Arunabh Kumar &
Pravir Kumar with
ECE Final Year,R.P.S.I.T Patna.
SAHID MASWOOD B.C.NAYAK
(HRD PATNA) (CDMA LEAD)
Mobile communication history
Multiple Access methods
GSM And CDMA
Departments of CDMA
R F Overview
We got this great opportunity to present project on
CDMA Overview prepared on the basis on four week
training in Reliance Info COM Pvt. Ltd. Patna.
We owe our sincere thanks to
Shahid Maswood (HRD Patna)
B. C. Nayak (CDMA LEAD)
Manoj Sinha (MCN Cluster in charge)
We express sincere thanks to the management at
RELIANCE INFOCOMM Pvt. Ltd. Mr. R.N.Rathore &
MCN Patna, in particular to Mr. Saurav Chaurasiya,Mr.
Amar Nath Prasad & Mr. Dhananjay Kumar, all are
arranging and scheduling our training for 4 weeks. Without
their generous support, We could not have completed our
training so efficiently. At last, we are really thankful to Mr.
Himanshu Shekhar & Miss. Priyanka Priya without there
co-operation ,it couldn’t be possible.
MOBILE COMMUICATION HISTORY
2nd. Generation IMT-2000
Analog DCS1800 CT2
NMT CT0 PHS
TACS CT1 IS-54
1946 Mobile communication Appeared St. Louis USA
1946to1970 Slow growth of mobile networks all over world.
1970 BELL LAB introduced Cellular Principle.
1979 AMPS System in US
Analogue technology used.
Modules cumbersome & heavy.
1980s TACS & NMT systems introduced by Europe
& Nordic countries.
1990s Digital Systems introduced.
1946- 1960s 1980s 1990s 2000s
Appeared 1G 2G 3G
Analog Digital Digital
Multi Multi Unified
Standard Standard Standard
Terrestrial Terrestrial Terrestrial
AMPS: Advanced Mobile Phone
(US, 800 MHz Band)
TACS: Total Access Communication
(UK , 900 MHz Band)
NMT450: Nordic Mobile Telephone Service
(Scandinavian, 450 MHz &
900 MHz Band)
( 2nd Generation) 1990’s
DAMPS: Digital AMPS
(US, 800 MHz Band, IS-54
CDMA: Code Division Multiple Access System
(US, 900 MHz Band, 1S-95)
GSM: Global System For Mobile
(Europe, 900 / 1800 MHz Band)
Requirements for 3rd generation Mobile
Tolerance for interference
Tolerance for fading
Ability to various data rate transmission
Flexible Quality of Service (QoS)
Multiple access method
*Multiple Accesses is the simultaneous use of a
communication system by one or more user.
*Each user’s signal must be kept uniquely
distinguishable from user’s signals to
allow private communications on demand.
*Users can be separated many ways:
.Physically: on separated wires
. By arbitrarily defined “channels” established in frequency, time,
or any other variable imaginable.
Very High Data Rate up-to 155 Mbps.
Wireless No Mobility.
High Data Rate up-to 54 Mbps.
54 Mbps W-LAN Little Mobility. Data Rate
Moderate Data Rate.
Cellular High Mobility.
Moderate Data Rates.
2 Mbps In-door
Very long distances.
Out-door very high Mobility.
FDMA TDMA CDMA
MULTIPLE ACCESS METHODS
Mobile Station Mobile Station
Frequency Division Multiple Access
Oldest &most familiar method of radio
Each user is assigned with unique channel of
Acts as private freq. for its call duration
As call terminates, the channel is released and
available for new call.
Number of users are less
Time Division Multiple Access
A user’s channel is a specific frequency
But only allotted for a certain duration
It belongs to the user for certain time slots in
Numbers of users are much greater
Groupe Special Mobile (GSM) uses this technique
Code Division Multiple Access
Each user has specified frequency for all time
Each user has been given a unique code pattern
From these codes connections are identified.
This unique code is buried within a shared signal, mingled
with other user’s code patterns.
If a user’s code pattern is known, the presence or absence of
their signal can be detected, thus conveying information.
