1. GSM SEMINAR ON TECHNOLOGY

2. Md. Omar Ali Shamim Ahmed Nasrin Akter Khandakar Menhaz Morshed Speakers

3. # What’s a cellular phone? Now all of these mobile devices are shining in your hands.

4. # Why it calls cellular? > Uses hexagonal Cells

5. # Why use cells? # If there was no cell Limited frequency spectrum for available Mobile Communication Frequency utilization is inefficient Single high power antenna => limited number of users

6. # Why use cells? # Benefits of cellular technology Smaller cells => frequency reuse possible => more number of users As demand increases (more channels needed) –N–Number of base stations is increased (by reducing cell size) –T–Transmitter power is decreased correspondingly to avoid interference (to eliminate adjacent-channel interference)

7. # Frequency reuse: Adjacent cells assigned different frequencies to avoid interference or crosstalk. The same frequency is reused in different areas for different transmissions In GSM networks a frequency reuse patternwith k = 3, 4, 7, 12 or 21. Here, k= Frequency reuse factor Each ‘k’ number of cells make a cluster.

8. # Frequency reuse: >Reuse factor = 3 3 cell Cluster >Reuse factor = 4 4 cell Cluster

9. # Frequency reuse: >Reuse factor = 7 7 cell Cluster

10. # Frequency Reuse Problems: Adjacent-channel interference Co-channel Interference

11. # Adjacent-channel interference Comes from imperfect filters that allow frequency leakage into the band Serious problem if interferer is nearby, near-far effect –N–Nearby mobile transmits on a frequency near to that of a weak mobile Base station receivers need high-Q filters to reject adjacent channel interference.

12. # Adjacent-channel interference

13. # Co-channel Interference One of the primary forms of man-made signal degradation associated with digital radio, co-channel interference occurs when the same carrier frequency reaches the same receiver from two separate transmitters

14. # Co-channel Interference F1 MS

15. # Co-channel Interference

16. # Sectored Cells To reduce the adjacent channel interference & co-channel interference a cell can divide into 3 or 6 sectors according to the demand.

17. 3 sectors per cell 3 cells per cluster 1 23 2 3 1 2 3 2 3 2 3

18. 3 sectors per cell 4 cells per cluster 31 2 4 3 2 4 13 1 2 4 3 1 2 4 4 1

19. 21 6 sectors per cell 2 cells per cluster 1 2 1 2 111 2 22

20. # Original view of sectors

21. # Multiplexing & Access Methods SDMASDM CDMACDM TDMATDM FDMAFDM Access MethodMultiplexing

22. # FDM & FDMA Time F r e q u e n c y F3F3 F2F2 F1F1

23. # TDM & TDMA Time A m p l i t u d e T3T3 T2T2 T1T1 F r e q u e n c y

24. # CDM & CDMA Time C o d e Code 3 Code 2 Code 1 F r e q u e n c y

25. # SDM & SDMA

26. # Frequency Spectrum Down link 935~960MHz Up link 890~915MHz MS BTS

27. # Channels GSM 900 uses 25 MHz frequency spectrum with 124 channels for uplink & downlink. Each channels have 200 KHz bandwidth. Each two channels are separated by 1.6 KHz guard band. Each channel have 8 time slots which allows 8 subscribers to use same frequency by TDMA.

28. # Channels 124561231243 14235867 Channels with 200 KHz bandwidth Time slots 4.615 ms

29. # Cell Types Cells can be classified into three types according to cell size Macro cell Micro cell Pico cell

30. # Cell Types

31. # Antenna Two types of antenna used Unidirectional antenna Omni directional antenna

32. # Unidirectional antenna

33. # Omni directional antenna Semi omni directional antenna

34. # Modulation Technique BPSK Two phases represent two binary digits

35. # Modulation Technique QPSK & OQPSK Each signal element representing more than one bit

36. # Modulation Technique MSK Just like OQPSK, but the rectangular pulses are replaced by half-sinusoids

37. # Modulation Technique GMSK Using FSK modulation

38. On the next session Shamim Ahmed will with you

39. BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller MS — Mobile Station NSS — Network Sub-System MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC GSM 2G Architecture SS7 BTS BSC MSC VLR HLR AuC GMSC BSS PSTN NSS A E C D PSTN Abis B H MS GSM — Global System for Mobile communication

40. GSM Sub-Systems Radio Sub System (RSS) RSS = MS + BSS BSS = BTS+ BSC Network Sub System (NSS) NSS = MSC+ HLR + VLR + GMSC Operation Sub System OSS = EIR + AuC

41. GSM network layer #Radio resource management (RR) sublayer –Establishment, maintenance, and termination of radio channel connections #Mobility management (MM) sublayer –Registration, authentication, and location tracking #Call control (CC) sublayer –Establishment, maintenance, and termination of circuit-switched calls

42. SS7 BTS BSC MSC VLR HLR AuC GMSC BSS PSTN NSS A E C D PSTN Abis B H MS BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller NSS — Network Sub-System MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC 2.5G Architectural Detail SGSN — Serving GPRS Support Node GGSN — Gateway GPRS Support Node GPRS — General Packet Radio Service IP 2G+ MS (voice & data) PSDN Gi SGSN Gr Gb Gs GGSN Gc Gn 2G MS (voice only)

43. 3G rel99 Architecture (UMTS) — 3G Radios SS7 IP BTS BSC MSC VLR HLR AuC GMSC BSS SGSNGGSN PSTN PSDN CN C D Gc Gr GnGi Abis Gs B H BSS — Base Station System BTS — Base Transceiver Station BSC — Base Station Controller RNS — Radio Network System RNC — Radio Network Controller CN — Core Network MSC — Mobile-service Switching Controller VLR — Visitor Location Register HLR — Home Location Register AuC — Authentication Server GMSC — Gateway MSC SGSN — Serving GPRS Support Node GGSN — Gateway GPRS Support Node A EPSTN 2G MS (voice only) 2G+ MS (voice & data) UMTS — Universal Mobile Telecommunication System Gb 3G UE (voice & data) Node B RNC RNS Iub IuCS ATM IuPS

44. 3G rel4 Architecture (UMTS) — Soft Switching

45. GSM Speech Coding Low-pass filter Analog speech A/D RPE-LTP speech encoder Channel encoder 8000 samples/s, 13 bits/sample 104 kbps 13 kbps

46. MS Hands off

47. GSM Call Routing For Incoming Call 1. MSISDN 2. MSISDN VLR HLR AUC EIR GMSC/I WF MSC BSC BTS ISDN 3. MSRN 4. MSRN 5. MSRN 6. TMSI 7. TMSI 8. TMSI LA2 LA1 MS

48. PSTN-to-Mobile Call (STP) (SCP) PSTNPLMN (SSP) BSSMS PLMN (Home)(Visitor) (STP) HLR GMSC (SSP) VMSC VLR IAM 6 2 Where is the subscriber? 5 Routing Info 3Provide Roaming 4 SCP 1 IAM 514 581... ISUP MAP/ IS41 (over TCAP) Signaling over SS7

49. Mobile-Terminated Short Message Example (MTSM)

50. Mobile-Originated Short Message Example (MOSM)

51. GSM Security Fetched triplets are stored in VLR –Every call uses up one triplet (discarded) –Another set must be fetched when exhausted Visited system Registration request IMSI/TMSI identifies user, LAI points to old VLR, requests data to authenticate user IMSI/TMSI + LAI Subscriber data Old VLR

52. GSM Security Visited system Challenge Requests triplets from home system, chooses a triplet Calculates response by authen- tication algorithm Challenge response Compares to stored response in triplet, registration successful if matches New TMSI Acknowledge Assigns new TMSI

53. GSM Security Visited system Registration cancel Location update Acknowledge HLR Old VLR

54. Next Speaker Nasrin Akter

55. Enhancing GSM Speech coder –Trade off speech and error correction bits –Fewer dropped calls DTX — discontinuous transmission –Less interference (approach 0 bps during silences) –More calls per cell

56. Data transfer over GSM Four enhancements to GSM for data –HSCSD - High Speed Circuit Switched Data –GPRS - General Packet Radio Service –EGPRS: Enhanced GPRS –EDGE: Enhanced Data rates for the GSM Evolution Technically EGPRS and EDGE are same

57. GPRS — 2.5G for GSM General packet radio service –First introduction of packet technology Aggregate radio channels –Support higher data rates (115 kbps) –Subject to channel availability –From 1 to 8 time slot / TDMA frame can be allocated for particular service –Physical Channel are taken from common pool of available channel in the cell Share aggregate channels among multiple users No changes to voice network, but only new GPRS logical channels are defined

58. GPRS features Radio resources are allocated for only one or a few packets at a time, so GPRS enables –many users to share radio resources, and allow efficient transport of packets –fast setup/access times –connectivity to external packet data networks GPRS also carries SMS in data channels rather than signaling channels as in GSM

