Title: Theory / Unimportant / CS / Hardware / Computer Network - Tanenbaum / 2 Physical
Tags: cossin_ab
On every note of this deck, unless a note says otherwise:
Chapter: 2

Name: hertz
Abbreviation: Hz
Chapter: Appendix 1
Page: 91
Represents: Number of cycle by second
s: -1
Other fields (not shown on cards):
SI types: s^-1

Name: The fundamental frequency of \(g\)
Definition: The inverse of the least period of \(g\)
Page: 90
Section: 1.1
Variables: \(g(t)\) a «reasonnably behaved» periodic function
Denoted by: \(f\)

Name: An harmonic of \(g\)
Definition: Some \(a_n\sin(2\pi nft)\) or \(b_n\cos(2\pi nft)\)
Page: 90
Section: 1.1
Variables: \(g(t)\) a «reasonnably behaved» periodic function
\(\frac12 c+\sum_{n=1}^\infty a_n\sin(2\pi nft)+\sum_{n=1}^\infty b_n\cos(2\pi nft)\) its Fourier series

Name: The Fourier series of \(g\)
Definition: An expression of the form \(\frac12 c+\sum_{n=1}^\infty a_n\sin(2\pi nft)+\sum_{n=1}^\infty b_n\cos(2\pi nft)\), equal to \(g(t)\)
Page: 90
Section: 1.1
Variables: \(g(t)\) a «reasonnably behaved» periodic function
\(f\) its frequency

Definition: [$]\frac2T\int_0^Tg(t)\sin(2\pi nft)\dd t[/$] with \(T\) the period
Page: 90
Section: 1.1
Variables: \(g(t)\) a «reasonnably behaved» periodic function
\(f\) its frequency
Context: Fourier Series
Notation: \(a_n\)
Extra: Suspended, because it contradicts Zorich's book

Definition: [$]\frac2T\int_0^Tg(t)\cos(2\pi nft)\dd t[/$] with \(T\) the period
Page: 90
Section: 1.1
Variables: \(g(t)\) a «reasonnably behaved» periodic function
\(f\) its frequency
Context: Fourier Series
Notation: \(b_n\)
Extra: Suspended, because it contradicts Zorich's book

Definition: [$]\frac2T\int_0^Tg(t) \dd t[/$] with \(T\) the period
Page: 90
Section: 1.1
Variables: \(g(t)\) a «reasonnably behaved» periodic function
\(f\) its frequency
Context: Fourier Series
Notation: \(c\)

Name: (Analog) Bandwidth
Definition: The width of the frequency range transmitted without being strongly attenuated (diminshed by half)
Page: 91
Section: 1.1

Name: Baseband signal
Definition: Signals that run from 0 up to a maximum frequency
Page: 91
Section: 1.1

Name: Passband signal
Definition: Signals that are shifted to occupy a higher range of frequencies
Page: 91
Section: 1.1

Name: Voice-grade line
Definition: An ordinary telephone line
Page: 91
Section: 1.1
Definition2: an artificially introduced cutoff frequency just above 3000 Hz

Name: Digital bandwidth
Definition: Number of bit per second that can be transmitted through a channel
Page: 93
Section: 1.1

Smaller0: the signal has been passed through a low-pass filter of bandwidth \(B\)
Greater0: \(g(t)\) can be reconstructed by making only \(2B\) samples per second
Page: 93
Chapter: 2
Section: 1.1
Variables: \(g(t)\) a signal
Greater1: \(2B\log_2 V\) bps, where \(V\) is the number of discrete levels
Connect Greater0: and the maximum data rate is

Name: Signal-to-Noise ratio
Definition: \(10\log_{10} S/N\) with \(S\) the signal power and \(N\) the noise power
Page: 93
Section: 1.1
Variables: \(g(t)\) a signal
Context: Network
Abbreviation: SNR
Intuition: The amount of thermal noise present
Typ: decibels

Question: The maximum number of bps is
Answer: \(B\log_2(1/+S/N)\)
Page: 93
Chapter: 2
Section: 1.1
Variables: \(S/N\) the signal-to-noise ration
\(B\) the bandwidth
Context: Network

Name: Guided media
Page: 95
Example: copper wire, coaxial cable, fiber optics
Example2: Power line
Example3: Magnetic media (dvd, usb stick)

Name: Unguided media
Page: 95
Example: radio transmission satellite
Example2: lasers through the air
Example3: Electromagnetic spectrum

Name: Delay
Definition: Time between some media is sent and received
Page: 96
Section: 22
Context: Network

Question: Why are pair of copper wires twisted
Answer: Message is sent as difference between the two pairs. Twisting ensure that the waves from different twists cancel out, so the wire radiates less effectively. (I.e. message goes through the wire and does not radiate from it)
Page: 96
Chapter: 2
Section: 22

Name: Telephone company
Page: 96
Section: 22
Abbreviation: Telco

Name: Full-duplex links
Definition: A link which can be used in both direction simultaneously
Page: 97
Section: 22

Name: Half-duplex links
Definition: A link which can be used in both direction but not simultaneously
Page: 97
Section: 22

Name: A simpler links
Definition: A link which can be used in a single direction
Page: 97
Section: 22

Name: Unshielded Twisted Pair
Definition: Links consisting simply of wires and insulator
Page: 97
Section: 22
Abbreviation: UTP

Name: Coaxial cable
Definition: Copper core
Page: 98
Definition2: Insulating material
Conjdef: From inside to outside
Definition3: Braided outer conductor
Intuition: Better than twisted pair to resist interference
Definition4: Protective plastic covering

