통신시스템(Gsm network)
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통신시스템(Gsm network)

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About GSM Network

About GSM Network

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통신시스템(Gsm network) 통신시스템(Gsm network) Presentation Transcript

  • Telecommunication Basics (GSM Network) Software Engineering Lab - 김영기 책임
  • Remember Again !!! 1G 2G 3G 3.5G 4G WiMAX track 802.15e Wave1 802.15e Wave2 802.16e 802.16n (Mobile WiMAX) (Mobile WiMAX) WiMAX R1.5 WiMAX R2.0 CDMA-1X CDMA-1X CDMA-1XCDMA track EV-DO r0 EV-DO rA EV-DO rB UMB AMPS IS-95 A IS-95 B CDMA-1X EV-DVGSM track EDGE LTE LTE Advanced NMT GSM GPRS W-CDMA W-CDMA W-CDMA W-CDMA W-CDMA R5 R6 R7 HSPA+ R3 (HSCPA) (HSUPA) (HSPA+) Phase2음성 통화 통화, 문자, 이메일 통화, 문자, 멀티미디어, 무선인터넷 초고속 인터넷 초고속 무선 인터넷 유,무선간 연동
  • GSM Characteristics MS Transmission BS Transmission Year Introduced 1990 Band : 890 – 915 Band : 935 – 960 MHZ MHZ Access method TDMA 45 MHz Channel 200 kHz Bandwidth Number of duplex 1 125 channels 2 3 Users per channel 8 4 5 Speech coding bit 13 kbps 6 rate 7 Data coding bit 12 kbps F1 F2 F1 F2 8 rate Frequency Frame size 4.6 ms
  • GSM Nework Architecture Base Station Subsystem Network Subsystem MS Abis A SIM HLR VLR ME BSC PSTN ISDN, PSPDN Mobile CSPDN BTS Station MSC UM BSC BTS EIR AuC O&M Database Network Planning Data Sever System Communication Network Measurement System Network Network Management SubsystemSIM : Subscriber Identity Module BSC : Base Station Controller MSC : Mobile Service Switching StationME : Mobile Equipment HLR : Home Location Register AuC : Authentication CenterMS : Mobile Station VLR : Visitor Location Register UM : Radio LinkBTS : Base Transceiver Station EIR : Equipment Identify Register NMS : Network Management System
  • GSM Interface (1/2) Interface Description  The "air" or radio interface standard that is used for exchanges between a mobile (ME) and a Um Interface base station (BTS / BSC). For signaling, a modified version of the ISDN LAPD, known as LAPDm is used  This is a BSS internal interface linking the BSC and a BTS, and it has not been totally Abis Interface standardized. The Abis interface allows control of the radio equipment and radio frequency allocation in the BTS  The A interface is used to provide communication between the BSS and the MSC. The interface carries information to enable the channels, timeslots and the like to be allocated to A Interface the mobile equipment being serviced by the BSSs. The messaging required within the network to enable handover etc to be undertaken is carried over the interface  The B interface exists between the MSC and the VLR . It uses a protocol known as the MAP/B protocol. As most VLRs are collocated with an MSC, this makes the interface purely an B Interface "internal" interface. The interface is used whenever the MSC needs access to data regarding a MS located in its area  The C interface is located between the HLR and a GMSC or a SMS-G. When a call originates from outside the network, i.e. from the PSTN or another mobile network it ahs to pass through the gateway so that routing information required to complete the call may be gained. C Interface The protocol used for communication is MAP/C, the letter "C" indicating that the protocol is used for the "C" interface. In addition to this, the MSC may optionally forward billing information to the HLR after the call is completed and cleared down  The D interface is situated between the VLR and HLR. It uses the MAP/D protocol to D Interface exchange the data related to the location of the ME and to the management of the subscriber  The E interface provides communication between two MSCs. The E interface exchanges data E Interface related to handover between the anchor and relay MSCs using the MAP/E protocol
