6Channels Physical Channels Logical Channels Associated with frequency bands, time slots, codesPhysical channels transfer bits from one network element to anotherLogical ChannelsDistinguished by the nature of carried information and the way to assemble bits into data unitsThree typesone-to-one: traffic channels between a BTS and a MSone-to-many: synchronization signals from BTS to MSs in a cellmany-to-one: from MSs to the same BTS
9Frame Types There are two types of multiframe 26 TDMA-frame multiframe is used to carry TCH, SACCH and FACCH51 TDMA-frame multiframe is used to carry BCCH, CCH, SDCCH and SACCH
10Burst and FramesThe information contained in one time slot on the TDMA frame is call a burst.Five types of burstNormal Burst (NB)Frequency Correction Burst (FB)Synchronization Burst (SB)Access Burst (AB)Dummy Burst
11Logical Channel List Traffic Two-way channels (TCH) Base-to- mobile TCH/F: Full-rate Traffic ChannelTrafficchannels(TCH)Two-wayTCH/H: Half-rate Traffic ChannelFCCH: Frequency correctionBCHSCH: SynchronizationBCCH: Broadcast controlBase-to-mobileSignalingchannelPCH: PagingCCCHAGCH: Access grantRACH: Random accessSDCCH: Stand-alone dedicated controlDCCHSACCH: Slow associated controlTwo-wayFACCH: Fast associated control
12Logical Channels Control Channels Traffic Channels (TCH) Broadcast Channels (BCH)Common Control Channels (CCCH)Dedicated Control Channels (DCCH)Traffic Channels (TCH)Full Rate (TCH/F)Half Rate (TCH/H)
13UP / Down-LinkDown-link: the transmission path from Base Station to Mobile StationUp-link: the transmission path from Mobile Station to Base Station
14Control Channels Broadcast Channels (BCH) Frequency Correction Channel (FCCH)Synchronization Channel (SCH)Broadcast Control Channel (BCCH)Common Control Channels (CCCH)Paging Channel (PCH)Random Access Channel (RACH)Access Grant Channel (AGCH)Dedicated Control Channels (DCCH)Stand alone Dedicated Control Channel (SDCCH)Cell Broadcast Channel (CBCH)Slow Associated Control Channel (SACCH)Fast Associated Control Channel (FACCH)
22Broadcast Channels (BCH) To help the MH (Mobile Handset) measuresto turn to a BTSto listen for the cell informationto start roaming, waiting for calls to arrive, making callsBecause BTSs are not synchronized with each other, every time a MH decides to camp to another cell, its FCCH, SCH, and BCCH must be read.
23Frequency Correction Channel (FCCH) Provide MH with the frequency reference of the systemTo enable the Mobile Handset (MH) to synchronize with the frequencyTransmission propertiesTransmit on the down-linkPoint to multi-point.
24Synchronization Channel (SCH) MH synchronize with the structure within the locative cellMH can receive information from the proper time slots on the TDMA structureTo ensure a GSM BTS is choseThe Base Station Identity Code (BSIC) can only be decoded by a GSM BTSTransmission propertiesTransmit on down-linkPoint to multi-point.
25Broadcast Control Channel (BCCH) BTS broadcast cell information to MHLAI ( Location Area Identity), to start roaming, waiting for calls to arrive, making callsmaximum output power allowed in the cellinformation about BCCH carriers for the neighboring cellsMH will perform measurement to BTSTransmission propertiesTransmit on down-linkPoint to multi-point
26Common Control Channels (CCCH) CCCH support the establishment of a dedicated communication path (dedicated channel) between the MH and the BTSThree types of CCCHPaging Channel (PCH)Random Access Channel (RACH)Access Grant Channel (AGCH)
27Paging Channel (PCH) Used by BTS to page particular MH in the cell MH actively listen to PCH to check contact info within certain timeContact could be incoming call or short messageContact info on PCH includeIMSI (MH’s identity number), orTMSI (temporary number)Transmission propertiesTransmit on down-linkpoint to point
28Random Access Channel (RACH) Used by MH to request a dedicated channel for call setupShared by any MH attempts to access the networkChannel request message contains the reason for the access attemptTransmission propertiesTransmit on up-linkPoint to pint.
29Access Grant Channel (AGCH) The network assigns a signaling channel via AGCHA Stand alone Dedicated Control Channel (SDCCH) is assignedTransmission propertiesTransmit on down-linkPoint to point
30Dedicated Control Channels (DCCH) DCCH are used for transferring nonuser information between the network and the MHMessages on DCCH Includingchannel maintenancemobility managementradio resource managementFour kinds of DCCHStand alone Dedicated Control Channel (SDCCH)Cell Broadcast Channel (CBCH)Slow Associated Control Channel (SACCH)Fast Associated Control Channel (FACCH)
31Stand alone Dedicated Control Channel (SDCCH) Transfer signaling information between the BTS and the MHTypically used for location updating prior to use of a traffic channelTransmission propertiesBidirectional channel, transmit on both up and down-linkPoint to point.
