GSM




Mobile Computing
            GSM


      Mike Spence

Department of Computer Science
     Trinity College Dublin

...
GSM




Outline



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Mobile Computing - GSM

  1. 1. GSM Mobile Computing GSM Mike Spence Department of Computer Science Trinity College Dublin Trinity Term 2008 Mike Spence Mobile Computing
  2. 2. GSM Outline 1 GSM Background Network Infrastructure GSM Lower Layers Mobility Management Short Messaging Service Mike Spence Mobile Computing
  3. 3. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service History 1980s Analog cellular technology services rolled out throughout Europe, Japan & North America Different (Incompatible) standards NMT, AMPS, etc Even within Europe Late 1980s CCITT begins work on a Global System for Mobile communication (GSM) Pan-European digital land mobile system Initially intended to serve motor vehicles Later extended to pedestrians Mike Spence Mobile Computing
  4. 4. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service History 1980s Analog cellular technology services rolled out throughout Europe, Japan & North America Different (Incompatible) standards NMT, AMPS, etc Even within Europe Late 1980s CCITT begins work on a Global System for Mobile communication (GSM) Pan-European digital land mobile system Initially intended to serve motor vehicles Later extended to pedestrians Mike Spence Mobile Computing
  5. 5. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service History 1990s GSM begins deployment in Europe (1991) GSM provides a number of services Voice communication to both mobile and landline users Data services such as SMS, dial-up Internet Additional services such as call waiting, call barring, voice mail, etc. 2000s Approximately, 70% of mobile phone users in the world use GSM. Over 1 Billion people around the world are using some GSM network. Mike Spence Mobile Computing
  6. 6. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service History 1990s GSM begins deployment in Europe (1991) GSM provides a number of services Voice communication to both mobile and landline users Data services such as SMS, dial-up Internet Additional services such as call waiting, call barring, voice mail, etc. 2000s Approximately, 70% of mobile phone users in the world use GSM. Over 1 Billion people around the world are using some GSM network. Mike Spence Mobile Computing
  7. 7. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Cell structure is needed for frequency re-use N channels (frequencies) are assigned to each set of 7 numbered hexagons. For example, if we have 63 channels in total. First 9 channels would be allocated to cell 0, next 9 channels to cell 1, etc. This allocation would be repeated at each numbered cell. Mike Spence Mobile Computing
  8. 8. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Cell structure is needed for frequency re-use N channels (frequencies) are assigned to each set of 7 numbered hexagons. For example, if we have 63 channels in total. First 9 channels would be allocated to cell 0, next 9 channels to cell 1, etc. This allocation would be repeated at each numbered cell. Mike Spence Mobile Computing
  9. 9. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Cell structure is needed for frequency re-use N channels (frequencies) are assigned to each set of 7 numbered hexagons. For example, if we have 63 channels in total. First 9 channels would be allocated to cell 0, next 9 channels to cell 1, etc. This allocation would be repeated at each numbered cell. Mike Spence Mobile Computing
  10. 10. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Cell structure is needed for frequency re-use N channels (frequencies) are assigned to each set of 7 numbered hexagons. For example, if we have 63 channels in total. First 9 channels would be allocated to cell 0, next 9 channels to cell 1, etc. This allocation would be repeated at each numbered cell. Mike Spence Mobile Computing
  11. 11. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Hexagons are a convenient idealization (approximating a circle). Sub-division of N channels to cells depends on: local propagation environment traffic demand / number of users Cell size determines: likelihood of mobile changing cells likelihood of interference from other cells Two types of interference: Adjacent channel interference Co-channel interference Mike Spence Mobile Computing
  12. 12. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Hexagons are a convenient idealization (approximating a circle). Sub-division of N channels to cells depends on: local propagation environment traffic demand / number of users Cell size determines: likelihood of mobile changing cells likelihood of interference from other cells Two types of interference: Adjacent channel interference Co-channel interference Mike Spence Mobile Computing
