Telecommunications Engineering

The following sections are included:

• Preface
• Acknowledgements
• About the Author
• Contents

This opening chapter introduces readers to the subject matter being discussed, and some fundamental topics which trick many students. In particular, we study:

• An introduction to the engineering discipline, and in particular telecommunications engineering.
• The meaning of telecommunications systems engineering.
• Examples of telecommunications systems.
• Basic transmission parameters, e.g. decibel, noise figure, bit error rate, transmission impairments (attenuation, phase distortion, noise), and quality of service.
• Signals and their basic parameters.

This chapter reviews some fundamental topics in telecommunications and computer networks. Not too long ago, we used different autonomous networks for television, radio, voice communications, and data transfer. In modern times all these single-service networks have converged into a single multimedia or multi-application network, called the Internet. All devices attached to the Internet are more or less computers. Therefore, telecommunications networks have become computer networks, and the distinction between the two has blurred up. Upon completing this chapter readers are expected to understand and apply these foundational topics, and in particular:

• The purposes and types of communications networks.
• Basic computer network components and their purposes.
• OSI/ISO and TCP/IP protocol models and their features.
• Meaning and purpose of protocols, encapsulation and standardisation.
• Types of standards and standards-making organisations.
• Network topologies.
• Basics of network design and Cisco’s network hierarchies.
• Duplexing, i.e. data flow directivity.
• Serial and parallel data transmission.
• Transmission media types

Real life signals, such as voice, video and music/sound, are in analog form. [The words analog (in American English) and analogue (in British English) are synonymous, although analog is more popular in telecommunications.] An analog signal is continuous in both dimensions of time and amplitude. Human senses can also process information only if it is in analog form. However, for many reasons as discussed below, most part of communication systems are digital in the 21st century, and the trend is digital systems. Thus, topics studied in this chapter is needed for every generation of telecommunication systems so long as it uses digital techniques and/or transmission systems. The bridge between the analog and the digital realms of communications signals and systems is provided by digitisation mechanisms. We study some fundamental topics in the digitisation of analog signals, as well as their reconstruction at the receiver. These are fundamental topics in digital communications systems. In particular, we study:

• Sampling and Nyquist sampling theorem.
• Common sampling functions.
• Analog-to-digital signal converter’s components, including quantiser and sampler.
• Signal reconstruction (digital-to-analog conversion).
• Pulse modulation schemes, including PCM used in PSTN/POTS.

Every real-life information source generates signals containing superfluous components which can be discarded without destroying the information that they contain. We want to use minimum resources to process, store, and transfer signals. Therefore, scrapping a signal of all its redundant components is very essential in telecommunications. The art of achieving this objective is called source coding. Indeed, source coding is a type of data compression. We study the two related topics of data compression and source coding in this chapter. In particular, we study:

• The purposes for data compression.
• Run-length encoding
• ASCII and IRA encoding.
• One’s and two’s complement number representations.
• Gray coding.
• Huffman coding.
• Shannon-Fano data compression algorithm.
• Shannon-Fano-Elias data compression algorithm.
• Arithmetic encoding.
• Lempel-Ziv-Welch (LZW) algorithms.
• Speech and audio compression schemes: differential pulse code modulation (DPCM), linear prediction code (LPC), code excited linear prediction (CELP), algebraic CELP (ACELP), and adaptive multirate (AMR) coding.

The storage, processing and transmission systems used in communication systems are not ideal and thus usually introduce errors into the signal or data that they handle. The errors are caused by the variations in their quality over time and space. This may be counteracted using link adaptation. Another cause of errors is random receiver noise and interference, which do not lend themselves to link adaptation. Effective and efficient communications therefore requires mechanisms to convert erroneous transmission systems into error-free transmission systems in the ideal case. We study the mechanisms used to control errors in communications systems in this chapter. Another name for error control is channel coding. The idea is to add redundant bits to the original data at data source and exploit the redundancy to correct errors at the receiver.

In order to reduce the length of each chapter and also provide an in-depth treatment of error-control coding, the topic has been divided into two consecutive chapters: Channel Coding for Error Control: Part I and Channel Coding for Error Control: Part II. Error control schemes can be divided into backward-error control (BEC) and forward-error control (FEC). This first part treats the fundamental principles in error control and BEC schemes in an in-depth manner, in particular:

• The basis of error control coding.
• Classification of error control coding schemes, including the differentiation between backward-error correction (BEC) and forward-error correction (FEC) techniques, and between block-error and bit-level FEC schemes.
• TCP/IP and ISO/OSI layers hosting which error control coding type.
• Discuss some applications of polynomials for error control in telecommunications systems.
• We explore several traditional and state-of-the-art backward-error control techniques, including parity codes, cyclic redundancy check and all variants of automatic repeat request schemes.

