1 Elements of Digital Communications

History of Long-Distance Communication

arose in the technology of transmission of electrical signals over wire communications lines. People tend to create methods and improvements in order to relay information

Smoke Signals

This is one of the oldest forms of long-distance communication for transmitting information. American Indians used this as a distress signal. This was also used in the Great Wall of China to relay messages of incoming threats

Pigeon Courier

This form is often used by ancient Persians, Romans, and Greeks to send messages using a bird as a courier

Semaphore Flags

In 1792, Claude Chappe developed a messaging system that uses flags as methods of communication

Pony Express

In 1860, this mail service delivers messages, newspapers, and mails using relays of horse-mounted riders

Electrical Telegraph

It revolutionized long-distance communication by sending electric signals (Morse code) in between two (2) stations

Wireless Telegraphy (Radio)

It is a transmission of electric current projected into space in the form of radio waves

Telephone

It is an instrument designed for the simultaneous transmission of human voice

1st Generation (1G)

This generation uses analog wireless technology in communications

2nd Generation (2G)

In this generation, Cellphones are upgraded from analog to digital. In this generation, the concept of Code Division Multiple Access (CDMA) and Global System for Mobiles (GSM) were implemented. It is the generation where Short Message Service (SMS), General Packet Radio Service (GPRS), and Packet Switching Network (PSN) is introduced

3rd Generation (3G)

This generaation uses a new technology called Universal Mobile Telecommunication Systems (UMTS) in which it can render multimedia services along a line with streaming. Evolved High-Speed Packet Access (HSPA+) is established in this generation

4th Generation (4G)

The key technologies that have made in this generation are Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM). The two (2) important 4G standards are WiMAX (Worldwide Interoperability for Microwave Access) and LTE (Long- Term Evolution

5th Generation (5G)

This generation rolls out faster data transfer speeds up to 10 times faster than 4G. It is presently happening like the Internet of Things (IoT), autonomous smart systems, and beamforming

Data Representation

Data is a piece of information that can be analog or digital. It can be in the form of a number, character, text, audio, or video. It can be created, deleted, stored, or transferred

Analog data

refers to continuous information

Digital data

takes on discrete values.
o These consist of ones and zeros (1’s and 0’s)

bits

can be a file, information, or instruction.

Digital communication

means communication through data bits (as in electric currents and voltages switching on or off). It is decoding information into a binary code and transmitting it in the form of a signal

Information Theory

According to Claude Shannon, a representation of the conditions and parameters affecting the transmission and processing of information. It overlaps heavily with communication theory, but it is more oriented toward the fundamental limitations on the processing and communication of information and less oriented toward the detailed operation of devices

Data communication

refers to the exchange of data between a source and a receiver in a network. It enables the movement of electronic or digital data between two (2) or more nodes, regardless of geographical location, technological medium, or data contents

A source

that generates the information Examples: computers, smartphones, tablets (terminal devices)

source encoder

A that converts the information into an electrical form called message signal

Example: modem

transmitter

A that is used to convert the message signal into a form acceptable to the channel
Examples: amplifiers and antennas

channel

A which is the path or link that connects the transmitter and the receiver

Example: may be in physical medium space such as wires or radio frequency (RF) signals

receiver

A performs an inverse function of that of the transmitter to recover the message signal Examples: filters and antennas

source decoder

A converts the electrical signal back to a form acceptable to the receiver

Example: modem

sink

A is the user of the information generated by the source
Example: computers, smartphones, tablets (terminal devices)

Point-to-Point (P2P) topology

It is a link that permanently connects two (2) nodes or network devices.

Point-to-Multipoint topology

One (1) node is connected to multiple nodes, each in a P2P manner

Multidrop topology

All nodes are interconnected by a single link with one (1) node that is the master node and the other nodes are secondary or slave nodes

Bus topology

It is like the multidrop topology with the exception that there is no master–slave relationship; all nodes are peers. The line terminator is used to prevent a signal that comes to the end of a transmission line from bouncing back and corrupting other signals on the line

Ring topology

The nodes are connected serially in a P2P manner with the last node connected to the first node to form a loop

Tree topology

It is formed by connecting multiple buses to form a system of branching links with no closed loop

Star topology

It is a topology in which each node is connected in a P2P manner to a central node called a hub

Mesh topology

The network nodes are interconnected arbitrarily. Generally, users are connected to only a subset of the nodes, and another set of internal nodes provides a switching facility that moves data from one node to another until it reaches its destination

Personal area networks (PANs)

are networks that interconnect devices within the reach of an individual, usually within a range of 10 meters. These devices are usually cellphones, tablets, and laptops

Local area networks (LANs)

cover small geographical areas, typically a building, a floor, or a campus. Examples include the Ethernet and token ring networks

Metropolitan area networks (MANs)

interconnect LANs in a campus or metropolitan area. An example includes the fiber distributed data interface (FDDI).

Wide area networks (WANs)

cover much larger areas such as a country (e.g., public switched telephone network [PSTN]) or the globe (e.g., the Internet).