  13. 13. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Hexagons are a convenient idealization (approximating a circle). Sub-division of N channels to cells depends on: local propagation environment traffic demand / number of users Cell size determines: likelihood of mobile changing cells likelihood of interference from other cells Two types of interference: Adjacent channel interference Co-channel interference Mike Spence Mobile Computing
  14. 14. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Cellular Communication Hexagons are a convenient idealization (approximating a circle). Sub-division of N channels to cells depends on: local propagation environment traffic demand / number of users Cell size determines: likelihood of mobile changing cells likelihood of interference from other cells Two types of interference: Adjacent channel interference Co-channel interference Mike Spence Mobile Computing
  15. 15. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure Base Station Subsystem (BSS) is located at the center of the hexagon. BSS is equipped with a number of omni-directional antennas. BSS is responsible for managing the radio resources of a cell. BSS can divide a cell into 3 120-degree sectors to increase spectrum efficiency. This requires directional antennas. 1 or more BSSs are connected by point-to-point links to a Mobile Switching Center (MSC). Mike Spence Mobile Computing
  16. 16. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure Base Station Subsystem (BSS) is located at the center of the hexagon. BSS is equipped with a number of omni-directional antennas. BSS is responsible for managing the radio resources of a cell. BSS can divide a cell into 3 120-degree sectors to increase spectrum efficiency. This requires directional antennas. 1 or more BSSs are connected by point-to-point links to a Mobile Switching Center (MSC). Mike Spence Mobile Computing
  17. 17. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure Base Station Subsystem (BSS) is located at the center of the hexagon. BSS is equipped with a number of omni-directional antennas. BSS is responsible for managing the radio resources of a cell. BSS can divide a cell into 3 120-degree sectors to increase spectrum efficiency. This requires directional antennas. 1 or more BSSs are connected by point-to-point links to a Mobile Switching Center (MSC). Mike Spence Mobile Computing
  18. 18. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure Base Station Subsystem (BSS) is located at the center of the hexagon. BSS is equipped with a number of omni-directional antennas. BSS is responsible for managing the radio resources of a cell. BSS can divide a cell into 3 120-degree sectors to increase spectrum efficiency. This requires directional antennas. 1 or more BSSs are connected by point-to-point links to a Mobile Switching Center (MSC). Mike Spence Mobile Computing
  19. 19. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure MSC contains most intelligence in the system. Responsible for handoff of a mobile phone from one BSS to another BSS. MSCs are also connected to each other. MSC is connected to the local public switched telephone network (PSTN) Set-up and termination of calls to mobile phones is done using the MSC. Mike Spence Mobile Computing
  20. 20. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure MSC contains most intelligence in the system. Responsible for handoff of a mobile phone from one BSS to another BSS. MSCs are also connected to each other. MSC is connected to the local public switched telephone network (PSTN) Set-up and termination of calls to mobile phones is done using the MSC. Mike Spence Mobile Computing
  21. 21. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Infrastructure MSC contains most intelligence in the system. Responsible for handoff of a mobile phone from one BSS to another BSS. MSCs are also connected to each other. MSC is connected to the local public switched telephone network (PSTN) Set-up and termination of calls to mobile phones is done using the MSC. Mike Spence Mobile Computing
  22. 22. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Databases A Home Location Register (HLR) is used to maintain up to date information about a mobile host. HLR stores mobile device’s current location, subscriber’s profile, etc. Each MSC maintains a Visiting Location Register (VLR) The VLR maintains the same information as the HLR. MSC assigns a Mobile Station Roaming Number (MSRN) for each mobile device in its coverage area. MSRN is a temporary number allocated by the MSC (VLR) and sent to the mobile device’s HLR. Mike Spence Mobile Computing
  23. 23. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Databases A Home Location Register (HLR) is used to maintain up to date information about a mobile host. HLR stores mobile device’s current location, subscriber’s profile, etc. Each MSC maintains a Visiting Location Register (VLR) The VLR maintains the same information as the HLR. MSC assigns a Mobile Station Roaming Number (MSRN) for each mobile device in its coverage area. MSRN is a temporary number allocated by the MSC (VLR) and sent to the mobile device’s HLR. Mike Spence Mobile Computing