The storage, processing and transmission systems used in communication systems are not ideal and thus usually introduce errors into the signal or data that they handle. The errors are caused by the variations in their quality over time and space. This may be counteracted using link adaptation. Another cause of errors is random receiver noise and interference, which do not lend themselves to link adaptation. Effective and efficient communications therefore requires mechanisms to convert erroneous transmission systems into error-free transmission systems in the ideal case. We study the mechanisms used to correct errors in communications systems at the data receiver in this chapter. This chapter is the second chapter on error control. Beginners in the field are advised to first study the previous chapter before this one for a better accessibility of the topics. This chapter focuses on forward-error control in communications systems, going considerably in-depth on:

• Repetition codes
• Golay codes and Hamming codes
• Hadamard matrices and Hadamard codes
• Reed-Muller codes and Reed-Solomon codes
• Convolutional codes
• Turbo codes
• Low-density parity-check codes (LDPC) and
• Polar codes.

Thus, we explore all the popular state-of-the-art error correction coding schemes.

A secure computing resource is one which is dependable or available to use by its authorised users when needed, and functions as expected. A system has privacy if the data it stores, processes and/or transmits cannot be accessed by unauthorised users or processes. The process of systematically scrambling text into a jumbled mess with random characters is referred to as encryption. The reverse process of retrieving the original text from the scrambled text is called decryption. Cryptography is the application of mathematics (i.e. number theory and probability) to develop algorithms to encrypt and decrypt data so that they can be processed, stored and/or transmitted over insecure computing systems used by untrusted people securely and privately. Despite all the efforts, the likelihood of a security hole in even a small computer system is almost 100%. Fortunately, the likelihood of a cryptanalyst discovering the the vulnerability is almost 0%. Usually, the network administrator looks for vulnerabilities and fixes them, while hackers seek to find them and break into. This is referred to as the battle of wits. This chapter discusses security and privacy in communications and computing systems and services, including some of the algorithms used to achieve them. In particular, we study:

• An introduction to communications and computing security and privacy.
• Computer security software and their vendors, as well as popular industry certifications in computer security.
• Hash functions and hash algorithms used in cryptography.
• State-of-the-art cryptographic algorithms, including both block and stream encryption and decryption algorithms.

Modulation is the process of piggybacking an information-bearing signal over another signal to achieve effective transfer between two locations. Every transmission medium or channel has some undesirable filtering effects on signals, such as blocking of parts of signal, interference, noise, attenuation and distortion. Modulation is used to condition a signal to suit the characteristics of the channel. The reverse process of modulation is called demodulation. Both modulation and demodulation (aka modem) are ISO/OSI Layer 1 (i.e., physical layer) techniques. Information transfer over communications networks cannot work without modem. For this reason, the understanding of the basic principles and practice of modem schemes is fundamental in the communications disciplines. This chapter presents a wide-scope treatment of modulation techniques, and topics treated include:

• Basic principles and practical applications of modulation methods.
• Analog and digital modulation methods.
• Carrier and carrierless modulation methods.
• Baseband modulation methods and broadband modulation methods.
• Trellis-coded modulation (TCM), integrating error control and modulation.
• Performance metrics of modulation schemes, e.g., bit error rate, bandwidth efficiency and power efficiency.
• Modulation schemes for LTE-A/4G and 5G mobile systems.
• M-ary single-carrier modulation methods (e.g., M-PSK, M-QAM).

Both multiplexing and multiple access methods have a three-fold purpose: allowing multiple users to share finite communications resources equitably and efficiently with acceptable mutual disturbance. The main resource shared is the transmission medium, which has a few degrees of freedom, such as space, frequency, spreading code, time, and power. This chapter explores multiplexing and multiple access principles and practice, including:

• The need for multiplexing and multiple access schemes, and how these two techniques differ from each other.
• Classification of multi-access schemes into orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA), and case studies of each type.
• Treatment of all fundamental multiplexing schemes, including FDM, TDM, CDM, WDM, and OFDM.
• Treatment of all fundamental orthogonal multiple access schemes, including FDMA, TDMA, CDMA, WDMA, and OFDMA.
• Principles of NOMA and study of some popular NOMA schemes, e.g., LDS, LDS-OFDM, PDMA, MUSA, and SCMA.

The largest scale of multiplexing, specifically, frequency division multiplexing (FDM), is the division of the radio frequency spectrum and the consequential allocation of each portion to a specific set of wireless communications technologies, such as 3-30 kHz band for maritime communications, 3-30 GHz for satellite and Wi-Fi, and 87.5-108 MHz for FM radio.

