18629611 rf-and-gsm-fundamentals

GSM Fundamentals & RF
GTL welcomes you to the Basic
course on GSM Fundamentals &
RF (GTL-GSM RF-001)

What you will learn here?
• Basic Telecom concepts
• Various Wireless Technologies
• Cellular concepts & Principal of cellular Comm.
• GSM Network Architecture
• GSM channel Architecture
• Call Flows in GSM
• GSM Planning steps (Nominal Plan & RF surveys)
• GSM Optimization Steps ( Performance, Drive testing &
Benchmarking)

BASIC Telephony
•Off Hook
•Dial Tone
•Dialing Digits
•RBT
•Conversation
•Ring
•Off Hook &
Conversation
•Signaling
•Traffic
SWITCH / EXCHANGE

Wireless Communication
• Alternative means of wireless communication
– Walkie - Talkie
– Pagers
– Trunked private radios
• Mobile Phone - the magic technology that enables
everyone to communicate anywhere with anybody.

Wireless Telephony
BSC
BTS BTS
Mobile Subscriber...
MSC

Different Standards Worldwide
• Till 1982 Cellular Systems were exclusively Analog Radio
Technology.
• Advanced Mobile Phone Service (AMPS)
– U.S. standard on the 800 MHz Band
• Total Access Communication System (TACS)
– U.K. standard on 900 MHz band
• Nordic Mobile Telephone System (NMT)
– Scandinavian standard on the 450 & 900 MHz band

GSM - 900GSM - 900
The term GSM-900 is used for any GSM system which operates in any 900 MHz band.
P-GSM - 900
P-GSM-900 band is the primary band for GSM-900 Frequency band for primary GSM-900 (P-GSM-900) : 2 x
25 MHz
890 – 915 MHz for MS to BTS (uplink)
935 – 960 MHz for BTS to MS (downlink)
E-GSM - 900
In some countries, GSM-900 is allowed to operate in part or in all of the following extension band. E-GSM-
900 (Extended GSM-900) band includes the primary band (P-GSM-900) and the extension band :
R-GSM-900R-GSM-900
R-GSM-900 (Railway GSM-900) band includes the primary band (P-GSM-900) and the following extension
band:
GSM-1800GSM-1800
Frequency band: 2 x 75 MHz
1710 – 1785 MHz for MS to BTs (uplink)
Different Standards Worldwide

Industry Vs Technology Spread
• Telecom Service Providers/Operators
– GSM
– CDMA
– Basic-WLL
– Internet Services
– Long Distance
• Vendor
• Telecom Consultancy

Analog Mobile Telephony
• End of 1980’s Analog Systems unable to meet continuing
demands
– Severely confined spectrum allocations
– Interference in multipath fading environment
– Incompatibility among various analog systems
– Inability to substantially reduce the cost of mobile
terminals and infrastructure required

Digital Mobile Telephony
• Spectrum space - most limited and precious resource
• Solution - further multiplex traffic (time domain)
• Can be realized with Digital Techniques only

GSM History and Organization
• 1979 Europe wide frequency band reserved for
Cellular
• 1982 “Groupe Speciale Mobile” created within
CEPT
• 1986 GSM had full time in Paris
• 1988 ETSI takes over GSM Committee
• 1990 The phase 1 GSM Recommendations
frozen
• 1991 GSM Committee renamed “Special Mobile
Group” and GSM renamed as “Global
System for Mobile Communication”
• 1992 GSM launched for commercial
operations

Service Industry
• Service Provider is not a Equipment Manufacturer.
• The Service Provider has a license to operate in a
geographical boundary (state/circle/ country).
• It buys equipment from OEM Suppliers (Vendors).
• Installs & commissions the equipment thus making it’s
own Network.
• Provides the desired service to it’s subscribers.

Vendor
• Vendor is a Equipment Manufacturer.
• It supplies Product, Consultancy and Trainings
• Service provider has the option of taking the Consultancy
and Training

Cellular Communication
• A cellular system links Mobile subscribers to Public
Telephone System or to another Mobile subscribers.
• It removes the fixed wiring used in a traditional telephone
installation.
• Mobile subscriber is able to move around, perhaps can travel
in a vehicle or on foot & still make & receive call.