  • GSM Interface (1/2) Interface Description  The F interface is used between an MSC and EIR. It uses the MAP/F protocol. The F Interface communications along this interface are used to confirm the status of the IMEI of the ME gaining access to the network  The G interface interconnects two VLRs of different MSCs and uses the MAP/G protocol to G Interface transfer subscriber information, during e.g. a location update procedure  The H interface exists between the MSC the SMS-G. It transfers short messages and uses the H Interface MAP/H protocol  The I interface can be found between the MSC and the ME. Messages exchanged over the I I Interface interface are relayed transparently through the BSS CM CM MM MM DTAP RR BSSMAP BSSMAP/DTAP RR SCCP SCCP RR BTSM BTSM MTP 3 MTP 3 LAPDm LAPDm LAPD LAPD MTP 2 MTP 2 GSM RF GSM RF Layer 1 Layer 1 MTP 1 MTP 1 UM Abis A The layered model of the GSM architecture integrates and links the peer-to-peer communications between two different systems
  • Mobile Station GSM MSs consist of MS Mobile Equipment SIM SIM (Subscriber Identity Module) Functions of Mobile Station ME Voice and data transmission & receipt Mobile Can receive, store, send SMS up to 160 charactors Station Frequency and time synchronization Monitoring of power and signal quality of the surrounding cells Power levels of 20W, 8W, 5W, 2W and .8W Provision of location updates even during inactive state MS identified by unique IMEI shown on pressing “*#06#”
  • SIM (Subscriber Identity Module) (1/2) SIM has microprocessor and memory Fixed data stored for the subscription IMSI Authentication Key , Ki Security Algorithms : Kc, A3, A8 PIN & PUK Network Identities IMEI (International Mobile Equipment Identity) Unique Code and is checked in the EIR White list : IMEI, assigned to valid ME. Black list : IMEI reported stolen White List, Grey List, Black List Gray list : IMEI having problems like faulty software, wrong make of equipment etc. MSISDN (Mobile Station ISDN Number) Is register in the telephone directory and used by the calling party for dialing Shall not exceed 15 digits 1 to 3 digits Variable Variable NDC : National Destination Code CC NDC SN SN : Subscriber Number
  • SIM (Subscriber Identity Module) (2/2) Network Identities (cont.) IMSI (International Mobile Subscriber Identity) An unique identity which is used internationally and used within the network to identify the mobile subscribers Stored in the SIM, the HLR, VLR database TMSI (Temporary Mobile Subscriber Identity) Is a temporary IMSI No. made known to an MS at registration The VLR assigns a TMSI to each mobile subscribers entering the VLR area Assigned only after successful authentication MSRN (Mobile Station Roaming Number) Used in the GMSC to setup a connection to the visited MSC/VLR Is a temporary identity which is assigned during the establishment of a call to a roaming subs
  • NSS (Network Subsystem) Network Subsystem contains MSC, VLR, HLR, AC and EIR Main Functions Call control Identifies the subscriber, establish a call, and clear connection Charging Collect the charging information about a call and transferers it to the Billing Center Mobility management Maintain information about subscriber’s location Signaling Interface with the BSS and PSTN Subscriber data handling Permanent data  HLR Temporary data  VLR
  • NSS Entities Entity Functionality  Call control (Switching and call routing)  Initiation of paging MSC  Charging data collection (Mobile service Switching Center)  Service provisioning  Communication with other NEs (HLR, VLR, MSCs, BSCs)  Temporary data (data valid when subscriber is within its service area)  Identification numbers of the subscribers VLR  Security information for authentication of the SIM card and for ciphering (Visitor Location Register)  Services that the subscriber can use  Data in VLR : IMSI & TMSI, MSISDN, MSRN, Location Area, Supplementary service parameters, MS category, Authentication Key  Permanent data HLR  Keeps track of the current location of its customers (Home Location Register)  Same functionality the VLR AC  Provides security information to the network (for verify the SIM cards) (Authentication Center) - TRIPLET : RAND, SRES, Kc EIR  Responsible for IMSI checking (for verify the mobile equipment) (Equipment Identity Register)  Only one EIR per PLMN
