Uploaded byNeelesh Srivastava
Global System for Mobile (GSM)
The document discusses cellular network basics and generations, including: 1) Cellular networks use radio waves to allow cell phones to operate within certain frequency bands and connect to nearby base stations. 2) Cellular networks have evolved through generations from early analog mobile phones to current digital networks that support high-speed data and multimedia services. 3) Cellular networks face the problem of allowing multiple mobile users to access the network simultaneously, which they address through multiple access schemes like FDMA, TDMA, and CDMA that divide available airlink resources.
More Related Content
![Gsm Global System For Mobile Comm[1]. Really Nice](https://cdn.slidesharecdn.com/ss_thumbnails/gsmglobal-system-for-mobile-comm1-really-nice-1217487402967288-9-thumbnail.jpg?width=640&height=640&fit=bounds)
Similar to Global System for Mobile (GSM)
Global System for Mobile (GSM)
- 1.
- 2. Cellular Network Basics •There are many types of cellular services; before delving into details, focus on basics (helps navigate the “acronym soup”) • Cellular network/telephony is a radio-based technology; radio waves are electromagnetic waves that antennas propagate • Most signals are in the 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz frequency bands Cell phones operate in this frequency range (note the logarithmic scale)
- 3. Cellular Network Generations •It is useful to think of cellular Network/telephony in terms of generations: • 0G: Briefcase-size mobile radio telephones • 1G: Analog cellular telephony • 2G: Digital cellular telephony • 3G: High-speed digital cellular telephony (including video telephony) • 4G: IP-based “anytime, anywhere” voice, data, and multimedia telephony at faster data rates than 3G (to be deployed in 2012–2015)
- 4. Evolution of CellularNetworks 1G 2G 3G 4G2.5G
- 5. The Multiple AccessProblem • The base stations need to serve many mobile terminals at the same time (both downlink and uplink) • All mobiles in the cell need to transmit to the base station • Interference among different senders and receivers • So we need multiple access scheme
- 6. Multiple Access Schemes •Frequency Division Multiple Access (FDMA) • Time Division Multiple Access (TDMA) • Code Division Multiple Access (CDMA) 3 orthogonal Schemes:
- 7. Frequency Division MultipleAccess • Each mobile is assigned a separate frequency channel for the duration of the call • Sufficient guard band is required to prevent adjacent channel interference • Usually, mobile terminals will have one downlink frequency band and one uplink frequency band • Different cellular network protocols use different frequencies • Frequency is a precious and scare resource. We are running out of it • Cognitive radio frequency
- 8. Time Division MultipleAccess • Time is divided into slots and only one mobile terminal transmits during each slot • Like during the lecture, only one can talk, but others may take the floor in turn • Each user is given a specific slot. No competition in cellular network • Unlike Carrier Sensing Multiple Access (CSMA) in WiFi Guard time – signal transmitted by mobile terminals at different locations do no arrive at the base station at the same time
- 9. Code Division MultipleAccess • Use of orthogonal codes to separate different transmissions • Each symbol of bit is transmitted as a larger number of bits using the user specific code – Spreading • Bandwidth occupied by the signal is much larger than the information transmission rate • But all users use the same frequency band together Orthogonal among users
- 10.
- 11. GSM Architecture OMC Home LocationRegister AuC Equipment ID Network Management Center BT S BT S BT S ME ME ME Subscriber Identity Module Subscriber Identity Module Subscriber Identity Module Base station controller PSTN Mobile switching center Data communication network BTS = Base Transceiver Station AuC = Authentication Center OMC = Operation and Maintenance Center PSTN = Public Switched Telephone Network ME = Mobile Equipment Source: Stallings, 313 Source: Mehrotra, 27 Visitor Location Register
- 12. But what’s cellular? HLR,VLR, AC, EIR MSC PSTN BS
- 13. GSM Architecture F1 F2F1' F2' Frequency 1 2 3 4 5 6 7 8 45 MHz BS Transmission Band : 935 – 960 MHZ MS Transmission Band : 890 – 915 MHZ Year Introduced 1990 Access method TDMA Channel Bandwidth 200 kHz Number of duplex channels 125 Users per channel 8 Speech coding bit rate 13 kbps Data coding bit rate 12 kbps Frame size 4.6 ms