Numbers of users are very large
In Technology CDMA Has Plus Point Over
CDMA is faster
CDMA is more secure
Connection on a CDMA network will never get
dropped when moving from cell to cell
CDMA base stations cover a large area
1 Billion GSM Subscriber’s To CDMA’s
GSM replaced archaic analogue system
Late appearance of CDMA
Adopting CDMA means paying royalty to
World standard for mobile communication
Availability of international roaming
GSM & CDMA both are moving towards improved
technology based on CDMA technique
These techniques are Wideband-CDMA & CDMA
DEPARTMENTS OF CDMA
OSP FIXED ACCESS
R F OVERVIEW
What is cell?
A cell is a small area of service
within a city, serviced by its own
Frequency Reuse In CDMA-
All users use same frequency
Universal frequency reuse
applies to the users in the same cell
as well as to those in others
Complicated reuse pattern is not
Spread Spectrum Concept
1800 1850 1910 1930 1990 2000MHz
Mobile TX Cell TX
User 1 Code 1
User 2 Code 2
User 3 Code 3
User n Code n
Spread spectrum uses much larger slice(1.25MHz) of the available bandwidth.
Same slice is used for all user with no time multiplexing but user is assigned
with a different code of to uniquely identify them.
CDMA Cellular Spectrum
824MHz 835MHz 845MHz 849MHz
A” A B A’ B’
869MHz 880MHz 890MHz 894MHz
A” A B A’ B’
870MHz FORWARD LINK 891.5MHz
Band Of CDMA
The 850MHz CDMA band is most popularly used all over the world
This band works between
824-849MHz used for the Reverse link communication
869-894MHz used for the Forward link communication each of 25MHz.
The total band of 25MHz is divided into small channels of 30KHzeach.An actual CDMA
carrier will be using a multiple of the 30KHz channels.
This means for an actually utilized bw of 1.23MH will need 41*30KHz channels.
Relationship between the channel numbers and actual freq.
Reverse link frequency =(825+N0.03)MHz
Forward link frequency=(870+N0.03)MHz
N=CDMA Channel Number
Spread Spectrum Concept
Spread spectrum uses much larger slice (1.25 MHz) of the available
bandwidth. Same slice is used for all users with no time multiplexing but each
user is assigns with a different code to uniquely identify them.
CDMA uses a modulation technique called “Spread Spectrum” to transport a
narrow band voice signal over a wide bandwidth channel .The wide bandwidth
for IS-2000 is 1.23 MHz .
The CDMA modulation technique uses three methods for spectrum spreading:
. frequency hopping (FH)
. time hopping (TH)
. direct sequence (DS)
While FH is more popular in CDMA system used for military purpose in
commercial CDMA system DSSS is popularly used.
Direct Sequence-Spread Spectrum (DSSS)
CDMA is a scheme in which multiple users are assigned radio
resources using the DSSS techniques.
Although all users are transmitting in the same RF band, all users’
arte separated from each other via the use of orthogonal codes (Walsh
Each user has full time use of the entire spectral allocations.
Each user’s signal is spread over the entire bandwidth and codes so as
to appear like broadband noise to every other user.
In a spread system the data information signal, b(t),
is multiplied by a wideband signal, c(t), which is the
output signal of the Direct Sequence (DS) generator – a
pseudorandom noise (PN) output signal. The signal
which will eventually be transmitted, y(t) = b(t) c(t), will
occupy bandwidth far in excess of the minimum m
bandwidth to transmit the data information.
Spreading Gain or Processing Gain (G) = Tb/Tc,
Where, Tb is the bit interval of the Information steam &
Tc is the bit interval of the DS stream. Tc is also called
Chip Time .
The Processing Gain & Capacity Relation
CDMA spreading gain consider a user with a 9600 bps Vocoder
talking on a CDMA signal 1,228,800 Hz wide.
The processing gain is 1228800/9600 = 128, which is 21 db.
. Shannon’s work suggests that a certain bit rate of information deserves a certain bandwidth .If
one CDMA user is carried alone by a CDMA signal, the processing gain is large (roughly 21 db
for an 8k vocoder).
. Each doubling of the number of users consumes 3 db of the processing gain.
. Somewhere above 32 users, the signal-to-noise ratio becomes undesirable and the ultimate
capacity of the sector is reached.
. Practical CDMA systems restrict the number of users per sector to ensure processing gain
remains at usable levels.
64 are available
64 Chips long – lasts 1/19200 sec
The user signal (or control channel) is multiplied by
the Walsh code.
The Walsh code provides each user or channel with an
unique identifier and, in DS spreading, spreads the frame
across the entire 1.23MHz bandwidth.