Advantage of Cellular
Communication
• Mobility
• Flexibility
• Convergence
• Greater QOS
• Network Expansion
• Revenue/Profit

WHAT IS CELLULAR TELEPHONY ?
CONSIDERATIONS -
TFREQUENCY
TSUBSCRIBER
DENSITY
TCOVERAGE
Base Station
Base Station
Base Station
Base Station
Base Station
Base Station

The Cell
• Cellular Radio involves dividing a large service area into
regions called “cells.”
• Each cell has the equipment to switch, transmit and receive
calls.
• Cells - Reduce the need of High powered transmission
• Cells - Conventionally regarded as being hexagonal, but in
reality they are irregularly shaped.
• Cell shape is determined by the nature of the surrounding
area e.g. Hills , tall building etc.

Cell Size
• Large Cells
• 35 Km
• Remote Areas
• High Transmission
Power
• Few subscribers
• Small Cells
• Near about 1 KM
• Urban Areas
• Low Transmission
Power
• Many Subscribers

Coverage & Capacity
• Coverage
– Percentage of the geographical area covered by cellular
service where mobile telephony is available
• Capacity -
– Number of calls that can be handled in a certain area
within a certain period of time.
– Capacity can also refer to the probability that users will
be denied access to a system due to the simple
unavailability of radio channels.

Frequency Spectrum
Designation Abbreviation Frequencies Free-space Wavelengths
Very Low Frequency VLF 9 kHz - 30 kHz 33 km - 10 km
Low Frequency LF 30 kHz - 300 kHz 10 km - 1 km
Medium Frequency MF 300 kHz - 3 MHz 1 km - 100 m
High Frequency HF 3 MHz - 30 MHz 100 m - 10 m
Very High Frequency VHF 30 MHz - 300 MHz 10 m - 1 m
Ultra High Frequency UHF 300 MHz - 3 GHz 1 m - 100 mm
Super High Frequency SHF 3 GHz - 30 GHz 100 mm - 10 mm
Extremely High Frequency EHF 30 GHz - 300 GHz 10 mm - 1 mm

GSM - IN CELLULAR
TELEPHONY
• Each Cell in the Cellular Network consists of one or more
RF carriers.
• An RF carrier is a pair of radio frequencies
– One used in upward direction by MS - Uplink
– Other used in downward direction by BTS - Downlink
– The transmit and receive frequencies are separated by a
gap of 45 MHz in GSM of 75 MHz in DCS.
• There are 124 carries in GSM Band. With each carrier
carrying 7 timeslots, only 124 x 7 = 868 calls can be made!
• Frequency Reuse is the solution

Frequency & ARFCNul=890to915MHz
dl=935to960MHz
Ful(n) = 890.0 + (0.2) *n MHz
Fdl(n) = Ful + 45 MHz
where n =ARFCN ; 1 ≤ n ≤ 124

Power
Frequency
Time
F
DMA
Frequency
Power Time
TDMA
FrequencyCDMA
Power
Time
Multiple Access
Methods

Frequency
Time
Power
TDMA
Frequency
Time
Power
FDMA
Frequency
Time
Power
CDMA
CODE
FDMA: AMPS & NAMPS
•Each user occupies a private Frequency,
protected from interference through physical
separation from other users on the same
frequency
•TDMA: IS-136, GSM
•Each user occupies a specific frequency but
only during an assigned time slot. The
frequency is used by other users during
other time slots.
•CDMA
•Each user occupies a signal on a particular
frequency simultaneously with many other
users, but is uniquely distinguishable by
correlation with a special code used only by
this user
Multiple Access Methods

Frequency Reuse Pattern
Three types of frequency reuse patterns
• 7 Cell reuse pattern
• 4 cell reuse pattern
• 3 cell reuse pattern

3 Site Reuse Pattern
c2
c1
c3
a1
a2
a3
b1
b2
b3
c1
c2
c3
Cell Re-use

Cell Dia = R
FREQUENCY RE - USE
– Frequency Re-use
7/21 cell cluster
1
2
3
4
5
6
7
D D=R (3N)
where N is Cluster size

Principal Of Sectorization
• Omni Directional Cells
• 120 degree Sectors
• 60 Degree sectors
– Each Sector in a Site has its own allocation of Radio
Carriers
• Advantage
– By frequent reuse of frequency more capacity can be
achieved

