The Cellular Communication System


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  • Like a broadcast radio. When u want to listen to CBC, u just adjust ur receiver to the right frequency, and u get it. But for the radio, the same content is share by many listeners, our phone calls can not be shared. Actually, bcz the cell phone is duplex working, there are two links between the handset and the base station, which are a upload linker and a download linker, two carrier frequency would be occupied during a phone call.
  • The Cellular Communication System

    1. 1. The Wireless Communication System Xihan Lu
    2. 2. Wireless Communication <ul><li>Cellular phone system </li></ul><ul><li>Cordless telephone system </li></ul><ul><li>Bluetooth </li></ul><ul><li>Infrared communication </li></ul><ul><li>Microwave communication </li></ul><ul><li>IEEE Wireless LANs (Wi-Fi) </li></ul><ul><li>Satellite communication </li></ul>
    3. 3. Why “Cellular”?
    4. 4. Three Generations AMPS NMT TACS HCMTS GSM GPRS WCDMA CDMA2000 TD SCDMA 2G 3G 1G
    5. 5. 1G <ul><li>Start early 80’s </li></ul><ul><li>Analogue technique </li></ul><ul><li>AMPT ( Advanced Mobile Phone System ): North America </li></ul><ul><li>NMT ( Nordic Mobile Telephony ): North Europe </li></ul><ul><li>TACS ( Total Access Communication Service ): Europe, China </li></ul><ul><li>HCMTS ( High Capacity Mobile Telephone System ): Japan </li></ul>
    6. 6. FDMA <ul><li>Frequency Division Multiple Access </li></ul><ul><li>Different carrier frequencies are assigned to different traffic channels(speech) </li></ul><ul><li>One carrier frequency can only carry one single speech channel at one time </li></ul>
    7. 7. FDMA
    8. 8. Shortage <ul><li>Voice information only </li></ul><ul><li>Unsafe ( eavesdropping ) </li></ul><ul><li>Waste of frequency resource </li></ul>
    9. 9. 2G <ul><li>Start early 90’s </li></ul><ul><li>Digital technique </li></ul><ul><li>GSM : Global System of Mobilephone </li></ul><ul><li>GPRS : General Packet Radio Service </li></ul><ul><li>D-AMPS : Digital AMPS </li></ul>
    10. 10. GSM <ul><li>TD/FDMA: A mix of FDMA and TDMA </li></ul><ul><li>The whole useable spectrum was divided to many 200k Hz carrier frequencies —FD </li></ul><ul><li>Each carrier was divided into 8 timeslots (burst) —TD </li></ul><ul><li>Each burst is assigned to a user(a logical traffic channel) </li></ul><ul><li>One carrier frequency can carry up to 8 logical traffic channels (voice or data) at the same time </li></ul><ul><li>The maximum data communication rate is 14.4 kbps </li></ul>
    11. 11. FD / TDMA
    12. 12. Network Structure
    13. 13. BTS,BSC and MSC <ul><li>BTS & BSC: Base Transceiver System and Base Station Controller . Radio signal transceiver, a connection between handset and MSC </li></ul><ul><li>MSC: Mobile services Switching Center , switching center of the GSM network, and connect to other networks </li></ul>
    14. 14. Databases <ul><li>HLR : Home Location Register , contains static information of subscribers and location update data </li></ul><ul><li>VLR : Visitor Location Register , embedded in MSC to avoid delay, contains current location information of handsets </li></ul><ul><li>AUC : Authentication Center , stores secret keys for authentication and encryption of the radio channel </li></ul><ul><li>EIR : Equipment Identity Register , contains a list of all valid mobile equipment in the network, by its International Mobile Equipment Identity (IMEI) </li></ul>
    15. 15. GPRS <ul><li>Upgrade of existed GSM network </li></ul><ul><li>Improves the data communication ability </li></ul>
    16. 16. GPRS
    17. 17. Network nodes <ul><li>GGSN: Gateway GSM Support Node , </li></ul><ul><li>Protocol transferring, data encapsulation, a connection to external networks </li></ul><ul><li>SGSN: Service GSM Support Node , </li></ul><ul><li>Communicate with HLR and mobile handsets, authorization and admission control, charging, mobility management </li></ul>
    18. 18. Data communications <ul><li>In GSM, one user occupies one traffic channel to exchange voice/data information </li></ul><ul><li>In GPRS, up to 8 traffic channels(a whole carrier) can be dynamically combined together for one data communication application </li></ul><ul><li>The theoretically maximum data transmission rate: 14.4k bps * 8 = 115.2k bps </li></ul>
    19. 19. Advantages of GPRS <ul><li>Higher data rate </li></ul><ul><li>Seamless connection to internet </li></ul><ul><li>Packet switching rather than circuit switch, bandwidth is only used when the data is actually used, even though it is always connected </li></ul><ul><li>A primary step to 3G </li></ul>
    20. 20. shortage <ul><li>Not fast enough for the multimedia service </li></ul><ul><li>The data rate falls when the network is busy </li></ul><ul><li>Upgrade of handset </li></ul>
    21. 21. 3G
    22. 22. 3G-Standards <ul><li>Three CDMA standards approved by ITU: </li></ul><ul><li>Direct Spread CDMA(WCDMA) : Europe, Japan </li></ul><ul><li>Multi-Carrier CDMA(CDMA 2000) : North America </li></ul><ul><li>TD-Synchronous CDMA(CDMA TDD) : Europe, China </li></ul>
    23. 23. 3G-CDMA <ul><li>Code Division Multi Address </li></ul><ul><li>Spread spectrum technology </li></ul><ul><li>Each single traffic channel occupies the whole spectrum, but distinguished by a unique digital code </li></ul><ul><li>Walsh code: an orthogonal 64 bit pattern, unique in the network </li></ul>
    24. 24. CDMA
    25. 25. Features <ul><li>Better voice quality </li></ul><ul><li>Up to 2 Mbps data communication rate </li></ul><ul><li>Increase battery life </li></ul><ul><li>Soft hand-off </li></ul><ul><li>Excellent data safety </li></ul><ul><li>More effective spectrum usage than 2G </li></ul>
    26. 26. Conclusion
    27. 27. Conclusion Good OK Weak Communication safety 10~20X 5~6X X Spectrum usage ~2M ~115K N/A Data communication Good OK OK Voice Quality 3G 2G 1G
    28. 28. References <ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul>