Chapter 3: Data and Signals PDF

DATA AND SIGNALS The communication between two devices occurs across five different layers: ________, ________, ________, ________, and ________. Answer: Application, Transport, Network, Data-Link, Physical Logical communication takes place at the ________, ________, ________...

DATA AND SIGNALS The communication between two devices occurs across five different layers: ________, ________, ________, ________, and ________. Answer: Application, Transport, Network, Data-Link, Physical Logical communication takes place at the ________, ________, ________, and ________ layers, while physical communication happens at the ________ layer. Answer: Application, Transport, Network, Data-Link; Physical In addition to routers, ________ are involved in physical communication Answer: Switches At the physical layer, data is exchanged in the form of ________ rather than raw data. Answer: Signals The primary purpose of communication is to exchange ________, but at the physical layer, this involves exchanging ________. Answer: Data; Signals Data transmission requires converting data into ________ that can travel across a medium, which can either be ________ or ________ in form. Answer: Signals; Analog; Digital Communication from host to router, router to router, and router to host involves both ________ and ________ layers of communication. Answer: Logical; Physical The physical layer is distinct from the higher layers because it focuses on the ________ transmission of ________. Answer: Physical; Signals Analog and Digital Data Analog data refers to information that is ________, while digital data refers to information that has ________ states. Answer: Continuous; Discrete An example of analog data in everyday life is a ________ , while an example of digital data is ________. Answer: Human voice ; Binary data in computer memory A microphone captures analog sound waves and can convert them into either an ________ signal or a ________ signal. Answer: Analog; Digital Digital data is stored in a computer in the form of ________ and ________, which can be converted into a ________ signal or modulated into an ________ signal. Answer: 0s; 1s; Digital; Analog The binary values ________ and ________ are fundamental to how digital data is stored and transmitted in computers. Answer: 0; 1 Unlike analog data, which is continuous, digital data consists of ________ values. Answer: Discrete An analog signal can have ________ levels of intensity over time, while a digital signal can only have a ________ number of defined values. Answer: Infinite; Finite  In analog signals, the transition between values is ________, while in digital signals, the change is ________ and occurs in defined steps. Answer: Smooth; Sudden The infinite number of possible values in an analog signal contrasts with the ________ number of values in a digital signal. Answer: Finite Signals are typically represented on a graph where the vertical axis shows ________ and the horizontal axis shows ________. Answer: Signal strength; Time The curve representing an analog signal is ________, while the vertical lines in a digital signal plot demonstrate ________ jumps between values. Answer: Continuous; Sudden Digital signals are often preferred in computing because of their ________ representation, which makes them more resistant to ________. Answer: Discrete; Noise The two most common states in digital signals are represented by ________ and ________, which correspond to binary data. Answer: 0; 1 __________is an example of analog signals and __________is an example of digital signals. Answer: traditional voice communication (e.g., landline telephones), internet data transmission and digital TV. Periodic and Nonperiodic Signals A periodic signal has a repeating pattern over a fixed time interval, known as a ________, and this repetition is called a ________. Answer: Period; Cycle Nonperiodic signals do not follow a repeating ________ or ________ over time. Answer: Pattern; Cycle The repetition of one complete cycle in a periodic signal is called a ________, and it can occur in both ________ and ________ signals. Answer: Cycle; Analog; Digital In most data communication systems, ________ analog signals are used for efficient transmission, while ________ digital signals handle data that does not repeat in patterns. Answer: Periodic; Nonperiodic Nonperiodic signals are commonly used for transmitting ________ data, such as computer files, while periodic signals are more suitable for ________ data, such as radio waves. Answer: Irregular; Regular The prefix "a-" in "aperiodic" comes from Greek and means ________, highlighting the absence of a ________ pattern. Answer: Non-; Repeating Periodic signals are crucial in systems where synchronization is required, such as ________, whereas nonperiodic signals excel in ________ data exchange. Answer: Radio communications; File Aperiodic signals do not follow a repetitive