  24. 24. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Databases A Home Location Register (HLR) is used to maintain up to date information about a mobile host. HLR stores mobile device’s current location, subscriber’s profile, etc. Each MSC maintains a Visiting Location Register (VLR) The VLR maintains the same information as the HLR. MSC assigns a Mobile Station Roaming Number (MSRN) for each mobile device in its coverage area. MSRN is a temporary number allocated by the MSC (VLR) and sent to the mobile device’s HLR. Mike Spence Mobile Computing
  25. 25. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Network Databases A Home Location Register (HLR) is used to maintain up to date information about a mobile host. HLR stores mobile device’s current location, subscriber’s profile, etc. Each MSC maintains a Visiting Location Register (VLR) The VLR maintains the same information as the HLR. MSC assigns a Mobile Station Roaming Number (MSRN) for each mobile device in its coverage area. MSRN is a temporary number allocated by the MSC (VLR) and sent to the mobile device’s HLR. Mike Spence Mobile Computing
  26. 26. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Addressing CCITT has specified that each mobile device is allocated a globally unique MSISDN MSISDN - Mobile Subscriber Integrated Services Digital Network. MSISDN consists of a country code (CC) and a subscriber number Mike Spence Mobile Computing
  27. 27. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Addressing CCITT has specified that each mobile device is allocated a globally unique MSISDN MSISDN - Mobile Subscriber Integrated Services Digital Network. MSISDN consists of a country code (CC) and a subscriber number Mike Spence Mobile Computing
  28. 28. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Physical Layer GSM uses two frequency bands: 890 - 915 MHz 935 - 960 MHz The 890 - 915 MHz band is for communication from the mobile device to the BSS. 935 - 960 MHz is for communication in the opposite direction. FDMA is used to sub-divide the frequency bands into 124 pairs of carrier frequencies (each pair is called a channel) The carrier frequencies are spaced 200kHz apart Mike Spence Mobile Computing
  29. 29. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Physical Layer GSM uses two frequency bands: 890 - 915 MHz 935 - 960 MHz The 890 - 915 MHz band is for communication from the mobile device to the BSS. 935 - 960 MHz is for communication in the opposite direction. FDMA is used to sub-divide the frequency bands into 124 pairs of carrier frequencies (each pair is called a channel) The carrier frequencies are spaced 200kHz apart Mike Spence Mobile Computing
  30. 30. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Physical Layer GSM uses two frequency bands: 890 - 915 MHz 935 - 960 MHz The 890 - 915 MHz band is for communication from the mobile device to the BSS. 935 - 960 MHz is for communication in the opposite direction. FDMA is used to sub-divide the frequency bands into 124 pairs of carrier frequencies (each pair is called a channel) The carrier frequencies are spaced 200kHz apart Mike Spence Mobile Computing
  31. 31. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Physical Layer GSM uses two frequency bands: 890 - 915 MHz 935 - 960 MHz The 890 - 915 MHz band is for communication from the mobile device to the BSS. 935 - 960 MHz is for communication in the opposite direction. FDMA is used to sub-divide the frequency bands into 124 pairs of carrier frequencies (each pair is called a channel) The carrier frequencies are spaced 200kHz apart Mike Spence Mobile Computing
  32. 32. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM MAC Layer Each carrier frequency pair is further divided into a set of time slots (using TDMA). 8 TDMA slots form a TDMA frame. Slot duration = 0.577ms, Frame duration = 4.615ms Same TDMA structure is used on the uplink and the downlink. TDMA slots are staggered since a mobile host cannot transmit and receive at the same time. TDMA scheme has a total data rate of 270 kb/s Mike Spence Mobile Computing
  33. 33. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM MAC Layer Each carrier frequency pair is further divided into a set of time slots (using TDMA). 8 TDMA slots form a TDMA frame. Slot duration = 0.577ms, Frame duration = 4.615ms Same TDMA structure is used on the uplink and the downlink. TDMA slots are staggered since a mobile host cannot transmit and receive at the same time. TDMA scheme has a total data rate of 270 kb/s Mike Spence Mobile Computing
  34. 34. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM MAC Layer Each carrier frequency pair is further divided into a set of time slots (using TDMA). 8 TDMA slots form a TDMA frame. Slot duration = 0.577ms, Frame duration = 4.615ms Same TDMA structure is used on the uplink and the downlink. TDMA slots are staggered since a mobile host cannot transmit and receive at the same time. TDMA scheme has a total data rate of 270 kb/s Mike Spence Mobile Computing
