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Mobile Communications system Evolution

UNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICS UNESCO PROJECT Advanced Course on Networking Introduction to Cellular Wireless Networks On the Road to UMTS. Mobile Communications system Evolution. Outline. GSM GPRS UMTS CDMA WCDMA Summery. What is GSM??.

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Mobile Communications system Evolution

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  1. UNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICSUNESCO PROJECT Advanced Course on Networking Introduction to Cellular Wireless NetworksOn the Road to UMTS

  2. Mobile Communications system Evolution

  3. Outline • GSM • GPRS • UMTS • CDMA • WCDMA • Summery

  4. What is GSM?? (Global System for Mobile Communications)

  5. GSM Architecture • Three broad parts • Mobile Station (MS): carried by the subscriber • Base Station Subsystem: control radio link with MS • Network Subsystem: its main part is MSC • Interfaces: • Um Interface : known as air interface or radio link. • Abis Interface: between BTS and BSC • A Interface: between BSC and MSC

  6. ME(mobile equipment) the terminal SIM (Subscriber identity Module) provides personal mobility. Caninsert the SIM card into another GSM terminal and use Mobile Station

  7. BTS (Base Transceiver Station) handle the radio link protocols with the Mobile Station many BTSs in a large urban area BSC (Base Station Controller) manages the radio resources for one or more BTSs handles such as: channel setup , frequencehopping and handovers. connection between MS and MSC Base Station Subsystem

  8. MSC (Mobile Services Switching Center) acts like a normal switching node of the PSTN or ISDN provides the connection to the fixed networks (such as the PSTN or ISDN). HLR (Home Location Register ) contains information of each subscriber registered in the corresponding GSM network, along with the current location of the mobile. logically one HLR per GSM network Network Subsystem

  9. Network Subsystem cont. • VLR (Visitor Location Register) • contains selected information from the HLR, necessary for call control and provision of the subscribed services, • each mobile currently located in the geographical area controlled by the VLR. • EIR (The Equipment Identity Register) • a database that contains a list of all valid mobile equipment on the network, • AuC (The Authentication Center) • is a protected database:secret key of SIM

  10. GSM Features • Multiple access: use TDMA/FDMA to share the limited radio spectrum • The FDMA part involves the division by frequency of the (maximum) 25 MHz bandwidth into 124 carrier frequencies spaced 200 kHz apart. • Each of these carrier frequencies is then divided in time, using a TDMA scheme. • GSM is a digital network • Based on Circuit-switch

  11. GSM Features cont. • SMS: Short Message Service • is a bi-directional service for short (up to 160 bytes) messages. Messages are transported in a store-and-forward fashion. • an acknowledgement of receipt is provided to the sender. • can also be used in a cell-broadcast mode, for sending messages such as traffic updates or news updates. Messages can also be stored in the SIM card for later retrieval

  12. GPRS System (General Packet Radio Service)

  13. GPRS Architecture • Introduce two new nodes into GSM network • SGSN (the Serving GPRS Support Node): • Keep track of the location of the mobile within its service area and send/receive packets from the mobile , passing them on, or receiving them from the GGSN • GGSN (Gateway GPRS Support Node): • convert the GSM packets into other packet protocols (e.g.IP or X.25) and send them out into another network.

  14. GPRS Features • Log on to GPRS • A GPRS-capable terminal communicates with GSM base Stations, but unlike circuit-switched data calls which connects to MSC, GPRS packets are sent from the base station to SGSN, SGSN communicates with GGSN. • Establishes a Packet Data Protocol (PDP) which is logical connection between the mobile and GGSN • now visible to the outside fixed networks

  15. GPRS Features Cont. • SGSN and GGSN use GPRS tunnel protocol (GTP) which operates over the top of TCP/IP to encapsulate the packets • Tunnels: information may be encrypted and additional data is added to each packet to prevent tampering • Packed based • No dial-up, just as with a LAN connection. • No delay for sending data

  16. GPRS Features Cont. • pay for the amount of data they actually communicate, and not the idle time • users need to confirm their agreement to pay for the delivery of content from the service. This is performed by using WAP (Wireless Application Protocol) • unsolicited packets may not be charged • voice and Data Communication at the same time • can be viewed as a sub-network of the Internet