5 Multipath Fading results in variations in signal strength which is known as
Rayleigh Fading.
5 Rayleigh Fading phenomenon is dependent on path difference and hence
frequency of reception.
5 A fast moving mobile may not experience severe effect of this fading since
the path difference is continuously changing.
5 A slow moving mobile ( or a halted mobile ) may experience severe
deterioration in quality.
5 But, if the frequency of reception is changed when this problem occurs,
could solve it.
5 The fading phenomenon is fast and almost continuos, this means the
frequency change should also be continuos.
5 This process of continuously changing frequency is known as Frequency
Hopping.
Frequency Hopping

5 Frequency Hopping is done in both Uplink and Downlink .
5 Frequency is changed in every TDMA Frame
5 Mobile can Hop on maximum 64 frequencies
5 The sequence of Hopping can be Cyclic or Non-Cyclic
5 There are 63 Non-Cyclic Hopping sequences possible
5 Different Hopping sequence can be used in the same cell.
5 BCH Timeslot can never HOP, but the remaining Timeslots can
very well hop.
Frequency Hopping

Reduction in Average Interference
5 With Frequency Hopping consistent interference will become bursty.
5 So even though, both the co-channel cells will be using the same set of ARFCN's for
Hopping, interference will not be continuos.
5 This is because, GSM cells are not Frame synchronized, and change in frequency is
related to Frame nos.
5 If same HSN is used in two cells, then either the interference will be nil , or if a phase
correlation exists then it will be continuos.
5 So the two cells should preferably use different HSN's .
5 Sectorial cells ( controlled by the same BTS) can use same HSN, since the sectors don't
come up at the same time.
5 Cells if they are synchronized, can use same HSN, if each cell has an offset of some
TDMA frames.
5 Offset of TDMA frames is also required to avoid SACCH occurring at the same time in all
synchronized cells, as they kills away the objective of DTX.
Frequency Hopping

a1
a2
a3a3
a4a6
a5
Cell Sectorisation
OMNI CELL
1 ANTENNA
b1
b2
b3
120O
CELLS
3 ANTENNAS
60O
CELLS
6 ANTENNAS

Features of GSM
• Compatibility
• Noise Robust
• Increased Capacity & Flexibility
• Use of Standard Open Interfaces
• Improved Security & Confidentiality
• Cleaner Handovers
• Subscriber Identification
• ISDN Compatibility
• Enhanced Range of Services

Handovers
Hard Handoff
Analog, TDMA and GSM
Soft Handoff
CDMA
Break before Make Make before Break

120
181
198
200
132
41
44
24
69
75
113
28
71
73
70
80
7
8
11
12
13 16
17
18
19
20
22
25
32
40
171
173
175
182
187
197
199
201
213
214
215
216
218
219
220
221
222
225
Handovers

Cleaner Handovers
• The mobile measures up to 32 adjacent cells for
– Signal Strength (RxLevel)
– Signal Quality (RxQual)
– updated every 480 mS and sends to BTS
• Sophisticated Handover based on
– RxLevel
– Interference
– RxQual
– Timing Advance
– Power Budget

BT
S
BT
S
BT
S
BT
S
BT
S
BT
S
BT
S
BT
S
BSC
VL
R
HL
R EI
R
OM
C
S
MSC
B
C
AU
C
V
MSC
MS
C
A
bis
A
MS
BTS
BTS
BTS
BTS BTS
BTS
BTS
BTS
BSC
BSC
PSTN
VLR
TRAU
HLR
EIR
OMC
SMSC
BC
AUC
VMSC
MSC
A
bis
A
OML
GSM NETWORK ELEMENTS

Mobile Station Identities
MSISDN : Human Identity used to call a Mobile Station
IMEI: Serial number unique to every Mobile Station
IMSI : Network Identity unique to a SIM
3
digits
2
digits
10
digits TMSI : Identity unique in a LAI
MSRN : Mobile Station
Roaming NoCC NDC SN
98 XXX 12345
MCC MNC MSIN
404 XX 12345
TAC FAC SNR S
6 digits 2 digits 6 digits 1 digit

GSM Network Components
• Mobile Station consists of two parts-
– Mobile Equipment (ME)
– Subscriber Identity Module (SIM)
• ME
– Hardware e.g. Telephone, Fax Machine, Computer.
• SIM
– Smart Card which plugs into the ME.

