Saleh Faruque

Phase Shift Keying (PSK)

In phase shift keying (PSK), the phase of the carrier changes in discrete levels in accordance with the input digital signal, while the amplitude of the carrier remains the same. In this chapter, the PSK modulation will be presented, along with the respective spectrum and bandwidth. These materials have been augmented by diagrams and associated waveforms to make them easier for readers to grasp.

Free Space Propagation

Electromagnetic waves differ in energy according to their wavelength. Their ability to propagate is also different in different propagation environments. In free space (vacuum) they are characterized by their ability to propagate without obstruction and without atmospheric effects. The path loss under these conditions is said to be free space path loss.

Time Division Multiple Access (TDMA)

Time division multiple access (TDMA) is a method of transmitting and receiving multiple independent signals over a single transmission channel. The TDMA at the transmit side, known as the multiplexer, assigns multiple channels in preassigned time slots. The TDMA at the receive side, known as the de-multiplexer, separates the incoming composite signal into parallel streams. Both multiplexer and de-multiplexer are synchronized by a common clock to receive data in accordance with the transmit sequence. This chapter presents the key concepts, underlying principles and practical applications of TDMA used in land-mobile telecommunication systems.

Orthogonal Frequency Division Multiple Access (OFDMA)

This chapter presents a brief overview of the OFDMA technique used in 4G WiMAX (Worldwide Interoperability for Microwave Access) and 4G LTE (Long-Term Evolution) cellular system. It is shown that OFDMA is an extension of FDMA, where each frequency band is placed at the null of the adjacent frequency band. This is governed by the well-known “Fourier transform,” so that adjacent frequency bands are orthogonal to each other. OFDMA is a full-duplex communication system. The communication link is maintained in both directions in the time domain known as time division duplex (TDD). Numerous illustrations are used to bring students up to date in key concepts, underlying principles, and practical applications of “Fourier transform,” spectrum, and orthogonal properties of spectrum, leading to OFDMA. Construction of OFDMA channels from the FCC-allocated band is presented to illustrate the concept.

Code Division Multiple Access (CDMA)

This chapter presents a brief overview of spread spectrum technique and shows how it relates to CDMA technology. Orthogonal codes and their properties are presented and show how orthogonal codes are generated and used to design CDMA radio. It is shown that CDMA capacity directly relates to code length.

Frequency Division Multiple Access (FDMA)

FDMA (frequency division multiple access) is the oldest communication technique used in broadcasting, land-mobile two-way radio, etc. It begins with a band of frequencies, which is allocated by the FCC (Federal Communications Commission). This band of frequency is further divided into several narrow bands of frequencies, where each frequency, also known as channel, is used for full-duplex communication. The communication link is maintained in both directions, either in the frequency domain or in the time domain. This is governed by two basic modes of operations known as the Frequency Division Duplex (FDD) and Time Division Duplex (TDD). These topics, along with FDMA spectrum management and its attributes, are presented in this chapter.

Introduction to Modulation

Modulation is a technique that changes the characteristics of the carrier frequency in accordance with the input signal. Figure 1.1 shows the conceptual block diagram of a modern wireless communication system, where the modulation block is shown in the inset of the dotted block. As shown in the figure, modulation is performed at the transmit side and demodulation is performed at the receive side. This is the final stage of any radio communication system.

Frequency Shift Keying (FSK)

In frequency shift keying (FSK), the frequency of the carrier changes in discrete levels in accordance with the input digital signal, while the amplitude of the carrier remains the same. In this chapter, the FSK modulation will be presented along with the respective spectrum and bandwidth. These materials have been augmented by diagrams and associated waveforms to make them easier for readers to grasp.

Amplitude Shift Keying (ASK)

In amplitude shift keying (ASK), the amplitude of the carrier changes in discrete levels in accordance with the input digital signal, while the frequency of the carrier remains the same. In this chapter, the ASK modulation is presented along with the respective spectrum and bandwidth. These materials have been augmented by diagrams and associated waveforms to make them easier for readers to grasp.

Frequency Modulation (FM)

In Frequency Modulation (FM), the frequency of the carrier changes in accordance with the input analog signal, while the amplitude of the carrier remains the same. The modulated carrier contains several spectral components, requiring frequency domain analysis. The key concept and the underlying principle of FM and FM bandwidth dilemma are presented with numerous illustrations to make them easier for readers to grasp.