  17. GPRS Features Cont. • Spectrum Efficiency • users can share the resource (Radio link),it is used only when users are actually sending or receiving data • Speed: Based on GMSK • a modulation technique known as Gaussian Minimum-shift keying. • Theoretical Max speeds up to 171.2kbps.(GSM:9.6Kbps)

  18. GPRS Features Cont. • a channel that is 200kHz wide, is divided into 8 separate data streams, each carrying maximum 20kbps(14.4kbps typical), GSM only use one channel, GPRS combine up to 8 of these channels. • complement rather than replace the current data services available through today’s GSM • doesn't require new radio spectrum • supports TDMA: also use for IS-136

  19. Scenario for Migration from 2G to 3G

  20. What are 3G Technologies? • UMTS (Universal Mobile Telecommunications Service) • EDGE can co-exist with UMTS • e.g. Edge provide high speed services for wide-area coverage while UMTS is deployed in urban hot spots. • Cdma 2000 • based on the cdma One standard, two air modes: • one based on the parallel use of 3 contiguous cdmaOne carriers (multi-carrier approach), • the other one on the use of the corresponding 3 carriers width spreading (direct spread approach)

  21. What does UMTS provide? • Circuit- and Packet-Oriented Services • Seamless Global Roaming • Capacity and Capability to serve more than 50% population • A Wide Range of Services • Voice, low-rate data and high-rate data • 144kb/s, 384kb/s , 2Mb/s

  22. UMTS coverage vs. bit rate UMTS Vehicle Outdoors Broadband Radio Walk Fixed Indoors GSM 155Mb/s 0.5 2.0

  23. UTRAN-UMTS Terrestrial Radio Access Network Core Network lu lu lu lur lur RNC RNC RNC lub Node B Node B Node B Node B Node B Node B Uu MH

  24. Frequency Allocation • 1920-1980 MHz paired with 2110-2170 MHz • Total 35 MHz unpaired band C MSS B C A’ A MSS 2170 2110 1920 2010 1980 2200 2025

  25. FDD vs. TDD • Both FDD and TDD are available in UMTS • TDD has been designed for use in high density areas • The highest bearer rate: • TDD-2.048Mb/s • FDD-384kb/s

  26. CDMA(Coded Division Multiple Access) • In CDMA, every user assigned a unique Code

  27. WCDMA • Radio Parameters • Performance Improvement • Channels • Channel Generation • Power Control • Handoff

  28. WCDMA Radio Parameters • Group 200KHz bands into 4.2-5.0 MHz carriers • Chip Rate is 4.096 Mchips/sec • System Capacity of 128 channels per cell provided by 5 MHz bandwidth

  29. WCDMA Performance Improvement • Capacity Improvement • No Frequency Planning • Multiple Services per Connection • Frequency Handoff • HCS • Hot Spot

  30. HCS & Hot-Spot HCS-Scenario Hot-Spot Scenario Hot-Spot Macro Micro Macro f2 f2 f1 f1 f1 f1 f1 Handoff between layers is alwayse needed Handoff at Hot-Spot is sometimes needed

  31. WCDMA Channels • Transport channels are the services which the physical layer provides to higher layers. • The number of transport channels is much higher than for GSM as more services are needed. • Transport channels are grouped into two classes: • Common channels (where information is transmitted to all mobile terminals without distinction) • Dedicated channels (where communication takes place towards a single terminal by associating it with a physical channel, i.e. a code and a frequency or, in the case of TDD, also a time slot).

  32. WCDMA Channels.. Cont. • The following common channels are provided: • BCH (Broadcast Channel): used on the downlink to transmit system information in the entire cell. • FACH (Forward Access Channel): used on the downlink to transmit control information to mobile terminal. It also can be used to transport short data packets (as with GSM Short Message Service). FACH is used when the system knows the cell in which the terminal is registered. • PCH (Paging Channel): used on the downlink to transmit control information to mobile terminal whose location is not known. Transmission here is associated with paging indicator which informs the mobile terminal that the information is present on the paging channel, thus permitting lower battery consumption. • SCH (Synchronization Channel): used on the downlink to permit synchronization between the mobile terminal and base station. • RACH (Random Access Channel): used on the uplink to transport control information transmitted by the mobile terminal. • CPCH (Common Packet Channel): used on the uplink to transport data packets especially burst traffic. • DSCH (Downlink Shared Channel): used in the downlink to transport data packets. Access is shared by various users and is regulated by the base station.