  • BSS (Base Station Subsystem) Base Satation Subsystem contains BSC, BTS and TC (Transcoder) Main Functions Radio path control Taking care of radio resources (channel allocation and quality of the radio connection) Synchronisation It is a critical issue in the GSM network due to the nature of the information transferred Air-and A-interface signalling Connection establishment between the MS and the NSS May be either Signalling connection or a traffic(speech, data) connection Mobile management and speech transcoding Handover and transcoding
  • BSS Entities Entity Functionality  Connection establishment between the MS and the NSS  Mobility management (Handling of MS connections) BSC  Statistical raw data collection (Internal BSC O&M) (Base Station Controller)  Air-and A-interface signaling support (Radio Resource Management)  BTS and TC control  Air interface signaling (Radio resource, Signaling link management) BTS  Ciphering (Synchronization) (Base Transceiver Station)  Speech processing (Signal processing) TC(SM)  To enable an efficient transmission, the digital speech signal is (Transcoder (SubMultiplexer)) compressed A ter Interface A ter’ Interface A Interface TC TC TC SM2M TC BSC TCSM (Transcoder and Submultiplexer) MSC TC is a device that takes 13 KBPS speech data and multiplexes four of them into standard 64 Kbps data
  • NMS (Network Management Subsystem) Network Management Subsystem contains Workstation, Servers, and router, etc Main Functions Fault management Ensure the smooth operation of the network Rapid correction of any kind of problems that are detected Configuration management Maintain up-to-date information about operation and configuration status of NE Including management of the radio network, S/W and H/W , time synchronization, security operation Performance management Collects measurement data from individual network elements and stores it in a database Network operator is able to compare the actual performance of the network with the planned performance
  • OMC (Operations and Maintenance Centre) Dynamic monitoring & Controlling of the network The centralized operation of the various units in the system and functions needed to maintain the subsystems Functions O&M data function Configuration management Fault report and alarm handling Performance supervision/management Storage of system software and data
  • GSM Frame Structure Hyperframe = 2048 Superframes 0 1 2 3 4 5 6 7 0 Base station transmit Slot Superframe = 51 Traffic Multiframe numbers Corresponding Or 26 Control Multififrame receive frame 5 6 7 0 1 2 3 4 5 Base station receive Traffic Multifame Control Multiframes = 26 Frames = 51 Frames Time 120ms 235.4ms Traffic multiframe: The Traffic Channel frames are organised into multiframes consisting of 26 bursts and taking 120 ms. In a traffic multiframe, 24 bursts are used for traffic. These are numbered 0 to 11 and 13 to 24. One of the remaining Frame = 8 Slots bursts is then used to accommodate the SACCH, the remaining frame remaining free. The actual position used alternates between position 12 and 25. Control multiframe: the Control Channel multiframe that comprises 51 bursts and occupies 235.4 ms. This always occurs on the beacon frequency in time slot zero and it may also occur within slots 2, 4 and 6 of the beacon frequency as Slot = 577µs well. This multiframe is subdivided into logical channels which are time- scheduled - Frequency correction burst, Synchronization burst - Broadcast channel (BCH), Paging and Access Grant Channel (PACCH), Stand Alone Dedicated Control Channel (SDCCH)