32Cell Broadcast Channel (CBCH) To carry Short Message Service Cell Broadcast (SMSCB)Use the same physical channel as SDCCHTransmission propertiesTransmit on down-linkPoint to multi-point
33Slow Associated Control Channel (SACCH) Carries control and measurement parameters along with routine data necessary to maintain a radio link between the MH and the BTSOn the uplink, MS sends averaged measurements (signal strength and quality) of current and neighboring BCCHOn downlink, MS receives information about transmitting power to use and an instruction with time advance/retardTransmission propertiesBidirection channel, transmit on both up and down linkPoint to point
34Fast Associated Control Channel (FACCH) An FACCH is used over a TCH where it steals time slots from a TCHa 20 ms segment of speech is stolen to carry handover signaling informationAppears on demand
35Traffic Channels (TCH) TCH transport user information (speech/data)TCH are bidirectional dedicated channels between the network and the MH
39Burst The information contained in one time slot is a burst Five types of burstNormal Burst (NB)To carry information on traffic and control channelsFrequency Correction Burst (FB)To synchronize the frequency of the mobileSynchronization Burst (SB)To synchronize the frames of the mobileAccess Burst (AB)For random and handover accessDummy BurstFor padding the frame
40Bursts and Frames There are two types of multiframe 26 TDMA-frame multiframe is used to carry TCH, SACCH and FACCH51 TDMA-frame multiframe is used to carry BCCH, CCH, SDCCH and SACCH
43Normal Burst 148 bits = 0.54612 msec T3 S1 Training Sequence 26 S1 CodedData 57Coded Data57T3GP8.25148 bits = msecThis burst is used to carry information on TCH and on the control channelsBCCH, PCH, AGCH, SDCCH, ASCCH and FACCH.Note: GP (Guard Period)
44Random Access Burst 88 bits = 0.32472 msec Synchronizationsequence 41Coded Data36Guard Period68.25T8T388 bits = msec68.25 bits = msec which is equivalent to 75.5 kmpropagation delay.That is, the max. allowed distance between mobile stationand BTS is km. Based on other system parameters,the max cell size is 35 km in GSM.
47(Operation & Maintenance GSM System ArchitectureHLR/VLRUMHandsetA-bisASS7PSTNBSCMSCX.25BTSOMC(Operation & MaintenanceCenter)OperationTerminalData TerminalSIMcardMobilestationRadiosub-systemNetwork sub-systemPSTN
48GSM Network Elements Handset BTS: Base Transceiver Station MSC: Mobile Switching CenterBSC: Base Station ControllerHLR/VLR: Home Location Register/Visiting Location RegisterSIM Card: Subscriber Identity Module CardService Centers: USSD, SMS, ...
49Mobile Handset (MH)Used by the subscriber to access the GSM network via the air interfaceContains the hardware and software specific to the radio interfaceNeed a Subscriber Identity Module (SIM) which contains the subscriber-specific data to access GSM network, except emergency call
50Base Transceiver Station (BTS) / Base Station Responsible for communication to and from MHs via air interfaceMH communicates with the mobile system using a radio channel to a BTSBTS comprises radio transmission and reception devicesIncluding the antennae and signaling processing specific to the radio interfaceBTS separates the speech and control signaling associated with a MH and sends them to the BSC on separate channels
51Mobile services Switching Center (MSC) Responsible for all switching functions related to call processingCoordinate the setting up of calls to and from GSM usersMSC is the interface between GSM network & PSTN (Public Switched Telephone Network)
52Base Station Controller (BSC) Monitor and Control several base stationsFrequency administration, control of BTSs, exchange functionsResponsible for all the radio interface managementChannel allocation and release, handover managementBSC is the interface between MSC and BTSBSC is connected on one side to several BTSs and on the other side to the MSC
53Home Location Register (HLR) A database in charge of the management of mobile subscribersContains information of network subscribersInformation on teleservices and bearer services subscription, service restrictions, and supplementary servicesThe data stored in HLR is of a semipermanent nature and does not usually change from call to call