  35. 35. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Super-frames Super-frame structure built on top of TDMA frame. Two super-frame structures are used: 1st super-frame repeats every 26 TDMA frames lasting 120ms. 2nd super-frame repeats every 51 TDMA frames lasting 236ms. Super-frame is divided into traffic channels and control channels. Traffic channels carry either speech or data (at a number of different data rates - 2.4kbps, 4.8kbps, 9.6kbps). Mike Spence Mobile Computing
  36. 36. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Super-frames Super-frame structure built on top of TDMA frame. Two super-frame structures are used: 1st super-frame repeats every 26 TDMA frames lasting 120ms. 2nd super-frame repeats every 51 TDMA frames lasting 236ms. Super-frame is divided into traffic channels and control channels. Traffic channels carry either speech or data (at a number of different data rates - 2.4kbps, 4.8kbps, 9.6kbps). Mike Spence Mobile Computing
  37. 37. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service GSM Super-frames Super-frame structure built on top of TDMA frame. Two super-frame structures are used: 1st super-frame repeats every 26 TDMA frames lasting 120ms. 2nd super-frame repeats every 51 TDMA frames lasting 236ms. Super-frame is divided into traffic channels and control channels. Traffic channels carry either speech or data (at a number of different data rates - 2.4kbps, 4.8kbps, 9.6kbps). Mike Spence Mobile Computing
  38. 38. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Control channels are used to locate mobile devices, set-up / terminate calls, authenticate mobile devices. Different types of Control Channels. SDCCH Stand-alone Dedicated Control CHannel is used during call set-up to transfer control to the mobile device. SCH Synchronization CHannel used by BSS to allow mobile devices to synchronise to the start of each TDMA slot. Mike Spence Mobile Computing
  39. 39. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Control channels are used to locate mobile devices, set-up / terminate calls, authenticate mobile devices. Different types of Control Channels. SDCCH Stand-alone Dedicated Control CHannel is used during call set-up to transfer control to the mobile device. SCH Synchronization CHannel used by BSS to allow mobile devices to synchronise to the start of each TDMA slot. Mike Spence Mobile Computing
  40. 40. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Control channels are used to locate mobile devices, set-up / terminate calls, authenticate mobile devices. Different types of Control Channels. SDCCH Stand-alone Dedicated Control CHannel is used during call set-up to transfer control to the mobile device. SCH Synchronization CHannel used by BSS to allow mobile devices to synchronise to the start of each TDMA slot. Mike Spence Mobile Computing
  41. 41. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Different types of Control Channels (contd). FCCH Frequency Control CHannel carries information from the BSS about the carrier frequencies that it is using. BCCH Broadcast Control CHannel is used by BSS to transmit system information. Mobile devices monitor this channel to determine whether or not to initiate a handoff. PCH Paging CHannel is used to locate a mobile host in the system. Mike Spence Mobile Computing
  42. 42. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Different types of Control Channels (contd). FCCH Frequency Control CHannel carries information from the BSS about the carrier frequencies that it is using. BCCH Broadcast Control CHannel is used by BSS to transmit system information. Mobile devices monitor this channel to determine whether or not to initiate a handoff. PCH Paging CHannel is used to locate a mobile host in the system. Mike Spence Mobile Computing
  43. 43. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Different types of Control Channels (contd). FCCH Frequency Control CHannel carries information from the BSS about the carrier frequencies that it is using. BCCH Broadcast Control CHannel is used by BSS to transmit system information. Mobile devices monitor this channel to determine whether or not to initiate a handoff. PCH Paging CHannel is used to locate a mobile host in the system. Mike Spence Mobile Computing
  44. 44. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Control Channels Different types of Control Channels (contd). RACH Random Access CHannel used by mobile hosts to gain access to the network Mobile devices compete with each other using a slotted ALOHA protocol to transmit on this channel. Mike Spence Mobile Computing
  45. 45. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Mobility Management Mobility management is concerned with: handling connection handoffs tracking mobile devices registering appropriate information in network databases Connection Handoff can be done between: channels in the same cell channels in different cells under the same BSS cells under the coverage of different BSSs cells under the coverage of different MSC Mike Spence Mobile Computing
