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Questions and Answers
What is a network?
a collection of connected objects
Which of the following are characteristics of telecommunication networks? (Select all that apply)
What does Metcalfe's law state?
the value of a telecommunications network is proportional to the square of the number of connected users
Who are considered the fathers of the Internet?
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What does DNS stand for?
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Which media can signals be transmitted through?
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What is the frequency?
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What is the formula that relates frequency and wavelength?
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What does Fourier Transform do?
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Study Notes
Networks 101
- A network is a collection of connected objects.
- Telecommunication networks are graphs designed to transmit signals (information).
- Telecommunication networks are designed to optimize quality, minimize energy consumption, maximize capacity and speed, and minimize cost.
Network Effects
- Metcalfe's law states that the value of a telecommunications network is proportional to the square of the number of connected users (n^2).
Internet Architecture
- The Internet is made up of routers connecting Autonomous Systems (independent networks).
- The first message between computers on the ARPA Network was sent in 1969.
- Vinton Cerf and Bob Kahn, "the Fathers of the Internet," published the design of TCP in 1974.
- The Domain Name System (DNS) was established in 1983, creating the familiar .edu, .gov, .com, .mil, .org, .net, and .int system for naming websites.
- CERN introduced the World Wide Web to the public in 1991.
Information Transmission Media
- Signal transmission can occur via wired or wireless methods.
- Wired methods include coaxial cable, twisted-pair cable, and fiber-optics.
- Wireless methods include radio frequency.
From Copper to Fiber
- Fiber-optics offers higher carrying capacity, wider transmission band, less signal degradation, and no interference from light signals compared to copper.
Radio Spectrum
- Hertz (Hz) is a unit of frequency, measured in cycles per second.
- The Frequency Domain and Frequency Spectrum represent the range of frequencies present in a signal.
- Information signals are modulated onto carrier signals.
- Channels are defined by Bandwidth (B), the difference between lower and upper frequencies.
- Signal modulation enables sharing of transmission media.
What is Frequency?
- A signal is information that changes over time.
- A frequency is the speed of repetition.
- One hertz (Hz) is one repetition per second.
- Power refers to the strength of each frequency.
- Amplitude (A) is related to the power carried by the signal.
Time Domain vs Frequency Domain Representation
- For periodic signals (those that repeat the sequence of values after a fixed length of time), the Frequency Domain representation is a series of discrete values at each frequency present in the original signal.
- Time Series (Signals) typically comprise multiple frequencies.
Spectrum of Musical Notes
- The spectrum of musical notes can be presented as a series of frequencies.
- Music involves multiple frequencies combined, creating a sound.
Signal Modulation
- Information Signal travels modulated on a Higher Frequency Carrier Signal.
- A Channel is defined by its Bandwidth (B), the difference between the upper and lower frequencies in the range.
- Signal Modulation is critical to enable Transmission Media Sharing.
Carrier Frequency vs Channel Bandwidth
- Each Carrier Frequency (𝑓𝑐𝑖) carries the Information Signal over a Channel Bandwidth.
- WiFi uses 𝑓𝑐 = 2.4GHz over Channels of up to 40MHz.
Wireless (Radio) Communications
- Wireless communication involves radio waves for signal transmission.
mmWave Communications (95GHz to 3THz)
- The wavelength (𝜆) of a signal is inversely proportional to its frequency (𝑓) according to the formula 𝜆∙𝑓 =𝑐, where c=3 ∙ 108 m/s.
- mmWave communications use frequencies ranging from 95GHz to 3THz, resulting in wavelengths of 3.16mm or shorter.
- The Federal Communications Commission (FCC) has opened up experimental 6G mmWave frequencies for research and development.
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Description
Test your knowledge on the basics of networks, including telecommunication networks, internet architecture, and the historical milestones that shaped the internet. This quiz will cover key concepts, laws, and the technology behind information transmission.