pattern, and their irregular nature makes them suitable for ________ types of communication. Answer: Burst-mode or on-demand Basic Signal Concepts A simple periodic analog signal that cannot be decomposed into simpler signals is called a __________ signal. Answer: sine wave A composite periodic analog signal is composed of __________. Answer: multiple sine waves The peak amplitude of a signal is the __________ value of its highest intensity. Answer: absolute The unit of peak amplitude for electric signals is usually measured in __________. Answer: volts The formula for converting peak value to RMS value is __________ = Peak / √2. Answer: RMS If the voltage in U.S. homes is 110-120 V, the peak amplitude is approximately __________ volts. Answer: 155-170 V The period (T) is the __________ of the frequency (f). Answer: inverse The frequency of a signal with a period of 100 ms is __________ Hz. Answer: 10 Hz Wavelength (λ) is related to the frequency (f) and the propagation speed (c) by the formula __________ = c / f. Answer: λ Frequency and Wavelength The frequency of a sine wave in hertz is equivalent to the number of __________ it completes in one second. Answer: cycles A sine wave with a phase shift of 0° starts at time 0 with a __________ amplitude. Answer: zero The period of a sine wave is the time it takes to complete __________ cycle(s). Answer: one The wavelength of a signal is inversely proportional to its __________. Answer: frequency A signal’s __________ describes the position of the waveform relative to time 0. Answer: phase The phase shift of 180° corresponds to a shift of __________ period(s) in a sine wave. Answer: one-half In data communications, we often use the term wavelength to describe the transmission of __________ in optical fiber. Answer: light A sine wave with a phase shift of 180° starts at time 0 with __________ amplitude. Answer: zero The wavelength of red light in air with a frequency of 4 × 10^14 Hz is approximately __________ micrometers. Answer: 0.75 μm Period and Frequency Calculations A signal that does not change over time has a frequency of __________ Hz. Answer: 0 If a signal changes instantaneously, its period is __________ seconds. Answer: zero A signal that completes one cycle every 0.5 seconds has a frequency of __________ Hz. Answer: 2 Hz A sine wave with a frequency of 60 Hz will complete one cycle every __________ seconds. Answer: 1/60  In a signal with a frequency of 1 kHz, the period of the wave is __________ seconds. Answer: 0.001 Signal Phase and Amplitude The amplitude of a sine wave is proportional to the __________ it carries. Answer: energy The frequency of a sine wave is the __________ with respect to time. Answer: rate of change The phase of a sine wave is measured in __________ or __________. Answer: degrees, radians A phase shift of __________ corresponds to a shift of one complete period of the wave. Answer: 360° A phase shift of __________ corresponds to a shift of one-quarter of the wave's period. Answer: 90° A sine wave with a phase shift of 90° starts at time 0 with __________ amplitude. Answer: peak A signal with a phase shift of 0° starts at time 0 with __________ amplitude. Answer: zero A phase shift of 180° corresponds to a shift of __________ period(s). Answer: one-half The term used to describe a change in a sine wave’s position relative to time is __________. Answer: phase shift Extreme Signal Cases and Wavelength Properties A composite signal can be decomposed into __________ components. Answer: simpler sine waves Wavelength is a property of __________ type of signal. Answer: any  The propagation speed of electromagnetic signals is highest in a __________. Answer: vacuum The wavelength is normally measured in __________ in fiber-optic communications. Answer: micrometers (microns) The unit for frequency is __________. Answer: Hertz (Hz) A signal with a frequency of 1 GHz (1 × 10^9 Hz) will have a wavelength of __________ meters if it is traveling at the speed of light (3 × 10^8 m/s). Answer: 0.3 meters Time and Frequency Domains A sine wave is defined by its __________, __________, and __________. Answer: amplitude, frequency, phase A time-domain plot shows changes in signal __________ with respect to __________. Answer: amplitude, time Phase is not explicitly shown on a __________ plot. Answer: time-domain A __________ plot shows the relationship between amplitude and frequency. Answer: frequency-domain In a frequency-domain plot, the position of the spike shows the __________, and the height of the spike shows the __________. Answer: frequency, peak amplitude A single sine wave in the frequency domain is represented by __________ spike(s). Answer: one The frequency domain plot is more __________ and __________ than the time-domain plot. Answer: compact, useful  In the frequency domain, a composite signal can be represented by __________ spikes. Answer: multiple Composite Signals A composite signal is