Friday, 4 May 2012

6th entry

waaa it has been six posting already. I can't believe that I am a blogger although it just for my task-proud of myself : p.
ok so for the topic for this week is 


---media transport electromagnetic wave without physical conductor 
---signal are broadcasting through air or water & therefore available to anyone who has a devices capable   of receiving them.

---require line of sight transmission & reception equipment
---taller the antenna the longer the distance
---towers=on hill
---signals transmit 1 way direction at a time.
---to increase the distance - a system (repeater) can be installed with antenna.
Parabolic dish
Horn dish
.          Based on geometry of parabola
      Looks like gigantic scoop
           Works like a funnel - catching a wide range of waves and directing to a common point call focus
           Outgoing transmission are broadcast up a stem & deflected outward in  a series of source parallel beams by the scoop shaped of the horn
parabolic dish

horn dish

---same principle as microwave
---satellite acting as a super fall antenna & repeater
---single bounce
---capability=any location on earth no matter how   
---high quality communication without requiring a          huge investment in ground-based infrastructure..
---same speed as earth
---geosynchronous satellite=orbit speed is based on     distance from the planet
---minimum 3 satellite to provide full global transmission.
---uplink = transmission from earth to satellite
---downlink = transmission from satellite to earth

---rate of oscillation in the range of about  3kHz to 300 kHz.
---the mode of communication for wireless technology of all kinds such as-cordless phone,radar,ham radio        and many more
---These frequencies make up part of the electromagnetic radiation spectrum:
  • Ultra-low frequency (ULF) -- 0-3 Hz
  • Extremely low frequency (ELF) -- 3 Hz - 3 kHz
  • Very low frequency (VLF) -- 3kHz - 30 kHz
  • Low frequency (LF) -- 30 kHz - 300 kHz
  • Medium frequency (MF) -- 300 kHz - 3 MHz
  • High frequency (HF) -- 3MHz - 30 MHz
  • Very high frequency (VHF) -- 30 MHz - 300 MHz
  • Ultra-high frequency (UHF)-- 300MHz - 3 GHz
  • Super high frequency (SHF) -- 3GHz - 30 GHz
  • Extremely high frequency (EHF) -- 30GHz - 300 GHz
Radio frequency is also abbreviated as rf or r.f
 how it works??
========> A label -- basically a miniature, disposable electronic circuit and antenna -- attached to a product responds to a specific frequency emitted by a transmitter antenna (usually one pedestal of the entry/exit gate). The response from the label is then picked up by an adjacent receiver antenna (the other pedestal). This processes the label response signal and will trigger an alarm when it matches specific criteria. The distance between the two gates, or pedestals, can be up to 80 inches wide. Operating frequencies for RF systems generally range from 2 to 10 MHz (millions of cycles per second); this has become standard in many countries. Most of the time, RF systems use a frequency sweep technique in order to deal with different label frequencies.

---device that can make & receive telephone calls over a radio link whilst moving around a a wide geographic area
---it woks by connecting to a cellular network provided by a mobile phone operator, allowing access to the public telephone network.

---The common components found on all phones are:
  • A battery, providing the power source for the phone functions.
  • An input mechanism to allow the user to interact with the phone. The most common input mechanism is a keypad but touch screen are also found in some high-end smartphones.
  • Basic mobile phone services to allow users to make calls and send text messages.
  • All GSM phones use a SIM card to allow an account to be swapped among devices. Some CDMA devices also have a similar card called a R-UIM.
  • Individual GSM, WCDMA, iDEN and some satellite phone devices are uniquely identified by an International Mobile Equipment Identity (IMEI) number.
---stand for "Wireless Fidelity"
---refers to wireless networking technology
---allows computer & other devices to communicate over a wireless signal.
---transmit data using radio wave
wi-fi signal logo
---describe all network component that are based on one of the               802.11standards
---these standards were developed by IEEE (Institute of Electrical         and Electronic Engineers)
---have limited range
---the maximum amount of power that a Wi-Fi device can transmit is      limited by local regulations

3G & 4G
3rd generation
4th generation
The technologies are widespread used
The technologies are still in horizon
3G speeds can reach up to 3 Megabits per second (Mbps), with average speeds tending to be closer to 1Mbps or lower
4G average speeds are targeted to be in the 100Mbps to 1Gbps range, roughly 10 to 100 times (dependent on location) faster than 3G networks.
3G is a mix of circuit and packet switching network
4G is only a packet switching network

---short-distance wireless connections.
---It essentially is a cable-replacement technology. 
---allows two Bluetooth enabled devices to communicate with each other from a distance of 30 feet apart.
---Bluetooth takes small-area networking to the next level by removing the need for user intervention and          keeping transmission power extremely low to save battery power.
---Bluetooth is essentially a networking standard that works at two levels:

  •     It provides agreement at the physical level -- Bluetooth is a radio-frequency standard.
  •     It provides agreement at the protocol level, where products have to agree on when bits are sent,        how many will be sent at a time, and how the parties in a conversation can be sure that the message     received is the same as the message sent.

finish already fuhhh...
TQ  (^-^)

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