- 14. SIM (Subscriber IdentityModule) Billions of Calls Millions of Subscribers Thousand of Different Types of Telephones Hundreds of Countries Dozens of Manufacturers…. And only one Card: The SIM Source: Hillebrand, 369 http://ucables.com/products/simcards/ •Administrative data •Security data •Subscriber data •Roaming data •PLMN (Public Land Mobile Network
- 15. Implementation SIM = SubscriberIdentity Module Central processor, clock and tone, internal bus system, keyboard (HMI) Voice encoding Ciphering Modulation Voice decoding >Channel Decoding >De-Interleaving >Re-formatting Deciphering Amplifier >Channel encoding >Interleaving >Burst generation Receiver Transmitter Demodulation Source: Heine, 14
- 16. Implementation Abis- Interface O&M Module Operationand maintenance functionality/clock distribution Digital signal processing (NF functionality) HF Transmitter (HF- TX) Input filter Output filter HF Receiver (HF- RX) Slowfrequency hopping Transmission system TRX Block Diagram of a BTS with one TRX Source: Heine, 20
- 17. GSM Variants Variant Uplink (MHz) Downlink (MHz) Total Bandwidth Duplex- frequency Channels GSM-400451-458 and 479-486 461-468 and 489-496 Twice 14 MHz 10 MHz Twice 72 GSM-900 (primary band) 890-915 935-960 Twice 25 MHz 45 MHz Twice 124 Extended GSM-900 880-915 925-960 Twice 35 MHz 45 MHz Twice 174 GSM-R 876-880 921-925 Twice 4 MHz 45 MHz Twice 19 DCS-1800 1,710-1,785 1,805-1,880 Twice 75 MHz 95 MHz Twice 373 PCS-1900 1,850-1,910 1,930-1,990 Twice 60 MHz 80 MHz Twice 300 Source: Bekkers, 299
- 18. Outgoing Call 1. MSsends dialled number to BSS 2. BSS sends dialled number to MSC 3,4 MSC checks VLR if MS is allowed the requested service.If so,MSC asks BSS to allocate resources for call. 5 MSC routes the call to GMSC 6 GMSC routes the call to local exchange of called user 7, 8, 9,10 Answer back(ring back) tone is routed from called user to MS via GMSC,MSC,BSS
- 19. GSM Operation Speech decoding Channeldecoding De-interleaving Burst Formatting De-ciphering DemodulationModulation Ciphering Burst Formatting Interleaving Channel Coding Speech coding Radio Interface Speech Speech 13 Kbps 22.8 Kbps 22.8 Kbps 33.6 Kbps 33.6 Kbps 270.83 Kbps
- 20. Incoming Call 1. Callinga GSM subscribers 2. Forwarding call to GSMC 3. Signal Setup to HLR 4. 5. Request MSRN from VLR 6. Forward responsible MSC to GMSC 7. Forward Call to current MSC 8. 9. Get current status of MS 10.11. Paging of MS 12.13. MS answers 14.15. Security checks 16.17. Set up connection
- 21. Handovers • Between 1and 2 – Inter BTS / Intra BSC • Between 1 and 3 – Inter BSC/ Intra MSC • Between 1 and 4 – Inter MSC
- 22.
- 23.
- 24. • MS MobileStation = phone + SIM card • BTS Base Transceiver Station • BSC Base Station Controller • HLR Home Location Register • MSC Mobile services Switching Centre • VLR Visitor Location Register • AUC Authentication Centre Stand-alone or integrated in HLR • EIR Equipment Identity Register For blacklisting stolen and unwanted equipment • SMSC Short Message Service ”Support” Centre • VMS Voice Messaging System • PrePaid Node Hosting prepaid service system • IN Intelligent Network services • PSTN Public Switched Telephone Network • PABX Private Automatic Branch Exchange MSC/VLR Warid Telenore BSC SMSC EIR INTERNET MobilinkPSTN BSC PrePaid Node VMS HLR MSC w AUC
- 25.
- 26.
- 27.
- 28.
- 29. BSC Base Station Controller The call request reaches the BSC from the BTS and is forwarded to MSC. After call is established, the BSC will perform decoding of the call (in typical config.)
- 30. BSC HLR MSC SMSC EIR INTERNETIN PrePaid VMS Voicemail MSCBSC PABXPSTN International PSTN Fixed Network
- 31. BSC HLR MSC SMSC EIR INTERNETIN PrePaid VMS Voicemail MSCBSC PABXPSTN International PSTN Fixed Network
- 32. BSC HLR MSC SMSC EIR INTERNETIN PrePaid VMS Voicemail MSCBSC PABXPSTN International PSTN Fixed Network
- 33. • Checks Anumber. • To whom is A subscriber calling? (Checks B number) • Example : A subscriber has prepaid number. MSC Mobile Switching Centre
- 34. BSC HLR MSC SMSC EIR INTERNETIN PrePaid VMS Voicemail MSCBSC PABXPSTN International PSTN Fixed Network
- 35. BSC HLR MSC SMSC EIR INTERNETIN PrePaid VMS Voicemail MSCBSC PABXPSTN International PSTN Fixed Network
- 36. BSC HLR MSC SMSC EIR INTERNETIN PrePaid VMS Voicemail MSCBSC PABXPSTN International PSTN Fixed Network
- 37. • Does theA subscriber have money left on his/her account? • When the call is established and on-going the subscriber’s account is decremented accordingly. PrePaid Node
- 38.
- 39.
- 40.
- 41. • Where isthe B subscriber? • MSC interrogates in HLR. (HLR = Home Location Register) MSC Mobile Switching Centre
- 42.
