call flow gsm

GSM,GPRS,UMTS,HSDPA and HSUPA Protocols and Call flow

By

Kiran Koona

Overview

1. GSM Protocols and Call flow 2. GPRS Protocols and Call flow 3. UMTS Protocols and Call flow 4. HSDPA and HSUPA Protocols.

GSM

GSM Architecture-Interfaces

Layer 1 Protocol TDMA – Time Division Multiple Access G.703 – ITU PCM frame structure MTP – Message Transfer Part

Layer 2 Protocols LAPDm Link Access Protocol D-channel-mobile LAPD Link Access Protocol D-Channel

Layer 3 Protocols RR – Radio Resource Management MM – Mobility Management CM – Connection management BTSM – Base Transceiver Station Management SCCP – Signalling Connection Control Part BSSMAP – Base Station Subsystem MAP-Mobile Application Part DTAP – Direct Transfer Application Part

3-Layer Model

TUP , ISUP

Physical Layer

1. Txn of bits 2. Error detection and Correction 3. Interleaving 4. Burst Formating 5. Measurements 6. Power Control 7. Modulation and Demodulation BTS-BSC: 64Kbps BSC-MSC:2Mbps (32*64Kbps)

Physical Layer

Interfaces with Physical Layer

Layer-2: LAPDm and LAPD

1. Flow control 2. Sequence Numbering 3. Duplicate detection 4. Frame formatting

Layer-3: RRM Protocols: RR, RSM, BSSAP. 1. Cell selection and Reselection Control

2. Handover procedure 3. Establishing , maintaining, monitoring and releasing the channels 4. Monitoring and forwarding of radio connections 5. Introduction of encryption 6. Change in transmission mode ,Channel coding depending on

channel conditions Advise L1 and L2 7. MS level measurement commands control 8. Frequency redefinition Downlink Freq hopping 9. Broadcasting System Information Downlink 10. Paging

RRM Messages

Layer-3:MM

Protocols : DTAP,MAP. 1. Authentication request/response 2. Ciphering Information/Commands from MSC 3. Abort from MSC Auth Failure 4. Normal location Updating request/response 5. Periodic location update 6. TMSI Reallocation Procedure 7. IMSI attach/detach 8. IMEI request/response

MM Messages

Layer-3:CM 1. Call control (CC) - manages call connections, 2. Supplementary service support (SS) - handles special services 3. Short message service support (SMS) - transfers brief texts. CC: Mobile-originating call establishment Setup message Mobile-terminating call establishment Paging Call clearing initiated by the network Call clearing initiated by the Mobile DTMF SS: Call Forwarding Call waiting ,Call Hold and Conference Multi Call CLIP,CLIR ,COLP and COLR SMS:

CM Messages

SS 7 To provide General purpose Signaling system to be used globally.

CCS , Out of Band

ITU-T Q.700 series.

Elements: SSP,STP and SCP.

Access Links: A to F

Analogy: MTP3 IP and SCCPTCP

SCCP: GTT, Ext MTP (Supports CL or CO)

Message Discrimination & distribution

TCAP: Query and Response (CL or CO )

MTP 3: Routing within SPC

MTP2: Node to node delivery

SS 7 Architecture

SSP, STP and SCP

SS 7 Logical Network

MAP

MAP messages are carried by TCAP when dealing with Database centre.

MAP Sessions: Open, Close. Message Types: Request, Response, Notification and

Confirmation.

GTT

GSM Call flow

GSM Logical Channels

IMSI Attach

Location Update

Authentication and Ciphering

Identity (IMSI) checking

Call Origination

2929

Call Clearing

IMSI Detach

MSRN Usage

Our HLR Knows where our Customer is,

Only our GMSC can inquire our HLR

GPRS

GPRS Architecture-Interfaces

GPRS Protocol Stack

Packet Fragmentation

MAC

1. MAC arbitrates access to the shared medium between

multiple MSs and GPRS network. 2. Uplink: Managing limited resourcesSlotted Aloha 3. Downlink: Queuing and Scheduling of access attempts. 4. Priority handling between data flows of one UE 5. Priority handling between UEs by means of dynamic

scheduling—Downlink 6. Channel mapping 7. Traffic Volume monitoring

RLC

1. SAR 2. Concatenation 3. Padding 4. Error Correction---CRC, ARQ (For AM) 5. In-Sequence delivery of SDUs 6. Duplicate detection 7. Flow control 8. Sequence number check---UM 9. Suspend/resume functionality 10. SDU discard

LLC Provide a reliable logical link between MS and SGSN.

LLC messages are transparent to RAN.

Transmission in Asynchronous Disconnected Mode and

Asynchronous Balanced Mode

Ciphering.

Transfer of PDUs of Higher Layers

C-Plane: attach, authentication and PDP activation

U-Plane: carry actual data.

Can be AM or UM

SNDCP • Transparent over BSS. Used only in U-Plane • multiplexing of PDPs. Can be AM or UM

• compression of user data (including IP header compression) RFC 1154 & 2507

• segmentation of data packets to be passed to the LLC layer.

Frame Relay

Meshed N/W Frame Relay

Frame Relay

Speed up to 2 Mbps.

Simple.

Superseded by ATM

BSSGP

Transport both control and User data.

Provide the required QoS.

One-to-one mapping of BSSGP between SGSN and BSS.

BSSGP Data Frames

GTP 1. GTP-U and GTP-C. 2. Uses TCP for Reliable link 3. Uses UDP for non-Reliable link

IP, TCP and UDP

IP: IPv4 or IPv6. Datagram Service. Class full or Class less Addressing.

TCP: Connection Oriented.

