Existing Wireless Systems: 2G, GSM System and PCS


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Existing Wireless Systems: 2G, GSM System and PCS

  1. 1. Chapter 9: Existing Wireless Systems: 2G, GSM System <ul><ul><li>Associate Prof. Yuh-Shyan Chen </li></ul></ul><ul><ul><li>Dept. of Computer Science and Information Engineering </li></ul></ul><ul><ul><li>National Chung-Cheng University </li></ul></ul>
  2. 2. Introduction <ul><ul><ul><li>Global System for Mobile communication or Groupe Speciale Mobile (GSM) communication </li></ul></ul></ul><ul><ul><ul><ul><li>Initiated by European Commission </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Second-generation mobile cellular system </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Aimes at developing a Europe-wide digital cellular system </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Created in 1982 to have a common European mobile telephone standard that would formulate specifications for a pan-European mobile cellular radio system operating at 900 MHz </li></ul></ul></ul></ul><ul><ul><ul><ul><li>The main objective of GSM is to remove any incompatibility among the systems by allowing the roaming phenomenon for any cell phone </li></ul></ul></ul></ul>
  3. 3. Introduction <ul><ul><ul><ul><li>It also supports speed transmissions between MSs, emergency calls, and digital data transmission </li></ul></ul></ul></ul><ul><ul><ul><li>Specific functions of different constituents are as follows </li></ul></ul></ul><ul><ul><ul><ul><li>Base Station Controller (BSC): </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Mobile Switching Center (MSC): </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Authentication Center (AC): </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Equipment Identity Register (EIR): </li></ul></ul></ul></ul>
  4. 4. GSM infrastructure
  5. 5. Frequency Bands and Channels <ul><ul><li>GSM has been allocated an operational frequency from 890 MHz and 960 MHz </li></ul></ul><ul><ul><ul><li>MSs employ 890 MHz to 915 MHz </li></ul></ul></ul><ul><ul><ul><li>BS operates in 935 MHz and 960 MHz </li></ul></ul></ul><ul><ul><li>GSM follows FDMA and allows up to 124 MSs to be serviced at the same time </li></ul></ul><ul><ul><ul><li>The frequency band of 25 MHz is divided into 124 frequency division multiplexing (FDM) channels, each of 200 kHz (Fig. 10.9) </li></ul></ul></ul><ul><ul><ul><li>A guard frame of 8.25 bits is used between any two frames transmitted either by the BS or the MS </li></ul></ul></ul>
  6. 6. Frequency band used by GSM
  7. 7. GSM uses a variety of multiplexing techniques <ul><ul><li>GSM uses a variety of multiplexing techniques to create a collection of logical channels </li></ul></ul><ul><ul><li>Three control channels are used for broadcasting some information to all MSs </li></ul></ul><ul><ul><ul><li>Broadcast control channel (BCCH) </li></ul></ul></ul><ul><ul><ul><li>Frequency correction channel (FCCH) </li></ul></ul></ul><ul><ul><ul><li>Synchronization channel (SCH) </li></ul></ul></ul>
  8. 8. Channel in GSM
  9. 9. Cont. <ul><ul><li>Three common control channels are used for establishing links between the MS and the BS </li></ul></ul><ul><ul><ul><li>Random access channel (RACH): </li></ul></ul></ul><ul><ul><ul><ul><li>Used by the MS to transmit information regarding the requested dedicated channel from GSM </li></ul></ul></ul></ul><ul><ul><ul><li>Paging channel: </li></ul></ul></ul><ul><ul><ul><ul><li>Used by the BS to communicate with individual MSs in the cell </li></ul></ul></ul></ul><ul><ul><ul><li>Access grant channel: </li></ul></ul></ul><ul><ul><ul><ul><li>Used by the BS to send information about timing and synchronization </li></ul></ul></ul></ul>
