GSM is a form of multiplexing, which divides the available bandwidth among the different channels. Most of the times the multiplexing used is either TDM (Time division multiplexing) or FDM (Frquency division multiplexing). On the other hand CDMA is a type of multiple access sceheme( which means allotting the given bandwidth to multiple users) and makes use of spread spectrum technique which is essentially increasing the size of spectrum.
gsm used unique number throught word and coverage is very good.
cdma uses seperate code for each user so frequency is very
high for each user. entire bandwidth is dedicated to each
user.where as in gsm entire BW in divided into time slots
and frequency slot
GSM uses 900,1800&1900 band Systems.in india we are using
900 and 1800 band Systems but in CDMA we are using only 900
band system.
in GSM 900 Band System
uplink is varied form 890 MHz to 915 MHz
Downlink is Varied from 935 MHz to 960 MHz
but in CDMA 900 Band System
uplink is varied form 824 MHz to 849 MHz
Downlink is Varied from 869 MHz to 894 MHz
and Radiation distance of CDMA is more high than GSM.
more money required for establish a CDMA tower than GSM
tower.
CDMA tower should generate a random code for every User,and
CDMA mobile also generate one random code ,if two random
codes are same than Synchronization is ha pend between BTS
&Mobile station
but ,in GSM we are not using this type of System,the BTS
should identify the MS by ISDN(International subscriber
Destination Number)
a. Data Transfer Speed : With the advent of cellular phones
doing double and triple duty as streaming video devices,
podcast receivers and email devices, speed is important to
those who use the phone for more than making calls. CDMA
has been traditionally faster than GSM, though both
technologies continue to rapidly leapfrog along this path.
Both boast "3G" standards, or 3rd generation technologies.
EVDO, also known as CDMA2000, is CDMA's answer to the need
for speed with a downstream rate of about 2 megabits per
second, though some reports suggest real world speeds are
closer to 300-700 kilobits per second (kbps). This is
comparable to basic DSL. EVDO is in the process of being
deployed. It is not available everywhere and requires a
phone that is CDMA2000 ready.
GSM's answer is EDGE (Enhanced Data Rates for GSM
Evolution), which boasts data rates of up to 384 kbps with
real world speeds reported closer to 70-140 kbps. With
added technologies still in the works that include UMTS
(Universal Mobile Telephone Standard) and HSDPA (High Speed
Downlink Packet Access), speeds reportedly increase to
about 275—380 kbps. This technology is also known as W-
CDMA, but is incompatible with CDMA networks. An EDGE-ready
phone is required.
b. Subscriber Identity Module (SIM) cards : In most of the
countries only GSM phones use SIM cards. The removable SIM
card allows phones to be instantly activated, interchanged,
swapped out and upgraded, all without carrier intervention.
The SIM itself is tied to the network, rather than the
actual phone. Phones that are card-enabled can be used with
any GSM carrier.
The CDMA equivalent, a R-UIM card, is only available in
parts of Asia . CDMA carriers require proprietary handsets
that are linked to one carrier only and are not card-
enabled. To upgrade a CDMA phone, the carrier must
deactivate the old phone then activate the new one. The old
phone becomes useless
c. Roaming : For the most part, both networks have fairly
concentrated coverage in major cities and along major
highways. GSM carriers, however, have roaming contracts
with other GSM carriers, allowing wider coverage of more
rural areas, generally speaking, often without roaming
charges to the customer. CDMA networks may not cover rural
areas as well as GSM carriers, and though they may contract
with GSM cells for roaming in more rural areas, the charge
to the customer will generally be significantly higher.
d. International Roaming : If you need to make calls to
other countries, a GSM carrier can offer international
roaming, as GSM networks dominate the world market. If you
travel to other countries you can even use your GSM cell
phone abroad
GSM 900 & GSM 1800 are used in india, But, GSM 1900 used in
USA.
GSM and CDMA techniques can be explained with an example,
suppose there are 10 persons in a room and they want to
communicate with each other .How can they communicate?
First method:One persons speaks at one time that means we
have provided a definite time interval to that person.-GSM
Second method :all the peers speak at a time in a different
language which we call as CDMA
CDMA stands for Code Division Multiple Access and GSM
stands for Global system for Mobile Communication.
In CDMA phones the software is integral with the phone
instrument and in the case of GSM phones it is through the
SIM Card.
CDMA phone instruments are dedicated to the service
provider. GSM phone instruments are portable across service
providers through SIM cards.
If you want to detailed drescription about CDMA
Go & refer the link given below.
http://www.cdmauniversity.com/prodtech/cdma/training/cdma25/m5/m5p01.html
1. The GSM stands for global system for mobile communication and CDMA for code division multiple accesses.
2. GSM is a form of multiplexing, which divides the available bandwidth among the different channels. Most of the times the multiplexing used is either TDM (Time division multiplexing) or FDM (Frquency division multiplexing). On the other hand CDMA is a type of multiple access sceheme( which means allotting the given bandwidth to multiple users) and makes use of spread spectrum technique which is essentially increasing the size of spectrum.
3. In CDMA each user is provided a unique code and all the conversation between 2 users are coded. This provides a greater level of security to CDMA users than the GSM ones.
You can understand the basic difference between CDMA and GSM with the following example.
Suppose there is a big room in which there are 10 couples who wish to talk but in way that they are not disturbed. There are 3 ways of doing this-
1. Only one couple stay in the roo and rest 9 leave it for a while, say 5 minutes. For those 5 minutes that couple can talk with each other and at the end of that it will go out and the next couple will come. At the end of the time slot of 10th couple, the 1st couple will come back to continue its conversation and the cycle would continue.
This is analogous to TDMA (Time division Multiple acess) a technique derived from TDM.
2. Another way is to divide the area of the room in 10 equal parts and then ask these couples to stay within their respective areas and talk.
This is analogous to FDMA (Frequency Division Multiple Access), a technique derived from FDM.
3. Finally the couples can be allowed to stand anywhere in the room and converse. They need not wait to get their time slot or be confined in a particular place. The only condition now is that all of them must speak in different languages.
This is analogous to CDMA technique.
I hope it will help you to understand these technologies.
Which is the digital modulation used today in telecomn?
(whatever his question meant the answer was CDMA)
2) Why is walse code used? then, noncoherent detection,
coherent detection, Pn code(y it is used?) etc
1.What is the difference between Diplexer and Duplexer and
what position?
2. What is the different between CDU C and CDU A
3. How do you link a T1 from the 1st BTS to 2nd BTS
4. What is the value for TEI 1st T1?
5. What is the SSI?
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