Presentation on six months Industrial Training undertaken at

Submitted by:- Chanjot SinghUniv Roll No. 6120405841College Roll No. 606/06

COMPANY PROFILE• Nokia Siemens Networks is one of the largest telecommunications

solutions suppliers in the world.• Nokia Siemens Networks was created as the result of a joint

venture between Siemens COM division (minus its Enterprise business unit) and Nokia's Network Business Group. The new company was announced on 19 June 2006.

• Nokia Siemens Networks operates in approximately 200 countries worldwide, and has about 60,000 employees. Its major manufacturing sites are in China, Finland, Germany, Poland and India.

• About 1 billion people are connected through its networks.• It is foreseen that, at a combined revenue of more than € 15 billion,

the new company would be one of the largest telecommunication equipment makers in the world.

CONTENTS

• GSM Basics• GSM System Architecture• Identities used in GSM• GSM Channels• Mobility management • Call management• Abis mapping• Drive test• Troubleshooting

Background to GSM

• 1G : Advanced Mobile Phone Service (AMPS)

Analog, Circuit Switched, FDMA, FDD

• 2G : Digital Advanced Mobile Phone Service (D-AMPS)

Digital, Circuit Switched, FDMA, FDD

• 2G : Global System for Mobile (GSM)

Digital, Circuit Switched, FDMA and TDMA, FDD

• 2G : Code Division Multiple Access (CDMA)

Digital, Circuit Switched, FDMA, SS, FDD

Frequency band Uplink 890 - 915 MHz Downlink 935 - 960MHzDuplex Frequency Spacing 45MHzCarrier separation 200KHzFrequency Channels 124Time Slots /Frame(Full Rate) 8Voice Coder Bit Rate 13KbpsModulation GMSKAir transmission rate 270.833333 KbpsAccess method FDMA/TDMASpeech Coder RPE-LTP-LPC

GSM System specifications

GSM uses paired radio channels

0 124 0 124

890MHz 915MHz 935MHz 960MHz

UPLINK

DOWNLINK

FDMA-TDMA

GSM Architecture

It provides an overview of the GSM network architecture. This includes a brief explanation of the different network subsystems and a description of the functionality of the elements within each of the subsystems.

• General architecture overview

• The Mobile Station (MS) Subsystem and Elements

• The Base Station Subsystem (BSS) and Elements

• The Network Subsystem (NSS) and Elements

Base Station Subsystem

The BSC:

• Allocates a channel for the duration of a call

• Maintains the call:

monitors quality

controls the power transmitted by the BTS or MS

generates a handover to another cell when required

The BTS:

• Provide radio access to the mobile stations

• Manage the radio access aspects of the system

BSS Configuration

• Collocated BTS

• Remote BTS

• Daisy Chain BTS

• Star Configuration

• Loop Configuration

Collocated BTS: BTS is situated along with BSC or the

MSC and no additional E1 link is required.

BSC

BTS

Remote BTS : BTS is situated in a stand alone position and

additional E1 links are required to connect to BSC.

BSC

BTS

Daisy Chain

MSC

BSC

BTS 1

BTS 2

BTS 3

BTS 4

Star Configuration

MSC

BSC

BTS 1

BTS 2

BTS 3

BTS 4

BSC

BTS 3

Loop Configuration

MSC

BSC

BTS 1

BTS 2

BTS 3

BTS 4

Network Subsystem

• Can be considered as a heart of the GSM Network.

All the major activities like • Routing, • Security functions, • Call handling, charging,• Operation & maintenance, • Handover decisions,

• Various kinds of interfaces are used to communicate between the different entities. Different methods are used to optimize and provide the quality network with the minimum operating cost.