  10. 10. Cont. <ul><ul><li>Three dedicated control channels are used </li></ul></ul><ul><ul><ul><li>Slow associated control channel (SACCH): </li></ul></ul></ul><ul><ul><ul><li>Stand-alone dedicated control channel (SDCCH): </li></ul></ul></ul><ul><ul><ul><li>Fast associated control channel (FACCH): </li></ul></ul></ul>
  11. 11. Frames in GSM <ul><ul><li>GSM system uses the TDMA scheme with a 4.615 – ms long frame </li></ul></ul><ul><ul><ul><li>Dividing into eight time slots each of 0.557 ms </li></ul></ul></ul><ul><ul><ul><li>Each frame measured in terms of time is 156.25 bits long, of which 8.25 period bits are guard bits for protection </li></ul></ul></ul><ul><ul><ul><li>The 148 bits are used to transmit the information </li></ul></ul></ul><ul><ul><ul><li>The frame contains 26 training bits allow the receiver to synchronize itself </li></ul></ul></ul><ul><ul><ul><li>Many such frames are combined to constitute multiframes, superframes, and hyperframes </li></ul></ul></ul>
  12. 12. Frame structure of TDMA
  13. 13. Identify Numbers used by a GSM System <ul><li>International Mobile Subscriber Identity (IMSI) </li></ul>
  14. 14. Format of IMSI
  15. 15. Cont. <ul><li>Subscriber Identify Module (SIM) </li></ul><ul><ul><ul><li>Every time the MS has to communicate with a BS, it must correctly identify itself. </li></ul></ul></ul><ul><ul><ul><li>A MS does this by storing the phone number, personal identification number for the station, authentication parameters, and so on in the SIM card </li></ul></ul></ul><ul><ul><ul><li>Smart SIM cards have a flash memory </li></ul></ul></ul><ul><ul><ul><li>The main advantage of SIM is that is supports roaming with or without a cell phone, also called SIM roaming </li></ul></ul></ul><ul><li>Mobile System ISDN (MSISDN) </li></ul>
  16. 16. Format of MSISDN
  17. 17. Cont. <ul><ul><li>Location Area Identify (LAI) </li></ul></ul><ul><ul><ul><li>The GSM service area is usually divided into a hierarchical structure that facilitates the system to access any MS quickly </li></ul></ul></ul><ul><ul><ul><li>Each PLMN is divided into many MSCs </li></ul></ul></ul><ul><ul><ul><li>Each MSC typically contains a VLR to tell the system if a particular cell phone is roaming </li></ul></ul></ul><ul><ul><ul><li>If it is roaming, the VLR of the MSC in which the cell phone is reflects the fact </li></ul></ul></ul><ul><ul><ul><li>Each MSC is divided into many location areas (LAs) </li></ul></ul></ul><ul><ul><ul><li>A location area is a cell or a group of cells and is useful when the MS is roaming in a different cell but the same LA </li></ul></ul></ul>
  18. 18. Cont. <ul><ul><ul><li>Since any LA has to be identified as the part of the hierarchical structure </li></ul></ul></ul><ul><ul><ul><li>The identifier should contain the country code, mobile network code, and LA code </li></ul></ul></ul>
  19. 19. GSM layout
  20. 20. Cont. <ul><ul><li>International MS Equipment Identity (IMSEI) </li></ul></ul>
  21. 21. Format of IMSEI
  22. 22. Cont. <ul><ul><li>MS Roaming Number (MSRN) </li></ul></ul>
  23. 23. Format of MSRN
  24. 24. Layout, Planes, and Interfaces of GSM
  25. 25. Interface of GSM
  26. 26. Cont. <ul><ul><li>The GSM system can be divided into five planes </li></ul></ul><ul><ul><ul><li>OAM </li></ul></ul></ul><ul><ul><ul><li>CM </li></ul></ul></ul><ul><ul><ul><li>MM </li></ul></ul></ul><ul><ul><ul><li>RR </li></ul></ul></ul><ul><ul><ul><li>Physical </li></ul></ul></ul>
  27. 27. Functional planes in GSM
  28. 28. Authentication <ul><ul><li>Authentication is done with the help of a fixed network that is used to compare the IMSI (International Mobile Subscriber Identity) of the MS reliably </li></ul></ul>
