Unbounded media also known as unguided media.
What is unbounded media?
- a media transport electromagnetic wave without physical conductor.
- Electromagnetic wave in forms of signals that tramsmits through air/water and so available to anyone who has a device capable of receiving them.
i) TERRESTRIAL MICROWAVE
- Require line-of-sight transmission and reception equipment
- The taller the antennas, the longer the sight distance. Thus, the towers are built on the hills or mountains.
- Signals transmits 1 way direction at a time.
- To increase the distance, a system (repeater) can be installed with antenna.
How many types of antennas?
- 2 types:
a) Parabolic dish
b) Horn
a) Parabolic Dish
- Based on geometry of parabola.
- Works like a funnel (catching a wide range of waves and directing to a common point call focus)
b) Horn
- Looks like a gigantic scoop.
-Outgoing transmission are broadcast up a stem and deflected outward in a series of narrow parallel beams by the scooped shape of the horn.
ii) SATELLITE
- Same principle as terrestrial microwave.
- Acts as a super tall antenna and repeater
- Single bounce
- Any location of earth no matter how remote
- High quality communication without require a huge investment in ground-based infrastructure.
- Same speed as the earth
- Geosynchronous satellite as orbit speed is based on distance from the planet.
- Minumum 3 satellites to provide full global transmissions.
- Transmission of earth to satellite = uplink
- Transmission of satellite to earth = downlink
What is Wireless Techology?
- is also the branch of the unbounded media which means cable is unneeded.
- generally used for mobile IT equipment. It includes cellular telephones, personal digital assistance (PDA's) and wireless networking.
How cellular telephones transmit information?
- by 3 ways of technology
- Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Accefor ss (CDMA)
- FDMA = put each call into separate frequency
- TDMA = assignned each call a certain portion of time on a designed frequency.
- CDMA = gives a unique code to each call and spreads it over the available frequencies.
The blue words = access method, division = calls split based on access method, Multiple Access = more than 1 user can utilise each cell.
- Wireless networking technologies range from global voice and data networks, which allow users to establish wireless connections across long distances to infrared light and radio frequency technologies that are optimized for short-ranged wireless connections.
- Wireless network = any type of network that is wireless, refers to a telecommunication network whose interconnection between nodes is implemented without the use of wires such as computer network.
- Wireless network uses electromagnetic waves such as radio waves for the carrier.
- Wireless communication involves:
- radio frequency communication.
- microwave communication, e.g. long-range line-of-sight via highly directional antennas, or short-range communication.
- Infrared short-range communication, e.g. remote control or IRDA
- 4 types
- Wireless Wide Area Networks (WWANs), Wireless Metropolitan Area Networks (WMANs), Wireless Local Area Networks (WLANs), Wireless Personal Area Networks (WPANs)
WWAN
- Allows connection over remote public or private networks.
- Over large geographical areas such as cities or countries through the use of multiple antenna sites or satellite systems maintained by wireless service providers.
WMAN
- Allows connection between multiple locations within a metropolitan area (e,g, between multiple office buildings in a city/ on a university campus) withour high cost of laying fiber or copper cabling and leasing lines.
- An extension to wired LANs within a building and can provide the final few meters of connectivity between a wired and the mobile user.
WLAN
- Allow wireless connection within a local area
- Can be used in temporary offices or other spaces where the installation of extensive cabling would be prohibited so the users can work at different locations within a building at different times.
WPAN
- Allows users to establish ad hoc (special), wireless communications for devices (e.g. PDAs, cellular phones or laptops) that are used within a personal operating space (POS).
- POS = space surrounding a person, up to a distance of 10 meters.
Application of WPAN
- Voice and Messaging
- Hand- Held and other Internet - enabled device
- Data Networking
-Cell phones, pagers
-analog or digital standards
- The analog standard is the Advanced Mobile Phone Service(AMPS)
- Digital standards are Global System for Mobile Communication (GSM), Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA)
- Internet-enabled cell phones and Personal Digital Assistants (PDAs) can connect to the Internet across a digital wireless network.
- Uses Wireless Application Protocol (WAP), and Wireless Markup Language (WML)
- The majority of current internet content is not optimised for these devices; presently, only email, stock quotes, news, messages and simple transaction-oriented services are available.
- Certain limitations include low bandwidth (less than 14 Kbps), low quality of service, high cost and etc.
iii) Data Networking
- Application:
- Wireless Local Area Networks (WLANs)
- Wi-Fi uses the same radio frequency as bluetooth but with higher power consumption results in stronger connection.
- Broadband Wireless
- according to 802 16-2004 standard, broadband means 'having instantaneous bandwidth greater than around 1 MHz and supporting data rates greater than about 1.5 Mbit/s'
- Bluetooth
- provides a way to connect and exchange infomation between devices such as mobile phones, laptops, PCs, printers, digital cameras.
- developed by the Bluetooth Special Interest Group
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