ME (Classmark Information)
• Revision Level
– Phase of the GSM specs ME comply with.
• RF Power Capability
– Max power ME is able to Transmit.
• Ciphering Algorithm Used
– Presently A5
– Phase 2 specifies Algorithms A5/0 to A5/7.
• Frequency Capability
• SMS Capability

Typical
Settings
Mobile Equipment
Class Power O/p
1 20 W
2 8 W
3 5 W
4 2 W
5 0.8 W

SIM(IMSI)
• IMSI(International Mobile Subscriber
Identity)
– Transmitted over Air Interface on initialization
– Permanently stored on SIM card
– 15 digit Decimal

SIM (TMSI)
• Temporary Mobile Subscriber Identity
– Periodically changed by the System Management on
instances like location update etc.
• Reason for use of TMSI
– To prevent a possible intruder from identifying GSM
users, TMSI is used
• Management
– Assignment, Administration & Updating is performed
by VLR.

Transcoder
• Converts 64 Kbps PCM circuits from MSC to 16 Kbps
BSS circuits.
• Each 30 channel 2 Mbps PCM link can carry 120 GSM -
specified voice channels.

Base Station System (BSS)
• BSS (Base Station System)
– BSC (Base Site Controller)
– BTS (Base Transceiver Station)
– XCDR (Transcoder)
Network
Switching
System
(NSS)
XCDR
BSC
BTS

Base Station System (BSS)
• BSC
– Controls upto 40 BTS
– Conveys information to/from BTS
– Connects terrestrial circuits & Air Interface Channels
– Controls handovers between BTSs under itself
• BTS
– Contains RF Hardware
– Limited control functionality
– 1 - 6 carriers in a BTS Cabinet
– 7 - 48 simultaneous calls per BTS

BSS Configuration
• Collocated BTS
• Remote BTS
• Star Configuration
• Daisy Chain BTS Loop Configuration
BSC
BTS
BTS
BTS
AllBTSon1E1
BSC
BTS
B
T
S
BTS
BTS

Network Switching System(NSS)
• NSS (Network Switching System)
– MSC (Mobile Switching Centre)
– HLR (Home Location Register)
– VLR (Visitor Location Register)
– EIR (Equipment Identity Register)
– AUC (Authentication Centre)
– IWF (Interworking Function)
– EC (Echo Canceller)

GSM Network Component
• MSC
– Call Switching
– Operation & Management Support
– Internetwork Interworking
– Collects call billing data
• Gateway MSC
– MSC which provides interface between PSTN & BSS’s
in the GSM Network.

Home Location Register (HLR)
• Reference database for the Subscriber profiles-
– Subscriber ID (IMSI & MSISDN)
– Current VLR Address
– Supplementary Services subscribed
– Supplementary Service Information
– Subscriber Status (Registered/deregistered)
– Authentication Key and AUC functionality
– TMSI
– MSRN

Visitor Location Register (VLR)
• Temporary Data, which exists as long as the subscriber is
active in a particular Coverage area.
• Contains the following-
– Mobile Status (Busy/ Free/ No Answer/etc.)
– Location Area Identity (LAI)
– TMSI
– MSRN (Mobile Station Roaming Number)

Equipment Identity Register (EIR)
• Contains Database for validating IMEI
– White List (valid ME)
– Black List (Stolen ME)
– Grey List (Faulty ME)

• Provides function to enable the GSM System to
interface with Public/Private Data Networks.
• The basic feature of the IWF are
– Rate Conversion
– Protocol adaptation
• IWF incorporates Modem Bank.
e.g. GSM DTE PSTN DTE
IWF Analogue Modem
Inter Working Function

Echo Canceller
• Echo is apparent only in Mobile - Land conversation
& is generated at the 2 wire to 4 wire interface.
• To avoid it, Echo Canceller (EC) is used.
– Echo is irritating to MS Subscriber
– Total Round Trip delay of 180 ms in the GSM system
– EC is placed on the PSTN side of the Switch
– Cancellation up to 68 ms with EC

Operation & Maintenance Centre
• Event & Alarm Management
• Fault Management
• Performance Management
• Configuration Management
• Security Management

