It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

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A User’s Guide

A key challenge of future mobile communication research is to strike an attractive compromise between wireless network's area spectral efficiency and energy efficiency. This necessitates a clean-slate approach to wireless system design, embracing the rich body of existing knowledge, especially on multiple-input-multiple-ouput (MIMO) technologies. This motivates the proposal of an emerging wireless communications concept conceived for single-radio-frequency (RF) large-scale MIMO communications, which is termed as SM. The concept of SM has established itself as a beneficial transmission paradigm, subsuming numerous members of the MIMO system family. The research of SM has reached sufficient maturity to motivate its comparison to state-of-the-art MIMO communications, as well as to inspire its application to other emerging wireless systems such as relay-aided, cooperative, small-cell, optical wireless, and power-efficient communications. Furthermore, it has received sufficient research attention to be implemented in testbeds, and it holds the promise of stimulating further vigorous interdisciplinary research in the years to come. This tutorial paper is intended to offer a comprehensive state-of-the-art survey on SM-MIMO research, to provide a critical appraisal of its potential advantages, and to promote the discussion of its beneficial application areas and their research challenges leading to the analysis of the technological issues associated with the implementation of SM-MIMO. The paper is concluded with the description of the world's first experimental activities in this vibrant research field.

https://hal-supelec.archives-ouvertes.fr/hal-00840278/document

Spatial Modulation for Generalized MIMO: Challenges, Opportunities, and Implementation

Most recent semi-supervised video object segmentation (VOS) methods rely on fine-tuning deep convolutional neural networks online using the given mask of the first frame or predicted masks of subsequent frames. However, the online fine-tuning process is usually time-consuming, limiting the practical use of such methods. We propose a directional deep embedding and appearance learning (DDEAL) method, which is free of the online fine-tuning process, for fast VOS. First, a global directional matching module, which can be efficiently implemented by parallel convolutional operations, is proposed to learn a semantic pixel-wise embedding as an internal guidance. Second, an effective directional appearance model based statistics is proposed to represent the target and background on a spherical embedding space for VOS. Equipped with the global directional matching module and the directional appearance model learning module, DDEAL learns static cues from the labeled first frame and dynamically updates cues of the subsequent frames for object segmentation. Our method exhibits state-of-the-art VOS performance without using online fine-tuning. Specifically, it achieves a & mean score of 74.8% on DAVIS 2017 dataset and an overall score of 71.3% on the large-scale YouTube-VOS dataset, while retaining a speed of 25 fps with a single NVIDIA TITAN Xp GPU. Furthermore, our faster version runs 31 fps with only a little accuracy loss.

Ieee transactions on neural networks and learning systems

There has been a great deal of material in the area of discrete-time transforms that has been published in recent years. This book does an excellent job of presenting important aspects of such material in a clear manner. The book has 11 chapters and a very useful appendix. Seven of these chapters are essentially devoted to the Fourier series/transform, discrete Fourier transform, fast Fourier transform (FFT), and applications of the FFT in the area of spectral estimation. Chapters 8 through 10 deal with many other discrete-time transforms and algorithms to compute them. Of these transforms, the KarhunenLoeve, the discrete cosine, and the Walsh-Hadamard transform are perhaps the most well-known. A lucid discussion of number theoretic transforms i5 presented in Chapter 11. This reviewer feels that the authors have done a fine job of compiling the pertinent material and presenting it in a concise and clear manner. There are a number of problems at the end of each chapter, an appreciable number of which are challenging. The authors have included a comprehensive set of references at the end of the book. In brief, this book is a valuable contribution to the general areas of signal processing and communications. It can be used for a graduate level course in perhaps two ways. One would be to cover the first seven chapters in great detail. The other would be to cover the whole book by focussing on different topics in a selective manner. This book  by  Elliott  and Rao  is extremely  useful to researchers/engineers who are working  in the areas of signal processing and communications. It i s also an excellent reference book, and hence a valuable addition to one’s library

http://ieeexplore.ieee.org/iel5/5/31347/01457444.pdf

Multirate digital signal processing

A systematic approach to the modelling of multicellular power transistors is presented. It is based on characterisation and identification (modelling) of the elementary cell of the transistor, and modelling of input and output interconnections using the physical mask of the device. This model enables the small-signal performance of heterojunction bipolar transistors (HBT) to be predicted precisely. The obtained multicell model has been validated by comparison of its predictions with experimental measurements on various HBTs having different numbers of elementary cells.

Modelling of multicellular microwave transistors using the scaling approach

Delta-Sigma- Transmitters

Microwave transmitters comprise the cascade of several subsystems. Among these subsystems, the power amplifier (PA) is identified to be the main source of nonlinearity. Thus, modeling and compensating for the transmitter nonlinearity is often trimmed down to the modeling and compensation of the power amplifier's nonlinearity. Such compensation allows for the use of power-efficient and nonlinear PA topologies, which results in reducing the energy consumption and cost of wireless transmitters.



This article gives an overview of the nonlinear PA behavior and the origins of intermodulation distortions in this subsystem. It defines the most used distortion quantification metrics and the different types of distortions. Power amplifier modeling and digital predistortion principles are explained. The procedure and identification steps of digital predistortion are highlighted, and the different models used in digital predistortion technique are covered. Advanced digital predistortion models for linearizing the impairments in multiple-input–multiple-output (MIMO) PAs, dual-band PAs, and quadrature modulators are also covered.


Keywords:

power amplifiers;
digital predistortion;
modeling;
linearization;
nonlinear distortions

Digital Predistortion for Microwave Transmitters

Chapter 8 presents some advanced applications of load-pull and source-pull systems. The major emphasis of this chapter is on multi-tone and modulated load-pull systems and their applications. Subsequently, a six-port based transistor noise characterization system is described. A transistor based mixer’s characterization technique is also presented.

Advanced Configurations and Applications

Direct conversion transceivers are very attractive in wireless communications, due to their simplicity and ease of integration. However, their performances are degraded with radio frequency (RF) impairments. On the other hand, multiple input multiple output (MIMO) wireless communication systems promise higher spectral efficiency than what is possible with single input single output (SISO) wireless communications [1], [2]. However, the significant improvement in wireless system performance using MIMO is achieved by increasing the system complexity, which may result in higher sensitivity and lower performance in practical systems. Therefore, the degradations due to system impairments must be studied to evaluate the realistic behavior of the MIMO systems. Moreover, compensation techniques can be applied by understanding the effects of these impairment factors. These impairments may be noticed as phase noise, DC offset, in-phase / quadrature (I/Q) imbalance, and power amplifier nonlinearity [3]. In this chapter, the impairments due to phase noise, DC offset and I/Q imbalance are analyzed and the different techniques for their prevention and compensation are discussed. The power amplifier nonlinearity effects are investigated in the following chapter.

RF Impairments in MIMO Transceivers

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