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Mobile Phones

Wireless Standards
Home
History Of Mobile Phones
Advantages & Disadvantages
Latest Models
Developments in Design
Dream Phones..
Handphone User Survey & Data
Acknowledgments

Analog Service

  • information are carried around by altering the signals
  • analog cellular phones work like a FM radio : The receiver and transmitter are at identical frequency
  • sent out voice is varied within a small band to form a pattern that the receiver amplifies and sends to the speaker
  • disadvantage is the limited channels that can be used

Digital Service
  • encoding information using binary code of 1s and 0s
  • analog voice signal is converted into binary code and transmitted as on and off transmission
  • con: due to the fact that there exists three digital wireless technology, phones that work with one technology may not operate using the other  technology
TDMA IS-136
  • Time Division Multiple Access 
  • uses frequency bands and divides them into time slots and each user is allowed touse a time slot at regular time interval
  • exists in North America at both 800 MHz and 1900 MHz band
CDMA IS-95
  • spread spectrum technology that separates voice signals by allocating them digital codes within the same broad spectrum
  • this technology started in the 1940s when militants used it as a form of communication because it was not affected by interference from the enemy signals
GSM
  • Global System for Mobile Communications
  • an improved version of TDMA technology
  • permits users to travel around in Europe
  • 1987, GSM standard was created based on both analog and digital technologies
  • GSM engineers decided to use wider 200kHz channels and a total of 8 slots in the channels - increasing speed and having better sound quality
  • the only technology that provides data services like emailing, faxing, internet browsing and intranet wireless access
  • only service that allows users to call from North America or Europe
  • GSM-1900 cellular systems have been operating in US since 1996
  • in 1999, they improved GSM systems to 1800MHz

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