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#set page(
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#set page(
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paper: "a4",
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paper: "a4",
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//numbering: "1",
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numbering: "1",
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margin: (top: 2.5cm, left: 2.5cm, right: 2.5cm, bottom: 2cm)
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margin: (top: 2.5cm, left: 2.5cm, right: 2.5cm, bottom: 2cm)
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)
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)
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#if (context here().page()) != 1 [
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numbering: "1"
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)
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]
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#set page(
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footer: context {
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if here().page() > 1 {
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align(center)[#counter(page).display()]
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}
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}
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)
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#set text(
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#set text(
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//font: "Times New Roman",
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font: "Times New Roman",
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size: 12pt,
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size: 12pt,
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)
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)
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Marius Drechsler\
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Marius Drechsler\
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Process Essay\
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Process Essay\
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May 25th, 2025
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May 17th, 2025
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#align(center, text(size: 17pt, weight: "bold")[
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#align(center, text(size: 17pt, weight: "bold")[
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*The Digital Journey of a Message*
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*The Digital Journey of Your Voice*
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])
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])
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#set align(left)
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#set align(left)
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@ -43,68 +29,65 @@ May 25th, 2025
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#show: word-count
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#show: word-count
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// Have you ever wondered what happens with your voice when you are talking to someone on the phone?
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Have you ever wondered what happens with your voice when you are talking to someone on the phone?
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When speaking over the telephone, voice signals undergo complex transformations before reaching their intended recipient.
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From the instant the soundwaves leave your throat until they reach the ear of the person you are talking to,
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From the instant the sound waves are produced by the vocal cords until they reach the recipient,
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a series of analog and digital processes collaborate to carry your message.
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a series of analog and digital processes collaborate to carry the message.
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In fact, this whole process can be broken down into three major steps -- sampling, quantisation and modulation.
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This transformation process can be broken down into three major steps -- sampling, quantisation and modulation.
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In the course of this essay, we will investigate each of these steps in more depth to understand how modern
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These steps systematically convert analogue voice signals into digital information, allowing a reliable transmission over communication networks.
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This essay will investigate each of these steps in more depth to understand how modern
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communication works on a technical level.
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communication works on a technical level.
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// To start, we will take a closer look at the analogue signal that reaches your phone's microphone.
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To start, we will take a closer look at the analoue signal that reaches your phone's microphone.
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To begin, it is necessary to examine the analogue signal that reaches the microphone of a telephone.
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Every sound wave, like your voice or the tone of a guitar string, is so called time and value continuous.
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Every sound wave, such as human speech or musical tones, is called time and value continuous.
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That means, such a signal has an infinitely accurate value at each imaginable point in time.
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That means that such a signal has an infinitely accurate value at each imaginable point in time.
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However, an electronic device, for example a computer or a phone, cannot understand such an analogue signal, thus we have to first transform it into some kind of electrical signal the device can understand.
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However, an electronic device, for example a computer or a phone, cannot understand such an analogue signal, thus, it must first be transformed into an electrical signal the device can process.
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In general, we can assume that an electrical device can only process time and value disteet signals.
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//In general, we can assume that an electrical device can only process time and value discrete signals.
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To transform our original continuous signal into its discreet or rather digital representation, we can make use of the sampling and
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Generally, electronic devices can only process signals that are discrete both in time and amplitude.
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quantization steps in our communication process.
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To transform the original continuous signal into its discrete or rather digital representation, sampling and
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quantization steps are used in the communication process.
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In the sampling process, the analogue signal is transformed into a time-discrete and value-continuous signal.
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In the sampling process, the analogue signal is transformet into a time discreet and value continuous signal.
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Conceptually, an analog-to-digital converter (ADC) takes rapid snapshots of the amplitude of the input signal at uniform intervals and records each reading.
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Conceptually, an analog-to-digital converter (ADC) takes rapid "snapshots" of the amplitude of the input signal at uniform intervals and records each reading.
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The rate at which these snapshots occur is called sampling frequency.