Mobile Switching Center (MSC)

• Performs call switching

• Interface of the cellular network to PSTN

• Routes calls between PLMN and PSTN

• Queries HLR when calls come from PSTN to mobile user

• Inter-BSC Handover

• Paging

• Billing

Home Location Register (HLR)

• Stores user data of all Subscribers related to the GMSC

– International Mobile Subscriber Identity(IMSI)

– Users telephone number (MS ISDN)

– Subscription information and services

– VLR address

– Reference to Authentication center for key (Ki)

• Referred when call comes from public land network

Visitor Location Register (VLR)

• Database that contains Subscriber parameters and location information for all mobile subscribers currently located in the geographical area controlled by that VLR

• Identity of Mobile Subscriber

• Copy of subscriber data from HLR

• Generates and allocates a Temporary Mobile Subscriber Identity(TMSI)

• Location Area Code

• Provides necessary data when mobile originates call

Authentication Center (AuC)

• Stores Subscriber authentication data called Ki, a copy of which is also stored in in the SIM card

• Generates security related parameters to authorize a subscriber (SRES-Signed RESponse)

• Generates unique data pattern called Cipher key (Kc) for user data encryption

• Provides triplets - RAND, SRES & Kc, to the HLR on request.

EIR (Equipment Identity Register)

• EIR is a database that contains a list of all valid mobile station equipment within the network, where each mobile station is identified by its International Mobile Equipment Identity(IMEI).

• EIR has three databases.,– White list - For all known,good IMEI’s– Black list - For all bad or stolen handsets– Grey list - For handsets/IMEI’s that are

on observation

Transcoder and Rate Adaptor Unit (TRAU)

The primary function of the TRAU is to convert 16kps GSM speech channels to 64kbps PCM channels in the uplink direction and the reverse in the downlink direction.

The reason this process is necessary is because MSCs only switch at the 64kbps channel level.

TRAU LocationsTRAU can be physically located in the BTS, BSC or MSC

and hence leads to a variety of installation configurations.

AuC

MS

MS

BTS

BTS

BTS

BSC

BSC

MSC

MSC

VLR

VLR

GMSC

HLR

PSTN

EIR

Um

Abis

Abis

A

A

OMC Server

Um

Interfaces between components

B

E

E

X.25

C

F

H

X.25

Abis Mapping

Besides the traffic channels, the Abis interface also carries the required signaling information in 64 Kbit/s channels. One signaling channel is normally provided for each transceiver within a BTS for controlling upto 8 subscribers per carrier frequency.

Sig TRX 2

Sig TRX 1

TS 0

BSC

TRX 1

TRX 2

1 2 3

4 5 6 7

0

1 2 3

4 5 6 7

0

TS BTS 1 BTS 2 0 PCM Management Information 1 TRX 1 2 TRX 1 3 TRX1 4 TRX1 5 TRX 2 6 TRX 2 7 TRX 2 8 TRX 2 9 TRX 3 10 TRX 3 11 TRX 3 12 TRX 3 13 TRX 4 14 TRX 4 15 TRX 4 16 TRX 4 17 TRX 5 18 TRX 5 19 TRX 5 20 TRX 5 21 TRX 6 22 TRX 6 23 TRX 6 24 TRX 6 25 Signalling BTS1, Sector1 26 Signalling BTS1, Sector2 27 Signalling BTS1, Sector3 28 Signalling BTS2, Sector1 29 Signalling BTS2, Sector2 30 Signalling BTS2, Sector3 31 Control Ring

TS Arrangement on PCM Link :

1 Sector occupies 2TS for TCH (64 Kbps)1TS for signaling

Total number of Time slot in one PCM 32Out of which 1 is used as sync and other for internal signaling.

TS available for carrying the information 30

Therefore total number of TRXs that can be cater on one PCM = 30/3 = 10

Identities used in GSM

IMEI – International Mobile Equipment Identifier.