made up of many simple __________ waves. Answer: sine __________ showed that any composite signal is a combination of simple sine waves. Answer: Fourier A periodic composite signal can be decomposed into a series of simple sine waves with __________ frequencies. Answer: discrete A nonperiodic composite signal can be decomposed into an infinite number of simple sine waves with __________ frequencies. Answer: continuous The frequency of the sine wave with frequency __________ is called the fundamental frequency, or first harmonic. Answer: f The sine wave with frequency 3f is called the __________ harmonic. Answer: third The sine wave with frequency 9f is called the __________ harmonic. Answer: ninth The frequency decomposition of a periodic signal is __________. Answer: discrete The frequency decomposition of a nonperiodic signal results in a __________ curve. Answer: continuous Bandwidth The range of frequencies contained in a composite signal is called its __________. Answer: bandwidth  The bandwidth is normally the difference between the __________ and __________ frequencies. Answer: highest, lowest The bandwidth of a periodic signal contains __________ integer frequencies between the highest and lowest frequencies. Answer: all The bandwidth of a nonperiodic signal has the same frequency range but with __________ frequencies. Answer: continuous The bandwidth of a signal that contains frequencies between 1000 Hz and 5000 Hz is __________ Hz. Answer: 4000 If a periodic signal is decomposed into sine waves with frequencies 100 Hz, 300 Hz, 500 Hz, 700 Hz, and 900 Hz, its bandwidth is __________ Hz. Answer: 800 Hz If a periodic signal has a bandwidth of 20 Hz and a highest frequency of 60 Hz, the lowest frequency is __________ Hz. Answer: 40 Hz Signal Analysis and Decomposition A composite signal is made up of many simple sine waves with different __________, __________, and __________. Answer: frequencies, amplitudes, phases Fourier analysis allows us to decompose a composite signal into its __________ components. Answer: sine wave The process of decomposing a signal into its constituent frequencies is called __________ analysis. Answer: Fourier The frequency decomposition of a periodic signal results in __________ frequencies. Answer: discrete  A __________ signal can be decomposed into a combination of an infinite number of simple sine waves. Answer: nonperiodic The decomposition of a composite signal into sine waves is done using both __________ and __________ tools. Answer: hardware, software The frequencies in the frequency domain of a periodic signal are always represented as __________. Answer: discrete spikes Practical Examples and Applications In power distribution, a single sine wave is used to carry __________ from one place to another. Answer: electric energy A sine wave can also be used as an __________ signal, such as sending an alarm to a security center. Answer: alert In telecommunication, to convey a conversation over the phone, we need to send a __________ signal. Answer: composite The decomposition of a periodic composite signal into simple sine waves involves calculating the __________ and __________ of the sine waves. Answer: amplitude, frequency The decomposition of a nonperiodic composite signal involves an infinite number of sine waves with __________ frequencies. Answer: continuous A microphone creates a __________ composite signal when a person speaks. Answer: nonperiodic Bandwidth and Frequency Spectrum The __________ of a composite signal is the range between the highest and lowest frequencies present. Answer: bandwidth If a composite signal contains frequencies from 100 Hz to 1000 Hz, its bandwidth is __________ Hz. Answer: 900 The bandwidth of a periodic signal can be measured by counting the number of __________ frequencies present. Answer: integer A signal with continuous frequencies will have a __________ bandwidth. Answer: continuous the bandwidth is the difference between the __________ frequency and the __________ frequency. Answer: highest, lowest The bandwidth of a periodic composite signal with frequencies 1 MHz and 5 MHz is __________ MHz. Answer: 4 The frequency spectrum of a nonperiodic signal is shown as a __________ curve. Answer: continuous The total bandwidth dedicated to an FM radio signal in the United States is __________ MHz. Answer: 200 An AM radio signal uses a bandwidth of __________ kHz. Answer: 10 The frequency spectrum of a typical analog color TV signal occupies a bandwidth of __________ MHz. Answer: 6 The __________ frequency decomposition of a signal results in a graph with discrete spikes, each representing a harmonic. Answer: periodic The __________ in an FM radio signal determines how much frequency variation is allowed. Answer: bandwidth  Digital Signal Representation A digital signal can have more than two levels, and for a signal with L levels, each level requires _______ bits. Answer: log₂ L For a signal with