1.1 Components & Characteristics
Data communication is the transfer of information among two or more networked devices.
5 Key Components
- 1. Message: The data to be communicated (text, video, audio).
- 2. Sender: The device sending data (Computer, Phone).
- 3. Receiver: The appliance receiving messages.
- 4. Medium: The physical/wireless path (Cables, Radio).
- 5. Protocol: Rules governing data communication.
Key Characteristics
1.2 Analog vs Digital Signals
Comparing continuous variations with discrete values.
Analog Signal
Continuous and varies smoothly over time. Represents infinite values within a range.
Digital Signal
Discrete and quantized. Takes only specific distinct values (0s and 1s).
1.3 Encoding & Modulation
Translating data into transportable formats.
Digital Modulation Simulator
Modulation shifts digital baseband signals to a higher frequency using a carrier wave. Try different modulation types below for the binary sequence: 1 0 1 1 0
Amplitude Shift Keying (ASK)
Each symbol gives a unique amplitude to the carrier wave. (e.g., Logic 1 = High Amplitude, Logic 0 = Zero/Low Amplitude).
Line Encoding
Converts digital data to digital signals. Types include:
- Unipolar (NRZ): 1 is pulse, 0 is no pulse (ON-OFF Keying).
- Polar (NRZ, RZ, Manchester): Uses positive and negative voltage levels.
- Bipolar (AMI): Three levels (+, -, 0). 0 is neutral, 1 alternates between positive and negative.
1.4 Transmission Modes
Directionality of data flow between devices.
Simplex Mode
Unidirectional communication (One-way street). Device can only transmit OR receive.
Example: Keyboard to Monitor.
Half-Duplex Mode
Bidirectional, but not at the same time. Entire channel capacity used by one at a time.
Example: Walkie-Talkie.
Full-Duplex Mode
Simultaneous bidirectional communication. Channel capacity is shared.
Example: Telephone Network.
1.5 Transmission Media
The physical and wireless paths that carry data.
Guided Media (Wired)
Unguided Media (Wireless)
Optical Fiber
Uses the concept of total internal reflection of light through a core made of glass. Very high capacity and immune to electromagnetic interference.