Communication in a Connected World

Module 1.

The Bit

Computers only work in binary digits, each bit has one of two possible values: 0 or 1. Bit is an abbreviation of "binary digit" and represents the smallest piece of data. Bits are stored and transmitted as one of two discrete states. This can include two directions of magnetization, two voltage or current levels, two levels of light intensity or any other system of two discrete states.

Every input device translates human interaction into binary code for processing, every output will take binary code and translate it into human understandable form. Computers use binary to represent and interpret letters, numbers and characters with bits. ASCII (American Standard Code for Information Interchange) is used commonly, where each character is represented by eight bits.

Each group of eight bits is called a byte.

Data Transmission

Bits must be converted to signals which can be sent across network media to a destination. Media can be copper wire, fiber-optic cable or electromagnetic waves through the air. Signals consist of electrical or optical patterns, the patterns represent digital bits and travel from source to destination as pulses of electricity, pulses of light or radio waves. Three common methods of signal transmission are:

• Electrical Signals : represents data as electrical pulses on copper wire.

• Optical Signals : converts electrical signals into light pulses.

• Wireless Signals : uses infrared, microwave or radio waves over the air.

Bandwidth & Throughput

Bandwidth is the capacity of a given medium to carry data. This measures the amount of data that can travel from one place to another in a given amount of time. This is typically measured by number of bits that can be sent per second. Measurements are as follows:

Unit of Bandwidth	Abbreviation	Equivalence
Bits per Second	bps	1bps = fundamental unit
Kilobits per Second	Kbps	1 Kbps = 1,000 bps
Megabits per Second	Mbps	1 Mbps = 1,000,000 bps
Gigabits per Second	Gbps	1 Gbps = 1,000,000,000 bps
Terabits per Second	Tbps	1 Tbps = 1,000,000,000,000 bps

Throughput is the measure of the transfer of bits across media over a period of time. Throughput does not normally equal bandwidth, a few factors influence this:

• Amount of data being sent & received over the connection

• Types of data transmitted

• Latency created by network devices between source & destination

Latency is the amount of time for data to travel from point A to point B. Throughput does not account for validity or usefulness of bits transmitted and received. For example, network control messages that correct errors would be counted. In an internetwork or network with multiple segments, the throughput cannot be faster than the slowest link of the path from sender to receiver.