Download - Call Setup Procedure 2
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Objective Call setup,Mobility&Integrity is a Key of Optimization
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Outline GSM Protocol Architecture for Signaling International Signaling relation via ISDN GSM Interface & Layers Function Call setup Overview Key points in Call Setup. Explanation of each point with layer 3&2 message & logical channels. Question &Answers3LCC Pakistan
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GSM Protocol Architecture for Signaling
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GSM Signaling Network Continue
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International Signaling relation via ISDN
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SS7 Signaling Architecture
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SS7 Layer in GSM Network
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SS7 Layers in GSM Network
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SS7 Layers in GSM Network
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SS7 Layers in GSM Networky Mobile Application Part (MAP)
Mobile-specific extension of C7 standard. All messages exchanged between NSS Elements (MSC,HLR,VLR) A connectionless transport service provided by the SCCP Provides core functionality to support roaming Allows its users to access other users via worldwide C7/SS7 network Logical signalling connection between MSC and MS to support Layer 3 (MM/CM) message transfers Uses reduced set of C7 signalling instructions Routes messages via STPs C7 protocols responsible for routing and transport of signalling messages
y Transaction Capabilities Application Part (TCAP)
y Signalling Connection Control Part (SCCP)
y Message Transfer Part (MTP)
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SS7 Layers in GSM Network
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GSM Protocol Summery
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GSM Interfaces & Layers
Um Interface
Abis Interface
Other Interfaces
GSMA Interface E Interface B,C Interface
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A Interface
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A InterfaceBSSMAP - deals with procedures that take place logically between the BSS and MSC, examples : Trunk Maintenance, Ciphering, Handover, Voice/Data Trunk Assignment DTAP - deals with procedures that take place logically between the MS and MSC. The BSS does not interpret the DTAP information, it simply repackages it and sends it to the MS over the Um Interface. examples: Location Update, MS originated and terminated Calls, Short Message Service, User Supplementary Service registration, activation, deactivation and erasure
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A Interface
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A Interface
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Abis Interface
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Abis Interfacey Messages exchanges between the BTS and BSC.
Traffic exchanges Signaling exchanges y Physical access between BTS and BSC is PCM digital links of E1(32) or T1(24) TS at 64kbit/s. y Speech: Conveyed in timeslots at 4X16 kbit/s y Data: Conveyed in timeslots of 4X16 kbit/s. The initial user rate, which may be 300, 1200, is adjusted to 16 kbit/s
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Abis InterfaceLevel 1-PCM transmission (E1 or T1) Speech encoded at 16kbit/s and sub multiplexed in 64kbit/s time slots. Data which rate is adapted and synchronized. Level 2-LAPD protocol Radio Signaling Link (RSL) Operation and Maintenance Link (OML). Level 3-Application Protocol Radio Subsystem Management (RSM) Operation and Maintenance procedure (OAM)
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Abis Interface
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LAPD Message
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LAPD Message..y The length is limited to 260 octets of information. y LAPD has the address of the destination terminal, to
identify the TRX, since this is a point to multipoint interface. y Each TRX in a BTS corresponds to one or several signaling links. These links are distinguished by TEI (Terminal Equipment Identities).y SAPI=0, SAPI=3, SAPI=62 for OAM.
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Um Interfacey Level 1-Physical
TDMA frame Logical channels multiplexing y Level 2-LAPDm(modified from LAPD) No flag No error retransmission mechanism due to real time constraints y Level 3-Radio Interface Layer (RIL3) involves three sub layers RR: paging, power control, ciphering execution, handover MM: security, location IMSI attach/detach CM: Call Control(CC), Supplementary Services(SS), Short Message Services(SMS),
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Layer1 Signaling
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Layer 2 Signaling
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LAPDm Message In LAPDm the use of flags is avoided. LAPDm maximum length is 21 octets of information. It makes use of more bit to distinguish last frame of a message. No frame check sequence for LAPDm, it uses the error detecting performance of the transmission coding scheme offered by the physical layer
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LAPDm Message.y The acknowledgement for the next expected frame in the indicator N(R ). y On radio interface two independent flows(one for signaling, and one for y y y y
SMS) can exist simultaneously. These two flows are distinguished by a link identifier called the SAPI(service access point identifier). LAPDm SAPI=0 for signaling and SAPI=3 for SMS. SAP1=0 for radio signaling, SAPI=62 for OAM and SAPI=63 for layer 2 management on the Abis interface. There is no need of a TEI, because there is no need to distinguish the different mobile stations, which is done by distinguishing the different radio channels.
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Layer 3 Signaling
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Layer3 Signaling Message Format at air Interface
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Protocol Discriminator
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Transaction Identifier
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Message Type
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Information Element
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Measurement Report
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Layer 3 Function
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RR Management
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Mobility Management
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Connection Management
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RR Massage, Channel & MT Code
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MM Massage
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CM Message
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Call Setup Overview MS Idle Mode Behavior Call setup signaling flow with Layer2&Layer3 explanation Handover signaling flow Location updated signaling Flow
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MS Idle Mode Behavior
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Idle Mode Measurements..explain in call Setup
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Call Setup Signaling Flow
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Call Setup Signaling Flow
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Call Setup With Counters
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Paging Typesy Paging locates MS to cell Level for call
routing
y Three paging message types:
Type 1 - 2 MSs using IMSI/TMSI Type 2 - 3 MSs (1xIMSI, 2xTMSI) Type 3 - 4 MSs using TMSI onlyy Paging message requires 4 bursts (1
CCCH block)
y Paging messages may be stored at BSS y Transmitted on PCH y If DRX is implemented MS listens only
to allocated paging group
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Timers involved in Call Process
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Layer2&3 involved in Call setup
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Call Setup Measurements Layer3 RR Management Message MM Management Message CM Management Message
Layer2 RR-RSP I-CMD SABM-CMD UA-RSP DISC-CMD Call Setup Call Establishment Call End
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Layer3 Message. RR Management Message
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RR Paging Message StructureProtocol Discriminator
The Channel Field (bits 1-2 of octet 2) indicates the further combination of channel which will be needed. It is coded as follows
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RR-Paging MessagePaging Request Type1
Channel Needed To indicate what type of channel is required for the transaction linked to the paging procedure. First Channel 00 Any channel 01 SDCCH 10 TCH/F 11 TCH/H or TCH/F Second Channel Same as first channel
Page mode To control the action of MS belonging to the paging subgroup corresponding to the paging subchannel. Page Mode 00 Normal Paging 01 Extended Paging 10 Paging Re organisation 11 Same as before
Mobile Identity To provide either the IMSI, the (P) TMSI but notthe IMEI bases paging. IMSI