Physical Layer Flashcards
Where is the Network Express card implemented in TCP/IP model?
The NIC is implemented by both the physical and data link layer through physical connection to the network(sockets, antenna) and the unique data link address(MAC Address), respectively.
Function of NIC?
Its function is to implement protocols for error detection, frame construction, modulation, encoding,etc.
Where is the NIC in computers?
The client and server both have NIC’s. It is connected by the computer through either being built-in the motherboard or connected separately(USB, PCI express,etc)
Use of network cables?
In a LAN, network cables are used connected the switch to the client and server. They provide physical connection between network devices.
Different types of Network cables?
Unshielded twister pair(UTP)-
no aluminium or copper shielding to protect from electromagnetic interferences from electrical machines and interferes with signal. used in office environment
Shielded Twister Pair(STP)- used in industry with electrical machines protecting from EMI. expensive, heavy 10x more than UTP.
Optical fibre-
not common in LANS
pairs sending and receiving data
long distance communication within kms.
Coaxial -
-thick ethernet
-old LANS
How do physical signals work?
Information is transmitted through physical signals and signals are transferred through a medium.
For e.g electric signals from copper wires
radio waves through air
light signals through air or optic fibre.
Digital vs Analog data?
Digital data are discrete values from one to the next(for e.g 0 or 1, letters of alphabet)
waveform with discrete values
Analog data are a range or possible values where there is a continuous variation over time.(e.g temperature, air pressure)
continuous often sinusoidal wave.
What are the different transmission types?
There can be-
Analog signals for analog data
-analog AM, FM radio.
Digital signals for digital data
-old ethernet, USB, computer bus
Digital signals for analog data!
-modems, ADSL,ethernet,WiFi, 4G,etc.
What is digital transmission?
Digital signals are usually transmitted through copper cables by encoding 0 and 1 into different voltages on the cable. The result is a square wave. Simple encoding→ unipolar.
NRZ- non return to zero - 0 is 1(positive) and 1 is 0 (negative).
What is manchester encoding*
Self clocking for e.g on cat 5 ethernet cables.
Mid bit transition
How does analog transmission work?
Through sine waves with
Amplitude is the height of the wave, its loudness and voltage level , e.g AM radio
Frequency is the number of clock cycles, measured in Hertz, E.g FM radio
Phase angle- initial angle through which wave began
What is modulation(changing a signal) Types of modulation?
Analog signals are waves, hence we have a constant carrier wave(constant amplitude, frequency , or phase angle) while modulating one of the characteristics to encode(representing a signal) the bits-
- Amplitude Modulation- 1 is high height, 0 is low height
- Frequency modulation-clock cycles- kinda width - 1 dense(more cycles), 0 wide(less clock cycles).
- Phase Modulation-
1 starting from 90 degreee
0 starting from 0 degree
How to combine Amplitude Modulation(AM) and Phase Modulation(PM)?
4 different A amplitudes, 2 different phase angles = 8 different symbols
There is 3x the data transmission rate
