Chapter 6 - Physical layer. In this chapter, we study the duties of the physical layer, first as a converter that converts data to signals, then as a manager that controls the medium. After reading this chapter, the reader should be able to: Distinguish between analog and digital data, distinguish between analog and digital signals, understand the concept of bandwidth and the relationship between bandwidth and data transmission speed,. | Chapter 6 Physical Layer Distinguish between analog and digital data. Distinguish between analog and digital signals. Understand the concept of bandwidth and the relationship between bandwidth and data transmission speed. Understand digital-to-digital, digital-to-analog, and analog-to- digital encoding. After reading this chapter, the reader should be able to: OBJECTIVES Understand multiplexing and the difference between a link and a channel. DIGITAL AND ANALOG Figure 6-1 Digital and analog entities Figure 6-2 Digital data Figure 6-3 Analog data Figure 6-4 Digital signal Figure 6-5 Bit and bit interval Technical Focus: Units of Bit Rate 1 bps 1 kbps = 1000 bps 1 Mbps = 1,000,000 bps 1 Gbps = 1,000,000,000 bps 1 Tbps = 1,000,000,000,000 bps Figure 6-6 A sine wave Figure 6-7 Amplitude Figure 6-8 Period and frequency Technical Focus: Units of Frequency 1 Hz 1 kHz = 1000 Hz 1 MHz = 1,000,000 Hz 1 GHz = 1,000,000,000 Hz 1 THz = 1,000,000,000,000 Hz Technical Focus: Frequency and . | Chapter 6 Physical Layer Distinguish between analog and digital data. Distinguish between analog and digital signals. Understand the concept of bandwidth and the relationship between bandwidth and data transmission speed. Understand digital-to-digital, digital-to-analog, and analog-to- digital encoding. After reading this chapter, the reader should be able to: OBJECTIVES Understand multiplexing and the difference between a link and a channel. DIGITAL AND ANALOG Figure 6-1 Digital and analog entities Figure 6-2 Digital data Figure 6-3 Analog data Figure 6-4 Digital signal Figure 6-5 Bit and bit interval Technical Focus: Units of Bit Rate 1 bps 1 kbps = 1000 bps 1 Mbps = 1,000,000 bps 1 Gbps = 1,000,000,000 bps 1 Tbps = 1,000,000,000,000 bps Figure 6-6 A sine wave Figure 6-7 Amplitude Figure 6-8 Period and frequency Technical Focus: Units of Frequency 1 Hz 1 kHz = 1000 Hz 1 MHz = 1,000,000 Hz 1 GHz = 1,000,000,000 Hz 1 THz = 1,000,000,000,000 Hz Technical Focus: Frequency and Change The concept of frequency is similar to the concept of change. If a signal (or data) is changing rapidly, its frequency is higher. If it changes slowly, its frequency is lower. When a signal changes 10 times per second, its frequency is 10 Hz; when a signal changes 1000 times per second, its frequency is 1000 Hz. Figure 6-9 Phase Zero frequency and infinite frequency Figure 6-10 Phase describes the position of a waveform relative to other waveforms. Note: Business Focus: Two Familiar Signals A familiar signal in our daily lives is the electrical energy we use at home and at work. The signal we receive from the power company has an amplitude of 120 V and a frequency of 60 Hz (a simple analog signal). Another signal familiar to us is the power we get from a battery. It is an analog signal with an amplitude of 6 V (or 12 or 24) and a frequency of zero. Business Focus: The Bandwidth of Telephone Lines The conventional line that connects a home or business to the telephone office .
