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Lecture Wireless and mobile computing – Chapter 3: Wireless and mobile computing transmission fundamentals

Chapter 3: Wireless and mobile computing transmission fundamentals. The following will be discussed in this chapter: Signals for conveying information, analog and digital data transmission, channel capacity. | Wireless and Mobile Computing Transmission Fundamentals Lecture 3 Overview Signals for Conveying Information Relationship between Data Rate and Bandwidth Analog and Digital Data Transmission Analog and Digital Data Analog and Digital Signaling Analog and Digital Transmission Channel Capacity Nyquist Bandwidth Shannon Capacity Formula 1 1 Data Rate and Bandwidth There is a direct relationship between data rate and bandwidth. The greater the bandwidth, the higher the information-carrying capacity. 2 2 Data and Computer Communications, Ninth Edition by William Stallings, (c) Pearson Education - Prentice Hall, 2011 Suppose that we let a positive pulse represent binary 0 and a negative pulse represent binary 1. Then the waveform represents the binary stream 0101. . . . The duration of each pulse is 1/(2f); thus the data rate is 2f bits per second (bps). What are the frequency components of this signal By adding together sine waves at frequencies f and 3f, we get a waveform that begins to resemble the square wave. 3 Square wave Data Rate and Bandwidth cont. Data Rate and Bandwidth cont. Let us continue this process by adding a sine wave of frequency 5f, and then adding a sine wave of frequency 7f, as shown in fig. Additional odd multiples of f are added, suitably scaled, the resulting waveform approaches that of a square wave more and more closely. Frequency components of the square wave with amplitudes A and -A can be expressed as follows: 4 Data Rate and Bandwidth cont. This waveform has an infinite number of frequency components and hence an infinite bandwidth. However, the peak amplitude of the kth frequency component, kf, is only 1/k, so most of the energy in this waveform is in the first few frequency components. What happens if we limit the bandwidth to just the first three frequency components? We have already seen the answer, in Figure a. As we can see, the shape of the resulting waveform is reasonably close to that of the original square wave. 5 Data . | Wireless and Mobile Computing Transmission Fundamentals Lecture 3 Overview Signals for Conveying Information Relationship between Data Rate and Bandwidth Analog and Digital Data Transmission Analog and Digital Data Analog and Digital Signaling Analog and Digital Transmission Channel Capacity Nyquist Bandwidth Shannon Capacity Formula 1 1 Data Rate and Bandwidth There is a direct relationship between data rate and bandwidth. The greater the bandwidth, the higher the information-carrying capacity. 2 2 Data and Computer Communications, Ninth Edition by William Stallings, (c) Pearson Education - Prentice Hall, 2011 Suppose that we let a positive pulse represent binary 0 and a negative pulse represent binary 1. Then the waveform represents the binary stream 0101. . . . The duration of each pulse is 1/(2f); thus the data rate is 2f bits per second (bps). What are the frequency components of this signal By adding together sine waves at frequencies f and 3f, we get a waveform that begins to