Preface

This book presents information on modulation and examines methods for improving the deployment and technical characteristics of wireless communication systems and networks.

Chapter 1 shows that low-energy transmitters with adaptive amplitude modulation (AM) may transmit narrowband signals without coding in real time and with spectral–energy efficiency, attaining the limits established by Shannon's theorems. The only requirement is high-quality feedback channels delivering controls from base stations to the forward transmitter.

Chapter 2 presents an original and low-complexity method for fast and accurate analysis and demodulation of orthogonal frequency-division multiplexing (OFDM) signals with unknown structure and parameters in conditions of uncertainty and noise. The focus is on identifying the type of modulation and parameters of the subcarrier as well as eliminating inter-channel interference and phase errors.

Chapter 3 presents research on the capabilities and advantages of electro-optic lithium niobate (LiNbO3) modulators for optical communications. It discusses methods of fiber integration, connection to microwave electrodes, box sealing, and fabrication for on-chip implementation. In addition, it presents results of interferometric optical sensing via an electro-optic manipulating light field.

Chapter 4 considers possibilities of using polarization of radio frequency (RF) signals and propagation direction as additional carriers of information. Attention is paid to the most important aspects of the proposed modulation schemes: polarization-agile antennas and active integrated array antennas, which integrate an oscillator and modulators, and polarization discrimination antennas. The chapter also introduces receiving antennas.

Chapter 5 discusses the main optical phase-modulation techniques, and the most appropriate technique is used for the elaboration of original phase modulation processes for the optical Sagnac interferometer gyroscope. It is shown that closed-loop configuration of gyroscope provides a greater accuracy (sensitivity to declinations) and scale-factor stability than the open-loop analog.

Chapter 6 presents the results of studies on the analysis and design of injected oscillators generating carrier signals. New results concern the analytical methods of locking and pulling phenomena. The chapter also reviews the application of injected oscillators, in particular, injection-locked frequency dividers. It also proposes an original method of enhancing locking range.

The final chapter contains a review of dual-band, multiband, and ultra-wideband antennas. The review classifies and compares antennas according to antenna feeding and loading of antennas using slots, notch, and coplanar structures. It also discusses the basic geometry of patch antennas along with their equivalent circuit diagram and particularities of their applications.

> **Anatoliy Platonov, DSc, PhD.** Professor, Institute of Electronic Systems Warsaw, Warsaw University of Technology, Poland

**Chapter 1**

**Abstract**

communications.

Shannon's limits

**1. Introduction**

*Anatoliy Platonov*

Perfect Signal Transmission Using

Adaptive Modulation and Feedback

The research results show that adaptive adjusting of modulators over feedback enables development of the "perfect" communication system (CS) transmitting analog and digital signals in real-time without coding with a bit rate equal to the forward channel capacity and limit energy spectral efficiency. These and other feasibilities unattainable for known CS are the result of transition from the direct transmission of samples of the input signal to the transmission of sequences of their estimation errors cyclically formed at the input of forward transmitter (FT) modulator. Each transmitted error is formed as a difference between the value of input sample and its current estimate computed in the receiver in previous cycle and delivered to FT over feedback. Growing accuracy of estimates decreases estimation errors and permits their transmission permanently increasing the modulation index and maximizing the amount of information delivered to the receiver. Unlike CS with coding, adaptive feedback CS (AFCS) can be optimized using Bayesian estimation and information theory. Absence of coders simplifies the construction of FT and reduces their energy consumption and cost. Moreover, adaptive properties of AFCS permit to maintain the perfect mode of transmission in every scenario of application. The chapter presents analytical backgrounds, experiments results and research genesis including the reasons for absence of AFCS in modern

**Keywords:** wireless, adaptive modulation, feedback, Bayesian optimization, perfect transmission, limit energy-spectral efficiency, channel capacity,

The publication of Shannon's fundamental works [1, 2] coincided with the appearance of the first computers and urgent need for the development of fast and reliable channels for digital data transmission. Shannon's theory led to the almost immediate development of backgrounds of the coding and digital CS theory. The parallel fast development of high-resolution AD-DA converters and digital technol-

The side effect of the successes of digital CS was initial lack of interest in CS with feedback channels (FCS) and codeless signals transmission, although this possibility was noted by Shannon in [1, 2]. The first work of Elias [3] in this direction was published seven years later, in 1956. The results of the work showed that ideal feedback channel and proper setting of the modulation gains permit to transmit

ogies made digitizing and coding the basic principle of signal transmission.

### **Chapter 1**