IMEI = TAC + FAC + SNR +sp

TAC = Type Approval Code by central GSM body

FAC = Final Assembly Code, identifies the manufacturer

SNR = Serial Number, unique six digit number

sp = spare for future use

IMSI – International Mobile Subscriber Identifier

When a subscriber registers with a network operator, a unique subscriber IMSI identifier is issued and stored in the SIM of the MS as well as in the HLR . An MS can only function fully if it is operated with a valid SIM inserted into an MS with a valid IMEI. IMSI consist of three parts:

IMSI = MCC + MNC + MSIN

MCC = Mobile Country Code

MNC = Mobile Network Code

MSIN = Mobile Station Identification Number

TMSI –Temporary Mobile Subscriber Identity

A TMSI is used to protect the true identity (IMSI) of a subscriber. It is issued by and stored within a VLR (not in the HLR) when an IMSI attach takes place or a Location Area (LA) update takes place. At the MS it is stored in the MS’s SIM. The issued TMSI only has validity within a specific LA.

Since TMSI has local significance, the structure may be chosen by the administration. It should not be more than four octets.

MSISDN – Mobile Station ISDN Number

The MSISDN represents the ‘true’ or ‘dialled’ number associated with the subscriber. It is assigned to the subscriber by the network operator at registration and is stored in the SIM.

It is composed in the following way:

MSISDN = CC + NDC + SN

CC = Country Code

NDC = National Destination Code

SN = Subscriber Number

MSRN – Mobile Station Roaming Number

The MSRN is a temporary, location-dependant ISDN number issued by the parent VLR to all MSs within its area of responsibility. It is stored in the VLR and associated HLR but not in the MS. The MSRN is used by the VLR associated MSC for call routing within the MSC/VLR service area.

LAI – Location Area Identity

Each Location Area within the PLMN has an associated internationally unique identifier (LAI). The LAI is broadcast regularly by BTSs on the Broadcast Control channel (BCCH), thus uniquely identifying each cell with

an associated LA.

LAI = MCC + MNC + LAC

MCC = Mobile Country Code, same as in IMSI

MNC = Mobile Network Code, same as in IMSI

LAC = Location Area Code, identifies a location area within a GSM PLMN network. Maximum length of LAC is 16 bits.

GSM Channels

TCH (traffic)

CCH(control)

BCH

CCCH

Dedicated

2.4 kbps4.8 kbps

9.6 kbps

FCCH(Frequency correction)

SCH(Synchronization)

PCH(Paging)

RACH(Random Access)

AGCH(Access Grant)

SDCCH(Stand Alone)

SACCH(Slow-associated)

FACCH(Fast-associated)

Half rate 11.4kbps

Full rate 22.8kbps

Speech

Data

0 1 2 3 4 5 6 2043 2044 2045 2046 2047

0 1 2 3 4 48 49 50

0 1 2 24 25

0 1 2 3 24 25

0 1 2 3 4 48 49 50

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0

1 HYPER FRAME = 2048 SUPERFRAMES = 2 715 648 TDMA FRAMES ( 3 H 28 MIN 53 S 760 MS )

1 SUPER FRAME = 1326 TDMA FRAMES ( 6.12 S ) LEFT (OR) RIGHT

1 MULTI FRAME = 51 TDMA FRAMES (235 .4 ms )

1 SUPER FRAME = 26 MULTI FRAMES

1 SUPER FRAME = 51 MULTI FRAMES

1 MULTIFRAME = 26 TDMA FRAMES ( 120 ms )

TDMA FRAME NO.0 1

0 1

HIERARCHY OF FRAMES

1 2 3 4 155 156

1 TIME SLOT = 156.25 BITS ( 0.577 ms)

(4.615ms)

(4.615 ms)

1 bit =36.9 micro sec

TRAFFIC CHANNELS

SIGNALLING CHANNELS

Mobility Management

• Location updating- normal,periodic, IMSI attach

• Paging

• Security Management

– Preventing unauthorized users- authentication

– Maintaining Privacy of users- ciphering

• Providing roaming facility

• MM functionality mainly handled by MS, HLR, MSC/VLR.

