Telecommunication Basics(GSM Network)

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음성 통화 통화, 문자, 이메일 통화, 문자, 멀티미디어, 무선인터넷 초고속 인터넷 초고속 무선 인터넷유,무선간 연동

IS-95 A IS-95 B

GSM GPRS

CDMA-1X

EV-DV

CDMA-1XEV-DO r0

W-CDMA R3

W-CDMA R5

(HSCPA)

CDMA-1XEV-DO rA

W-CDMA R6

(HSUPA)

CDMA-1XEV-DO rB

W-CDMAR7

(HSPA+)

LTEEDGE

UMB

W-CDMAHSPA+Phase2

AMPS

NMT

LTE Advanced

802.15e Wave1(Mobile WiMAX)

802.15e Wave2(Mobile WiMAX)

802.16eWiMAX R1.5

802.16nWiMAX R2.0

GSM track

CDMA track

WiMAX track

GSM Characteristics

F1 F2 F1' F2'

Frequency

1

2

3

4

5

6

7

8

45 MHz

BS Transmission Band : 935 – 960 MHZ

MS Transmission Band : 890 – 915 MHZ

Year Introduced 1990

Access method TDMA

Channel Bandwidth

200 kHz

Number of duplex channels

125

Users per channel 8

Speech coding bit rate

13 kbps

Data coding bit rate

12 kbps

Frame size 4.6 ms

GSM Nework Architecture

MS

SIM

MEPSTN

ISDN, PSPDNCSPDN

SIM : Subscriber Identity Module

ME : Mobile Equipment

MS : Mobile Station

BTS : Base Transceiver Station

BSC : Base Station Controller

HLR : Home Location Register

VLR : Visitor Location Register

EIR : Equipment Identify Register

MSC : Mobile Service Switching Station

AuC : Authentication Center

UM : Radio Link

NMS : Network Management System

Mobile Station

Base Station Subsystem Network Subsystem

UM

A

BTS

BTS

BSC

BSC

MSC

VLRHLR

EIR AuC

Network Management Subsystem

O&M

DataCommunication

Network

Abis

DatabaseSever

Network PlanningSystem

Network MeasurementSystem

GSM Interface (1/2)

Interface Description

Um Interface The "air" or radio interface standard that is used for exchanges between a mobile (ME) and a

base station (BTS / BSC). For signaling, a modified version of the ISDN LAPD, known as LAPDm is used

Abis Interface This is a BSS internal interface linking the BSC and a BTS, and it has not been totally

standardized. The Abis interface allows control of the radio equipment and radio frequency allocation in the BTS

A Interface

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 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

B 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 "internal" interface. The interface is used whenever the MSC needs access to data regarding a MS located in its area

C Interface

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. 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

D Interface The D interface is situated between the VLR and HLR. It uses the MAP/D protocol to

exchange the data related to the location of the ME and to the management of the subscriber

E Interface The E interface provides communication between two MSCs. The E interface exchanges data

related to handover between the anchor and relay MSCs using the MAP/E protocol

GSM Interface (1/2)

The layered model of the GSM architecture integrates and links the peer-to-peer communications between two different systems

UM Abis A

GSM RF MTP 1GSM RF Layer 1 Layer 1 MTP 1

LAPDm MTP 2LAPDm LAPD LAPD MTP 2

MTP 3RR BTSM BTSM

MTP 3

SCCPSCCP

BSSMAP/DTAPRRDTAP

BSSMAP

RR

MM MM

CM CM

Interface Description

F Interface The F interface is used between an MSC and EIR. It uses the MAP/F protocol. The

communications along this interface are used to confirm the status of the IMEI of the ME gaining access to the network

G Interface The G interface interconnects two VLRs of different MSCs and uses the MAP/G protocol to

transfer subscriber information, during e.g. a location update procedure

H Interface The H interface exists between the MSC the SMS-G. It transfers short messages and uses the

MAP/H protocol

I Interface The I interface can be found between the MSC and the ME. Messages exchanged over the I

interface are relayed transparently through the BSS

Mobile Station

GSM MSs consist of

Mobile Equipment

SIM (Subscriber Identity Module)

Functions of Mobile Station

Voice and data transmission & receipt

Can receive, store, send SMS up to 160 charactors

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#”

MS

SIM

ME

Mobile Station

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, Grey List, Black List

MSISDN (Mobile Station ISDN Number)

Is register in the telephone directory and used by the calling party for dialing

Shall not exceed 15 digits

White list : IMEI, assigned to valid ME.Black list : IMEI reported stolenGray list : IMEI having problems like faulty

software, wrong make of equipment etc.