GSM Terrestrial Interfaces
Broadly classified into two types of interfaces-
• Standard Interfaces
– 2 Mbps Trunks (E1)
– Signalling System No. 7 SS7 ( CCS7)
– X.25 (Packet Switched Mode)
• GSM Interfaces

GSM Interfaces
• Um MS - BTS
• Abis BTS - BSC
• A BSC - MSC
• B MSC - VLR
• C MSC - HLR
• D VLR - HLR
• E MSC - MSC
• F MSC - EIR
• G VLR - VLR
• H HLR - AUC

GSM protocols are basically divided into three layers:
Layer 1: Physical layer
± Enables physical transmission (TDMA, FDMA, etc.)
± Assessment of channel quality
± Except on the air interface (GSM Rec. 04.04), PCM 30 or
ISDN
links are used (GSM Rec. 08.54 on Abis interface and
08.04 on
A to F interfaces).
Layer 2: Data link layer
± Multiplexing of one or more layer 2 connections
on control/signaling channels
± Error detection (based on HDLC)
± Flow control
± Transmission quality assurance
± Routing
Layer 3: Network layer
± Connection management (air interface)
± Management of location data
± Subscriber identification
± Management of added services (SMS, call forwarding,
conference
calls, etc.)
GSM Protocol Layers

Basic Processes
• AUTHENTICATION
• CIPHERING
• REGISTRATION
• CALL ESTABLISHMENT
• HANDOVER / HANDOFF
• ROAMING

AUTHENTICATION ALGORITHM
NSS
MS
HLR
AUC
AUTH.
ALGORITHMS
A3
SIM
MS
AUTH.
ALGORITHMS
A3
Ki
RAND
RAND
COMPARE
SRES
SRES
Ki
AIR INTERFACE

Ciphering
• Data protection is required on air interface.
• A specific key called Ciphering Key (Kc), is
generated from RAND and A8 algorithm.
• A8 is on the SIM.
A8
RANDKi
Kc

Ciphering
A5Data
Kc
Ciphered
Data
A5
Kc
Data

Transmission Media
• Access Network
– Microwave 15 /23 GHz
• Backbone Network
– Microwave 7 GHz
– Optical Fibers
– Leased Line( From Dot or any other service provider
on any media)

Optical Fiber
• Different Possible Combinations
• Mono Mode Step Index 10 / 125 µm
• Mono Mode Graded index
• Multi Mode Step Index 100 / 300 µm
• Multi Mode Graded Index 75 / 130 µm
• Mono Mode Graded Index would have been the best
but fabrication not possible
140 Mbps OLTE , Mono Mode Step Index in our case

Channels On Air Interface
• Physical Channel
• Logical Channel
• Physical Channel
– Physical channel is the medium over which the
information is carried.
• Logical Channel
– Logical channels consists of the information carried
over the Physical Channel.

LOGICAL CHANNELS
0 1 2 3 4 5 6 7
3
57
encrypted
57
encrypted
26
training
1
S
1
S
3
T
8.25
GP
3
T
577µS
577µS x 8 = 4.615mS
TDMA Frame
Normal Burst
26 Frame Multi-frame

Traffic Channel
TCH carries payload data - speech, fax, data
• Connection may be:
- Circuit Switched - voice or data or - Packet Switched – data
• TCH may be:
• Full Rate (TCH/F)
- one channel per user
- 13 kb/s voice, 9.6 kb/s data or
• Half Rate (TCH/H)
- one channel shared between two users
Traffic Channels
TCH/F
Full rate 22.8kbits/s
TCH/H
Half rate 11.4 kbits/s
• Time is divided into discrete
periods called “Timeslots”

Control Channel
DCCH(Dedicated Channels)
Downlink & Uplink
CCCH(Common Control Chan)
Downlink & Uplink
Synch.
Channels
RACH
Random
Access Channel
CBCH
Cell Broadcast
Channel
SDCCH
Standalone
dedicated
control channel
ACCH
Associated
Control Channels
SACCH
Slow associated
Control Channel
FACCH
Fast Associated
Control Channel
PCH/
AGCH
Paging/Access grant
FCCH
Frequency
Correction channel
Control Channels
BCH ( Broadcast channels )
Downlink only
BCCH
Broadcast
control channel
SCH
Synchronization
channel