MS BTS BSC (G)MSC VLR HLR

Action

Channel Request (RACH)

Channel Assignment (AGCH)

Authentication Request (SDCCH)

Authentication Response (SDCCH)

Comparison of Authentication params

Accept LUP and allocTMSI (SDCCH)

Ack of LUP and TMSI (SDCCH)

Entry of new area and identity into VLR and HLR

Channel Release (SDCCH)

MS Location Update (registration)

Location Update Request (SDCCH)TMSI + old LAI

Security - Authentication

Authentication center provides RAND to MobileAuC generates SRES using Ki of subscriber and RANDMobile generates SRES using Ki and RANDMobile transmits SRES to BTSBTS compares received SRES with one generated by AuC

MSKi RAND

A3

SRES

RAND

SRES

SRES

Auth Result

AuCBTSMS

Cell Selection

BTS-2

BTS-1

This cell

BTS-3

BTS-4

BTS-51

1

1

12

3

45

Purpose: get synchronization with the GSM network prior establishing any communication.

FCCH

SCH

BCCH

1

Immediate Assignment

MS BSC MSC

CM SERVICE REQUEST

SDCCH or TCH6

CHANNEL REQUEST

RACH1

BTS

CHANNEL REQUIRED2

CHANNEL ACTIVATION3

IMMEDIATE ASSIGNMENT

AGCH5

IMMEDIATE ASSIGNMENTCOMMAND

5

CHANNEL ACTIVATIONACK.

4

ImmediateAssignment

LOCATION UPDAT. REQU.

SDCCH or TCH6

OR

Registration: the Very First Location Update

LAI HLR

IMSIVLR id

TMSI

IMSI

TMSI

Release

VLR

IMSITMSILAI

MSC

BTS

BSS

BSC

2

4

5

2

6

1

2

4

5

6

3

4TMSI 5

MSCBTS

BSS

BSC

VLR

3

4

5

4

6

1 CHANNELREQUEST

2IMMEDIATEASSIGNMENT

LOCATION UPDATINGREQUEST (IMSI Attach)

3

5LOCATION UPDATINGACCEPT (LAC, TMSI)

4AuthenticationProcedure

IMSI Attach

ACM = Address Complete Message ANM = ANswer MessageIAM = Initial Address Message

MS BSS MSCCHANNEL REQUEST

1

PSTN

CM SERVICE REQUEST2 CM SERVICE REQUEST

2

CALL PROCEEDING7CALL PROCEEDING

7

Assignment procedure7

IAM6

IMMEDIATE ASSIGNMENT2

ACM8

VLR

Ring

ANM10

ALERTING 9

SETUP (basic) or

EMERGENCY4 SETUP

4

CONNECT11

CONNECT ACKnowledge11

Authentication procedure3

Ciphering procedure3

5

Dialing

Ringing

PathEstablished

Ringing

SendingNumber

Mobile Originating Call

PSTN

LA1

LA2

BTS11

BTS21

BTS22

BTS31

BTS12

BTS23

HLR

4

3

5

1

2

5

6

6

BSC1

BSC2

BSC3

MSC/VLR

GMSC

Mobile Terminating Call1 - Paging Principle

VMSCBSS

VLR

Visitor PLMN

GMSC

HLR

Home PLMN

RoutingInformation

(MSRN)

6

IAM : Initial Address MessageMSISDN : Mobile Station Integrated Services Digital

network NumberMSRN : Mobile Station Roaming Number

IMSI : International Mobile Subscriber IdentityGMSC : Gateway MSCVMSC : Visitor MSCTMSI : Temporary Mobile Subscriber Identity

PN

InternationalSS7

ISDNIAM (MSRN)

7IAM

(MSISDN)2

SendRoutingInformation(MSISDN)

3

Provide Roaming Number (IMSI)

4

PAGE(TMSI + LA)

9

Send info to I/C(MSRN)

