis on downlink, we describe a computationally efficient one-shot method to estimate and mitigate the cascaded multipath channel and transmitter nonlinear distortion effects at terminal receiver, building on demodulation reference symbols (DMRSs). We also describe a DMRS boosting approach to match the envelope characteristics of the DMRS and the actual data-bearing multicarrier symbols such that accurate mitigation is feasible. We provide RF measurement results with a state-of-the-art 28 GHz active antenna array and 256-QAM data modulation, demonstrating larger performance enhancements in received signal error vector magnitude (EVM) compared to existing computationally expensive iterative methods.Peer reviewe

Design Considerations of Dedicated and Aerial 5G Networks for Enhanced Positioning Services

Dedicated and aerial fifth generation (5G) networks, here called 5G overlay networks, are envisaged to enhance existing positioning services, when combined with global navigation satellite systems (GNSS) and other sensors. There is a need for accurate and timely positioning in safety-critical automotive and aerial applications, such as advanced warning systems or in urban air mobility (UAM). Today, these high-accuracy demands can partially be satisfied by GNSS, though not in dense urban conditions or under GNSS threats (e.g. interference, jamming or spoofing). Temporary and on-demand 5G network deployments using ground and flying base stations (BSs) are indeed a novel solution to exploit hybrid GNSS, 5G and sensor algorithms for the provision of accurate three-dimensional (3D) position and motion information, especially for challenging urban and suburban scenarios. Thus, this paper first analyzes the positioning technologies available, including signals, positioning methods, algorithms and architectures. Then, design considerations of 5G overlay networks are discussed, by including simulation results on the 5G signal bandwidth, antenna array and network deployment.Peer reviewe

The influence of TV to preschool children social relations and parents approaches to this subject

This study aim to social relations of the influence TV preschool children, television viewing habits and approaches on the issue of families. Study includes a total of 747 people and half of this number 4-5 year old children from public preschool and the other half of the parents of these children. This study were Adana province located in southern Turkey. The "Social Relationship Sub-Dimension of Behavior Grading Scale" was used to evaluate the behavioral development of children, while the "General Information Form" was used to obtain certain information about children and their families. Mother's age and education level were effected on children score form social relationship. Also, children of parent setting rules on TV watching time and program qualification. Furthermore, 47 % of children spend 1-2 hours with TV, 82,7 % of children prefer childrens' programme or cartoon of the finding were obtained

Cor Triatriatum with Ankylosing SpondylitisAnkilozan

Cor triatriatum is a rare congenital defect that one of the atrial chambers especially left atrium, is divided into two by a fibromuscular membranee. Ankylosing spondylitis is a chronic systemic inflammatory rheumatic disorder that cardiovascular involvement can be seen. 27-year-old woman, who has been followed for ankylosings pondylitis searched for cardiac involvement, Cor triatriatum was diagnosed with echocardiography and diagnosis was confirmed with MRI and CT angiography. Membrane was resected surgically under cardiopulmonary bypass with cardioplegic arrest. Patient was discharged from the hospital with recovery. In conclusion, patient with ankylosing spondylitis must be searched for cardiac involvement

Penetrating cardiac injuries

BACKGROUN

On-pump beating heart mitral valve surgery without cross-clamping the aorta

Background and Aim: Cardiac reperfusion injury is a well-described complication occurring after ischemia or following cardioplegic arrest. Various strategies have been developed to prevent ischemic reperfusion injury. The aim of this study was to assess the efficacy and applicability of the on-pump beating heart mitral valve surgery without cross-clamping the aorta in order to prevent reperfusion injury. Methods: The prospective study (between April 2005 and December 2006) included 88 consecutive patients who underwent mitral valve surgery. The operations were carried out on a beating heart using normothermic cardiopulmonary bypass without cross-clamping the aorta, therefore perfusing the heart antegradely through the aortic root. Venting the heart from the aorta and the pulmonary vein provided adequate visualization of the operative field. Results: Seventy-eight patients (88.6%) underwent mitral valve replacement and 10 patients (11.3%) underwent mitral valve repair with this technique. Concomitant surgery was required in 29 patients (32.9%). Twenty-five patients (28.4%) had also undergone previous open heart surgery. Mean cardiopulmonary bypass time was 57.4 +/- 18.4 minutes. Mean duration of ventilation was 12.2 +/- 3.5 hours, mean intensive care unit stay was 1.3 +/- 1.6 days, and mean hospital stay was 6.9 +/- 4.5 days. One-year survival was 96.6% for all causes of mortality. Conclusions: In this study, we showed that on-pump beating heart operations without cross-clamping is an acceptable surgical choice for mitral valve disease. Complication rates are low and perioperative mortality is lower than that generally reported with conventional technique