presentation on samsung

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presentation on samsung

  1. 1. GSM and CDMA What is it all about ? By Manjit Chandel
  2. 2. Marketing You can change your GSM SIM card to get rid of your girlfriend…. Shewag ki Maa ka phone CDMA pe aaya tha…
  3. 3. Questions ??? How is one better than the other ??? Which one is cheaper ??? Which one is more reliable ??? What is the difference in technology ….if any ???
  4. 4. More Questions…. Is there a single security code that will permit me to make changes to my phone ??? What role does bandwidth play ??? What provides protection from eavesdropper ??? How a mobile subscriber on one network access his home network ???
  5. 5. What is the underlying Difference ?? TDMA FDMA CDMA Layman’s view… Are all different versions of digital technology…
  6. 6. Time Division Multiple Access Users separated in time Requires digital transmission Normally wider bandwidth compared to FDMA Used for GSM
  7. 7. Frequency Division Multiple Access(FDMA) Users separated in frequency Only possible in analog system
  8. 8. Code Division Multiple Access Users separated by code Requires digital transmission Wider bandwidth compared to TDMA
  9. 9. Time for History…. GSM originated in Europe… GSM earlier known as Group Special Mobile, a study group appointed to study and develop European public land mobile system One important criteria that the proposed system had to meet was ISDN compatibility..
  10. 10. And now CDMA… Introduced in 1980 IN North America…. Purpose…. What else ……but Military usage Used in Cellular Communication System , in the early 90’s
  11. 11. Finally ….What is CDMA? ….. A way to transmit bits of information through wideband, spread spectrum radio interface. IS-95 is the transmission protocol that employs CDMA. Evolution from IS-95A to IS-95B to CDMA2000 Better utilization of radio spectrum by allowing multiple users to access the same physical channel.
  12. 12. How CDMA Works? Generating a CDMA signal 1.analog to digital conversion 2.vocoding 3.encoding and interleaving 4.channelizing the signals 5.conversion of the digital signal to a Radio Frequency (RF) signal
  13. 13. How does it works……
  14. 14. Code GeneratorClock Multiplier FilterModulator Data Clock Data Carrier Transmit Signal Working of CDMA Channel Establishment
  15. 15. Voice Compression ..How is it accomplished?? CDMA uses a device called a vocoder to accomplish voice compression. The term "vocoder" is a contraction of the words "voice" and "code." Vocoders are located in the phone.
  16. 16. Channelizing The encoded voice data is further encoded to separate it from other encoded voice data. The encoded symbols are then spread over the entire bandwidth of the CDMA channel. This process is called channelization. The receiver knows the code and uses it to recover the voice data.
  17. 17. Codes… CDMA uses two important types of codes to channelize users. Walsh codes channelize users on the forward link (BTS to mobile). Pseudorandom Noise (PN) codes channelize users on the reverse link (mobile to BTS).
  18. 18. CDMA Call Processing State System Idle State System Initialization State System Access State Traffic Channel State
  19. 19. Hand Off ??? Advantage of CDMA is the ability to communicate with more than one base station at one time during a call This functionality allows the CDMA network to perform soft handoff How does it all HAPPEN ?
  20. 20. Soft Handover…
  21. 21. MS BSC/MSCSecondary BS ‘B’Primary BS ‘A’ Pilot Strength Measurement Pilot Measurement Request Pilot Strength Measurement Handoff Request Handoff Direction ACK Handoff Information ACK ACK ACK Frame Selector Join
  22. 22. Roaming in CDMA Mobile Station Base Station Visited MSC VLR Home MSC HLR Originating Switch User Dials CallIAM HLR Query HLR Response SS7 IAM Normal Call Processing Continues
  23. 23. Why is roaming charged more ??? The Directory number of the MS is dialed Originating Switch sends an ss7 initial address message (IAM) to home MSC MSC queries the HLR for the location of the MS The HLR returns the locations of the visited System
  24. 24. Roaming Contd.. The MSC invokes call forwarding to the MSC in the visited system.. The forwarding MSC switch send an SS7 IAM to the visited MSC Call processing……
  25. 25. Call Waiting…. Base Station MSC VLR Home MSC HLR Originating Switch User Dials CallIAM VLR Query VLR Response Mobile Station ISDN Hold Ack MSC Applies Call waitingFlash ISDN Hold MSC puts Call1 on Hold connects call2
  26. 26. GSM NSS BSS MS OSS UsersExternal Networks Operators GSM Subsystems
  27. 27. Entities MS: Physical equipment used by the subscribers BSS: Physical equipment that provides radio coverage NSS: Switching functions of GSM Databases required for subscribers Done through MSC
  28. 28. When an MS is switched on…What happens?? • It first has to determine if it has access to PLMN • It does a location update for the same informing its PLMN about its location • Location of an MS is stored in a central database
  29. 29. MS MSCBSS PSTNVLR GSM CALL FLOW Setup Send info for outgoing signal Complete Call Call Proceeding Assignment Assignment Assignment Complete Assignment Complete IAM Assignment Complete (ACM) Alerting Answer Connect Connect Acknowledge
  30. 30. Privacy and Security in GSM Each subscriber is identified using a cryptographic security mechanism Subscriber security information is stored in the SIM Card The algorithm are stored in the SIM card and in the authentication center.
  31. 31. Security Algorithms for GSM 1.Authentication Algorithm(A3) • Used by handset to compute a signed response to a random number transmitted by BS 2.Private key generation(A8) •Uses the same random number and K(i) to generate a private key(K©)that is used for voice and data privacy A3 A8 K(I) on SIM Card RAND(from BS) SRES to BS K© privacy mask
  32. 32. Generation Next… 3G No boundary between telephony, information and entertainment services It will range from voice only to voice, data, and other multimedia application Wireless users will be able to make video conference calls and surf the internet simultaneously WHAT IS ALL THIS
  33. 33. How is it related to my topic…. People demand access for information and services wherever they are GSM should provide this connectivity. Internet access and a whole range of mobile multimedia capability. Thus GPRS in GSM
  34. 34. Pay for what you use… GPRS enhances GSM data services There is no end to end connection to be established, so setting up a GPRS call is almost instantaneous and users can be continuously online And users pay for the actual data transmitted, rather than for connection time
  35. 35. A GPRS architecture in GSM BSS EIR SGSN MSC/VLR SMS-GMSC GGSNTE HLR MT PDN TE GGSN Other PLMN SM-SC
  36. 36. Finally Everything Together GSM CDMAone PDC TDMA CDMA2000 IX GPRS CDMA200 IXEV WCDMA EDGE

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