Broadcast Channels (BCH)
BCH channels are all downlink and are allocated to timeslot zero.
Channels are:
• FCCH: Frequency control channel sends the mobile a burst of all ‘0’ bits which
allows it to fine tune to the downlink frequency
• SCH: Synchronization channel sends the absolute value of the frame number
(FN), which is the internal clock of the BTS, together with the Base Station Identity
Code (BSIC)
• BCCH: Broadcast Control Channel sends radio resource management and control
messages, Location Area Code and so on.
Some messages go to all mobiles, others just to those that are in the idle state

Common Control Channels (CCCH)
CCCH contains all point to multi-point downlink channels (BTS to
several MSs) and the uplink Random Access Channel:
• CBCH: Cell Broadcast Channel is an optional channel for general
information such as road traffic reports sent in the form of SMS
• PCH: Paging Channel sends paging signal to inform mobile of a call
• RACH: Random Access Channel is sent by the MS to request a channel from
the BTS or accept a handover to another BTS.
A channel request is sent in response to a PCH message.
• AGCH: Access Grant Channel allocates a dedicated channel (SDCCH) to the
mobile
• NCH: Notification Channel informs MS about incoming group or
broadcast calls

Dedicated Control Channels (DCCH)
SDCCH( Standalone Dedicated Control Channel )
Uplink and Downlink
Used for call setup, location update and SMS.
SACCH( Slow Associated Control Channel )
Used on Uplink and Downlink only in dedicated mode.
Uplink SACCH messages - Measurement reports.
Downlink SACCH messages - control info.
FACCH( Fast Associated Control Channel )
Uplink and Downlink.
Associated with TCH only.

BURST
• The Time Slots are arranged in a sequence ,
conventionally numbered 0 to 7.
• Each repetition of this sequence is called a TDMA
Frame.
• The information content carried in one time slot is
called a “burst”.

BURST
• Information
– Main Area where the Speech, Data or Control info is held
• Guard Period
– To enable the burst to hit the time slot (0.031ms)
• Stealing Flags
– 2 bits are set when TCH is to stolen by a FACCH
• Training Sequence
– For estimation of transfer characteristics of physical media
• Tail Bits
– Used to indicate beginning and end of the burst.

GSM Burst & TDMA Frame
0 1 2 3 4 5 6 7 2 4 5 6 730 1
FRAME 1 FRAME 2
Training
Sequence
Information Information
GUARD
PERIOD
GUARD
PERIOD
TAIL BITS TAIL BITS

Five Types of Burst
• Normal Burst
Traffic & Control Channels Bi-directional
• Frequency Correction Burst
FCCH Downlink
• Synchronization Burst
SCH Downlink
• Dummy Burst
BCCH Carrier Downlink
• Access Burst
RACH Uplink

Call Scenarios
• Mobile to Mobile
– Intra-city
– Inter-city
• Mobile to Land
– Intra-city
– Inter-city
• Land to Mobile
– Intra-city
– Inter-city

Mobile To Land Sequence
1
3
CHANNEL REQUEST
DCCH ASSIGN
SIGNALLING LINK
ESTABLISHED
REQUEST FOR SERVICE
SET CIPHER MODE
SET-UP
EQUIPMENT ID
REQUEST
AUTHENTICATION
MS BSS MSC VLR HLR PSTNEIR
RACH
AGCH
SDCCH
SDCCH
Call
Info7
4
6
5
2
CR
CC

8
COMPLELTE CALL
CALL PROCEEDING
9 ASSIGNMENT COMMAND
INITIAL & FINAL
ADDRESS (IFAM)
ASSIGNMENT COMPLETE
(ACM)
10
ANSWER(ANS)
11
CONNECT ACKNOWLEDGE
SDCCH
SDCCH
ASSIGNMENT COMPLELTE
MS HEARS RINGTONE
FROM LAND PHONE
ALTERING
RING TONE
STOPS
CONNECT
(channel)
(TCH)
FACCH
FACCH
FACCH
TCH
(circuit)
FAACH
BILLING STARTS
Hello!
MS BSS MS
C
VLR HLR PSTN EIR
Call Contt.

