Communication and networking
Definition of Networking:-
A computer network is a set of computers or devices that are connected with each other to carry on data and share information. In computing, it is called a network as a way to interconnect two or more devices to each other using cables, signals, waves or other methods with the ultimate goal of transmitting data, share information, resources and services.
A computer network is a set of computers or devices that are connected with each other to carry on data and share information. In computing, it is called a network as a way to interconnect two or more devices to each other using cables, signals, waves or other methods with the ultimate goal of transmitting data, share information, resources and services.
Purpose of networking:
The purpose of a network is, generally, to facilitate and expedite communications between two or more instances on the same physical space or connected remotely. Such systems also allow cost savings and time.
The most known type of network is the Intranet, which is a private network that uses Internet as a basic architecture in order to connect various devices. Internet, however, is a technology that connects devices throughout the world, and that is why it is called “network of networks.”
Classifications of Networks:
The networks are classified by range (personal, local, campus, metropolitan or wide area), as well as by method of connection (cable, fiber optics, radio, infrared, wireless, etc..) or by functional relationship (client – server or peer‐to‐peer). Also in the topology field there is a classification to be aware of (bus, star, ring, mesh, tree etc.) and directional (simplex, half duplex or full duplex).
The networks are classified by range (personal, local, campus, metropolitan or wide area), as well as by method of connection (cable, fiber optics, radio, infrared, wireless, etc..) or by functional relationship (client – server or peer‐to‐peer). Also in the topology field there is a classification to be aware of (bus, star, ring, mesh, tree etc.) and directional (simplex, half duplex or full duplex).
Use of a network:
The use of a network in an office, for example, in which all employees have the same access to resources such as programs and applications or devices like a printer or scanner. Moreover, configuring a large‐scale network facilitates communication among different geographic locations, so a company with multiple branches in the world can keep in communication with its members in a simple and quick. Finally, a network can be used as a home to share files or maximize the available space.
The use of a network in an office, for example, in which all employees have the same access to resources such as programs and applications or devices like a printer or scanner. Moreover, configuring a large‐scale network facilitates communication among different geographic locations, so a company with multiple branches in the world can keep in communication with its members in a simple and quick. Finally, a network can be used as a home to share files or maximize the available space.
Analog Network Signaling:
An analog signal is best compared to a wave. It has similar properties to an ocean wave, and can be
described using three specific characteristics: amplitude, frequency, and wavelength.
To use the ocean wave analogy an analog signal's amplitude is like the height of a wave rolling in onto the beach. The frequency of an analog signal can be compared to how fast the waves roll in. Wavelength can be compared to the distance between one wave and the next wave. Wavelength is measured as the distance between the peak of one wave and the next.
described using three specific characteristics: amplitude, frequency, and wavelength.
To use the ocean wave analogy an analog signal's amplitude is like the height of a wave rolling in onto the beach. The frequency of an analog signal can be compared to how fast the waves roll in. Wavelength can be compared to the distance between one wave and the next wave. Wavelength is measured as the distance between the peak of one wave and the next.
Advantages and Disadvantages of Analog Signals
Analog signals are variable and can convey more subtly than a digital signal. For example the human
voice is analog, and has more tone than a digital representation of the same voice. However, analog
signals are very vulnerable to interference from outside forces and other waves which can cancel them out.
Analog signals are variable and can convey more subtly than a digital signal. For example the human
voice is analog, and has more tone than a digital representation of the same voice. However, analog
signals are very vulnerable to interference from outside forces and other waves which can cancel them out.
Digital Network Signaling:
A digital signal is made up of on/off states. Unlike the smooth curve of an analog wave, the digital signal cuts on and off. This happens to perfectly fit the type of communication inside a computer, which is made up of on/off states as well.
A digital signal is made up of on/off states. Unlike the smooth curve of an analog wave, the digital signal cuts on and off. This happens to perfectly fit the type of communication inside a computer, which is made up of on/off states as well.
Advantages and Disadvantages of Digital Signals:
Digital signals are much more reliable than analog signals because they are less vulnerable to interference and errors. However, digital equipment costs more and is much more complex.
Modulation (AM, FM, PM)
In telecommunications, modulation is the process of conveying a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted. Modulation of a sine waveform is used to transform a base band message signal into a pass band signal, for example lowfrequency audio signal into a radio-frequency signal (RF signal). In radio communications, cable TV
systems or the public switched telephone network for instance, electrical signals can only be transferred over a limited pass band frequency spectrum, with specific (non-zero) lower and upper cutoff frequencies. Modulating a sine-wave carrier makes it possible to keep the frequency content of the transferred signal as close as possible to the center frequency (typically the carrier frequency) of the pass band.