54Visitor Location Register (VLR) Contains the relevant data of all MHs currently located in a serving MSCThe permanent data is the same as data in the HLRThe temporary data includesTemporary Subscriber Identity (TMSI)Location Area Identity (LAI) of an MHVLR allocates mobile subscriber roaming numbers (MSRNs) for the incoming call setup
55Subscriber Identity Module (SIM) Containsphone number (MSISDN)international mobile subscriber identity (IMSI)status of SIMservice codeauthentication keyPIN (personal identification code)PUK (personal unlock code)
56SIM Cards SIM cards are embedded with a microprocessor Memory capacity Stores customer identity information and is made to fit inside the cellular phoneMemory capacity1K, 3K, 8K, 16KWith/Without OTAC (Over The Air Customization)Two types of SIM card form factorsID-1 SIMPlug-In SIM
57Application Service Centers Responsible for GSM network add-on servicesOperation and Maintenance Center (OMC)Monitoring and control the networkUsually connect with MSC, BSC, HLR, and other service centersShort Message Service Center (SMSC)provide short message servicesusually connect to MSCUnstructured Supplementary Service Data Center (USSDC)provide USSD service in the form of *ID*ID*info#usually connect to HLR
58Geographical Network Structure Location UnitsCellLocation Area (LA)MSC/VLR Service AreaPLMN (Public Land Mobile Network) Service AreaGSM Service AreaCell Planning
59Location Information -- GSM Service Area Hierarchy The area in which a subscriber can access the network.GSM Service AreaPLMN Service Area(one per operator)MSC/VLRLocation Areacell
60Cell Characteristics The Basic Union In The System defined as the area where radio coverage is given by one base station.Addressed by Cell Global Identity (CGI)A cell has one or several frequencies, depending on traffic load.Frequencies are reused, but not used in neighboring cells due to interference.
61Cell Planning Reusing frequencies in different geographic areas: 7 cell repeat pattern is typical, but other patterns are also common7-cell reusepatternG3G1G2F3F1F2C3C1C2A3A1A2B3B1B2E3E1E2D3D1D2A1A3A2B1G1B3G3B2G2C1C3C2D1F1D3F3D2F2E1E3FrequencyreuseE2
63Frequency Utilization v.s. K Frequency can’t be reused in the same patternLarger KMore channels in a patternHigher subscriber numberWorse frequency reusabilitySmaller KLess channels in a pattern, high channel distortionSmaller subscriber numberBetter frequency reusability
65Numbering Mobile Subscriber ISDN Number (MSISDN) Mapping to Mobile Station Roaming Number (MSRN) by HLRInternational Mobile Subscriber Identify (IMSI)Stored in SIM/HLRTemporary Mobile Subscriber Identity (TMSI)Assigned by VLR, Stored in VLRInternational Mobile Equipment Identity (IMEI)Unique ID to handset, used by air interface
66ID-Numbers MSISDN = CC + NDC + SN IMSI = MCC + MNC + MSIN MSISDN: Mobile Station ISDN NumberCC Country CodeNDC National Destination CodeSN Subscriber NumberIMSI = MCC + MNC + MSINIMSI International Mobile Subscriber IdentityMCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Station Identification Number
67ID-Numbers (cont.) IMEI = TAC + FAC + SNR + spare IMEI Internal Mobile Equipment IdentityTAC Type Approval Code, determined by a central GSM/PCS bodyFAC Final Assembly Code, identifies the manufacturerSNR Serial Number, uniquely identifies all equipment within each TAC and FACIMEISV = TAC + FAC + SNR + SVNIMEISV International Mobile Equipment Identity and Software Version NumberSVN Software Version Number
68ID-Numbers (cont.) MSRN = CC + NDC + SN LAI = MCC + MNC + LAC MSRN Mobile Station Roaming NumberCC Country CodeNDC National Destination CodeSN Subscriber Number. In this case, the address to the serving MSCLAI = MCC + MNC + LACMCC Mobile Country CodeMNC Mobile Network CodeLAC Location Area Code
69ID-Numbers (cont.) CGI = MCC + MNC + LAC + CI BSIC = NCC + BCC CGI Cell Global IdentityCI Cell IdentityBSIC = NCC + BCCBSIC Base Station Identity CodeNCC Network Color Code (3bits)BCC Base Station Color Code (3bits)LN = CC + NCD + LSPLN Location NumberCC Country CodeNCD National Destination CodeLSP Locally Significant Part
70ID -Numbers (cont.) LN = CC + NCD + LSP RSZI = CC + NDC + ZC LN Location NumberCC Country CodeNCD National Destination CodeLSP Locally Significant PartRSZI = CC + NDC + ZCRSZI Regional Subscription Zone IdentityNDC National Destination CodeZC length of the Zone code (2 octets)
71Routing Information resident in MS & SIM IMSI, TMSI, IMEI, and misc. informationRouting Information used by NetworkMSISDN, MSRN