8

Roaming Number (MSRN)

5

PAGINGREQUEST

(TMSI + LA)10

PAGINGREQUEST

(TMSI)

11

MSISDN

1

Mobile Terminating Call2 - Detailed Procedure

MS BSS MSC

Call in progress1

RELEASE COMPLETE4

PSTN

DISCONNECT2 DISCONNECT

2

RELEASE3RELEASE

3

RF Channel Release procedure 8

Release5

RELEASE INDICATION7

CHANNEL RELEASE 6

Releasetone

9

Call Release

Discontinuous Transmission

• Discontinuous Transmission(DTX) allows the radio transmitter to be switched off most of the time during speech pauses.

• A Silence Indicator Block is transmitted at 500bps, which generates a comfort noise

• Down Link interference is decreased.

• Up link battery is saved

What is Drive Test?

Drive test involves setting up a call to best carrierand driving along the roads.

While driving, the radio parameters and air Interference signal data are collected as a log file.

DRIVE TEST

Drive Test Setup

Drive Test system comprises of

A Test mobile phone :Single or Dual Band.with Netmonitor software

SIM Card : Test SIM.

Laptop:Min config. 1GB RAM,1GB HD

Software to control and log data from the phone.:Depend on different vendor

Global Positioning System(GPS) receiver for position information

PCMCIA Card/USB Hub: To add more Ports.

Local Maps :Indicating all site-mark, with BCCH/BSIC values.

Transportation: Car with Charger

External Antenna for Test mobile phone can also be used for drive test

Battery Charger Or Inverter

Objective of Drive testFollowing steps are taken to fulfill the objective of using a drive test tool.

To verify whether the network meets the given requirements, on the basis of which network was designed.

To verify whether the parameters and configurations are defined correctly or not.

To investigate network problems related to poor quality, signal level, Interference etc…

Tune and optimize networks

Perform fault-tracing and troubleshooting

DRIVE TEST contd..

DRIVE TEST contd..

Rx Level Plot

Rx Quality Plot

RxQual measurement

RXQUAL, is the Bit error rate (BER) derived from the 26 bits Mid amble on TDMA burst. Speech quality is inferred by the RXQUAL measurements during the drive test. Its level characterizes speech quality where 0 indicates the highest quality and 7 the worst.BER = Errors/Total Number of Bits

Thus during drive test, poor quality areas can be found and marked by looking over the quality on the scale of 0 to 7.RXQUAL can be poor due to poor RXLEV, Co-channel interference, adjacent channel interference or Multipath.

DRIVE TEST contd..

Quality BER Comments0 less than 0.2% Good1 0.2% to 0.4% Good2 0.4% to 0.8% Good3 0.8% to 1.6% Good4 1.6% to 3.2% Good5 3.2% to 6.4% Bad6 6.4% to 12.8% Bad7 greater than 12.8% Bad

-47dBm level 63 Class 63 -70dBm level 40

Class 40 -80dBm level 30

Class 30 -90dBm level 20

Class 20 -95dBm level 15

Class 15 -100dBm level 10 Class 10

-110dBm level 0

6 classes for Level dimension (7 levels)

RX Level Measurement

DRIVE TEST contd..

ANTENNA DOWNTILTING

Antenna downtilting is the downward tilt of the vertical pattern towards the ground by a fixed angle measured w.r.t the horizon.

Downtilting of the antenna changes the position of the half-power beamwidth and the first null relative to the horizon.

Normally the maximum gain is at 0• tilt (parallel to the horizon) and never intersects the horizon.

With appropriate downtilt, the received signal strength within the cell improves due to the placement of the main lobe within the cell radius and falls off in regions approaching the cell boundary and towards the reuse cell.

There are two methods of downtilting

Mechanical downtilting

Electrical downtilting.

MECHANICAL DOWNTILTING

DRIVE TEST contd..

THANK YOU

QUESTIONS?