Question: What currently limite fiber optic speed
Answer: Conversion between electrical data and light
Page: 100
Chapter: 2
Section: 2.4

Name: Fiber to the Home
Page: 100
Section: 2.4
Abbreviation: Ftth

Name: Fiber optics
Definition: ultra-thin fiber of glass
Page: 100
Section: 2.4
Definition2: a detector sending electrical pulse when light falls on it
Definition3: A light source emitting ligth when electrical pulse is received

Question: Why does light remains in fiber of glass
Answer: When a light ray passes from one medium to another—for example, from fused silica to air—the ray is refracted (bent) at the silica/air boundary, as shown in Fig. 2-6(a). For an angle high enough, the light remain in the fiber.
Page: 100
Chapter: 2
Section: 2.4
Context: Fiber optics

Name: Multimode fiber
Definition: A fiber in which multiple ray of light may bounce simultaneously at differente angle
Page: 100
Section: 2.4

Name: single-mode fiber
Definition: A fiber in which light propagate in straight line
Page: 100
Section: 2.4

Name: The attenuation of light through F
Definition: the ratio of input to output signal power in F
Page: 100
Section: 2.4
Variables: some glass fiber F

Name: Chromatic dispersion
Definition: The way light pulses spead out in the fiber
Page: 103
Section: 2.4
Context: glass fiber

Name: A soliton
Definition: A kind of light pulse such that chromatic dispertion of two successive pulse cancel
Page: 103
Section: 2.4
Context: glass fiber

Name: Fiber cable
Page: 103
Section: 2.4

Question: How to connect fiber cables
Answer: They terminate in connectors
Page: 103
Chapter: 2
Section: 2.4
Answer2: Two fibre cables are placed next to each other, and adjusted to increase light transmitted
Answer3: Fusing two fiber cables together.

Name: Wavelength
Definition: Difference between two consecutive maxima in signal \(f\)
Page: 106
Section: 3
Variables: \(f\) a signal
Context: Period?
Denoted by: \(\lambda\)

Name: Speed of light
Abbreviation: \(c\)
Chapter: 2
Page: 106
Exponant: 8
Section: 3
Typ: m/sec
s: -1
m: 1

Name: Frequency hopping spread spectrum
Definition: the transmitter hops from frequency to frequency hundreds of times per second
Page: 106
Section: 3
Intuition: Ensure communication is hard to detect and to jam

Name: Direct sequence spread spectrum
Definition: Communication which uses a code sequence to spread the data signal over a wider frequency band
Page: 108
Section: 3

Name: Spread spectrum
Definition: Frequency hopping spread spectrum
Page: 108
Section: 3
Definition2: Direct sequence spread spectrum
Conjdef: Either
Definition3: Ultra-wide band

Name: Ultra-wide band
Definition: signals that have a bandwidth of at least 500 MHz or at least 20% of the center frequency of their frequency band
Page: 108
Section: 3
Abbreviation: UWB
Intuition: Communication which sends a series of rapid pulses, varying their positions to communicate information

Name: A signal which underlay other signals
Definition: A signal which can be sent without disturbing other signals
Page: 108
Section: 3

Name: Radio frequency
Page: 109
Section: 3.2
Abbreviation: RF

Question: Why is usage of radio frequency limited by governement
Answer: Because they travel long distance and easily interferes with each other
Page: 109
Chapter: 2
Section: 3.2

Question: Which radio frequencies follows earth curvature
Answer: All except for high frequency
Page: 109
Chapter: 2
Section: 3.2

Question: Which radio frequencies bounce of ionosphere
Answer: High frequency.
Page: 109
Chapter: 2
Section: 3.2

Name: Microwave transmission
Definition: Radiofrequency over MHz
Page: 109
Section: 3.2

Name: Multipath fading
Definition: In a microwave transmission, the fact that a directional beam get les focused due to weather or other various condition
Page: 109
Section: 3.2

Name: Beauty contest
Definition: To allocate part of the spectrum of radio wave, each carrier explain why its service best serve public interest
Page: 109
Section: 3.2
Context: Bandwidth

Question: How do government allocate part of the spectrum of radio wave
Answer: Beauty contest
Page: 112
Chapter: 2
Section: 3.2
Answer2: Lottery
Answer3: Auction
Answer4: Letting anyone use a part, and limitting the transmitting power

Name: Industrial, Scientific, Medical
Definition: there is no restriction, anyone can use it; but with small transmission power
Page: 112
Section: 3.2
Context: Computer network
Abbreviation: ISM
DefType: Part of the spectrum of wireless communication

Name: Unlicensed National Information Infrastructure
Page: 113
Section: 3.2
Abbreviation: U-NII

Name: White space
Definition: frequency bands that have been allocated but are not being used locally
Page: 113
Section: 3.2
Context: Electromagnetic Spectrum

Question: What is the particularity of radio waves above 60GHz
Answer: It's absorded by oxygen, and thus have short range
Page: 113
Chapter: 2
Section: 3.2

Question: Advantages of laser transmission
Answer: Don't require FCC license
Page: 114
Chapter: 2
Section: 3.2
Answer2: Can not be easily taped by ennemy
Answer3: Quick
Answer4: Low cost

Question: Problem of laser transmission
Answer: Require quite high precision, and
Page: 114
Chapter: 2
Section: 3.2
Answer2: can be disturbed by weather or movement