  46. 46. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Mobility Management Mobility management is concerned with: handling connection handoffs tracking mobile devices registering appropriate information in network databases Connection Handoff can be done between: channels in the same cell channels in different cells under the same BSS cells under the coverage of different BSSs cells under the coverage of different MSC Mike Spence Mobile Computing
  47. 47. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Mobility Management Mobility management is concerned with: handling connection handoffs tracking mobile devices registering appropriate information in network databases Connection Handoff can be done between: channels in the same cell channels in different cells under the same BSS cells under the coverage of different BSSs cells under the coverage of different MSC Mike Spence Mobile Computing
  48. 48. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Mobility Management Mobility management is concerned with: handling connection handoffs tracking mobile devices registering appropriate information in network databases Connection Handoff can be done between: channels in the same cell channels in different cells under the same BSS cells under the coverage of different BSSs cells under the coverage of different MSC Mike Spence Mobile Computing
  49. 49. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Mobility Management Mobility management is concerned with: handling connection handoffs tracking mobile devices registering appropriate information in network databases Connection Handoff can be done between: channels in the same cell channels in different cells under the same BSS cells under the coverage of different BSSs cells under the coverage of different MSC Mike Spence Mobile Computing
  50. 50. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Mobility Management Mobility management is concerned with: handling connection handoffs tracking mobile devices registering appropriate information in network databases Connection Handoff can be done between: channels in the same cell channels in different cells under the same BSS cells under the coverage of different BSSs cells under the coverage of different MSC Mike Spence Mobile Computing
  51. 51. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Connection Handoff An MSC is involved in connection handoff between two BSSs When a BSS indicates to the MSC that a handoff is required, the MSC decides when and to which BSS the mobile device should switch to. Each BSS sends signal quality information for each mobile device in its area to the MSC. MSC uses this information to determine which BSS should be assigned to manage the mobile device. An MSC could also initiate a handoff in an attempt to balance traffic in the network. Mike Spence Mobile Computing
  52. 52. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Connection Handoff An MSC is involved in connection handoff between two BSSs When a BSS indicates to the MSC that a handoff is required, the MSC decides when and to which BSS the mobile device should switch to. Each BSS sends signal quality information for each mobile device in its area to the MSC. MSC uses this information to determine which BSS should be assigned to manage the mobile device. An MSC could also initiate a handoff in an attempt to balance traffic in the network. Mike Spence Mobile Computing
  53. 53. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Connection Handoff An MSC is involved in connection handoff between two BSSs When a BSS indicates to the MSC that a handoff is required, the MSC decides when and to which BSS the mobile device should switch to. Each BSS sends signal quality information for each mobile device in its area to the MSC. MSC uses this information to determine which BSS should be assigned to manage the mobile device. An MSC could also initiate a handoff in an attempt to balance traffic in the network. Mike Spence Mobile Computing
  54. 54. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Connection Handoff An MSC is involved in connection handoff between two BSSs When a BSS indicates to the MSC that a handoff is required, the MSC decides when and to which BSS the mobile device should switch to. Each BSS sends signal quality information for each mobile device in its area to the MSC. MSC uses this information to determine which BSS should be assigned to manage the mobile device. An MSC could also initiate a handoff in an attempt to balance traffic in the network. Mike Spence Mobile Computing
  55. 55. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Connection Handoff An MSC is involved in connection handoff between two BSSs When a BSS indicates to the MSC that a handoff is required, the MSC decides when and to which BSS the mobile device should switch to. Each BSS sends signal quality information for each mobile device in its area to the MSC. MSC uses this information to determine which BSS should be assigned to manage the mobile device. An MSC could also initiate a handoff in an attempt to balance traffic in the network. Mike Spence Mobile Computing