two levels, we can send __________ bit per level. Answer: 1 A signal with four levels allows us to send __________ bits per level. Answer: 2 A digital signal with eight levels requires __________ bits per level. Answer: 3 Bit Rate The __________ is the number of bits sent in 1 second, expressed in bits per second (bps). Answer: bitRate The bit rate for high-definition TV (HDTV), assuming a screen resolution of 1920 × 1080 pixels at 24 bits per pixel and 30 frames per second, is __________ bps. Answer: 1,492,996,000 bps The bit rate of HDTV can be reduced to a range of __________ to __________ Mbps through compression. Answer: 20, 40 Bit Length The distance one bit occupies on the transmission medium is called the _______. Answer: bit length Digital Communications Examples A digital signal has a bit rate of 1 Mbps. If each character requires 8 bits, the number of characters transmitted per second is __________. Answer: 125,000  The bit rate required for transmitting audio with a bandwidth of 4 kHz at 8 bits per sample is __________ bps. Answer: 64,000 Fourier Analysis of Digital Signals A digital signal is a composite _______ signal. Answer: analog The bandwidth of a digital signal is _______. Answer: infinite A vertical line in the time domain indicates a frequency of _______. Answer: infinity A horizontal line in the time domain indicates a frequency of _______. Answer: zero Going from a frequency of zero to infinity implies that all _______ in between are part of the domain. Answer: frequencies For a periodic digital signal, the frequency-domain representation has _______ bandwidth and _______ frequencies. Answer: infinite, discrete For a nonperiodic digital signal, the frequency-domain representation has _______ bandwidth and _______ frequencies. Answer: infinite, continuous Transmission of Digital Signals A digital signal can be transmitted using _______ transmission or _______ transmission. Answer: baseband, broadband Baseband transmission requires a _______-pass channel with a bandwidth starting from _______. Answer: low, zero Broadband transmission involves _______. Answer: modulating A low-pass channel with infinite bandwidth is _______ but not achievable in real life. Answer: ideal In a bus topology LAN, only _______ stations can communicate at one time. Answer: two In a star topology LAN, the entire channel between each station and the _______ is used for communication. Answer: hub Low-Pass Channel with Wide Bandwidth To preserve the exact form of a nonperiodic digital signal, the entire spectrum between _______ and _______ is needed. Answer: zero, infinity Frequencies at the _______ of the bandwidth can be ignored in practical situations. Answer: border Digital signals transmitted over coaxial or fiber optic cables with wide bandwidth retain _______ accuracy. Answer: very good Even if the output signal is not an exact replica, the _______ can still be deduced. Answer: data Low-Pass Channel with Limited Bandwidth In a low-pass channel, the digital signal is approximated by an _______ signal. Answer: analog The level of approximation depends on the available _______. Answer: bandwidth The worst-case sequence for digital signals is _______ or _______. Answer: 01010101, 10101010 The frequency needed to simulate a worst-case digital signal is _____ Answer: f/2 Better approximations require more _______ of the frequencies. Answer: harmonics Increasing the number of harmonics increases the _______. Answer: bandwidth Bit Rate and Bandwidth Calculations The bandwidth required to send 1 Mbps using baseband transmission with only the first harmonic is _______ kHz. Answer: 500 Using the first and third harmonics for 1 Mbps requires a bandwidth of _______ MHz. Answer: 1.5 The maximum bit rate for a 100 kHz low-pass channel using the first harmonic is _______ kbps. Answer: 200 Broadband Transmission (Modulation) Broadband transmission requires a _______-pass channel with bandwidth starting above _______. Answer: band, zero Modulation involves converting a digital signal into a _______ signal for transmission. Answer: composite analog  A telephone line, with a bandwidth of 4 kHz, is typically treated as a _______-pass channel. Answer: band A device that converts digital signals to analog and vice versa is called a _______. Answer: modem Digital cellular phones convert ________ voice signals to _______ signals for better reception. Answer: Analog digital The available bandwidth for digital cellular services is divided among multiple users, so the channel for each is only a _______ of the total bandwidth. Answer: fraction 3.4 Transmission Impairment General Concepts Transmission media imperfections cause _______ in signals. Answer: impairment Three main causes of signal impairment are _______, _______, and _______. Answer: attenuation, distortion, noise 3.4.1 Attenuation Attenuation refers to the _______. Answer: loss of energy in a signal Attenuation occurs because the