Baseband transmission systems transfer digital signals in the form of a train of pulses. Signals transferred in baseband systems are not moved from their original frequency bands as no sinusoidal carrier modulation is used. As there is no frequency shifting in baseband systems, only one signal occupies the entire bandwidth of the system at a time. Any remaining bandwidth is therefore wasted. However, multiple signals transferred in baseband can share a transmission medium using time-division multiplexing. A popular application of baseband transmission is in Ethernet-based wired local area networks.

This chapter presents an in-depth treatment of the principles underpinning baseband data transmission. Topics studied include:

• Basis of baseband transmission, including the fundamental laws.
• Line coding and its applications, e.g., in IEEE 802.3-based LANs.
• Binary and multi-amplitude pulse amplitude modulation (PAM).
• Inter-symbol interference (ISI), its causes and mitigation mechanisms, including equalisation and pulse shaping filtering.
• Eye diagrams and their importance in data transmission.
• Design of Nyquist pulses and Nyquist rate-achieving pulses.
• Design of equalisers, including zero-forcing and MMSE equalisers.
• Design of optimum receivers, including matched filters and correlators.
• Maximum a posteriori probability (MAP) detector, maximum likelihood estimation (MLE) of symbols, and RAKE receiver.

Reliability engineering is important in system design as there are various uncertainties in product development. In engineering designs and assets reliability engineering seeks to maximise reliability and availability, avoid or at least reduce risks and maximise value, all at lowest possible cost. Reliability engineering enables engineers to keep track of system or device failure factors. Factors affecting the reliability of telecommunications systems include user behaviour, operating conditions, business processes, and decision criteria. This chapter provides an introduction to system reliability engineering. Upon completing this chapter readers are expected to have acquired a good introductory knowledge in the application of reliability engineering in telecommunications systems, and in particular:

• System lifecycle reliability models and curves, including the bathtub curve.
• Common measures of system reliability, including MTBF, MTTF, MTTR, MTBM, FIT and availability.
• Common reliability and failure probability distributions.
• Strategies used to improve system reliability, including maintenance and redundancy. Various types of redundancies and maintenance are discussed.
• Reliability standards and prediction tools.

This chapter considers the principles used for the systematic economic evaluations of the different alternatives that are available to solve a given telecommunications engineering problem. Interesting factors on alternative solutions are expressed in economic terms to enable proper comparison and choice-making. Upon completing this chapter readers are expected to know the basic principles in economics and/or accounting used for the economic evaluations of telecommunications infrastructure, and in particular:

• Basic economic principles applied in telecommunications engineering.
• Market structures as they affect telecommunications products and services.
• Telecommunications infrastructure lifecycle costs.
• Time value of money.
• Analysis of capital expenditure in telecommunications infrastructure, including PWA, FWA, AWA, rate of return (RoR), break-even analysis, payback analysis.
• Depreciation and infrastructure replacement.

Three types of budgets are necessary in microwave link design. These are link/power budget, height budget, and economic budget. We have discussed all these three budgets in the ensuing sections.

The load carried on a telecommunication network is called traffic. Telecommunications traffic engineering, aka teletraffic engineering, is a set of techniques used to dynamically optimise the performance of the network through the prediction, analysis, and regulation of the behavior of the traffic transported by the network. A telecommunication network must support two types of traffic: signalling traffic and user traffic. Service providers raise revenue from user traffic and thus we refer to it as payload. Signalling traffic in data networks usually occurs in the form of packet header field. The header of IP packet in the Internet is akin to the in-band signalling in PSTN. We use traffic engineering to determine how much traffic a given telecommunication network can support at a given service quality and network performance. This chapter discusses the fundamentals of traffic engineering, and in particular, we study:

• PSTN as the origin of teletraffic engineering.
• Definition and calculation of basic teletraffic parameters, e.g. busy hour, grade of service, service levels, and traffic intensity.
• Importance of traffic modelling in traffic engineering, and study a sample of traffic models used in modern networks.
• Basics of queueing theory and its application in traffic engineering, and Kendall’s notation.
• Network dimensioning or capacity planning using Erlang-B and Erlang-C formulas.
• Technologies used to transport telecommunications traffic, including xDSL, SONET/SDH, DWDM, OTN, and T-SDN.

This chapter summarises some of the mathematics topics that are applied in the succeeding topics. As this is not a mathematics textbook we skip much of the theoretical details. The idea is to make the book somewhat self-contained.

The following sections are included:

• Bibliography
• Index