PN SHORT CODES
one pair is used (I & Q)
32 K long –lasts 26-2/3 ms, repeats 75x in 2sec.
Generated in 15 – bit tapped shift register.
Nearly self – orthogonal if compare out of sync
On the Reverse link it is used only for quadrature spreading
without any offset or
The PN Short Code is used only for tracking the
mobile that means to calculate the round trip delay or path
delay for the mobile.
PN LONG CODE
only one is used
(2)42 – 1 chips long – lasts 40+ days!
generated in 42 – bit shift register.
Any short sample is nearly orthogonal with any other short sample.
Information about the long code is broadcast to the mobile station by the sync
channel to help the mobile lock onto the base station and helps provide separation
from other station.
It is used to scrambled the interleaved signal and provide additional security against
interception and interference.
An additional advantage of the long code is that it allows the transmitter to use less
power ,maintaining control over the ambient RF environment and increasing the
overall capacity of the cell.
Steps evolved for signal transmission
1. A pseudo random code is generated, different for
each channel& successive connections.
2. The information data modulates the pseudo
3. The resulting signal modulates the carrier.
4. The modulated carrier is amplified and broadcast.
Steps evolved for receiving the signals
1.The carrier is received and amplified.
2.The received signal is now demodulated by
receiving the codes.
3.The receiver acquires the received code and phase
locks its own code to it.
4.The received signal is correlated with the generated
code, extracting the information
CDMA Switch Overview
CDMA Network Architecture
This consists of the mobile telephone, fax machine etc. This is the part of the
network that the subscriber will see.
The MS consists of two parts, the Mobile Equipment (ME) and an electronic
‘smart card’ called a Universal Identity module (UIM).
The ME(Mobile Equipment) is the hardware used by the subscriber to access the
network. The hardware has an identity number associated with this identity number
is called the International Mobile Equipment Identity (IMEI).
The UIM is a card which plugs into the ME or programmed into it. This identifies
the MS subscriber. The subscriber is identified by an identity number called the
International Mobile Subscriber Identity (IMSI).
Mobile Equipment may be purchased from any store but the UIM must be obtained
from the CDMA network provider. Without the it, the ME will only be able to make
BTS(Base Tranciever Station)
This is a part of the CDMA network which communicates with MS .
The BTS contains the RF components that provide the air interface for a particular
cell.The antenna is included as part of the BTS.
The BTS comprises the radio equipment such as transreceivers and antennas which are
needed to serve each cell in the network .
A group of BTSs are controlled by a BSC.
BTS in Trans-direction does:
BTS in Receive-direction does:
Digital to Analog (D/A) conversion.
BTS is usually located in the center of the cell.
BTS has 1 to 16 RF channels. These channels are to be different
from those of the adjacent cells
It acts as mobile interface to the cellular network.
BSC(Base Station Controler)
The BSC manages all the radio-related functions of a CDMA network.
It is a high capacity switch that provides functions such as MS handover,radio channel
assignment and the collection of cell configuration data.A number of BSCs may be
controlled by each MSC.
Performs radio resource management
Assigns and releases frequencies and time slots for all the MS’s in its area
Reallocation of frequencies among cells
Hand over protocol is executed here.
Time and Frequency Synchronization signals to BTS’s.
Time Delay Measurement and notification of an MS to BTS
Power Management of BTS and MS.
Handover occurs when a call has to be passed from one cell
to another as the user moves between cells. In a traditional
"hard" handover, the connection to the current cell is broken,
and then the connection to the new cell is made. This is
known as a "break-before-make" handover. Since all cells in
CDMA use the same frequency, it is possible to make the
connection to the new cell before leaving the current cell.
This is known as a "make-before-break" or "soft" handover.
Soft handovers require less power, which reduces
interference and increases capacity.
MSC(Mobile ServicesSwitching Centers)
The MSC is included in the CDMA system for call-switching.
Its overall purpose is the same as that of any telephone
Each MSC provides service to MSs located within a defined
geographic coverage area.
One MSC is capable of supporting a regional capital with
approximately one million inhabitants. An MSC of this size will be
contained in about half a dozen racks.
GMSC(Gateway Mobile Services Switches
Connects mobile network to a fixed network.
Entry point to a PLMN.
Usually one per PLMN.
Request routing information from the HLR
and routes the connection to the local MSC
MSC(Mobile ServicesSwitching Centers)
The functions carried out by the MSC are listed below:
a. Call Processing
b. Operations and Maintenance Support
Signaling protocol with BSC.
