Presentation on 2 nd generation telecommunication systemPresentation Transcript
2G (or 2-G) is short for second-generation wireless telephonetechnology. Second generation 2Gcellular telecom networks werecommercially launched on theGSM standard.
Three primary benefits of 2G networksover their predecessors were that phoneconversations were digitally encrypted;2G systems were significantly moreefficient on the spectrum allowing forfar greater mobile phone penetrationlevels; and 2G introduced data servicesfor mobile, starting with SMS textmessages.
While radio signals on 1G networks areanalog, radio signals on 2G networksare digital. Both systems use digitalsignaling to connect the radio towers(which listen to the handsets) to therest of the telephone system.
GSM (global system for mobilecommunication) is a common secondgeneration cell phone standard..GSM is a digital standard that was adoptedover the original analog system..THE GSM network operates at 850MHZOr 1900MHZ bands in the US.
GSM (Global System for Mobilecommunication) is a digital mobiletelephone system that is widely used inEurope and other parts of the world. GSMuses a variation of time division multipleaccess (TDMA) and is the most widely usedof the three digital wireless telephonetechnologies (TDMA, GSM, and CDMA).GSM digitizes and compresses data, thensends it down a channel with two otherstreams of user data, each in its own timeslot.
.GSM uses GMSK or Gaussian minimum shiftkeying for modulation.GMSK is a kind of continous frequency shift keying
.The on-off binary signal is firsttransformed to a polar binary signal..The polar binary signal is filteredsuch that a Gaussian-shaped signal isproduced..Frequency modulation is thenapplied to signal.
.The weaker digital signal may not beable to reach cell tower..Digital signal will drop out faster thenan analog signal.
.Users separated by code.Require digital transmission.Wider bandwidth compared to TDMA.Introduced in 1980.Used in cellular communicationsystem
.Generating a CDMA signal1. Analog to digital conversion2. Vocoding3. Encoding and interleaving4. Channelizing the signal5. Conversion of digital to radio frequency signal
Three of the more commontransmission schemes include FDMA(Frequency Division MultipleAccess), TDMA (Time Division MultipleAccess), and CDMA (Code DivisionMultiple Access).
FDMA divides the given spectruminto channels by the frequencydomain. Each phone call isallocated one channel for the entireduration of the call.
Frequency Division Multiple Access
TDMA enhances FDMA by furtherdividing the spectrum into channels bythe time domain as well. A channel inthe frequency domain is dividedamong multiple users. Each phone callis allocated a spot in the channel for asmall amount of time, and "takesturns" being transmitted
Unlike FDMA and TDMA, CDMAtransmission does not work byallocating channels for each phonecall. Instead, CDMA utilizes the entirespectrum for transmisson of each call.Each phone call is uniquely encodedand transmitted across the entirespectrum, in a manner known asspread spectrum transmission.