- 43.
- 44.
- 45. • HLR says’I am the home of the B subscriber and I know where he/she is right now’ (i.e. which VLR) • Tells this VLR ’Give me a visitor address for this subscriber’ (Roaming Number) HLR Home Location Register
- 46.
- 47.
- 48.
- 49.
- 50.
- 51. • Hosting MSC/VLRreturns TEMPORARILY assigned visitor/roaming address for B- subscriber to HLR. MSC Mobile Switching Centre
- 52.
- 53.
- 54.
- 55.
- 56.
- 57. • ’Thanks forthe visitor address!’ • ’I will send this address to the MSC that requested for it.’ HLR Home Location Register
- 58.
- 59.
- 60.
- 61. • ’Thank you,HLR!’ • Speech connection path will set up now towards the MSC/VLR where the B subscriber is presently located. MSC Mobile Switching Centre
- 62.
- 63.
- 64.
- 65. • Sets upa speech connection towards BSC. • Delivers B-subscriber ID to BSC and asks to page for the subscriber using that ID. MSC Mobile Switching Centre
- 66.
- 67.
- 68.
- 69. • BSC nowsends a PAGING MESSAGE to all the BTSs that it covers/controls. • Carrys PAGING RESPONSE from called MS back to MSC. • Allocates a RADIO channel through a BTS with best available and allowable SIGNAL STRENGTH for called MS. • Performs SPEECH CODING when call is established. BSC Base Station Controller
- 70.
- 71. Key generation andEncryption
- 72. 3G, 3.5G and4G (LTE)
- 73. 3G Overview • 3Gis created by ITU-T and is called IMT-2000
- 74. Evolution from 2G IS-95IS-136 & PDCGSM- EDGE GPRS HSCSD IS-95B Cdma2000-1xRTT Cdma2000-1xEV,DV,DO Cdma2000-3xRTT W-CDMA EDGE TD-SCDMA 2G 3G 2.5G 3GPP3GPP2
- 75. Service Roadmap Improved performance,decreasing cost of delivery Typical average bit rates (peak rates higher) WEB browsing Corporate data access Streaming audio/video Voice & SMS Presence/location xHTML browsing Application downloading E-mail MMS picture / video Multitasking 3G-specific services take advantage of higher bandwidth and/or real-time QoS A number of mobile services are bearer independent in nature HSDPA 1-10 Mbps WCDMA 2 Mbps EGPRS 473 kbps GPRS 171 kbps GSM 9.6 kbps Push-to-talk Broadband in wide area Video sharing Video telephony Real-time IP multimedia and games Multicasting CDMA 2000- EVDO CDMA 2000- EVDV CDMA 20001x
- 76. GSM Evolution to3G GSM 9.6kbps (one timeslot) GSM Data Also called CSD GSM General Packet Radio Services Data rates up to ~ 115 kbps Max: 8 timeslots used as any one time Packet switched; resources not tied up all the time Contention based. Efficient, but variable delays GSM / GPRS core network re-used by WCDMA (3G) GPRS HSCSD High Speed Circuit Switched Data Dedicate up to 4 timeslots for data connection ~ 50 kbps Good for real-time applications c.w. GPRS Inefficient -> ties up resources, even when nothing sent Not as popular as GPRS (many skipping HSCSD) EDGE Enhanced Data Rates for Global Evolution Uses 8PSK modulation 3x improvement in data rate on short distances Can fall back to GMSK for greater distances Combine with GPRS (EGPRS) ~ 384 kbps Can also be combined with HSCSD WCDMA
- 77. UMTS • Universal MobileTelecommunications System (UMTS) • UMTS is an upgrade from GSM via GPRS or EDGE • The standardization work for UMTS is carried out by Third Generation Partnership Project (3GPP) • Data rates of UMTS are: – 144 kbps for rural – 384 kbps for urban outdoor – 2048 kbps for indoor and low range outdoor • Virtual Home Environment (VHE)
- 78. UMTS Frequency Spectrum •UMTS Band • 1900-2025 MHz and 2110-2200 MHz for 3G transmission • In the US, 1710–1755 MHz and 2110–2155 MHz will be used instead, as the 1900 MHz band was already used.
- 79. UMTS Architecture SD Mobile Station MSC/ VLR BaseStation Subsystem GMSC Network Subsystem AUCEIR HLR Other Networks Note: Interfaces have been omitted for clarity purposes. GGSN SGSN BTS BSC Node B RNC RNS UTRAN SIM ME USIM ME + PSTN PLMN Internet
- 80. 4G (LTE) • LTEstands for Long Term Evolution • Next Generation mobile broadband technology • Promises data transfer rates of 100 Mbps • Based on UMTS 3G technology • Optimized for All-IP traffic
- 81.
- 82. Comparison of LTESpeed
- 83. LTE vs UMTS •Functional changes compared to the current UMTS architecture