  • GSM Channels GSM Channels Traffic Channels Signaling Channels Broadcast Channels Common Control Channels Dedicate Control ChannelsFull-rate Half-rate downlink uplink slow fast TCH/F TCH/H BCCH FCCH SCH PCH AGCH RACH TCH/H TCH/H TCH/H  The forward common channels are used for paging to inform a mobile of an incoming call, responding to channel requests, and broadcasting bulletin board information.Common Channel  The return common channel is a random access channel used by the mobile to request channel resources before timing information is conveyed by the BSS  The signaling channels are used for maintenance of the call and for enabling call set up, providingDedicate Channel facilities such as handover when the call is in progress, and finally terminating the call.  The traffic channels handle the actual payloadTCHf : Full rate traffic channel. RACHMS : access requests, response to call announcement,TCH h : Half rate traffic channel. location update, etc.BCCH : Broadcast Network information, FACCHt : For time critical signalling over the TCHSCH : Synchronisation of the MSs. (e.g. for handover signalling)FCHMS : frequency correction. SACCHt : TCH in-band signalling, (e.g. for link monitoring)AGCH : Acknowledge channel requests from MS and allocate SDCCH : For signalling exchanges, a SDCCH. (e.g. during call setup, registration / location updates)PCHMS : terminating call announcement. FACCHs : FACCH for the SDCCH. SACCHs : SDCCH in-band signalling (e.g. for link monitoring)
  • GSM Call Scenario 1 Location update Previous BSS MSC/VLR HLR/AuC MSC/VLR Channel Request Immediate Assignment Location Update Request Complete L3 Info (location updating request) Send Authentication Info Send Authentication Info RR Authentication Request Authentication Response Update Location Cancel Location Cancel Location RR Insert Subscriber Data Insert Subscriber Data RR Update Location RR Location Updating Accept Clear Command Clear Complete Channel Release
  • GSM Call Scenario 2 Mobile to Network Cell Site MSC PSTN CM Service Request (Service type = mobile originated call) Complete Layer3 Info (CM Service Request) Authentication Request Authentication Response Cipher Mode Command Cipher Mode Command Cipher Mode Complete Cipher Mode Complete Setup Calling Proceeding Assignment Request Assignment Command Assignment Complete Assignment Complete IAM ACM Alerting ANM Connect Connect Acknowledge
  • GSM Call Scenario 3 Network to Mobile BSS MSC/VLR HLR GMSC PSTN IAM SRI (MSISDN) PRN (IMSI) PRN RR (MSRN) PRI RR (MSRN) IAM (MSRN) Paging Paging Request Channel Request Immediate Assignment Paging Response Complete Layer 3 info (Paging Response) Cipher Mode Command Ciphering Mode Command Ciphering Mode Complete Ciphering Mode Complete Setup Call Confirmed Assignment Request Assignment Command Assignment Complete Assignment Complete Alerting ACM ACM Connect ANM ANM Connect Acknowledge
  • GSM Handover Scenario Handover between BSCs Serving BSS MSC/VLR Target BSS Measurement Report Measurement Report Handover Required Handover Request Handover Request Ack Handover Command Handover Command MS tunes to New channel Handover Access Handover Detect Handover Complete Handover Complete Clear Command Measurement Report Clear Complete Measurement Report Measurement Report
  • Appendix : Mobility Management In-session mobility management Move during an active call Hand-off management Out-of-session mobility management Move in standby mode Location management : Update (Registration) and Paging LA-1 LA-2
  • Appendix : Hand-off Hand-off = Handover Transfer of a MS from one cell to another Each BS constantly monitors the received power from each MS When power drops below given threshold BS asks neighbor station (with stronger received power) to pic up the MS, on a new channel Hand-off Types Intra-Cell Inter-Cell Soft Hand-off Hard Hand-off x
  • Appendix : Hand-off Problem Hand-off is the process of switching from one frequency channel to another by the user in midst of a communication Normally induced by … Received Signal Strength (RSS) Signal-to-Noise Ration (SNR) Bit Error Rate (BER) Triggered either by the BS or the mobile station In GSM, MAHO (Mobile-Assisted HandOver) Ratio of power Handover Threshold Received From current BS Receiver Threshold To next BS time t0 t1 Base Station 1 Base Station 2