  33. WCDMA Channels.. Cont. • There are certain physical channels which are not associated with a transport channel. They are used to transport physical layer information that does not need to be sent to higher layers. • These channels are as follows: • CPICH (Common Pilot Channel): a downlink channel on which a known un-modulated sequence is transmitted. • DPCCH (Dedicated Physical Control Channel): physical channel present on both links and used to transport physical layer signalling. • AICH (Acquisition Indication Channel): present on the downlink and used to inform the mobile terminal that there is a message on the FACH channel in response to an access attempt. • PICH (Paging indication Channel): present on the downlink and used to inform the mobile terminal that there is a message on the PCH channel.

  34. WCDMA Channels.. Cont. • Physical Channels: are typically based on the following structure: • Radio frame: has a length of 10 ms and consists of 15 time slots. • Time slot: has a length of 10/15 ms. Each slot consists of a number of symbols which varies according to the bit rate of the service to be transmitted. • Symbol: this is the information element after the channel encoding operations (i.e. after error correction codes are inserted)

  35. Power Control In WCDMA • Near-Far Problem in CDMA • Different Performance for Subscriber Links • A Few Subscribers closest to the BTS may contribute too much multiple Access Interference.

  36. Power Control In WCDMA • How to do power control • Force all users to transmit the minimum amount of power • Reduce the power transmitted by users closest to the BTS; increase the power transmitted by users farst to the BTS

  37. Power Control In WCDMA • Open Loop vs. Close Loop • Open Loop Power Control Subscriber measures the DL power and adjusts its transmission power • Close Loop Power Control BS measures the UL power. MS measures the DL power and reports to the BS. BS instructs the user to raise or lower it transmission power

  38. WCDMA Soft Handoff BS1 BS2 BS1 Active set = BS1 BS2 BS1 Active set = BS1 & BS2 BS2 SS > add threshold BS2 Active set = BS2 BS1 SS < drop threshold

  39. Active Research Topics • Cellular system architecture • UMTS air interface • Power control in CDMA • Handoff • Satellite-UMTS traffic • Integrated All-IP 3G-WLAN

  40. Reference • http://www.europe.alcatel.fr/telecom/rcd/keytech/ • http://www.comms.eee.strath.ac.uk/~gozalvez/gsm/ • http://www.gsmworld.com/ • http://www.ibctelecoms.com/ • http://www.span.net.au/ • http://www.cdg.org/tech/a_ross/ • http://www.nokia.com/networks/mobile/ • http://www.gsmdata.com/ • http://www.sds.lcs.mit.edu/~turletti/gmsk/ • http://www.wirelessweek.com/issues/3G/

  41. Reference • http://www.umts-forum.org/reports.html • http://www.itu.int/imt/ • http://www.etsi.org/ • Flavio Muratore: UMTS, Mobile Communications for future, John Wiley & Sons, 2001. • S. Dutnall, N. Lobley, A. Clapton, UMTS: The mobile part of broadband communications for the next century IEEE Atm Workshop, Proceedings. p242-252,1998 • S. Breyer, G. Dega, V. Kumar, L. Szabo, Global view of the UMTS concept Alcatel Telecommunications Review. n 3 1999. p 219-227 • M. Lee, CDMA Network Security , Prentice-Hall, 1998 • U. Black, Mobile & Wireless Networks, Prentice-Hall, 1999 • M. Gallagher, W. Webb, UMTS: The next generation of mobile radio, IEE Review. v 45 n 2 1999. p 59-63

  42. Reference • A. Samukic, UMTS Universal Mobile Telecommunications System:Development of standards for the third generation, IEEE Global Telecommunications Conference & Exhibition. v 4 1998. p 1976-1983 • N. Prasad, GSM evolution towards third generation UMTS/IMT2000, IEEE International Conference on Personal Wireless Communications 1999, p 50-54 • A. Samukic, UMTS universal mobile telecommunications system: Development of standards for the third generation, IEEE Transactions on Vehicular Technology. v 47 n 4 Nov 1998. p 1099-1104

  43. Thank you !!!

  44. UNESCO PROJECT Advanced Course on Networking Professor Khalid Al-BegainUNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICSUniversity of Damascus, Syria, 06 - 15 April 2004

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