Supplementary Services
• Calling Line Identification
– Present
– Absent
• Connect Line Identification
– Present
– Absent
• Closed User Group - CUG
– Only incoming
– Only outgoing
• Operator Controlled Barring

Data Services
Data rates supported as of today areData rates supported as of today are
2.4 Kbps2.4 Kbps
4.8 Kbps4.8 Kbps
 9.6 Kbps9.6 Kbps
GPRS & EDGE implementation takes the dataGPRS & EDGE implementation takes the data
capability to higher level of the order of 184capability to higher level of the order of 184
kbps and morekbps and more

Customer..Expectation
• Good coverage – where ever he goes
• Good quality
• No blocking
• Value added services
– SMS
– Voice mail
– MMS
– Call forward/call waiting
– Data/internet at high data rates
– prepaid

Basic Network Design
Objectives
The basic objectives of a wireless system are:
– COVERAGE: provide sufficient cell sites to deliver RF coverage
of the entire desired area.
– BUILDING/VEHICLE PENETRATION: deliver sufficient signal
levels to adequately penetrate buildings and vehicles where
appropriate.
– TRAFFIC: ensure that no cell captures more traffic than it can
handle at the desired grade of service (i.e., blocking
percentage)
– PERFORMANCE: design, construct, and adjust the network to
deliver reliable service free from excessive origination and call
delivery failures, dropped calls, quality impairments, and
service outages.
– ECONOMICS: provide return on investment sufficient to support
operating and capital expenses, expand the network to take
advantage of growth opportunities, and retire costs of
construction prior to depreciation of the network equipment.

High Level Design
Inputs
– Coverage objectives
• Area coverage objectives
• Coverage penetration objectives
– Morphology data/clutter information
– Terrain data and Vector maps
– Traffic objectives
• Number of subscribers defined
• Traffic per subscriber defined
• Desired grade of service defined
– City regulations
– BTS Hardware specifications
– Link Budget
– Business and Logistical objectives
• Capital budget
• Timing: launch data
• Operating revenue Vs. total costs
• Output
– Cell database and traffic model
– Composite coverage plot
– Equal power handoff boundaries plot

“Background” Issues Impacting
System Design
• Site acquisition
– Availability of suitable candidate (building or land)
– Owner interest
– Cost of leasing
– Frequency clearance (SACFA)
– Government authority approval
– Space constraints and other construction issues
• Candidate Location – line of sight to the objective
• Clutter type
• Terrain variations
• Physical Blocking – buildings, hoardings
• Water
• Mumbai – High end, high traffic areas are very close to
water….
Makes RF design much more challenging
• Deviation from desired location impacts surrounding
site locations

Design considerations of Network
(GSM/CDMA)
• Understand geographical area as per license agreement
• Define coverage expectations in terms
– On road coverage
– In-building coverage (different penetration margins)
• Capacity considerations – busy hour per subscriber call attempts and
minutes of use (Erlangs)
• 1 Erlang is 1 call of 1 hour duration
• Decide number of sites based on coverage capacity requirement
• Propagation tools used for this analysis
• Finalize exact site locations after field survey
• Initiate candidate identification process
• Site acquisition/antenna positioning
• Modify existing design if site location changes

Traffic &
Growth
Analysis
System
Optimisation
Site Coverage
Confirmation
Site Search &
Selection
Propagation
model
verification
System/Site
Dimensioning
RF &Network
Planning
Market
Requirement
Site Acquisition
Site Build
Operational
Network
Site Search
Plan
Performance
Monitoring
Flow Chart for Network Deployment

GSM Planning Steps
• Various steps are listed below
– CW survey
– Model Tuning
– Nominal Planning
– RF site Surveys
– Realized Planning
– Frequency Planning
• Implementation
• Optimization
– Drive Testing
– Performance Analysis

Nominal Planning
• It consists of planning a set of sites on planning
tool so as to predict the coverage of the target
area
• Tool needs to be made intelligent so as to predict
the coverage as close as possible to actual
coverage
• Coverage plots are based on customer intension
of providing indoor and outdoor coverage

Mumbai – Coverage
Expectation Boundary

Coverage Maps – Reverse Link.
Colaba
Malabar Hill
Mazgaon
>=30dB:: 3-4 wall coverage
25-30dB : 3 Wall Coverage
23-25 dB : 2-3 Wall Coverage
18-23dB: 2-3 Wall Coverage
16-18 dB : 2 Wall Coverage
8-16dB : 1-2wall Coverage
08 dB : On Road-1 Wall Coverage
00 dB : On Road/No Coverage
Indoor Coverage:
Penetration Margin Legend