  56. 56. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing When a call is initiated by a landline caller to a mobile device, the PSTN contacts the closest Gateway MSC. The Gateway MSC (GMSC) in turn interrogates the mobile device’s HLR. GMSC then gets the MSRN from HLR via the VLR where the mobile device was last located to contact that VLR. VLR then initiates a page operation which results in the BSSs of the MSC each broadcasting a page packet. The mobile device responds with a page response to a particular BSS. Mike Spence Mobile Computing
  57. 57. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing When a call is initiated by a landline caller to a mobile device, the PSTN contacts the closest Gateway MSC. The Gateway MSC (GMSC) in turn interrogates the mobile device’s HLR. GMSC then gets the MSRN from HLR via the VLR where the mobile device was last located to contact that VLR. VLR then initiates a page operation which results in the BSSs of the MSC each broadcasting a page packet. The mobile device responds with a page response to a particular BSS. Mike Spence Mobile Computing
  58. 58. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing When a call is initiated by a landline caller to a mobile device, the PSTN contacts the closest Gateway MSC. The Gateway MSC (GMSC) in turn interrogates the mobile device’s HLR. GMSC then gets the MSRN from HLR via the VLR where the mobile device was last located to contact that VLR. VLR then initiates a page operation which results in the BSSs of the MSC each broadcasting a page packet. The mobile device responds with a page response to a particular BSS. Mike Spence Mobile Computing
  59. 59. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing When a call is initiated by a landline caller to a mobile device, the PSTN contacts the closest Gateway MSC. The Gateway MSC (GMSC) in turn interrogates the mobile device’s HLR. GMSC then gets the MSRN from HLR via the VLR where the mobile device was last located to contact that VLR. VLR then initiates a page operation which results in the BSSs of the MSC each broadcasting a page packet. The mobile device responds with a page response to a particular BSS. Mike Spence Mobile Computing
  60. 60. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing VLR then sends the required parameters for call set-up to the MSC. When the callee answers, a “connect” message is sent from the mobile device to the BSS. The BSS then sets up a traffic channel with the mobile device. The “connect” message is then forwarded to the caller. Mike Spence Mobile Computing
  61. 61. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing VLR then sends the required parameters for call set-up to the MSC. When the callee answers, a “connect” message is sent from the mobile device to the BSS. The BSS then sets up a traffic channel with the mobile device. The “connect” message is then forwarded to the caller. Mike Spence Mobile Computing
  62. 62. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing VLR then sends the required parameters for call set-up to the MSC. When the callee answers, a “connect” message is sent from the mobile device to the BSS. The BSS then sets up a traffic channel with the mobile device. The “connect” message is then forwarded to the caller. Mike Spence Mobile Computing
  63. 63. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Call Routing VLR then sends the required parameters for call set-up to the MSC. When the callee answers, a “connect” message is sent from the mobile device to the BSS. The BSS then sets up a traffic channel with the mobile device. The “connect” message is then forwarded to the caller. Mike Spence Mobile Computing
  64. 64. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Short Messaging Service (SMS) provides a mechanism in GSM for transmitting short messages to and from mobile devices. SMS uses a Short Messaging Service Center (SMSC) to store and forward short messages. Some of the benefits of SMS: Asynchronous connectionless message transmission Alert / Notification Support for diverse information such as news, sport, etc Delivery of messages to multiple subscribers. Mike Spence Mobile Computing
  65. 65. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Short Messaging Service (SMS) provides a mechanism in GSM for transmitting short messages to and from mobile devices. SMS uses a Short Messaging Service Center (SMSC) to store and forward short messages. Some of the benefits of SMS: Asynchronous connectionless message transmission Alert / Notification Support for diverse information such as news, sport, etc Delivery of messages to multiple subscribers. Mike Spence Mobile Computing
  66. 66. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Short Messaging Service (SMS) provides a mechanism in GSM for transmitting short messages to and from mobile devices. SMS uses a Short Messaging Service Center (SMSC) to store and forward short messages. Some of the benefits of SMS: Asynchronous connectionless message transmission Alert / Notification Support for diverse information such as news, sport, etc Delivery of messages to multiple subscribers. Mike Spence Mobile Computing
