Unbounded / Unguided media

Unbounded / Unguided media or wireless media doesn't use any physical connectors between the two devices communicating. Usually the transmission is send through the atmosphere but sometime it can be just across the rule. Wireless media is used when a physical obstruction or distance blocks are used with normal cable media. The three types of wireless media are:

·         RADIO WAVES

·         MICRO WAVES

·         INFRARED WAVES

 RADIO WAVES it has frequency between 10 K Hz to1 G Hz. Radio waves has the following types. That is Short waves, VHF (Very High Frequency) and UHF (Ultra High Frequency)

SHORT WAVES

There are different types of antennas used for radio waves. Radio waves transmission can be divided into following categories.

·         LOW POWER, SINGLE FREQUENCY

·         HIGH POWER, SINGLE FREQUENCY

·         LOW POWER , SINGLE FREQUENCY

As the name shows this system transmits from one frequency and has low power out. The normal operating ranges on these devices are 20 to 25 meter.

CHARACTERISTICS LOW POWER , SINGLE FREQUENCY

• Low Cost
• Simple Installation With Pre-Configured
• 1 M Bps To 10 M Bps Capacity
• High Attenuation
• Low Immunity To EMI

HIGH POWER, SINGLE FREQUENCY is the similar to low power single frequency. These devices can communicate over greater distances.

CHARACTERISTICS HIGH POWER, SINGLE FREQUENCY

• Moderate Cost
• Easier To Install Than Low Power Single Frequency
• 1 Mbps To 10 Mbps Of Capacity
• Low Attenuation For Long Distances
• Low Immunity To EMI

MICRO WAVES

Micro waves travels at high frequency than radio waves and provide through put as a wireless network media. Micro wave transmission requires the sender to be inside of the receiver.

Microwave is divide by 2. That is Terrestial MicroWaves and Satellitte MicroWaves.

1.   TERRESTRIAL MICROWAVE
~ require line-of-sight transmission and reception microwave
~ the taller the antennas, the longer the sight distance
~ signals are propagate in one direction in a time
~ consist of repeater which function to increase the distance
~ two types of antenna

Parabolic Dish
~ catching a wide range of waves and directing to a focus
~ higher frequencies for higher data rates
~ 10-60 GHz
Horn
~ looks like a gigantic scoop
~ deflected the waves outward in a series of narrow parallel beams
~ received transmission are collected by the scooped shape

2. SATELLITE
~ acting as a super tall antenna and repeater
~ relay station : receive on one frequency, amplifies and repeats signal and transmits on another frequency
~ geosynchronous : orbital speed is based on distance from planet
~ 35.784km away from the planet
~ uplink : transmission from earth to the satellite
~ downlink : transmission from satellite to earth

3. WIRELESS @ Wi-Fi
~ transmits computer data over distances using radio waves
~ most commonly used is 802.11 b (11MBps)
~ 802.11 a (54MBps)

~ to communicate over the network, computer must be equipped with a Wi-Fi card
~ types of Wi-Fi card : Wi-Fi PC Cards, USB Adapter, PCI and ISA Adapter etc.