Paging and Short Message Services.
Routing of traffic and signaling.
It undertakes Radio Resource Management.
Verifying IMSI, Authentication, Interrogation of HLR.
HLR(Home Location Register)
n/w database that stores and manages all mobile subscriptions belonging to a
The information stores includes:
. Subscriber identity.
. Subscriber supplementary services.
. Subscriber location information.
. Subscriber authentication information.
The HLR is a centralized
VLR(Visitor Location Register)
The VLR database contains information’s about all mobile subscribers
currently located in an MSC service area.
There is one VLR for each MSC in a network.
When a subscriber roams into new MSC service area, the VLR connected to
that MSC requests information about the subscriber from the subscriber’s
The HLR sends the copy of the information to the VLR and updates its own
When subscriber makes a call,the VLR will already have the information
required for call set up.
EIR & AuC
Equipment Identity Register (EIR):
Contains three lists for IMEI check:
White list – contains mobile equipment approved without
Grey list – contains the equipment to be observed.
Black list – contains the unapproved equipment.
EIR checks whether the IMEI fits into one of these lists and passes
result to MSC. For example, if mobile fits into the black list, it
cannot participate in the call setup.
Authentication Center (AuC):
Security related functions.
Verifies individual parameters assigned to each mobile subscriber.
Mobile Subscriber ISDN (MSISDN):
Country Code (CC) (Up-to 3 decimal places)
National Destination Code (NDC) (2 to 3 digits).
Subscriber Number (SN) (Max up-to 10 digits).
A subscriber can hold several ISDN’s for selection of different services.
International Mobile Subscriber Identity (IMSI):
Mobile Country Code (MCC)
Mobile Network Code (MNC)
Mobile Subscriber Identification No. (MSIN)
IMSI is stored in the SIM. Mobile Station can be operated if SIM with the valid
IMSI is inserted in the equipment.
The Equipment should have valid IMEI.
Types Of Call
On Net Call Off Net Call
Local STD Local STD
o Net Call-call in same network
n Net Call-call in other network
Call Initiation, Setup and Termination
• The mobile user when decides to make a call, enters the desired phone
number. This initiates an access probe. The mobile uses the access
channel and attempts to contact the serving base station.
• Since no traffic channel has been established, the mobile uses open
loop power control. Multiple tries are allowed at random times to avoid
collisions that can occur on the access channel. Each successive
attempt is made at a higher power level. After each attempt, the mobile
listens to the paging channel for a response from the base stations.
Call Initiation, Setup and Termination
Once the access request has been received by the base station,
the base station responds with an assignment to a traffic
channel (Walsh code). The base station initiates the land
link, and conversation takes place.
Call termination can be initiated either from the mobile or
the land side. In either case the transmissions are stopped,
the Walsh code is freed, and the land line connection is
broken. The mobile unit resumes monitoring the page
channel of the current serving cell.
Receiving Incoming Call
CALL FLOW SCENARIO FOR 93……MOBILE
Call from 9334….to local 9334….
•Call from 9334….to STD Delhi No.093.
MSC GMSC GMSC MSC
Patna Patna Delhi Delhi
93 Local to B.S.N.L Local
MSC GMSC B (through BSNL tax POI)
A Patna Patna
93 Local to B.S.N.L. STD
MSC ILT ILT
A Switch Switch B (thr’bsnl
Patna Patna Delhi
WHAT IS E1?
E1 is a signal in which voice as well as data flow through it.
On It consists of 32 channels which can carry the data up to 2.04 mbps.
Multiplying 64kbps of data with the 32 channels it will be 2.04mbps of information
which is carried by 1E1.
E2=2E1=2 * 2.048 =4.096mpbs of data
As we go further,
E3=2E2=2*4.096=81.96mbps of data & so on.
The above mentioned hierarchy is called plieo digital hierarchy (PDH). These are
electrical transmission hierarchy.
If there is need to have more active channels we can add E1’s according to subscriber
and traffic needs, for having more active channels there is a hierarchy called
synchronous digital hierarchy i.e. SDH(STM).
1 STM = 63 E1.
1 STM = 63 * 2.048 +(Extra padding bits + dummy for synchronization) = 155.5mbps of
data is being carried.
