Wired and Wireless Networks

Transmission media:

In network communications, a transmission medium is a physical connection or an interface between the transmitter and the receiver.

There are two major categories of transmission media, namely
* guided and
* wireless (or unguided).

1. Guided Media /Wired Network/ Media

It is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.

Features:
• High Speed
• Secure
• Used for comparatively shorter distances

There are 3 major types of Guided Media:

The medium used to connect different devices in a network is called as Transmission media or channel. Networks/ channels can be guided(wired) or unguided(wireless).
Trans medium can be classified as

Wired or Guided media are also known as physical or conducted media. These media use various types of cables e.g. Twisted Pair Cable, Coaxial Cable and Fibre Optic Cable for transmitting data over various networks. Wired networks , also called Ethernet networks, are most common type of local area netwok(LAN) technology. A wired network is a collection of two or more computers , printers and other devices linked by Ethernet cables. Ethernet is the fastest wired network protocol with connection speed of 10 Mbps to 100 Mbps or higher.

Basic communications media types

• Copper
  • unshielded twisted pair (utp)
  • shielded twisted pair (stp)
  • coaxial cable (thinnet, thicknet)
• Fiber optic
  • single-mode
  • multi-mode
• Infrared
• Radio & microwave

Twisted Pair Cable

• These cables consist of two insulated copper wires twisted around each other in a double helix.
• Twisting of wires reduces crosstalk which is bleeding of a signal from one wire to another.

Types:

• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP

STP offers greater protection from interference and crosstalk due to shielding.

But it is heavier and costlier than UTP.

USE 1. In local telephone communication

2. For digital data transmission over short distances upto 1 km

Advantages:

• Easy to install and maintain
• Simple
• Inexpensive
• Low weight
• Suitable for small (Local) Networks

Disadvantages:

• Not suitable for long distance due to high attenuation.
• Low bandwidth support.
• Low Speed

Coaxial cable

• Coaxial cable consists of a solid copper wire core surrounded by a plastic cladding shielded in a wire mesh.
• Shield prevents the noise by redirecting it to ground.

Types:

Coaxial cable comes in two sizes which are called thinnet and thicknet.

• Thicknet : segment length upto 500 m
• Thinnet  : segment length upto 185 m

USE:

In TV channel communication

Advantages:

• Better than twisted wire cable.
• Popular for TV networks.
• Offers higher bandwidth & Speed

Disadvantages:

• Expensive than twisted wires.
• Not compatible with twisted wire cable.

Optical Fibres

• Thin strands of glass or glass like material designed to carry light from one source to another.
• Source converts (Modulates) the data signal into light using LED (Light Emitting Diodes) or LASER diodes and send it over the Optical fiber.

It consists of three parts:

1. The core: glass or plastic through which the light travels.
2. The cladding : covers the core and reflects light back to the core
3. Protective coating : protects the fiber

Advantages

• Not affected by any kind of noise.
• High transmission capacity
• Speed of Light
• Suitable for broadband communication

Disadvantages

• Installation requires care.
• Connecting two Optical fibers is difficult.
• Optical fibers are more difficult to solder
• Most expensive

Microwaves

Microwaves are transmitted from the transmitters placed at very high towers to the receivers at a long distance.

Microwaves are transmitted in line of sight fashion, and also propagated through the surfaces.

Advantages

• Maintenance easy than cables.
• Suitable when cable can not be used.

Disadvantages

• Repeaters are required for long distance communication.
• Less Bandwidth available

Satellite

Geostationary satellites are placed around 36000 KM away from the earth’s surface. In satellite communication transmitting station transmits the signals to the satellite. (It is called up-linking). After receiving the signals (microwaves) it amplifies them and transmit back to earth in whole visibility area.

Receiving stations at different places can receive these signals. (It is called down-linking).

Advantage

• Area coverage is too large

Disadvantage

• High investment