A device that performs modulation is known as a modulator and a device that performs the inverse operation of modulation is known as a demodulate (sometimes detector or domed). A device that can do both operations is a modem (modulator–demodulate).
In telecommunications, modulation is the process of conveying a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted. Modulation of a sine waveform is used to transform a base band message signal into a pass band signal, for example lowfrequency audio signal into a radio-frequency signal (RF signal). In radio communications, cable TV
systems or the public switched telephone network for instance, electrical signals can only be transferred over a limited pass band frequency spectrum, with specific (non-zero) lower and upper cutoff frequencies. Modulating a sine-wave carrier makes it possible to keep the frequency content of the transferred signal as close as possible to the center frequency (typically the carrier frequency) of the pass band.
A device that performs modulation is known as a modulator and a device that performs the inverse operation of modulation is known as a demodulate (sometimes detector or domed). A device that can do both operations is a modem (modulator–demodulate).
Amplitude Modulation (AM)
Amplitude modulation (AM) is a method of impressing data onto an alternating-current(AC) carrier waveform.The highest frequency of the modulating data is normally less than 10 percent of the carrier frequency.The instantaneous amplitude(overall signal power) varies depending on the instantaneous amplitude of the modulating data. In AM, the carrier itself does not fluctuate in amplitude. Instead, the modulating data appears in the form of signal components at frequencies slightly higher and lower than that of the carrier. These components are called side bands. The lower side band (L S B) appears at frequencies below the carrier frequency; the upper side band (USB) appears at frequencies above the carrier frequency. The LS B and USB are essentially "mirror images" of each other in a graph of signal amplitude versus frequency, as shown in the illustration. The side band power accounts for the variations in the overall amplitude of the signal. When a carrier is amplitude-modulated with a pure sine wave, up to 1/3 (33 percent) of the overall signal power is contained in the side bands. The other 2/3 of the signal power is contained in the carrier, which does not contribute to the transfer of data. With a complex modulating signal such as voice, video, or music, the side bands generally contain 20 to 25 percent of the overall signal power; thus the carrier consume 75 to 80 percent of the power. This makes AM an inefficient mode. If an attempt is made to increase the modulating data input amplitude beyond these limits, the signal will become distorted, and will occupy a much greater bandwidth than it should. This is called over modulation, and can result in interference to signals on nearby frequencies.
Amplitude modulation (AM) is a method of impressing data onto an alternating-current(AC) carrier waveform.The highest frequency of the modulating data is normally less than 10 percent of the carrier frequency.The instantaneous amplitude(overall signal power) varies depending on the instantaneous amplitude of the modulating data. In AM, the carrier itself does not fluctuate in amplitude. Instead, the modulating data appears in the form of signal components at frequencies slightly higher and lower than that of the carrier. These components are called side bands. The lower side band (L S B) appears at frequencies below the carrier frequency; the upper side band (USB) appears at frequencies above the carrier frequency. The LS B and USB are essentially "mirror images" of each other in a graph of signal amplitude versus frequency, as shown in the illustration. The side band power accounts for the variations in the overall amplitude of the signal. When a carrier is amplitude-modulated with a pure sine wave, up to 1/3 (33 percent) of the overall signal power is contained in the side bands. The other 2/3 of the signal power is contained in the carrier, which does not contribute to the transfer of data. With a complex modulating signal such as voice, video, or music, the side bands generally contain 20 to 25 percent of the overall signal power; thus the carrier consume 75 to 80 percent of the power. This makes AM an inefficient mode. If an attempt is made to increase the modulating data input amplitude beyond these limits, the signal will become distorted, and will occupy a much greater bandwidth than it should. This is called over modulation, and can result in interference to signals on nearby frequencies.
Frequency Modulation (FM)
Frequency modulation (FM) is a method of impressing data onto an alternating-current (AC) wave by
varying the instantaneous (immediate) frequency of the wave. This scheme can be used with analog or digital data.
Frequency modulation (FM) is a method of impressing data onto an alternating-current (AC) wave by
varying the instantaneous (immediate) frequency of the wave. This scheme can be used with analog or digital data.
Analog FM
In analog FM, the frequency of the AC signal wave, also called the carrier, varies in a continuous manner. Thus, there are infinitely many possible carrier frequencies. In narrow band FM, commonly used in two-way wireless communications, the instantaneous carrier frequency varies by up to 5 kilohertz (kHz, where 1 kHz = 1000 hertz or alternating cycles per second) above and below the frequency of the carrier with no modulation. In wide band FM, used in wireless broadcasting, the instantaneous frequency varies by up to several megahertz (MHz, where 1 MHz = 1,000,000 Hz). When the instantaneous input wave has positive polarity, the carrier frequency shifts in one direction; when the instantaneous input wave has negative polarity, the carrier frequency shifts in the opposite direction. At every instant in time, the extent of carrier-frequency shift (the deviation) is directly proportional to the extent to which the signal amplitude is positive or negative.