  29. 29. Authentication process in GSM
  30. 30. Handoff in GSM <ul><li>Intracell/intra-BTS handoff </li></ul><ul><li>Intercell/intra-BSC handoff </li></ul><ul><li>Inter-BSC/intra-MSC handoff </li></ul><ul><li>Inter-MSC handoff </li></ul>
  31. 31. Inter-MSC handoff
  32. 32. Personal Communication Service ( PCS ) <ul><ul><ul><li>PCS employs an inexpensive, lightweight, and portable handset to communicate with a PCS BS </li></ul></ul></ul><ul><ul><ul><li>The PCS is classified into high-tier and lower-tier standards </li></ul></ul></ul><ul><ul><ul><li>High-tier system includes high-mobility units with large batteries </li></ul></ul></ul><ul><ul><ul><ul><li>An MS in a car </li></ul></ul></ul></ul><ul><ul><ul><li>Low-tier system includes system with low mobility , capable of providing high-quality portable communication service over a wide area </li></ul></ul></ul><ul><ul><ul><li>The PCS lower-tier standards based on PACS (Personal Access Communication Systems) and DECT (Digital European Cordless Telecommunication) are given in Table 10.6. </li></ul></ul></ul>
  33. 33. FCC view of PCS
  34. 34. PCS High-Tier Standards
  35. 35. PCS Low-Tier Standards
  36. 36. Chronology of PCS Development <ul><li>CT2 (Cordless Telephone) </li></ul><ul><ul><ul><li>Using FDMA with a speed rate of 32 kbps using Adaptive Differential Pulse Code Mudulation (ADPCM) </li></ul></ul></ul><ul><ul><ul><li>The transmitter data rate is 72 kbps </li></ul></ul></ul><ul><ul><ul><li>Uses TDD, which allows BS and MS share one channel </li></ul></ul></ul><ul><ul><ul><li>D is called D-channel which includes 4 bits of control information </li></ul></ul></ul><ul><li>DECT (Digital European Cordless Telecommunication) </li></ul>
  37. 37. CT2 TDD Slot (First Generation)
  38. 38. DECT (Digital European Cordless Telecommunication) <ul><ul><li>The second-generation cordless telephone system </li></ul></ul><ul><ul><li>DECT operates on frequencies ranging from 1880 MHz to 1900 MHz </li></ul></ul><ul><ul><li>Uses ADPCM with 32 kbps speed rate </li></ul></ul><ul><ul><li>Uses TDD with two frames with 10-ms periods </li></ul></ul><ul><ul><li>Supports both voice and data transmission </li></ul></ul>
  39. 39. DECT TDD Slot (Second Generation)
  40. 40. Bellcore View of PCS <ul><ul><li>The Bellcore view of PCS is based on five different service provided between the Bellcore client company (BCC), BCC network, and the PCS wireless provider network </li></ul></ul><ul><ul><ul><li>PCS access service for networks (PAS N ) </li></ul></ul></ul><ul><ul><ul><ul><li>A connection service to and from the PCS service provider (PSP) </li></ul></ul></ul></ul><ul><ul><ul><li>PCS access service for controllers (PAS C ) </li></ul></ul></ul><ul><ul><ul><ul><li>A service for use with PCS wireless provider (PWP) across radio channels and some type of automatic link transfer capability </li></ul></ul></ul></ul>
  41. 41. Bellcore View of PCS <ul><ul><ul><li>PCS access service for ports (PAS P ) </li></ul></ul></ul><ul><ul><ul><ul><li>An interface into PWP </li></ul></ul></ul></ul><ul><ul><ul><li>PCS access service for data (PAS D ) </li></ul></ul></ul><ul><ul><ul><ul><li>A database information transport service </li></ul></ul></ul></ul><ul><ul><ul><li>PCS access service for external service providers (PAS E ) </li></ul></ul></ul><ul><ul><ul><ul><li>Is used to support specialized PCS service like voice mail and paging </li></ul></ul></ul></ul>
  42. 42. Bellcore PCS Architecture Radio Port Radio Port Control Unit Signaling System 7 Operation, Administration, & Maintenance
  43. 43. Description of the PCS Air Interface: Forward TDMA Frame for PCS