Chapters 5 and 6 Flashcards
analog signal
characterized by a continuous mathematical function, when the input changes from one value to the next
digital signal
has a fixed set of valid levels, and each change consists of an instantaneous move from one valid level to another
source coding
logical representation of data with no physical signal associated with it
Wavelength
Length of a single cycle as wave propagates across a medium
Frequency
number of oscillations per time unit (1 period per x seconds, 1/x Hz)
Amplitude
Difference between max and min signal height
Phase
Shift from a reference time
line coding
converts the stream of binary digits into a specific physical signal for transmisison
Digital Signal
signal that represents a bit stream, can be implemented using fixed signals of voltage, signal levels
Baud
number of times a signal can change, per second
the ability to send or receive a signal
Bit Rate (Network Bandwidth)
data transfer rate measured in bps
analog bandwidth
difference between the highest and lowest frequency of signal measured in Hz
bit
binary digit, 0 or 1
byte
group of eight bits representing 256 decimal numbers, 0-255, and hexadecimal numbers 00-FF
ASCII
American Standard Code for Information Interchange
7 bits per character
UTF-8
Newer character coding,
8 bits per character
Motivation for Data Communications
- The sources of information can be arbitrary types
- Transmission uses a physical system
- Multiple sources of information can share the underlying medium
Information Sources
A source of information can either be analog or digital. Important concepts include characteristics of signals (amplitude, frequency, phase). Classification is either periodic or aperiodic. The subtopic focuses on conversion between analog and digital representations of information
Source Encoder and Decoder
Once information has been digitalized, digital representations can be transformed and converted. Important concepts include data compression and its consequences for communications
Encryptor and Decryptor
To protect information and keep it confidential, the information can be encrypted before transmission and decrypted upon reception. Important concepts include cryptographic techniques and algorithms
Channel Encoder and Decoder
Used to detect and correct transmission errors. Important topics include methods to detect and limit errors, and practical techniques like parity checking, checksums, and cyclic redundancy codes that are employed in computer networks
Multiplexor and Demultiplexor
Multiplexing refers to the way information from multiple sources is combined for transmission across a shared medium. Important concepts include techniques for simultaneous sharing as well techniques that allow sources to take turns when using the medium
Modulator and Demodulator
refers to the way electromagnetic radiation is used to send information. Concepts include analog and digital modulation schemes, and devices known ad modems that perform the modulation and demodulation
Physical Channel and Transmission
The subtopic includes transmission media and transmission modes. Important concepts include bandwidth, electrical noise and interference, and channel capacity, as well as transmission nodes, such as serial and parallel
Manchester Encoding
1 = corresponds to a transition from 0 volts to a positive voltage level
0 = corresponds to a transition from a positive voltage level to 0