medium’s _______ resists the signal's passage. Answer: resistance To compensate for attenuation, _______ are used. Answer: amplifiers The unit used to measure the relative strength of signals is the _______. Answer: decibel (dB) The decibel is negative when the signal is _______ and positive when it is _______. Answer: attenuated, amplified  The formula for calculating decibel in terms of power is: Answer: dB=10log⁡10(P2/P1) A loss of 3 dB indicates a reduction of the signal’s power to _______ of its original value. Answer: half If a signal is amplified to 10 times its original power, the decibel gain is _______. Answer: 10 dB Decibel values are _______ when measuring signal strength at multiple points. Answer: additive The power of a signal in milliwatts can be expressed in dBm using the formula: Answer: dBm=10log⁡10(Pm) The power of a signal with −30 dBm is _______ mW. Answer: 0.001 mW The loss in a cable is often measured in _______. Answer: dB/km A cable with a loss of −0.3 dB/km and an initial signal power of 2 mW will have a signal power of _______ mW after 5 km. Answer: 1.41 mW 3.4.2 Distortion Distortion refers to a change in the signal’s _______ or _______. Answer: form, shape Distortion commonly occurs in composite signals with different _______. Answer: frequencies Signal components arrive at different times due to varying _______ speeds, causing distortion. Answer: propagation Distortion can result in single signals having different _______ at the receiver compared to the sender. Answer: phases 3.4.3 Noise Noise is a type of signal _______ caused by various external factors. Answer: corruption _______ noise is caused by the random motion of electrons in a wire. Answer: Thermal _______ noise comes from sources like motors and appliances. Answer: Induced _______ is the interference between two wires, where one acts as the sender and the other as the receiver. Answer: Crosstalk _______ noise is a short, high-energy spike from sources like lightning or power lines. Answer: Impulse The signal-to-noise ratio (SNR) is the ratio of _______ power to _______ power. Answer: signal, noise SNR is measured in _______ when expressed in logarithmic form. Answer: decibels (dB) For a signal with 10 mW power and 1 μW noise, the SNR is _______ and the SNRdB is _______. Answer: 10,000; 40 dB A noiseless channel has an SNRdB value of _______. Answer: infinite A noiseless channel is _______. Answer: ideal 3.6 Network Performance Metrics 3.6.1 Bandwidth Bandwidth can be measured in two ways: _______ and _______. Answer: hertz, bits per second Bandwidth in hertz refers to the _______ a channel can pass. Answer: range of frequencies  The bandwidth of a standard telephone line is typically _______ kHz. Answer: 4 Bandwidth in bits per second measures the maximum _______ a channel can transmit. Answer: data rate A Fast Ethernet network has a bandwidth of _______ Mbps. Answer: 100 The relationship between bandwidth in hertz and bits per second depends on whether the transmission is _______ or uses _______. Answer: baseband, modulation 3.6.2 Throughput Throughput measures the _______ rate of data transfer through a network. Answer: actual The throughput is always _______ than or equal to the bandwidth. Answer: less A link with 1 Mbps bandwidth but only 200 kbps throughput is limited by _______. Answer: device capability A network with a 10 Mbps bandwidth can send 12,000 frames per minute, each with 10,000 bits. The throughput is _______ Mbps. Answer: 2 3.6.3 Latency (Delay) Latency is the time it takes for an entire _______ to reach the destination from the source. Answer: message  The four components of latency are _______, _______, _______, and _______. Answer: propagation time, transmission time, queuing time, processing delay Propagation time is calculated as: Answer: Propagation Time=DistancePropagation /Speed If a signal travels 12,000 km at a speed of 2.4×10^8 m/s, the propagation time is _______ ms. Answer: 50 Transmission time depends on the _______ and the _______. Answer: message size, bandwidth The formula for transmission time is: Answer: Transmission Time=Message Size/ Bandwidth Queuing time increases with _______ on the network. Answer: heavy traffic 3.6.4 Bandwidth-Delay Product The bandwidth-delay product represents the number of _______ Answer: bits that can fill the link. In a link with 1 bps bandwidth and 5 seconds delay, the bandwidth-delay product is _______ bits. Answer: 5 To maximize link utilization in burst mode, the burst size should be _______ times the bandwidth-delay product. Answer: 2 The formula for calculating the amount of data in transit is: Answer: 2×Bandwidth×Delay Jitter Jitter refers to variations in _______ across different data packets. Answer: delay Jitter becomes a problem in _______-sensitive applications like audio and video. Answer: time  If the delays for packets are 20 ms, 45 ms, and 40 ms, the application will experience _______. Answer: jitter