Composite Coverage
Plot
• Propagation models are used to
predict coverage from a particular
site
• A composite coverage plot shows the
overall coverage produced by each
sector in the field of view
• The color of each pixel corresponds
to the signal level of the strongest
server at that point
• Such plots are useful for identifying
coverage holes and overall coverage
extent

Clutter Types
• Clutter types
– Dense Urban
– Urban
– Sub Urban
– Rural
– Water
– Vegetation
– Industrial
– Forest

RF surveys
• Each nominal has a search ring defined by the RF
Planner
• Candidates needs to be identified as close as
possible to the nominal within the search ring
• Height, orientations & antenna placement at site
are the key RF parameter which are based upon
the coverage requirement in the area
• Major obstructions and clutter type in various
directions to be observed on RF survey

RF surveys
• Equipment required for RF Survey
– GPS
– Digital Camera
– Binoculars
– Magnetic Compass
• There might be 3 or more candidates surveys for
one site
• Each candidate would have an RF survey form
and panoramic associated with it

Drive Testing
• Drive testing is an important activity to get statistics & graphs on
coverage, quality & capacity in the downlink direction
• Drive test setup – DT tool, Engineering Handset, GPS,
accessories
• Call in 2 modes
•Dedicated – while the mobile is on call
•Idle – while the mobile is idle
Important parameters observed during drive testing
•Coverage – Rx level (Full & Sub)
•Quality – RxQual & SQI
•Handover, Dropped call, Neighbor list, TA

Selecting and Tuning
Propagation Models
• Parameters of propagation
models must be adjusted for
best fit to actual drive-test
measured data in the area
where the model is applied
• The figure at right shows
drive-test signal strengths
obtained using a test
transmitter at an actual test
site
• Tools automate the process of
comparing the measured data
with its own predictions, and
deriving error statistics
• Prediction model parameters
then can be “tuned” to
minimize observed error

What is Performance
Optimization?
• The words “performance optimization” mean different things to
different people, viewed from the perspective of their own jobs
• System Performance Optimization includes many different smaller
processes at many points during a system’s life
– recognizing and resolving system-design-related issues (can’t
build a crucial site, too much overlap/soft handoff, coverage
holes, etc.)
– “cluster testing” and “cell integration” to ensure that new base
station hardware works and that call processing is normal
– “fine-tuning” system parameters to wring out the best possible
call performance
– identifying causes of specific problems and customer
complaints, and fixing them
– carefully watching system traffic growth and the problems it
causes - implementing short-term fixes to ease “hot spots”, and
recognizing problems before they become critical

Optimization
• Optimisation is an ongoing process of analysing network performance
against Quality of Service targets:

Performance
•Measurements of network performance cover:
• Traffic in erlangs
• TCH and SDCCH Grade of Service (Congestion)
• Call success rate
• Handover failure
• Coverage area
• Coverage quality
• Subscriber base and growth
• Key Performance Indicators (KPI) are measurable dynamic
parameters that help to target areas of concern

KPI’s
• Appropriate KPIs to use depend on:
• The nature of the network
• Data sources available
• Measurement tools available
• Ability of engineering team
• Cost of network infrastructure
• Sources of data include:
• Surveyed data - from drive tests
• Network statistics - from OMC
• Field engineer reports

Radio Interface Optimization
• Transmission Timing
• Power Control
• VAD Voice Activity Detector and DTX
• Multipath Fading
• Equalization
• Diversity
• Frequency Hopping
• Antenna Parameters ( Height, Azimuth, Tilts )

Benchmarking
•Surveyed data from test-mobile measurements can be used to
benchmark system performance against that of a competitor
• Problems that may be identified from surveyed data:
• Poor coverage
• Unexpected interference
• Missing handover definitions
• Installation problems at BTS
• Test-mobile measurements should include:
• continuous calls to test coverage
• repetitive short calls to test call-success

Overview
RF Planning Tool
Drive Test Tool
Optimization Tool
MapInfo

18629611 rf-and-gsm-fundamentals

18629611 rf-and-gsm-fundamentals

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