Digital Modulation Schemes / Techniques (Essay Sample)

Digital Modulation Schemes
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Table of Contents TOC \o "1-3" \h \z \u Abstract PAGEREF _Toc436044850 \h 31.0 Introduction PAGEREF _Toc436044851 \h 32.0 Change from analog to digital modulation techniques PAGEREF _Toc436044852 \h 43.0 The differences between ASK, FSK and PSK modulation schemes PAGEREF _Toc436044853 \h 44.0 Binary Amplitude Shift Keying (BASK) PAGEREF _Toc436044854 \h 65.0 Binary Frequency Shift Keying (BFSK) PAGEREF _Toc436044855 \h 66.0 Binary Phase Shift Keying (BPSK) PAGEREF _Toc436044856 \h 67.0 Quadrature Phase Shift Keying (QPSK) PAGEREF _Toc436044857 \h 78.0 Comparison of the digital modulation techniques PAGEREF _Toc436044858 \h 79.0 QAM modulation scheme PAGEREF _Toc436044859 \h 810.0 QAM applications PAGEREF _Toc436044860 \h 911.0 Conclusion PAGEREF _Toc436044861 \h 1012.0 References PAGEREF _Toc436044862 \h 1113.0 Appendix PAGEREF _Toc436044863 \h 12
Abstract
A rapid advancement in technology particularly in the 21st century has seen an exponential growth of digital communication marking a major shift from analogue communication system used in the past few decades. Better application techniques develop every single day. In this discussion, the paper discusses the reasons for a shift from analogue to digital modulation schemes, digital modulation schemes techniques, their characteristics and performance. Finally, the paper looks at the comparison between the various digital modulation schemes both theoretically and tabular presentation. The digital modulation schemes discussed here are ASK, FSK and PSK as well as their sub modulation schemes like BPSK, BFSK and QPSK.
Keywords: Analogue, digital modulation, BPSK, BFSK and QPSK
Digital Modulation Schemes
1.0 Introduction
The world today is a global village because communication technology advancement has literally networked every point through the World Wide Web (Frenzel, 2012).Transferring communication signal from one place to another through the web is however a challenge due to signal data spectral jam, corrupted data and signal frequency interference. This situation has led to intense research studies to avail better and convenient means of communication data transfer. This paper looks at digital communication modulation schemes/techniques, a shift from the analogue communication techniques. Communication technology involve audio, video or any form of electronic data transfer through the mobile phones, computers, tablets or any other internet device from one part of the world to another. The aim of modulation improvement is to find immunity to interference such as noise, corrupt data, and broader bandwidth for data passage. Digital modulations techniques like ASK, FSK and PSK together with their sub modulation techniques, offer solutions to some of these problems (Sharma, Mishra &Saxena, 2010). The paper also discusses the characteristics and performance of the various digital modulation techniques and compares their performance.
2.0 Change from analog to digital modulation techniques
Analogue modulation schemes are mainly three, namely; amplitude, Frequency and phase modulation schemes but with sub derivatives (Frenzel, 2012). The main limitation of analog technique is that there is noise along the communication channels because analog systems are very sensitive to noise until the receiving end. Digital signal modulation and transmission is less prone to noise during transmission from the sender to the receiver.
3.0 The differences between ASK, FSK and PSK modulation schemes
The basic form of digital modulation schemes technique are ASK,FSK, and PSK. Modulation is a technique or method of varying certain parameters of periodic waveforms to use the signal to pass information (Sharma, Mishra &Saxena, 2010). High frequency sinusoidal waveform is preferred for transfer of information using signals. A continuous variation of parameter of the input signal carrier, then it is analogue modulation technique while if the variation of the signal parameter is discrete then it is termed as digital modulation technique.
Conversion of analog signal to digital signals provides a combination of different types of digital modulation techniques.Conversion happens by varying different parameters of signal carrier. For instance, amplitude signal variation provides BSK, frequency variation provides BFSK phase variation provides BPSK.Additionally, combinational variation of different parameters yields a hybrid modulation technique like amplitude and phase keying (APSK) is a result a combinational variation.According to (Frenzel, 2012), there are many digital combinational techniques designed based on signal type and application.To attain a discrete signal, the modulation signal should be in NRZ rectangular pulse form to give discrete signal modulated parameter keying between binaryvalues.
Number