In analog FM, the frequency of the AC signal wave, also called the carrier, varies in a continuous manner. Thus, there are infinitely many possible carrier frequencies. In narrow band FM, commonly used in two-way wireless communications, the instantaneous carrier frequency varies by up to 5 kilohertz (kHz, where 1 kHz = 1000 hertz or alternating cycles per second) above and below the frequency of the carrier with no modulation. In wide band FM, used in wireless broadcasting, the instantaneous frequency varies by up to several megahertz (MHz, where 1 MHz = 1,000,000 Hz). When the instantaneous input wave has positive polarity, the carrier frequency shifts in one direction; when the instantaneous input wave has negative polarity, the carrier frequency shifts in the opposite direction. At every instant in time, the extent of carrier-frequency shift (the deviation) is directly proportional to the extent to which the signal amplitude is positive or negative.
Digital FM
In digital FM, the carrier frequency shifts abruptly, rather than varying continuously. The number of
possible carrier frequency states is usually a power of 2. If there are only two possible frequency states, the mode is called frequency-shift keying (F S K). In more complex modes, there can be four, eight, or more different frequency states. Each specific carrier frequency represents a specific digital input data state.
In digital FM, the carrier frequency shifts abruptly, rather than varying continuously. The number of
possible carrier frequency states is usually a power of 2. If there are only two possible frequency states, the mode is called frequency-shift keying (F S K). In more complex modes, there can be four, eight, or more different frequency states. Each specific carrier frequency represents a specific digital input data state.
Phase Modulation (PM):
Phase modulation (PM) is a method of impressing data onto an alternating-current (AC) waveform by varying the instantaneous phase of the wave. This scheme can be used with analog or digital data.
Phase modulation (PM) is a method of impressing data onto an alternating-current (AC) waveform by varying the instantaneous phase of the wave. This scheme can be used with analog or digital data.
Analog PM, The phase of the AC signal wave, also called the carrier, varies in a continuous manner.
Thus, there are infinitely many possible carrier phase states. When the instantaneous data input waveform has positive polarity, the carrier phase shifts in one direction; when the instantaneous data input waveform has negative polarity, the carrier phase shifts in the opposite direction. At every instant in time, the extent of carrier-phase shift(the phase angle) is directly proportional to the extent to which the signal amplitude is positive or negative.
Thus, there are infinitely many possible carrier phase states. When the instantaneous data input waveform has positive polarity, the carrier phase shifts in one direction; when the instantaneous data input waveform has negative polarity, the carrier phase shifts in the opposite direction. At every instant in time, the extent of carrier-phase shift(the phase angle) is directly proportional to the extent to which the signal amplitude is positive or negative.
Digital PM
In digital PM, the carrier phase shifts abruptly, rather than continuously back and forth. The number of possible carrier phase states is usually a power off. If there are only two possible phase states, the mode is called bi phase modulation. In more complex modes, there can be four, eight, or more different phase states. Each phase angle (that is, each shift from one phase state to another)represents a specific digital input data state. Phase modulation is similar in practice to frequency modulation (FM). When the instantaneous phase of a carrier is varied, the instantaneous frequency changes as well. The converse also holds: When the instantaneous frequency is varied, the instantaneous phase changes. But PM and FM are not exactly equivalent, especially in analog applications. When an FM receiver is used to demodulate a PM signal, or when FM signal is intercepted by a receiver designed for PM, the audio is distorted. This is because the relationship between phase and frequency variations is not linear; that is, phase and frequency do not vary in direct proportion.
In digital PM, the carrier phase shifts abruptly, rather than continuously back and forth. The number of possible carrier phase states is usually a power off. If there are only two possible phase states, the mode is called bi phase modulation. In more complex modes, there can be four, eight, or more different phase states. Each phase angle (that is, each shift from one phase state to another)represents a specific digital input data state. Phase modulation is similar in practice to frequency modulation (FM). When the instantaneous phase of a carrier is varied, the instantaneous frequency changes as well. The converse also holds: When the instantaneous frequency is varied, the instantaneous phase changes. But PM and FM are not exactly equivalent, especially in analog applications. When an FM receiver is used to demodulate a PM signal, or when FM signal is intercepted by a receiver designed for PM, the audio is distorted. This is because the relationship between phase and frequency variations is not linear; that is, phase and frequency do not vary in direct proportion.
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