  67. 67. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Short Messaging Service (SMS) provides a mechanism in GSM for transmitting short messages to and from mobile devices. SMS uses a Short Messaging Service Center (SMSC) to store and forward short messages. Some of the benefits of SMS: Asynchronous connectionless message transmission Alert / Notification Support for diverse information such as news, sport, etc Delivery of messages to multiple subscribers. Mike Spence Mobile Computing
  68. 68. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Short Messaging Service (SMS) provides a mechanism in GSM for transmitting short messages to and from mobile devices. SMS uses a Short Messaging Service Center (SMSC) to store and forward short messages. Some of the benefits of SMS: Asynchronous connectionless message transmission Alert / Notification Support for diverse information such as news, sport, etc Delivery of messages to multiple subscribers. Mike Spence Mobile Computing
  69. 69. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Short Messaging Service (SMS) provides a mechanism in GSM for transmitting short messages to and from mobile devices. SMS uses a Short Messaging Service Center (SMSC) to store and forward short messages. Some of the benefits of SMS: Asynchronous connectionless message transmission Alert / Notification Support for diverse information such as news, sport, etc Delivery of messages to multiple subscribers. Mike Spence Mobile Computing
  70. 70. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Transmission of an SMS can be broken into two parts: Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM) SMS functionality can be broken into 4 parts: Routing Request by SMSC to the HLR to locate the mobile host. Point-to-Point transmission of the message to the MSC currently serving the mobile device. Waiting Indication is used by the SMSC when a short message cannot be delivered due to temporary inaccessibility of the mobile device. Service Center Alert is used by the HLR to inform the SMSC that the mobile device is accessible again. Mike Spence Mobile Computing
  71. 71. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Transmission of an SMS can be broken into two parts: Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM) SMS functionality can be broken into 4 parts: Routing Request by SMSC to the HLR to locate the mobile host. Point-to-Point transmission of the message to the MSC currently serving the mobile device. Waiting Indication is used by the SMSC when a short message cannot be delivered due to temporary inaccessibility of the mobile device. Service Center Alert is used by the HLR to inform the SMSC that the mobile device is accessible again. Mike Spence Mobile Computing
  72. 72. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Transmission of an SMS can be broken into two parts: Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM) SMS functionality can be broken into 4 parts: Routing Request by SMSC to the HLR to locate the mobile host. Point-to-Point transmission of the message to the MSC currently serving the mobile device. Waiting Indication is used by the SMSC when a short message cannot be delivered due to temporary inaccessibility of the mobile device. Service Center Alert is used by the HLR to inform the SMSC that the mobile device is accessible again. Mike Spence Mobile Computing
  73. 73. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Transmission of an SMS can be broken into two parts: Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM) SMS functionality can be broken into 4 parts: Routing Request by SMSC to the HLR to locate the mobile host. Point-to-Point transmission of the message to the MSC currently serving the mobile device. Waiting Indication is used by the SMSC when a short message cannot be delivered due to temporary inaccessibility of the mobile device. Service Center Alert is used by the HLR to inform the SMSC that the mobile device is accessible again. Mike Spence Mobile Computing
  74. 74. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service Short Messaging Service Transmission of an SMS can be broken into two parts: Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM) SMS functionality can be broken into 4 parts: Routing Request by SMSC to the HLR to locate the mobile host. Point-to-Point transmission of the message to the MSC currently serving the mobile device. Waiting Indication is used by the SMSC when a short message cannot be delivered due to temporary inaccessibility of the mobile device. Service Center Alert is used by the HLR to inform the SMSC that the mobile device is accessible again. Mike Spence Mobile Computing
  75. 75. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service MO-SM Mike Spence Mobile Computing
  76. 76. Background Network Infrastructure GSM GSM Lower Layers Mobility Management Short Messaging Service MT-SM Mike Spence Mobile Computing

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