Tuesday 29 May 2012


Wireless Technology

Assalammualaikum...

Wireless technology is a technology without using wires or cables.  There are three examples of wireless technology which are BLUETOOTH, INFRARED and BROADBAND. 

BLUETOOTH



  • A worldwide standard wireless through Personal Area Networks (PANs).
  • Can be used anywhere within a range of 10 metres.
  • A radio-based technology and does not need the line of sight.
  • Two types of service:
    • Point-to-point - One device to one device connection only.
    • Point-to-multiple - One device to eight more devices connection. Also called Piconets.
      • With multiple 'piconets' in one room, it is called 'scatternet'.


INFRARED

  • Same function with bluetooth tech which is to share files.
  • Shorter range than bluetooth - 5 metres.
  • Only for one-to-one connection - direct connection between two devices.
  • Uses Light Emitting Diodes (LEDs) to transfer data.
  • Cannot go through wall or any physical obstacles - need direct line-of-sight.

BROADBAND

  • A high-speed internet connection through Wireless Local Area Networks (WLANs).
  • Two types of broadband:
    • Fixed broadband.

      • In permanent locations only. (e.g. House and office).
      • Includes LMDS (Local Multipoint Distribution System) and MMDS (Multichannel Multipoint Distribution Service).
    • Mobile broadband.
  • In temporary locations - anywhere.
  • In variety devices such as portable modem or mobile phones.
  • Same technology as the fixed broadband, but it can be brought anywhere. 

Unbounded Media/Wireless Transmission Media

Assalammualaikum...

Unbounded Media/Wireless Transmission Media. 

This kind of media is commonly used because it is more convenient and could be used in locations that is impossible to install cables. 

Example:



Other than that, we also learned two types of antenna which arePARABOLIC DISH and HORN ANTENNA

PARABOLIC DISH (SATELLITE DISH)

  • A reflective instrument with circular parabolic shape which collects and projects energy.
  • Receive microwaves signals from satellites.
  • Transmit data/broadcast television programs.
  • A motor-driven one is the one that has planned movement to change its position.
  • Also known as earth-based station.
  • From an earth-based station to satellite, it is called uplink (going UP).
  • From satellite to an earth-based station, it is called downlink(going DOWN).
  • Placed on high places to avoid obstructions and where it is difficult to install physical transmission media. 



Parabolic Dish

HORN ANTENNA

  • For transmission and reception of microwave signals.
  • Commonly used as the active element in dish antenna.
  • Pointed toward the center of the dish reflector.
  • Minimizes the response to unwanted signals.


Horn Antenna


Cabling

Assalammualaikum..

In networking, cabling is used as transmission media to exchange information between two or more devices. There are  4 types of cables which are unshielded twisted pair (UTP) cable, shielded twisted pair (STP) cable, co-axial cable, and fibre-optic cable. 

1. Unshielded Twisted Pair (UTP) cable.





This is called "twisted pair". This type of cable contains four pairs of wires and each of them are twisted so that it will avoid or prevent any interference from adjacent pair and other electrical devices. The standard connector for this cable is RJ-45 (Register Jack). 

The disadvantage of this type of cable is that it brings harm to radio and electrical frequency interference. 

2. Shielded Twisted Pair (STP) Cable



It is almost the same as the Unshielded Twisted Pair cable (above) because each of the wire is twisted. However, what makes it different is that each pair of the twisted wire is wrapped in a foil shielding so that it becomes more reliable for data communication. In addition, it is commonly used in a network that uses Token Ring topology.

3. Co-axial Cable


It consists of a single coopered wire with three layers which are: insulating material, waven/braided material, and outer plactic coating. The waven/braided material is to block any interference, while the outer plastic coating functions as insulator. This type of cable is usually used by Cable Television (CATV) because it can be cabled over long distance. It uses Bayone-Neill-Concelman (BNC) as the connector. 


4. Fibre-optic Cable




These are dozens/hundreds of thin strands-glass/plastic in the fibre-optic cable which act as the core. 


This type of cable uses light to transmit signals from one device to another. It also consists of insulating glass caddling and protective coating. The advantages of this cable are faster, less susceptible to noise/interference, better security, smaller and carry more signals. However, the disadvantages are it will costs more, and difficult to be installed and modified. 

Topology

Assalammualaikum... 


Topology

It is also known as - Network Topology. Network Topology is the arrangement of a connection between nodes. In addition, these devices/nodes are connected via links such as  twisted pair copper wire cable or optical fiber cable.

There are 5 types of network topology:
  • Bus

This type of network topology connects nodes in a linear arrangement which has a main connected at each end. Just like a bus (public transport) which sends passengers along the route from one end to another. In term of network, the information is transferred along the way from one end to another. Therefore, each nodes will get the same information. If one of the nodes fails to work, it will not affect other nodes. However, if the main is not working, the whole system will stop functioning. 

  • Star

The 'Star' Network Topology connects nodes to only one main. As you can see in the diagram above, the arrangement of this type of network is exactly like a star. The difference of this arrangement from the bus network topology is that the nodes are directly connected to the main. If one of the nodes malfunction, it will not affect other nodes. However, if the main malfunctions, the whole system will not run. 

  • Ring

From the arrangement, it is obvious why it is named RING network topology. Unlike the BUS and STAR network topology which is connected with a main, this type of network topology connects the nodes with each other. Each node is connected to two other devices (from left and right). However, if one of the nodes fails to function, the whole system will not be working. 

  • Tree


Introduction to Networking

Assalammualaikum..

This week, we've learned the Introduction to Networking. Firstly, networking is about linking two or more devices such as computers. The main purpose of networking is actually to share files. The network is formed through all sort of cables either wireless or direct cabling.


LAN- Local Area Network
  • Limited to geographical area (Home, school computer, office, etc.)
  • Less than a mile range.
  • Uses one computer as a server - connected via cables.
  • WLAN - Wireless LAN - same function, but without physical wires/cables.
MAN - Metropolitan Area Network
  • In metropolitan area (city or town).
  • Includes one or more LANs, but smaller geographical area than WAN.
  • Provided by a single network provider that sells the service. (telephone cables, television cables, etc.)

WAN - Wide Area Network
  • Large geographic area (city, country, world, etc.)
  • Use satellite communication.
  • One large network or connected two or more LANs.

PAN - Personal Area Network
  • By the word "personal", it is obviously not for public use. 
  • Personal Wi-Fi (Wireless Fidelity) - requires a password in order to access.

 Hubs, Bridges, Routers, Switches, Gateways and Repeaters are required to build a network... 

Hubs
  • A very simple device.
  • Build LANs by connecting computers.
  • Forward received data to other connected computers.


Switches
  • More advanced - checks the destination to forward data to specific receivers.
  • Built-in software chips - fast and come with many ports.

Bridges
  • Extend networks by maintaining signals and traffic.
  • Slower - use software to perform switching.
  • Limited network distance range.

Routers
  • Connect different LANs or LAN with WAN.
  • Send data specifically to the receiver's internet address. 

Gateways
  • Running the appropriate software to connect between networks that use different protocols or architecture. 
  • Very intelligent.