Day 7 - Wednesday, 9 May 2012

Hi everyone. The topic for this entry is WIRELESS TECHNOLOGY.

NETWORK COMMUNICATION STANDARDS

Today's networks connect terminals, devices, and computers from many different manufacturers across many types of networks, such as wide area, local area, and wireless. 

A network standard defines guidelines that specify the way computers access the medium to which they are attached.

Wi-Fi

Computers and devices that have the appropriate wireless capability can communicate via radio waves with other computers or devices using Wi-Fi (wireless fidelity), which identifies any network based on the 802.11 standards.

Develop by IEEE, 802.11 is a series of network standards that specifies how two wireless devices communicate over the air with each other.

BLUETOOTH 

Bluetooth is a network standard, specially a protocol, that defines how two Bluetooth devices use short-range radio waves to transmit data. The data transfers between devices at a rate of up to 3 Mbps. 

Bluetooth devices often must be within about 10 meters (about 33 feet) but can be extended to 100 meters with additional equipment in order to communicate with each other.

A Bluetooth device contains a small chip that allows it to communicate with other Bluetooth devices. Examples of Bluetooth - enabled devices can include desktop computers, notebook computers, handheld computers, smart phones, headsets, keyboards, mouse devices, microphones, digital cameras, GPS receivers and printers. 

INFRARED 

Some computers and devices use the IrDA standard to transmit data wirelessly to each other via infrared (Ir) light waves. The devices transfer data at rates from 115 Kbps (thousand bits per second) to 4 Mbps between their IrDA ports.

Infrared requires a line-of-sight transmission; that is, the sending device and the receiving device must be in line with each other so that nothing obstructs the path of the infrared light wave. 

BROADBAND

The term broadband refers to a telecommunications signal or device of greater bandwidth. A broadband signalling method is one that includes or handles a relatively wide range of frequencies. The wider the bandwidth of a channel, the greater the information- carrying capacity, given the same channel quality.

Broadband system usually use a different radio frequency modulated by the data signal for each band. The total bandwidth of the medium is larger than the bandwidth of any channel. In data communications, a 56 k modem will transmit a data rate of 56 kilo bits per second over 1 4 kilo hertz wide telephone line.

Broadband media transmit multiple signals simultaneously. In many cases, download transfer rates of broadband are faster than its upload transfer rates. Home and business users today opt for broadband Internet access because of the fast transfer rate.

That is all for this entry. Thank you for spending your time to read.

   

Day 6 - Wednesday, 2 May 2012

Hi everyone. The topic for this week lesson is regarding to WIRELESS TECHNOLOGY. Wireless is also known as Unbounded or Unguided Media.

Wireless networking technologies range from global voice and data networks, which allows users to establish wireless connections across long distances, to infrared light and radio frequency technologies that are optimized for short-range wireless connections.

Wireless connection

Wireless signals are used to send signal through the air between devices instead of using a physical cable.

Wireless network most commonly used to refer to a telecommunications network whose interconnections between nodes is implemented without the use of wires, such as a computer network.

Wireless telecommunication networks are generally implemented with some type of information transmission system that uses electromagnetic waves.

Wireless communication involves:

1. Radio frequency communication

2. Microwave communication

3. Infrared (IR) short-range communication 

TERRESTRIAL MICROWAVE

- require line-of-sight transmission and reception

two types of antennas:

parabolic dish and horn

- works like a funnel (catching a wide range of waves and directing to a common point called focus).

HORN

- looks like gigantic scoop.

- outgoing transmission are broadcast up a stem and deflected outward in series.

- broadcast up and deflected outward in a series of a narrow parallel beams by the scooped shape of the beam.

SATELLITE 

- same principle as terrestrial microwave.

- single bounce.

- satellite acting as a super tall antenna and repeater.

- capability= any location on earth no matter how remote.

- high quality(very clear) communication without requiring a huge investment.

- same speed as the earth.

- geosynchronous satellite = orbit speed is based on distance from planet.

- up link = transmission from earth to satellite

- down link = transmission from satellite to earth

- minimum 3 satellites to provide full global transmission.

Wi-Fi

- the underlying technology of wireless local area network (WLAN).

- based on the IEEE 802.11 specifications.

- used for mobile computing devices, such as laptops, in LANs, increasingly used for more services, including internet and VoIP phone access, gaming and basic connectivity of consumer electronics.

- frequency 2.4 GHz

- range 100-300 feet (indoor) 300-900 feet(outdoor)

3G

3G networks are in between standard. 3G is seen more as pre4G instead of a standard of its own. The advantage of 3G networks have over 2G networks speed. 3G networks are built to handle the needs of today's wireless users. This standard of wireless networks increase the speed of internet browsing, picture and video messaging, and handheld GPS use.

4G

4G (Beyond 3G) is like the other generations in that its advantages lies in promised increased speed in data transmission. There is  currently no formal definition for 4G, but there are objectives. One of these objectives is for 4G to become a fully IP-based system, much like modern computer network. The supposed speeds for 4G will be between 100 Mbit/s and 1 Gbit/s.

CELLULAR PHONE

One of the most interesting things about a cell phone is that it is really a radio. An extremely sophisticates radio, but a radio nonetheless. A good way to understand the sophistication of a cell phone is to compare it to a CB radio or a walkie-talkie. A CB radio is a simplex device. That is, two people communicating on a CB radio use the same frequency, so only one person can talk at a time. A cell phone is a duplex device, so it uses one frequency for talking and a second, separate frequency for listening. A CB radio has 40 channels. A cell phone can communicate on 1,664 channels. Cell phones also operate within cells and they can switch cells as they move around. Cells gives cell phones incredible range. Someone using a cell phone, on the other hand, can drive clear across a city and maintain a conversation the entire time. Cells are what give a cell phone its incredible range.

(http://peacecraft.tripod.com/infomining/cellphon.htm)

RADIO FREQUENCY

A radio wave is an electromagnetic wave propagated by an antenna. Radio waves have different frequencies and by turning a radio receiver to a specific frequency you can pick up a specific signal. 

BLUETOOTH

- An industrial specification for wireless personal area networks (PANs).

- Designed for very short range <10m.

- Connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles over a secure, globally unlicensed short-range radio frequency. 

- Frequency 2.4 GHz.

- Data speed up to 3Mbps.

That is all from me for this week.

Thank you for reading my entry.