CC NDC SN

1 to 3 digits Variable Variable

NDC : National Destination CodeSN : 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

MSC(Mobile service Switching Center)

Call control (Switching and call routing)

Initiation of paging

Charging data collection

Service provisioning

Communication with other NEs (HLR, VLR, MSCs, BSCs)

VLR(Visitor Location Register)

Temporary data (data valid when subscriber is within its service area)

Identification numbers of the subscribers

Security information for authentication of the SIM card and for ciphering

Services that the subscriber can use

Data in VLR : IMSI & TMSI, MSISDN, MSRN, Location Area,

Supplementary service parameters, MS category, Authentication Key

HLR(Home Location Register)

Permanent data

Keeps track of the current location of its customers

Same functionality the VLR

AC(Authentication Center)

Provides security information to the network (for verify the SIM cards)

- TRIPLET : RAND, SRES, Kc

EIR(Equipment Identity Register)

Responsible for IMSI checking (for verify the mobile equipment)

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

BSC(Base Station Controller)

Connection establishment between the MS and the NSS

Mobility management (Handling of MS connections)

Statistical raw data collection (Internal BSC O&M)

Air-and A-interface signaling support (Radio Resource Management)

BTS and TC control

BTS(Base Transceiver Station)

Air interface signaling (Radio resource, Signaling link management)

Ciphering (Synchronization)

Speech processing (Signal processing)

TC(SM)(Transcoder (SubMultiplexer))

To enable an efficient transmission, the digital speech signal is

compressed

SM2M

TC

TC

TC

TC

BSCMSC

TCSM(Transcoder and Submultiplexer)

A ter Interface A ter’ Interface A Interface

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

Superframe = 51 Traffic MultiframeOr 26 Control Multififrame

Traffic Multifame= 26 Frames

Control Multiframes= 51 Frames

Hyperframe = 2048 Superframes

Frame = 8 Slots

Slot = 577µs

120ms

0 1 2 3 4 5 6 7 0

5 6 7 0 1 2 3 4 5

Slot numbers

Time

Base station receive

Base station transmit

Correspondingreceive frame

235.4ms

Traffic multiframe: The Traffic Channel frames are organised into multiframesconsisting 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 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 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

Full-rate Half-rate

Broadcast Channels Common Control Channels Dedicate Control Channels

TCH/F TCH/H BCCH FCCH SCH PCH AGCH RACH TCH/H TCH/H TCH/H

downlink uplink fastslow

Common Channel

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.

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

Dedicate Channel The signaling channels are used for maintenance of the call and for enabling call set up, providing

facilities such as handover when the call is in progress, and finally terminating the call. The traffic channels handle the actual payload

TCHf : Full rate traffic channel.TCH h : Half rate traffic channel. BCCH : Broadcast Network information, SCH : Synchronisation of the MSs.FCHMS : frequency correction. AGCH : Acknowledge channel requests from MS and allocate

a SDCCH. PCHMS : terminating call announcement.

RACHMS : access requests, response to call announcement, location update, etc.

FACCHt : For time critical signalling over the TCH (e.g. for handover signalling)

SACCHt : TCH in-band signalling, (e.g. for link monitoring) SDCCH : For signalling exchanges,

(e.g. during call setup, registration / location updates)FACCHs : FACCH for the SDCCH. SACCHs : SDCCH in-band signalling (e.g. for link monitoring)

GSM Call Scenario 1

Location update

BSS MSC/VLR HLR/AuC

Channel Request

Immediate Assignment

Complete L3 Info(location updating request)

Send Authentication Info

PreviousMSC/VLR

Location Update Request

Send Authentication Info RR

Authentication Request

Authentication Response

Update Location

Cancel Location

Cancel Location RR

Insert Subscriber Data RR

Update Location RR

Insert Subscriber Data

Location Updating Accept

Clear Complete

Clear Command

Channel Release

GSM Call Scenario 2

Mobile to Network

Cell Site MSC

CM Service Request(Service type = mobile originated call) Complete Layer3 Info

(CM Service Request)

PSTN

Authentication Request

Authentication Response

Cipher Mode Command

Cipher Mode Command

Cipher Mode Complete

Cipher Mode Complete

Setup

Calling Proceeding

Assignment Request

Assignment Command

Assignment CompleteAssignment Complete

IAM

ACM

ANM

Alerting

Connect

Connect Acknowledge

GSM Call Scenario 3

Network to Mobile

BSS MSC/VLR HLR GMSC PSTN

IAMSRI (MSISDN)

PRN (IMSI)

PRN RR (MSRN)PRI RR (MSRN)

IAM (MSRN)Paging

Paging Request

Channel Request

Immediate Assignment

Paging ResponseComplete Layer 3 info (Paging Response)

Cipher Mode CommandCiphering Mode Command

Ciphering Mode Complete

Ciphering Mode Complete

Setup

Call Confirmed

Assignment Request

Assignment Command

Assignment CompleteAssignment Complete

Alerting

Connect

Connect Acknowledge

ACM

ANM

ACM

ANM

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 toNew channel

Handover Access

Handover Detect

Handover Complete

Handover Complete

Clear Command

Clear Complete

Measurement Report

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)

Base Station 1 Base Station 2

Ratio of powerReceived From current BS To next BS

time

Handover Threshold

Receiver Threshold

t0 t1