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The rate at which these snapshots occur is called sampling frequency.
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Ideally, it is desirable to maximize the interval between each of these snapshots, using the lowest possible sampling frequency.
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Ideally, we do want to maximize the timespan between each of these snapshots, using the lowest possible sampling frequency so to speak.
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The Nyquist Frequency defines this lowest possible sampling frequency as double the frequency of the originating signal @shannon.
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The Nyquist Frequency defines this lowest possible sampling frequency as double the frequency of the originating signal @shannon.
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For example, if the frequency of the original signal is 1 MHz, the analog-to-digital converter will need to take a snapshot of the signal at a frequency of at least 2 MHz.
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For example, if the frequency of our original signal is 1 MHz, the analog-to-digital converter will need to take a snapshot of the signal at a frequency of at least 2 MHz.
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At this moment, the signal is time-discrete and value-continuous.
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At this moment, our signal now is time-discreet and value-continuous.
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To convert these time-discrete values into quantized digital values a quantizer will be used in the next step.
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To convert these time-discreet values into real bits and bytes we will make use of the quantizer in the next step.
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Quantization describes the operation of transforming a continuous value into its discrete form.
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Quanization describes the operation of transforming a continuous value into a discreet form.
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Consider the random placement of dots in a row on a piece of paper.
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Imagine placing random dots in a row on a piece of paper.
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A simple quantization process would be to take a ruler and for each point record the next highest marking on the ruler.
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A simple quantization process now would be to take a ruler and for each point record which is the next highest marking on the ruler.
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Analogously, the quantizer of an electronic device maps the continuous input values to predefined codewords -- a collection of bits (for example "000", "110", or "011").
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In the same sense, the quantizer of an electronic device maps the continuous input vaulues to predefined codewords -- a collection of bits (for example "000", "110" or "011").
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Our signal has now fully arrived in the digital domain.
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// Note: Maybe expand more what happened up until now
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// Note: Maybe expand more what happened up until now
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The analogue message has now been fully digitally encoded.
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Up to this point we have completeley encoded our analogue message digitally.
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During the next steps, the digital signal will be further processed and prepared for transmission.
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During the next steps, the digital signal will be further processed and prepared for transmission.
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A digital signal in its raw form is inefficient to transmit because of the limited underlying bandwidth.
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A digital signal in its raw form is very inefficient to transmit because of the limited underlying bandwidth.
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Since the message has to be transported over some kind of communication channel, the amount of information that can be transported in a fixed period of time is limited.
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Because we need to transport our message over some kind of communication channel, the amount of information we can transport in a fixed period of time is limited.
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The first step in solving this issue is using compression by removing irrelevant and redundant information from the signal.
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The first step in solving this issue is using compression by removing irrelevant and redundant information from the signal.
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A popular example for a compression method is called Huffman Coding @huffman.
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A popular example for a compression method is called Huffman Coding @huffman.
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Conceptually, the Huffman Code consists of multiple codewords of varying length where symbols with a higher probability of occurrence are assigned to the shorter codewords, thus reducing the overall size of the message.
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Conceptually, the Huffman Code consists of multiple codewords of varying length where symbols with a higher probability of occurrence are assigned to the shorter codewords, thus reducing the overall size of the message.
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Since the assignment of symbols to codewords is based on their probability of occurrence, this method of compression requires information about the statistics of the incoming symbols.
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Since the assignment of symbols to codewords is based on their probability of occurrence, this method of compression requires information about the statistics of the incoming symbols.
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If these statistical information is not known, other compression methods such as the Lempel–Ziv–Welch algorithm can be used.
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If these statistical information are not known, other compression methods such as the Lempel–Ziv–Welch algorithm can be used.
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Furthermore, compression algorithms specifically tailored for different signal sources can be used, for example PNG for pictures, MP3 for audio or MPEG for video signals.
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Furtheremore, compression algorithms specifically tailored for different signal sources can be used, for example PNG for pictures, MP3 for audio or MPEG for video signals.
