Introduction to Telecommunications and Data Networks
1. Communication
Definition
Communication is the act by which an individual exchanges information with another.
2. Types of Data Networks
Node
A node is any computer connected to a network.
Local Area Network (LAN)
A LAN is a computer network limited to a small geographical area, typically within a single building or floor.
Metropolitan Area Network (MAN)
A MAN interconnects multiple LANs across a larger geographical area, such as a city. For example, government buildings in Santiago might be connected by a MAN.
Wide Area Network (WAN)
A WAN covers a broad geographical area, larger than a single building or campus. The internet is an example of a WAN.
Internet
The internet is a global network of computers that uses a set of protocols, the most prominent being TCP/IP.
3. Decibels in Telecommunications
Decibels (dB) measure the attenuation of a signal as it travels through a communication channel.
4. Calculating dB for Power Ratios
(Use 2 decimals)
5. Calculating Power Ratios for dB Values
(Use 2 decimals)
6. Plotting a Sine Wave
Plot a sine wave with a frequency of 4 Hz.
9. Switching in Telecommunications
Definition
Switching is a technique that connects two nodes in a telecommunications network to establish a communication path. It allows nodes to communicate without a direct physical link, reducing network congestion, traffic, and increasing bandwidth.
Switching Elements/Devices
- Switches
- Routers
- Hubs
- Gateways
10. Purpose of Switching Nodes
The main purpose of switching nodes is to receive and forward data packets.
11. Phases of Circuit Switching
Establishment of the Circuit
When communication is initiated, a circuit is established between the originating and destination stations. This process allocates channel capacity and determines the type of service.
Transmission of Communication
Once the circuit is established, information flows between the stations. The transmission can be digital or analog, and unidirectional or full-duplex, depending on the network service.
Disconnecting the Circuit
After data transmission is complete, one station initiates the session’s end and disconnects the circuit, freeing up resources for other communications.
12. Packet Switching Techniques
Datagram Technique
Each packet is treated independently. The sender adds information like packet number, source/destination address, and sends it to the destination. Packets may take different routes, potentially arriving out of order. The receiving station rearranges packets and handles lost packets.
Virtual Circuit Technique
A control packet establishes a logical path between sender and receiver before data transmission. All packets follow the same route, ensuring order of arrival. Virtual circuits can be permanent or switched.
1. Active Satellite Subsystems
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2. Channel Division
Logically dividing a transmission channel into multiple subchannels for simultaneous data transmission is called commutation.
3. Routing
Finding the best routes between pairs of nodes is called routing.
4. Fundamental Unit of Information Transport
The fundamental unit of information transport is a data packet.
5. Discovery of Electricity Transmission
Stephen Gray discovered that electricity could be transmitted in 1729.
6. Half-Duplex Transmission
Two-way transmission where only one transmitter can transmit at a time (e.g., telephone, walkie-talkies) is called half-duplex mode.
7. Alessandro Volta’s Invention
In 1801, Alessandro Volta introduced his invention called the “Voltaic Pile”.
8. Node Definition
Any computer connected to a network is called a node.
9. First Transoceanic Communication
Guglielmo Marconi established the first transoceanic communication between Cornwall, Britain, and Newfoundland, Canada, on December 12, 1901. The frequency used was 820 kHz (366 m) with a transmitter power of 15 kW.
10. Full-Duplex Transmission
Two-way transmission where simultaneous transmission is possible (e.g., chat, video conferencing) is called full-duplex mode.
11. Invention of the Coherer
Édouard Branly built the first electromagnetic wave receiver called the coherer, consisting of a tube filled with iron filings connected to a battery and a galvanometer.
12. First Telephone Patent
Alexander Graham Bell was granted the first telephone patent on February 14, 1876. His system consisted of a microphone and speaker.
13. Modem Definition
A modem (modulator-demodulator) converts digital signals (from a PC) to analog signals (for a phone line) and vice versa, enabling communication between computers via phone or cable lines.
14. Simplex Transmission
One-way transmission (e.g., television, radio) is called simplex mode.
15. Telecommunication Definition
Telecommunication is the transmission, emission, or reception of information, signs, signals, writing, images, sounds, etc., over a distance using physical lines, radio, optical, or other electromagnetic systems.
16. Minimum Unit of Information
The figure refers to the bit, the minimum unit that represents any information.
17. Interconnected Computers
When two or more computers are connected to share resources, it forms a network (or potentially the internet, depending on the scale and connection method).
18. Connecting Networks with Protocols
Connecting two or more networks with a set of protocols is called internetworking.
19. Attenuation Definition
Attenuation is the progressive decrease in signal strength with distance.
20. Interference Definition
Interference is any unwanted signal that mixes with the transmitted signal, causing undesirable changes to its information content.
21. Frequency Definition
Frequency is a measure of how often a phenomenon or event occurs per unit of time. It’s also the unit of measurement for different frequencies in telecommunications (measured in Hertz, Hz).
22. Peak/Crest and Valley/Trough
The maximum positive and negative values that a sinusoidal signal can reach are called the peak (or crest) and valley (or trough), respectively.
24. Distortion Definition
Distortion is the alteration of a signal caused by limitations within the transmission system itself.
25. Crosstalk Definition
Crosstalk is the distortion of a signal caused by interference from similar signals outside the system.
26. Noise Definition
Noise refers to random and unpredictable signals that are added to the information signal, causing partial or total deformation.
27. Bit Definition
A bit is the basic unit of information in computing, representing data as either 0 or 1.
28. Data Transmission and Storage Units
Data transmission speeds are typically measured in bits per second (bps), while storage or file sizes are specified in bytes.
29. Byte Definition
A byte is a group of eight bits used to store information electronically.
30. Electrical Signal Definition
An electrical signal is the electrical representation of information, typically a voltage or current that carries the message to be transmitted.