DATA TRANSMISSION

Data can be transferred from one point to another using various methods: 

• Copper cable using radio pulses 
• Wirelessly using radio frequency
• Optical fiber using light 
• Infrared 

Data packet: 

• A packet of data in a unit of data contains a
  • packet header
  • Payload
  • trailer

• The packet header includes the:
  • – destination address
  • packet number
  • originator’s address

A data packet is a unit of data made into a single package that travels along a given network path. Data packets are used in Internet Protocol (IP) transmissions for data that navigates the Web, and in other kinds of networks.

• Data is broken down into packets
• Each packet could take a different route
• A router controls the route a packet takes
• Packets may arrive out of order
• Once the last packet has arrived, packets are reordered

Serial and Parallel Data Transmission

There are 2 types of data transmission: Serial and Parallel

A serial line uses one channel whereas a parallel line uses multiple channels 

Serial transmission:

• Bits are sent one signal at a time over a single wire 
• Very high data transfer rates can be achieved
• Using fiber-optic cable, data transfer rates ranging from around 50 Megabits per second (Mbs) to 100 Gigabits per second (Gbs) can be achieved
• Used with USB (Universal Serial Bus) cables

Parallel transmission: 

• Signals (bits) are sent simultaneously over a number of parallel wires

Skew

Data skewing- data going at different speeds – is a disadvantage of using parallel line

• Each wire in a parallel cable has slightly different properties
• Signals travel down wires at different speeds
• Transmission must be over very short distances to reduce the problem
• Interference can also disrupt data transmission 

Bandwidth: the size of the data tunnel. The higher the bandwidth, the more data that can be transferred / The amount of data that can be carried at one time 

Integrated Circuits

• Known as a ‘chip’, an IC is made of semiconductor material called silicon
• The silicon layer assembles millions or billions of tiny resistors, transistors, and resistors sending data in parallel   

Advantage of serial over parallel transmission

• Smaller simpler and cheaper connectors such as those used for smartphones
• “Crosstalk” creates interference between parallel lines, and can result in corrupted lines, and can result in corrupted words which then need to be retransmitted
• Serial links are more reliable over much greater distances than parallel links 

Transmission direction

• Simplex, duplex, and half-duplex are terms referring to the direction of data during transmission
• These terms can be used in conjunction with serial and parallel transmission technology 

Simplex transmission (serial) 

•  data travels in one direction only (used for sending data from a keyboard to the CPU) 

Half-duplex transmission:  (serial)

• Data can travel in both directions on a single cable, but not simultaneously
• Used in parallel printer cables: the text is sent to a printer, and the printer can send ‘Out of paper’ messages back, but only when the computer has finished sending text. 

Full duplex transmission: (parallel) 

• Data can travel in both directions simultaneously using two cables
• Commonly used in fiber optical networking(/optic fiber) or internet cables for upload and download 
• Optic fiber uses light to transmit data 

The Internet

The internet is an example of a collection of WAN

LAN= local area network

WAN= wide area network

Internet Service Providers (ISPs)

• An ISP is a company supplying connectivity to the Internet
• They also offer:
• Email services
• Web hosting
• VOIP facilities (Voice over Internet protocol)

Accessing the World Wide Web

• What type of software do you use to access the WWW- Internet browser
• Name some examples of this type of software- google, yahoo, Internet Explorer, safari
• What type of software do use to get information from the www about a particular topic- search engine 
• Name some examples of this type of software – google, yahoo

Browser software:

• Internet Explorer, Google Chrome, Mozilla Firefox, and Safari are all examples of browser software
• One way of accessing a particular page on the www is to type its address into the address bar

HTTP: hypertext transfer protocol

HTTP: hypertext transfer protocol secure 

Advantages of using www for information: 

Relevant, time-efficient, and consistently accessible globally meaning that u can find answers to your questions anytime