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With the analogue message digitized and compressed for easier transport over the communication channel, the message must now be prepared on a physical level for it to be transmitted using a radio wave or a data cable.
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With the analogue message digizited and compressed for easier transport over our communication channel, we will now need to prepare our message on a physical level for it to be able to be transmitted using a radio wave or a data cable.
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To prepare the digital and compressed message for transmission over a physical channel, digital modulation -- such as amplitude modulation -- is used.
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Currently, the message to be transmitted can be represented as a set of codewords like "00 01 10 11".
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Currently, the message to be transmitted can be represented as a set of codewords like "00 01 10 11".
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Modulation works by defining a specific signal amplitude for every possible codeword, which is called Amplitude-Shift Keying (ASK) @modulation.
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To prepare our message digital and compressed message for transmission over a physical channel, digital modulation -- like amplitude modulation -- is used.
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The simplest form of ASK is On-Off Keying (OOK), in which a binary 1 is represented by the transmission of a wave, and a binary 0 by the absence of transmission.
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This works by defining a specific signal amplitude for every possible codeword, which is called Amplitude-Shift Keying (ASK) @modulation.
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Signal modulation is not limited to changing the amplitude of the transmission signal, thus it is also possible to alter the frequency or phase.
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The simplest form of ASK is called On-Off Keying (OOK), where we will either transmit a wave -- and signaling a binary 1 -- or not transmit anything -- and signal a 0.
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In the example above, four sine functions with varying amplitudes may be defined as the modulated signal that is being transported over the physical communication channel.
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In our example we may define four sine functions with varying amplitutes as the modulated signal that is being transported over the physical communication channel.
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Because four different Amplitude-Shifts were defined, this type of modulation is called "4 ASK" @modulation.
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Because we defined four different Amplitude-Shifts, this type of modulation is called "4 ASK" @modulation.
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Depending on the type of communication channel, a different modulation type may be used, using either one or a combination of different modulation parameters.
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Signal modulation is not limited to changing the ampliude of our transmission signal, thus we can also alter the phase or frequency of the signal.
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For example, a popular modulation type that uses a combination of amplitude shifts and phase shifts is called "Amplitude-Phase-Shift Keying (APSK)" @modulation.
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Depending on the type of communication channel we may want to choose a different modulation type using either one or a combination of different modulation parameters.
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Using modulation, the signal has been prepared on a physical level to instruct a communication interface -- such as an antenna or an optical transmitter -- to finally transmit the message.
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For example, a popular modulation type that uses a combination of amplitude shifts and phase shifts is called "Amplitude-Phase-Shift Keying (APSK) @modulation.
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Using modulation, we prepared our signal on a physical level to instruct a communication interface -- like an antenna or an optical transmitter -- to finally transmit our message.
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As final step, the receiver of the message has to process the received signals in exactly the reverse order to create a comprehensible message.
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As final step, the receiver of the message has to process the received signals in exactly the reverse order to create a comprehensible message.
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The most important prerequisite for this to work is that both sender and receiver have agreed on the same transmission and reception conditions.
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The most important prerequisite for this to work is that both sender and receiver have agreed on the same transmission and reception conditions.
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The receiver will first need to use the correct modulation type to convert their received signal back to a set of codewords.
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The receiver will first need to use the correct modulation type to convert their received signal back to a set of codewords.
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Proceeding, they will decompress the message based on the used compression algorithm and use a Digital-to-Analog Converter (DAC) to transform the digital message back into sound waves which will be output by the speaker of their phone.
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Going on, they will decompress the message based on the used compression algorithm and use a Digital-to-Analog Converter (DAC) to transform the digital message back into sound waves which will be output by the speaker of their phone.
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This whole process now happens at such a high speeds that real-time communication across the globe is made possible.
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This whole process now happens at such a high speed that makes it possible for us to talk to a person on the other side of the world.
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//Essay has a total of #total-words words.
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//Essay has a total of #total-words words.
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