Calling party off, hook lamp on
Verification of eligibility-query for called party information
Called party information-analysis by the operator
Ring to called party if true
Called party answer- connection
Either party on hook lamp off
Recapitulation of the link-disconnection
Compared to manual exchange, we can say
Hardware = Chords, Lamps Eyes ,Hands e.t.c.
Software = Brain ,Reasoning ,Judgment
ELEMENT OF AN
Subscriber Subscriber M.S.
M.S. Interface Switch Interface
Operation & Maintenance
Call Handling Function
O&M (Call handling
(Call handling N/W
P Subscriber Multiplex Local Exchange
RLL Switch Switch
Remote Subscriber Switch
Switching in telecom network
The ITU-T defines switching as :
“the establishing ,on demand, of an individual
connection from a desire inlet to a desired outlet within a
set of inlets &outlets for as long as is required for the
transfer of information”.
Today the word ‘information’ not
only denotes the speech we hear in our telephone receiver,
but also incorporate all types of information from
several telephone services
INTER EXCHANGE SIGNALING
Channel Associated Common Channel
e.g. R1,R2,system no.5 e.g. system no. 7
Muscles and Nerve’s of a N/W
A digital telecom n/w conist of a n/w of bearer channels (Muscles).
An overlaping n/w of signaling channels (Nerves).
Speech & Signaling Concepts
This signaling is message based signaling.It is widely used signaling in ckt
Signling is separated from speech.It can now travel on separate n/w.
Why a common channel signaling standard?
Obtimized for operation in digital telecommunication network in conjunction
with stored program controlled exchanges.
It can meet present and future requirements of information transfer for inter-
processor transactions within telecom network for call control, remote control &
management and maintenance signaling.
It provides a reliable means for transfer of information in correct sequence and
without loss or duplication.
The signaling system meets requirements of call control signaling for telephone,
ISDN & ckt switched data transmission services that can also be used as a
reliable transport system for other types of information transfer between
exchanges & specialized centers in telecom network (e.g. for management &
CCS#7 NETWORK : BASIC ELEMENTS
Signaling Point Code (SPC)
It is the identity of an exchange.
It is addresed by a 14 bits code (OPC,DPC).
A signaling point handles the signaling information.
One exchange may have more than one point code.
SPC can be 14 bits or 24 bits long.
Formats for its representation will depend on signaling network where it is used
Signaling End Point (SEP)
It’s a source or a sink of signaling traffic.
CCS#7 NETWORK : BASIC ELEMENTS
Signaling points are connected with signaling data links.
SP-Signaling point signaling
STP- Signaling transfer point speech
OWNSP-Own signaling point
Architecture OF CCS#7
MTP LEVEL 3
MTP LEVEL 2
MTP LEVEL 1
Architecture OF CCS#7
The message transfer part consists of three levels.
The lowest level MTP 1 is equivalent to the OSI Physical
layer. It defines the physical, electrical and functional
characteristics of the digital signaling.
The middle level MTP level 2 is equivalent to the OSI Data
link layer. It assures accurate end-to-end transmission of a
message across a signaling link. It implements flow control
message sequence validation and error checking. When an
error occurs on a signaling link, the message (or set of
messages) is retransmitted.
Architecture OF CCS#7
MTP level 3 is equivalent to OSI Network layer. It
provides message routing between signaling points in
the SS7 network.MTP level 3 re-routes traffic away
from failed links and signaling points and controls
traffic when congestion occurs.
SCCP provides connectionless and connection
oriented network services and global title translation
(GTT) capabilities above MTP level 3.
(Point of Interconnection)
Point of Interconnection (POI) is a sort of
interconnection established between two service
providers when communication to be made between
their subscribers. There are various types of POI,
such as NLD POI, ILD POI, SDC POI, etc. These
help to route an inter-network call at different
locations following different procedures and different
taxes such as: L1 tax, L2 tax, etc.
NLD/ILD (National Long Distance / International Long
When a subscriber makes a call, the signal is received by BTS and is
transmitted to MSC by transport equipments. MSC, after receiving the
signal, verifies the validity of the subscriber and then sends the signal
to ILT (Integrated Local Trunk) switch. The call now is routed
according to its destination code; such as 0 for national call, 00 for
international call, 2 for calls going to BSNL subscribers, 3 for calls
going to Reliance subscribers, etc. The ILT switch then sends the
signal to its destination based on the destination code through proper
routing. The STD calls are routed through the NLD route. The ISD
calls are routed through ILD route.