Ack ARQ. Sequence Number Checking.

Three-way handshake. Point-to-Point Add

Flow Control and Congestion Control.

UDP: Connection less.

Used for Delay Sensitive applications.

Supports Multicast Addressing.

GPRS Callflow

GPRS Logical Channels

GPRS Attach

PDP Context Activation

PDP

Data Transfer from MS

Data Transfer to MS

Web Access in GPRS

PDP Context Deactivation

Security

GPRS Detach

UMTS

Architecture-Interfaces

R99 Protocol Stack

Access Stratum

MAC Logical to Transport Conversion

Mac-b located at Node-B

Mac-c/sh and Mac-d are at SRNC.

MAC functionalities

1. Mapping between logical channels and transport channels 2. Selection of appropriate TF (from the TFCS) for each Transport

Channel, depending on the instantaneous source rate 3. Priority handling between data flows of one UE 4. Priority handling between UEs by means of dynamic scheduling—

Downlink 5. Identification of UEs on common transport channels 6. Multiplexing/demultiplexing of higher layer protocol data units

(PDUs) 7. Traffic volume monitoring—Down link 8. Dynamic Transport Channel type switching 9. Ciphering—RLC (TM) 10. Access Service Class (ASC) selection for RACH transmission

RLC

1. Transparent mode (Tr) , Unacknowledged Mode (UM) or

Acknowledged Mode (AM) 2. Tr and UM RLC entities are defined to be unidirectional, whereas the

AM-mode entities are described as bidirectional 3. Tr—Voice Call Video Call, UM—VOIP, Streaming

RLC functionalities

1. Segmentation and reassembly 2. Concatenation 3. Padding 4. Transfer of user data 5. Error correction----ARQ 6. In-sequence delivery of higher layer PDUs 7. Duplicate detection 8. Flow control 9. SN check (unacknowledged data transfer mode). 10. Ciphering is performed in the RLC layer for acknowledged and

unacknowledged modes. 11. Suspend/resume function for data transfer

RLC Dataflow

RRC

1. Broadcast of system information 2. Paging and notification 3. Initial cell selection and reselection 4. Establishment, maintenance and release of an RRC

connection 5. Establishment and release of Radio bearers 6. Control of ciphering 7. Integrity protection of signalling messages 8. UE measurement reporting and control of the reporting 9. RRC connection mobility functions 10. Support of SRNS relocation 11. Support for downlink outer loop power control in the UE 12. Open-loop power control 13. CBS-related functions (BMC) 14. Handovers---preparation and execution 15. Control of requested QoS 16. Routing of Higher layer PDUs (Direct transfer) 17. MBMS control

RRC States

BMC

BMC: Broadcast/Multicast Control Protocol

SMS-CB service

1. Storage of CB 2. Traffic volume monitoring and radio resource request for

CBS 3. Scheduling of BMC messages 4. Transmission of BMC messages to UE

PDCP

PDCP: Packet Data Convergence Protocol

1. PS Domain 2. PDCP contains compression methods, which are needed to get

better spectral efficiency over radio interface. 3. IP Packet header compression. Eg: 40 bytes for IPv4 and at least

60 bytes for IPv6. (RFC 2507) 4. Transfer of user data

Non Access Stratum

Protocol Interworking architecture

Transport : Carry Signaling and User data.

Radio N/W : Establish, maintain and Release RB.

System: Create Communication with Core network.

Transport Network protocols

Radio network protocols

System network protocols

UMTS Call flow

R99 Channels

Basic Model of Network transactions

RRC Connection Setup

RRC Connection CCCH (By passing Node-B)

Paging Paging Type 1 through PCCH

Paging Type-2 through DCCH

RRC Connection CCCH

Authentication and Security Control

DCCH Channel and MM messages

Transaction setup and RAB allocation (CS)

Setup : DCCH Call Proceeding: DTCH

Transaction setup and RAB allocation (PS)

Transaction Clearing with RAB release

RRC Connection release

LU in CS domain

RU in PS domain

HSDPA and HSUPA

R99 RRM Architecture

HSDPA and HSUPA RRM Architecture

New Functionalities

HSDPA and HSUPA Channels

R99 Protocol Stack

HSPA Protocol stack

HSDPA Protocol Stack

HSDPA user plane Protocol Architecture

Fast Node-B Scheduling

H-ARQ ,Incremental Redundancy

Soft Buffer at Node-B and UE

Retransmission at N/W borders No Soft Handover

HSUPA Protocol Stack

HSUPA user plane protocol Architecture

Mac-es/e : Uplink Scheduling

Mac-e: Hybrid ARQ , Buffer

Mac-es : In-sequence delivery (Soft Handover)

RLC re transmissions may take place if Physical layer re transmissions is exceeded initiated by RNC.

References

1. 3G TS 25.321, MAC Protocol Specification. 2. 3G TS 25.322, RLC Protocol Specification. 3. 3G TS 25.323, PDCP Protocol Specification 4. 3G TS 25.331, RRC Protocol Specification 5. 3G TS 25.324, Broadcast/Multicast Control Protocol (BMC)

Specification 6. 3G TS 25.302, Services Provided by the Physical Layer 7. 3GPP TS 25.331 RRC specification 8. 3GPP TS 25.413 RANAP 9. 3GPP TS 25.423 RANSAP 10. 3GPP TS 25.433 NBAP 11. GSM.System.Engineering.-.Artech BOOK, by Asha Mehrotra. 12. GPRS BOOK-MC-HIL by R.J. Bates. 13. WCDM for UMTS-Wiley –H.Holma and A.Toskala 14. SS7 –MC-HILL by Travel Russel

Datagram

Virtual Circuit