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What is the Difference Between GSM and CDMA?

نقدم لكم اليوم مقاله باللغه الانجليزيه عن الفرق بين GSM و CDMA حيث ان الان يتم استخدام خدمات الموبايل في كل مكان في العالم.وفي هذا العالم  GSM و CDMA هما التقنيتان المسيطره في عالم الاتصالات المتنقلة. تختلف هاتان التقنيتان في طريقة إجراء المكالمات ونقل البيانات عبر الشبكة والمحمول. وسنذكر تعريف GSM وتعريف CDMA ومميزات GSM و مميزات CDMA ومقارنه بين GSM و CDMA علي مدونه "مهندس اتصالات"

What is CDMA?

- CDMA stands for Code Division Multiple Access. It is used in cellular communication similar to GSM and is a second generation and third generation standard for mobile networks. It is the most secure mode of communication because of its spread spectrum property.

- CDMA is a form of multiplexing where a number of signals occupy a single transmission channel and optimizing the use of available bandwidth. This technology is used in ultra high frequency (UHF) cellular systems having a band ranging from 800MHz to 1.9GHz.

- CDMA uses to analog to digital conversion in combination with spread spectrum technology. First, the audio signal is digitized to binary elements.

-The frequency of the transmitted signal is then made to change according to the code. Thus, it can be intercepted only by a receiver whose frequency is programmed with the same code.

- The original CDMA standard called CDMA One offers a transmission speed of up to 14.4 kbps in its single channel form and up to 115kbps in an eight-channel form. -

- CDMA2000 and wideband CDMA deliver the data many times faster.

Advantages of CDMA

• Efficient utilization of fixed frequency spectrum.
• Flexible allocation of resources
• Multipath fading may be substantially reduced due to large signal bandwidth.
• No limit on a number of users.
• Impossible to decipher the code sent and better signal quality.
• No sense of hand-off when changing cells.
• The CDMA channel is nominally 1.23MHz wide.
• Soft hand-off minimizes signal breakup as the handset passes from one cell to another.
• CDMA is compatible with other cellular technologies, thus allowing a national wide roaming.

What is GSM?

- GSM stands for Global System for Mobile Communication. It is a digital mobile telephony system used for trans-receiving of the data and voice signals and is a second generation standard for mobile networks.

The GSM standard operates on three different carrier frequencies 900MHz, 1800MHz and 1900MHz. 900MHz band is used for original GSM system and the 1800MHz band is added to support the increasing number of customers. The 1900 MHz frequency band is used mainly in the United States.

- A GSM phone is a digital cellular technology used for transmitting mobile voice and data services. GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for transmitting signals.

- The GSM standard has led to the evolution of the wireless services like GPRS (General Packet Radio Service) UMTS (Universal Mobile Radio System) and EDGE (Enhanced Data Rates for GSM Evolution). Its users were the first to take the advantage of Short Message System (SMS).

- A GSM system makes use of cells to provide wireless communication to the subscribers. The GSM mobiles are identified by using Subscriber Identity Module (SIM). This is a removable smart card which contains the information of the subscriber. This SIM card allows the customer to switch from one mobile to another.

Advantages of GSM

• GSM provides improved spectrum efficiency
• Low-cost mobile set and base stations
• High-quality speech
• International roaming
• Compatibility with Integrated Services Digital Network (ISDN)

Compare between GSM and CDMA

GSM	CDMA
The GSM is based on wedge spectrum called a carrier.	The CDMA is based on spread spectrum technology.
This carrier is divided into time slots, and each user is assigned a different time slot. Thus, until the ongoing call is finished, no other user can access the same slot.	This technology allows each user to transmit over the entire frequency spectrum all the time.
Less security compared to CDMA technology.	More security is provided in CDMA technology.
No built-in encryption.	It has built-in encryption
Signals can be detected as the GSM signals are concentrated in the narrow bandwidth.	The signals cannot be detected easily in CDMA.
The GSM network operates in the frequency spectrum of 850MHz and 1900MHz.	The CDMA network operates in the frequency spectrum of 850MHz and 1900MHz.
GSM is used over 80% of the world’s mobile network.	CDMA is exclusively used in the United States, Canada and Japan.
GSM uses EDGE data transfer technology.	CDMA has faster data transfer as EVDO ready data transfer technology is used
It offers a maximum download speed of 384 Kbps.	It offers a maximum download speed of 2 Mbps.
A SIM card is required for the working of GSM device.	CDMA phones do not have these pulses.
A GSM is more flexible than CDMA as the SIM can be replaced with other GSM devices	A CDMA is not flexible.
GSM phones emit continuous wave pulse. Thus, there is a need to reduce the exposures to electromagnetic fields	CDMA phones do not have these pulses.
GSM phone emits about 28 times more radiations on an average as compared to CDMA	Very less radiation.

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