TRANSPORT and I&C
Transport provides the communication paths that carry user and
network control information between nodes in a network. In general,
transmission facilities consist of a medium (e.g., free space, the
atmosphere, copper or fiber optic cable) and electronic equipment
located at points along the medium. This equipment amplifies (analog
systems) or regenerates (digital systems) signals, provides termination
functions at points where transmission facilities connect to switching
systems, and may provide the means to combine many separate sets of
call information into a single "multiplexed" signal to enhance the
transmission efficiency .The Transport network consists of the SDH.
The SDH has various advantages in the respect that it can be used to
provide higher bandwidth that is so much in demand nowadays for
providing services such as internet, video on demand, etc.
Synchronous Digital Hierarchy (SDH)
Synchronous digital hierarchy (SDH) refers to a group of fiber-optic transmission
rates that can transport digital signals with different capacities.
As semiconductor circuits appears and demand for telephone capacity
increased, PCM (transmission method, in 1960) developed.
With PCM (multiple use of a single line by digital time domain multiplexing),
the analog telephone signal is first sampled at a bandwidth of 3.1 kHz, quantized
and encoded then transmitted at a bit rate of 64 kbps.
SDH overview contd…
When 30 such coded channels are collected together in a frame along
with the necessary signaling information, a transmission rate of 2048
kbps is achieved. This so-called primary rate is used throughout the
Only the USA, Canada and Japan use a primary rate of 1544 kbit/s,
formed by combining 24 channels instead of 30.
The growing demand for more bandwidth meant that more stages of
multiplexing were needed throughout the world. A practically
synchronous (or, to give it its proper name: plesiochronous) digital
hierarchy is the result
Towards the end of the 1980s, the so-called synchronous digital
hierarchy (SDH) was introduced
SDH overview contd…
This paved the way for a unified network structure
on a worldwide scale, resulting in a means of
efficient and economical network management for
The networks can easily be adapted to meet the ever-
growing demand for bandwidth-hungry applications
SDH overview contd…
Japanese Standard North American Standard European Standard
OSP (Out-Side Plant)
The OSP department in any telecom service provider looks after the
various utility items such as:
the DG set at the Switch
the Repeater stations
Ability to various data rate transmission
This is done to ensure that the equipments are never allowed to shut
down, as this may cause serious disruption of service. There are two
things that are necessary for the proper working of any telecom
network OSP and ISP (Inside Plant).
Fixed Access constitutes of the wireless (LMDS)/wireline
(DLC) services provide for voice and data transfer. Reliance
has deployed a nationwide Fibre Optic backbone, as its main
mode of transport of the network traffic.
LMDS is a broadband wireless point-to-multipoint
communication system operating above 20 GHz (depending
on country of licensing) that can be used to provide digital
two-way voice, data, Internet, and video services
MICROWAVES:- It is used when there is a lack of digging
area, for that we need to have the microwave’s for
transmitting and receiving for maturing the call or is used
when quick transmission is required.
COAXIAL CABLES:- It is generally used as transmission
media. It is underground & most of the places there is a use
of coaxial cable. This is less expensive.
OPTICAL FIBERS:- It is also known as OFT. There are
very less losses using optical fibers. Data is converted into
light rays. Transmission is done through glasses. This is
much expensive with concern to other transmission medias.
1. It has high capacity.
2. It has the capability of using signals that arrive in the receivers with different
3. It is interference limited multiple access system.
4. It uses unique spreading codes due to which it has low noise level.
5. High capacity increases as well as extended battery life for handsets.
6. Increased cellular communications security.
7. Simultaneous conversations.
8. Increased efficiency, meaning that the carrier can serve more subscriber.
9. Smaller phones.
10. Low power requirements and little cell-to-cell coordination needed by
1. It causes ‘near-far’ problem i.e. a transmitter ”near” the receiver
sending a different code than the receiver’s desired code produces
in the receiver a signal comparable wit that of a ”far” transmitter
sending the desired code.
2. Synchronization of the receiver and the transmitter is complex.
3. Due to its proprietary nature,all of CDMA’s flaws are not known
to the engg. Community.
4. CDMA is relatively new,and the network is not as mature as GSM.
5. CDMA cannot offer international roaming,a large GSM
CDMA Overview Supplied by RIL.
Fast Track Magazine 2006.
Study Materials Supplied by MCN Patna.