CDMA vs GSM | Difference between CDMA and GSM

This page compares CDMA vs GSM describes difference between CDMA and GSM technical specifications. It also mentions tutorial links on GSM and CDMA useful to derive further difference between GSM and CDMA.

Both the GSM and CDMA are cellular wireless technologies. They have been developed to support voice as well as data communications between various subscribers located across the world. In GSM, GPRS is used to support the data services.

GSM is developed and specified in 3GG as well as ETSI. CDMA is specified in US standard IS95 and also 3GPP.

About GSM

About GSM (Global System for Mobile Communication):
This technology uses TDMA/FDMA access scheme in order to assign channels to the different subscribers to utilize the service from the service operator's base stations. One frequency and one time slot (f1,t1) is needed for one way communication and a pair for two-way communication( (f1,t1) and (f2,t2) ).
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About CDMA

About CDMA (Code Division Multiple Access):
This technology uses PN codes for communication between subscribers and NodeBs. As the PN codes are unique to the users, information is extracted by despreading at the receiver using the same PN code which is used at the transmit side. Pls. note that information is not retrieved using (time,frequency) assignment in CDMA. All the different PN codes will utilize the same frequency/time in order to communicate. CDMA uses 1xEV-DO and EV-DV versions in 3rd generation. CDMA has edge over GSM due to its immunity to interference as well as jamming.
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In GSM, as the available transmission BW (Bandwidth) is small and hence leads to compromise in quality of voice transmission.
In CDMA entire transmission BW (Bandwidth) is utilized and hence voice quality can be enhanced.

In GSM(i.e. TDMA/FDMA), cell frequency planning is more tedium task as frequency and time planning need to be carried out in CDMA frequency planning is minimal.

GSM (due to TDMA) is a band-limited system. CDMA is a power limited system.

Difference between CDMA and GSM

Following table mentions difference between CDMA and GSM technologies.

Specifications	CDMA	GSM
Frequency Band(MHz)	UL:824-849,DL:869-894 UL:1850-1910, DL:1930-1990	UL:890-915,DL:935-960, UL:1710-1785, DL:1805-1885
Carrier Spacing(KHz)	1230	200
Physical channels per carrier	Soft capacity	8
Access	CDMA	FDMA/TDMA
Duplex	Frequency	Frequency
Frame Duration(ms)	20	4.6
Modulation Method	PSK	GMSK
Channel rate (Kb/s)	1228.8	270.833
Modulation Efficiency (b/s/Hz)	1.0	1.35
Maximum Terminal Transmitter Power (watt)	6.3	8
Speech coding	QCELP	RPE
Speech rate,including channel coding(kb/s)	Variable	22.8
Cellular Efficiency(conversations/cell/MHz)	12.1-45.1	5.0-6.6
Associated Control Channel	dim-and-burst	separate slots in each frame
Out-of-band ACCH rate(b/s)	4400-7600(Speech quality reduced when control channel is active)	950
Standard versions	CDMA-one(as per IS-95) ,CDMA-2000(as per CDMA2000), WCDMA(as per UMTS 3G std.)	GSM and GSM Advanced (supports MUROS, VAMOS,MSRD,AMR,SAIC)

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