59. EDGE Enhanced Data rates for Global Evolution Increased data rates with GSM compatibility –Still 200 KHz bands; still TDMA –8-PSK modulation: 3 bits/symbol give 3X data rate –Shorter range (more sensitive to noise/interference) –New GSM/ EDGE radios but evolved ANSI- 41 core network

60. The EDGE technology uses the same bandwidth allocated for GSM voice and GPRS data services, but It delivers a higher capacity and fast data services to the mobile network by using a new modulation scheme called 8 PSK (8-level Phase Shift Keying). With this 8 PSK modulation, there are eight distinct phase changes. Each phase represents a symbol and carries three bits of information.

61. GPRS and EGPRS Modulation Principles

62. GSM Evolution for Data Access 1997200020032003+ GSM GPRS EDGE UMTS 9.6 kbps 115 kbps 384 kbps 2 Mbps GSM evolution3G

63. SS7 BTS BSC MSC VLR HLR AuC GMSC BSS PSTN NSS A E C D PSTN Abis B H MS BSS Base Station System BTS Base Transceiver Station BSC Base Station Controller NSS Network Sub-System MSC Mobile-service Switching Controller VLR Visitor Location Register HLR Home Location Register AuC Authentication Server GMSC Gateway MSC GPRS architectural detail SGSN Serving GPRS Support Node GGSN Gateway GPRS Support Node GPRS General Packet Radio Service IP 2G+ MS (voice & data) PSDN Gi SGSN Gr Gb Gs GGSN Gc Gn 2G MS (voice only)

64. GSM to GPRS Element SoftwareHardware MSUpgrade required BTSUpgrade requiredNo Change BSCUpgrade requiredPCU Interface TRAUNo Change MSC/VLRUpgrade requiredNo Change HLRUpgrade requiredNo Change SGSNNew GGSNNew

65. GPRS capacity Difficult to estimate actual bandwidth available to the GPRS user - will vary a lot –depending on time of day –total number of active users –current geographical location and others... Technical Limitations to capacity –Allocation of time slots - between GSM and GPRS and which multislot classes available –Restrictions in terminals –Availability of coding schemes

66. GPRS charging Can be based on –data volume –duration of call –type of service –destination point Charging data output from SGSN and GGSN is encoded in ASN.1/BER and transferred via ftp to a Charging Gateway Function (CGF) node (Billing Gateway)

67. Modem Email Server Auth. Server Internet GSMPSTN User Email via GSM Email via GPRS Email Server GPRS User Auth. Server Internet Authenticated path to Email server Virtual GPRS Data Tunnel GSM v/s GPRS

68. Next Speaker Khandaker Menhaz Morshed

69. Types Of Billing System Post Paid: Pay After Use Pre Paid: Pay Before Use

70. Prepaid Advantages: operator has the money operator saves customer: no need for credit worthiness. prepaid fits well with the expectation of these customers many customers will never use up all their balance

71. Difference Between Mobile And Fixed Prepaid Mobile servers needs: more complex billing system due to more complex tariffs complex taxation real-time usage metering complexity of customer care

72. Four Alternatives For Mobile Prepaid Wireless Intelligent Network (WIN) Service Node Hot Billing Handset-Based

73. BTS MS BSC MSC Intelligent Peripheral SSP P-SCP Wireless Intelligent Network (WIN) Signaling Voice Trunk

74. WIN Call termination when called party pays BTS MS BSC MSC SSP P-SCP GMSC Signaling Voice Trunk

75. Service Node BTS MS BSC MSC Service Node SSP PBP Signaling Voice Trunk

76. Hot Billing BTS MS BSC MSC SSP PSC HLR/AuC Database Signaling Voice Trunk

77. Handset-Based BTS MS BSC MSC SSP Signaling Voice Trunk

78. GSM Summary Uplink frequencies890-915 MHz Downlink frequencies935-960 MHz Total GSM bandwidth25 MHz up + 25 MHz down Channel bandwidth200 kHz Number of RF carriers124 Multiple accessTDMA Users/carrier8 Number of simul. users992 Speech coding rate13 kb/s FEC coded speech rate22.8 kb/s

79. GSM service quality requirements Speech intelligibility90% Max one-way delay90 ms Max handoff gap150 ms if intercell Time to alert mobile of inbound cell 4 sec first attempt, 15 sec final attempt Release time to called network 2 sec Connect time to called network 4 sec

80. GSM 900 and GSM 1800

81. THANKS TO ALL