Modulation scheme/technique

Type

Notation

1

Digital modulation Schemes/techniques

Amplitude Shift Keying

A.S.K



Frequency Shift keying

F.S.K



Phase Shift keying

P.S.K

2

Sub digital modulation scheme/techniques

Binary Phase Shift Keying

BPSK



Binary Frequency Shift Keying

BFSK



Quadrature Phase shift Keying

QPSK

Table 1: Digital modulation techniques classification (Sharma, Mishra &Saxena, 2010)
4.0 Binary Amplitude Shift Keying (BASK)
The BASK modulation technique is obtained the amplitude of the carrier wave is altered. Being a coherent technique of modulation, there is a concept of correlation between the I&Q components, signal, number of basic functions and symbols (Sharma, Mishra &Saxena, 2010).The authors assert that it is a simple implementation technique with poor bandwidth efficiency and prone to noise interference. Because it only performs well in the linear regions, it is not viable for mobile or wireless communication applications as a digital technique in the current global situation. Combinational variation of this technique gives yield to QAM and Mary ASK, which perform much better because they have many important applications and improved parameters.
5.0 Binary Frequency Shift Keying (BFSK)
BFSK is a product of representing two different symbols using two different frequencies, which can be a wide or narrow band modulation technique, which depends on the separation between any two-carrier frequencies (Frenzel, 2012). Binary technique is cost effective and gives simple implementation procedures but it is not bandwidth efficient modulation technique hence often rejected due to receiver design complications.
6.0 Binary Phase Shift Keying (BPSK)
Phase Shift keying results from altering the phase of the carrier wave pulse and it is the simplest technique of phase modulation also called binary because only two states of the phase represented by the carrier phase (Frenzel, 2012). This technique is suitable for faster transfer of data application, it is simple and robust in implementinggiving an advantage of power compared to BASK. Its limitation is that it is inefficient user of given bandwidth. This technique gives small error ratings than all the other techniques.
7.0 Quadrature Phase Shift Keying (QPSK)
QPSK is an extension derivative of the PSK digital modulation scheme/technique whose phase of the signal carrier divided into four equal spaces for the phase angle(Sharma, Mishra &Saxena, 2010). The division of the phase carrier signal into four makes its information capacity double hence becoming a high bandwidth efficient modulation technique. However, the most important factor to consider in this design is the exact retrieval phase to the receiver for which may lead to erroneous signal detection if ignored. This receiver factor consideration however complicates the design problem, which is solved by pulse shaping carrier-modulated signal used in Root Raised Cosine Pulse design to achieve better performance. Even though performance improves, there is a lost continuous signal envelope property as a disadvantage.
8.0 Comparison of the digital modulation techniques
The BASK technique has simpler and economical implementation requirements (Frenzel, 2012). The technique is less error prone and gives less bandwidth efficiency hence operates more efficiently, only in the linear region thus make it it inefficient technique for wireless communication. Comparatively, BFSK is generally better, and is less error prone but same bandwidth as BASK. BFSK technique has receiver design complications because it needs a matched filer detection hence rarely used in mobile or wireless communication.
BFSK is applicable for high-speed data transfer, and used in satellite communication for its double information capacity, simple implementation, robust and technique(Sharma, Mishra &Saxena, 2010). The most commonly used digital modulation technique is QPSK with a double information capacity to that of BPSK on the same bandwidth. QPSK is a high BW efficient because it requires coherent detection.QPSK is spectrally efficient digital modulation technique because it has a constant modulation envelope thus has several advantages over BPSK.QPSK, has exact phase detection shift, which is an important criterion, though increases the receiver design complications but improvement through pulse shaping by half of co-sinusoidal wave gives better performance with minimum shift keying (MSK) consisting of two CPFSK signals.
9.0 QAM modulation scheme
QAM means Quadrature Amplitude Modulation. This is a type of modulation that is mostly applied in modulating data signals into a carrier for radio communications. QAM has advantages over other forms for example PSK that is why it is widely used. However, most forms of data modulation...