Preface

This book examines the concept of multiplexing through the lens of telecommunication electronics, digital signal processing, and robotics. Topics highlighted include multiple-input and multiple-output (MIMO) and 5G-related applications. It is fascinating to learn that the basic idea of multiplexing, which dates back to the time of telegraph systems, is still very valuable today and is, in fact, the basis for multicarrier systems such as Long-Term Evolution (LTE) communication, 5G technologies, optic systems, and the Internet of Things (IoT), among many others. However, it should be noted that multiplexing is not limited to only these areas, but is widely used in many fields. Multiplexing is mainly used to share resources and enable simultaneous processes, and these processes and resources may vary from one field to another.

To start, this work presents a brief history of multiplexing, including relevant definitions and an overview of the components used in multiplexing systems. Then, it goes on to discuss some of the most practical applications of multiplexing, such as Multiple-Input, Multiple-Output Orthogonal Frequency-Division Multiplexing (MIMO-OFDM), Direct-Sequence Optical Code-Division Multiple-Access (DS-OCDMA) systems, and optical multiplexing.

I want to thank my parents, Mrs. Shahin Mohammady and Mr. MohammadAli Mohammady, my husband, Dr. Pooria Varahram, and my children, Daniel and Denise, for all their compassion, consideration, and help.

I also want to thank my supervisors, Prof. Ronan Farrell and Dr. John Dooley, and my colleagues Joanna O'Grady, James Kinsella, and all members of the Department of Electronic Engineering at Maynooth University, for all their care, support, kindness, forgiveness, guidance, and advice.

This publication is a result of research conducted with the financial support of Science Foundation Ireland (SFI) and is co-funded under the European Regional Development Fund under Grant Number 13/RC/2077.

> **Somayeh Mohammady** National University of Ireland Maynooth, Ireland

**1**

Section 1

Introduction

Section 1 Introduction

**3**

**Chapter 1**

Introductory Chapter:

*Somayeh Mohammady and Pooria Varahram*

**1. Definition of multiplexing**

plexing on his dictionary book [1] as:

**2. Short history of multiplexing**

Multiplexing History - How It

Applies to Current Technologies

It is fascinating to know that the multiplexing can be employed and defined from different points of views and different disciplines. For example, Dr. E. Julius Dasch, former manager of the NASA National Space Grant Program, defines multi-

*…the simultaneous transmission of different data from a spacecraft using a single channel. The data stream is separated into frames that carry codes for different information, such as temperatures, pressures, and the state of on-board computers.*

In a media and communication dictionary book [2], multiplexing is mentioned as:

*Digital television transmission allows for multiplexing, whereby multiple channels* 

*…the process of combining multiple messages simultaneously on the same physical or logical transmission medium. There are two main types: time division multiplexing* 

The list continues for the Internet, optic engineering, graphics, phytography,

The history of multiplexing goes back to the 1800s, when Samuel Morse developed his telegraph system which enabled long-distance communications [4]. Later in 1874, Thomas Edison invented diplexing to transmit two individual messages over one line at the same time [5]. Later in 1894 and the 1930s, time-division multiplexing (TDM) and frequency division multiplexing (FDM) came into existence [6, 7].

One of the expectations about 5G technologies is to support enormous capacity, approximately 1000 times devices per squared kilometer [8]. In order to satisfy this

*are bundled together and sent simultaneously in a single stream of data.*

*(TDM) and frequency division multiplexing (FDM).*

laser and photonics geology, earth sciences, and many more.

**3. Application of multiplexing in current technology**

In a computer science dictionary book [3], multiplexing is described as:
